Airplane and Engine Certification Requirements in Supercooled Large Drop, Mixed Phase, and Ice Crystal Icing Conditions, 37311-37339 [2010-15726]
Download as PDF
<![CDATA[
37311
Proposed Rules
Federal Register
Vol. 75, No. 124
Tuesday, June 29, 2010
This section of the FEDERAL REGISTER
contains notices to the public of the proposed
issuance of rules and regulations. The
purpose of these notices is to give interested
persons an opportunity to participate in the
rule making prior to the adoption of the final
rules.
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 25 and 33
[Docket No. FAA–2010–0636; Notice No. 10–
10]
RIN 2120–AJ34
Airplane and Engine Certification
Requirements in Supercooled Large
Drop, Mixed Phase, and Ice Crystal
Icing Conditions
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
AGENCY: Federal Aviation
Administration (FAA), DOT.
ACTION: Notice of Proposed Rulemaking
(NPRM).
SUMMARY: The Federal Aviation
Administration proposes to amend the
airworthiness standards applicable to
certain transport category airplanes
certified for flight in icing conditions
and the icing airworthiness standards
applicable to certain aircraft engines.
The proposed regulations would
improve safety by addressing
supercooled large drop icing conditions
for transport category airplanes most
affected by these icing conditions,
mixed phase and ice crystal conditions
for all transport category airplanes, and
supercooled large drop, mixed phase,
and ice crystal icing conditions for all
turbine engines. These proposed
regulations are the result of information
gathered from a review of icing
accidents and incidents.
DATES: Send your comments on or
before August 30, 2010.
ADDRESSES: You may send comments
identified by Docket Number FAA–
2010–0636 using any of the following
methods:
• Federal eRulemaking Portal: Go to
https://www.regulations.gov and follow
the online instructions for sending your
comments electronically.
• Mail: Send comments to Docket
Operations, M–30; U.S. Department of
Transportation, 1200 New Jersey
Avenue, SE., Room W12–140, West
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
Building Ground Floor, Washington, DC
20590–0001.
• Hand Delivery or Courier: Bring
comments to Docket Operations in
Room W12–140 of the West Building
Ground Floor at 1200 New Jersey
Avenue, SE., Washington, DC, between
9 a.m. and 5 p.m., Monday through
Friday, except Federal holidays.
• Fax: Fax comments to Docket
Operations at 202–493–2251.
For more information on the
rulemaking process, see the
SUPPLEMENTARY INFORMATION section of
this document.
Privacy: The FAA will post all
comments we receive, without change,
to https://www.regulations.gov, including
any personal information you provide.
Using the search function of our docket
Web site, anyone can find and read the
electronic form of all comments
received into any of our dockets,
including the name of the individual
sending the comment (or signing the
comment for an association, business,
labor union, etc.). You may review
DOT’s complete Privacy Act Statement
in the Federal Register published on
April 11, 2000 (65 FR 19477–78) or you
may visit https://DocketsInfo.dot.gov.
Docket: To read background
documents or comments received, go to
https://www.regulations.gov at any time
and follow the online instructions for
accessing the docket. Or, go to Docket
Operations in Room W12–140 of the
West Building Ground Floor at 1200
New Jersey Avenue, SE., Washington,
DC, between 9 a.m. and 5 p.m., Monday
through Friday, except Federal holidays.
FOR FURTHER INFORMATION CONTACT: For
part 25 technical questions contact
Robert Hettman, FAA, Propulsion/
Mechanical Systems Branch, ANM–112,
Transport Airplane Directorate, Aircraft
Certification Service, 1601 Lind
Avenue, SW., Renton, WA 98057–3356;
telephone (425) 227–2683; facsimile
(425) 227–1320, e-mail
robert.hettman@faa.gov.
For part 33 technical questions
contact John Fisher, FAA, Rulemaking
and Policy Branch, ANE–111, Engine
and Propeller Directorate Standards
Staff, Aircraft Certification Service, 12
New England Executive Park,
Burlington, MA 01803; telephone (781)
238–7149, facsimile (781) 238–7199, email john.fisher@faa.gov.
For part 25 legal questions contact
Douglas Anderson, FAA, Office of the
PO 00000
Frm 00001
Fmt 4702
Sfmt 4702
Regional Counsel, ANM–7, Northwest
Mountain Region, 1601 Lind Avenue,
SW., Renton, WA 98057–3356;
telephone (425) 227–2166; facsimile
(425) 227–1007, e-mail
douglas.anderson@faa.gov.
For part 33 legal questions contact
Vince Bennett, FAA, Office of the
Regional Counsel, ANE–007, New
England Region, 12 New England
Executive Park, Burlington, MA 01803;
telephone (781) 238–7044; facsimile
(781) 238–7055, e-mail
vincent.bennett@faa.gov.
Later in
this preamble under the Additional
Information section, the FAA discusses
how you can comment on this proposal
and how the agency will handle your
comments. Included in this discussion
is related information about the docket,
privacy, and the handling of proprietary
or confidential business information.
The FAA also discusses how you can
get a copy of this proposal and related
rulemaking documents.
SUPPLEMENTARY INFORMATION:
Authority for This Rulemaking
The FAA’s authority to issue rules on
aviation safety is found in Title 49 of the
United States Code. Subtitle I, section
106 describes the authority of the FAA
Administrator. Subtitle VII, Aviation
Programs, describes in more detail the
scope of the agency’s authority.
This rulemaking is proposed under
the authority described in subtitle VII,
part A, subpart III, section 44701,
‘‘General requirements.’’ Under that
section, the FAA is charged with
promoting safe flight of civil aircraft in
air commerce by prescribing minimum
standards required in the interest of
safety for the design and performance of
aircraft; regulations and minimum
standards in the interest of safety for
inspecting, servicing, and overhauling
aircraft; and regulations for other
practices, methods, and procedures the
Administrator finds necessary for safety
in air commerce. This regulation is
within the scope of that authority
because it would prescribe—
• New safety standards for the design
and performance of certain transport
category airplanes and aircraft engines;
and
• New safety requirements that are
necessary for the design, production,
and operation of those airplanes, and for
other practices, methods, and
E:\FR\FM\29JNP1.SGM
29JNP1
37312
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
procedures relating to those airplanes
and engines.
Summary of the Proposal
The FAA proposes to revise certain
regulations in Title 14, Code of Federal
Regulations (14 CFR) part 25
(Airworthiness Standards: Transport
Category Airplanes) and part 33
(Airworthiness Standards: Aircraft
Engines) related to the certification of
transport category airplanes and turbine
aircraft engines in icing conditions. We
also propose to create new regulations:
§ 25.1324—Angle of attack systems;
§ 25.1420 SLD icing conditions; part 25,
appendix O (SLD icing conditions); part
33, appendix C (this will be
intentionally left blank as a
placeholder); and part 33, appendix D
(Mixed phase and ice crystal icing
conditions). To improve the safety of
transport category airplanes operating in
SLD, mixed phase, and ice crystal icing
conditions, the proposed regulations
would:
• Expand the certification icing
environment to include freezing rain
and freezing drizzle.
• Require airplanes most affected by
SLD icing conditions to meet certain
safety standards in the expanded
certification icing environment,
including additional airplane
performance and handling qualities
requirements.
• Expand the engine and engine
installation certification, and some
airplane component certification
regulations (for example, angle of attack
and airspeed indicating systems), to
include freezing rain, freezing drizzle,
ice crystal, and mixed phase icing
conditions. For certain cases, a subset of
these icing conditions is proposed.
The benefits and costs are
summarized below. The estimated
benefits are $405.6 million ($99.5
million present value). The total
estimated costs are $71.0 million ($54.0
million present value). On an
annualized basis, for the time period
2012–2064, the benefits are $7.0
million, and the costs are $3.8 million.
Nominal benefits
PV benefits
Benefits
Smaller & Medium Airplanes ........................................................................................................
Larger Airplanes ...........................................................................................................................
Total Benefits .........................................................................................................................
$249,580,915
156,004,884
405,585,799
$69,994,259
29,498,469
99,492,728
(7.0 million annually)
Costs
Nominal cost
PV cost
Engine Cert Cost ..........................................................................................................................
Engine Capital Cost ......................................................................................................................
7,936,000
6,000,000
6,931,610
5,240,632
Total Engine ..........................................................................................................................
13,936,000
12,172,242
Smaller Airplane Certification Cost ...............................................................................................
New Larger Airplane Certification Cost ........................................................................................
Derivative Larger Airplane Certification Cost ...............................................................................
Hardware Costs ............................................................................................................................
Fuel Burn All .................................................................................................................................
24,999,039
3,154,600
10,438,800
10,390,000
8,046,676
21,835,129
2,755,350
9,117,652
5,842,024
2,261,941
Total Costs ............................................................................................................................
70,965,115
53,984,338
($3.8 million annually)
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Background
In the 1990s, the FAA became aware
that the types of icing conditions
considered during the certification of
transport category airplanes and turbine
aircraft engines needed to be expanded
to increase the level of safety during
flight in icing. The FAA determined that
the revised icing certification standards
should include supercooled large drops
(SLD), mixed phase, and ice crystals.1
Safety concerns about the adequacy of
the icing certification standards were
brought to the forefront of public and
governmental attention by a 1994
accident in Roselawn, Indiana,
involving an Avions de Transport
Regional ATR 72 series airplane. The
1 Appendix 1 of this preamble contains
definitions of certain terms used in this notice of
proposed rulemaking (NPRM).
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
FAA, Aerospatiale, the French Direction
´ ´
General de l’Aviation Civile, Bureau
Enquete Accident, the National
Aeronautics and Space Administration,
the National Transportation Safety
Board (NTSB), and others conducted an
extensive investigation of this accident.
These investigations led to the
conclusion that freezing drizzle
conditions created a ridge of ice on the
wing’s upper surface aft of the deicing
boots and forward of the ailerons. It was
further concluded that this ridge of ice
contributed to an uncommanded roll of
the airplane. Based on its investigation,
the NTSB recommended changes to the
icing certification requirements.
The certification requirements for
icing conditions are specified in part 25,
appendix C. The atmospheric condition
(freezing drizzle) that contributed to the
Roselawn accident is currently outside
PO 00000
Frm 00002
Fmt 4702
Sfmt 4702
the icing envelope for certifying
transport category airplanes. The term
‘‘icing envelope’’ is used within part 25,
appendix C, and this NPRM to refer to
the environmental icing conditions
within which the airplane must be
shown to be able to safely operate. The
term ‘‘transport category airplanes’’ is
used throughout this rulemaking
document to include all airplanes type
certificated to part 25 regulations.
Another atmospheric icing condition
that is currently outside the icing
envelope is freezing rain. The FAA has
not required airplane manufacturers to
show that airplanes can operate safely
in freezing drizzle or freezing rain
conditions. These conditions constitute
an icing environment known as
supercooled large drops (SLDs).
As a result of this accident and
consistent with related NTSB
E:\FR\FM\29JNP1.SGM
29JNP1
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
recommendations 2 the FAA tasked the
Aviation Rulemaking Advisory
Committee (ARAC),3 through its Ice
Protection Harmonization Working
Group (IPHWG), to do the following:
• Define an icing environment that
includes SLDs.
• Consider the need to define a mixed
phase icing environment (supercooled
liquid and ice crystals).
• Devise requirements to assess the
ability of an airplane to either safely
operate without restrictions in SLD and
mixed phase conditions or safely
operate until it can exit these
conditions.
• Study the effects icing requirement
changes could have on §§ 25.773, Pilot
compartment view; 25.1323, Airspeed
indicating system; and 25.1325, Static
pressure systems.
• Consider the need for a regulation
on ice protection for angle of attack
probes.
This proposed rule is based on the
ARAC’s recommendations to the FAA.
Terms used in this notice of proposed
rulemaking (NPRM) are defined in
Appendix 1 of this preamble.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
A. Existing Regulations for Flight in
Icing Conditions
Currently, the certification regulations
applicable to transport category
airplanes for flight in icing conditions
require that: ‘‘The airplane must be able
to operate safely in the continuous
maximum and intermittent maximum
icing conditions of appendix C.’’ 4 The
certification regulations also require
minimum performance and handling
qualities in these icing conditions and
methods to detect airframe icing and to
activate and operate ice protection
systems.5 Icing regulations applicable to
engines are in §§ 33.68 and 33.77.
Operating regulations in parts 91
(General Operating and Flight Rules)
and 135 (Operating Requirements:
Commuter and On Demand Operations)
address limitations in icing conditions
for airplanes operated under these
parts.6 Part 121 (Operating
Requirements: Domestic, Flag and
Supplemental Operations) addresses
operations in icing conditions that
2 NTSB recommendations A–96–54 and A–96–56;
available in the Docket and on the Internet at:
https://www.ntsb.gov/Recs/letters/1996/
A96_48_69.pdf.
3 Published in the Federal Register, December 8,
1997 (62 FR 64621).
4 14 CFR 25.1419, Ice Protection.
5 For a complete discussion of the regulations see
Amendment 25–121 (72 FR 44665, August 8, 2007),
and Amendment 25–129 (74 FR 38328, August 3,
2009).
6 14 CFR 91.527, Operating in icing conditions;
and § 135.227, Icing conditions: Operating
limitations.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
might adversely affect safety and
requires installing certain types of ice
protection equipment and wing
illumination equipment.7
Some of the part 25 and 33
regulations specify that the affected
equipment must be able to operate in
some or all of the icing conditions
defined in part 25, appendix C. Other
regulations within these parts do not
specify the icing conditions that must be
considered for airplane certification,
but, historically, airplane certification
programs have only considered icing
conditions that are defined in appendix
C.
Appendix C addresses continuous
maximum and intermittent maximum
icing conditions within stratiform and
cumuliform clouds ranging from sea
level up to 30,000 feet. Appendix C
defines icing cloud characteristics in
terms of mean effective drop diameters,
liquid water content, temperature,
horizontal and vertical extent, and
altitude. Icing conditions that contain
drops with mean effective diameters
that are larger than the cloud mean
effective drop diameters defined in
appendix C are typically referred to as
freezing drizzle or freezing rain. Icing
conditions containing freezing drizzle
and freezing rain are not currently
considered when certifying an
airplane’s ice protection systems.
Because the larger diameter drops
typically impinge farther aft on the
airfoil, exposure to these conditions can
result in ice accretions aft of the ice
protection area, which can negatively
affect airplane performance and
handling qualities.
Likewise, mixed phase (supercooled
liquid and ice crystals) and 100% ice
crystal icing conditions are not
currently considered when certifying an
airplane’s ice protection systems.
Exposing engines and externally
mounted probes to these conditions
could result in hazardous ice
accumulations within the engine that
may result in engine damage, power
loss, and loss of or misleading airspeed
indications. The certification
regulations for transport category
airplanes and engines do not address
the safe operation of airplanes in SLD,
mixed phase, or ice crystal icing
conditions and the operating rules do
not specifically prohibit operations in
these conditions.
7 14 CFR 121.629(a), Operation in icing
conditions and § 121.341, Equipment for operations
in icing conditions.
PO 00000
Frm 00003
Fmt 4702
Sfmt 4702
37313
B. National Transportation Safety Board
Safety Recommendations
The NTSB issued NTSB Safety
Recommendation Numbers A–96–54 8
and A–96–56 9 as a result of the
Roselawn accident previously
discussed. This rulemaking activity
partially addresses the NTSB
recommendations because there are
separate rulemaking activities
associated with revisions to 14 CFR part
23 regulations for small airplanes and
14 CFR part 121 operational regulations.
The NTSB recommendations are as
follows:
1. A–96–54
Revise the icing criteria published in
14 Code of Federal Regulations (CFR),
parts 23 and 25, in light of both recent
research into aircraft ice accretion under
varying conditions of liquid water
content, drop size distribution, and
temperature, and recent developments
in both the design and use of aircraft.
Also, expand the appendix C icing
certification envelope to include
freezing drizzle/freezing rain and mixed
water/ice crystal conditions, as
necessary. (Class II, Priority Action) (A–
96–54) (Supersedes A–81–116 and—
118)
2. A–96–56
Revise the icing certification testing
regulation to ensure that airplanes are
properly tested for all conditions in
which they are authorized to operate, or
are otherwise shown to be capable of
safe flight into such conditions. If safe
operations can not be demonstrated by
the manufacturer, operational
limitations should be imposed to
prohibit flight in such conditions and
flightcrews should be provided with the
means to positively determine when
they are in icing conditions that exceed
the limits for aircraft certification. (Class
II, Priority Action) (A–96–56)
C. Related Rulemaking Activity
The ARAC’s Ice Protection
Harmonization Working Group (IPHWG)
submitted additional part 121 icing
rulemaking recommendations to the
FAA that may lead to future rulemaking,
but do not directly impact this NPRM.
Those recommendations would improve
airplane safety when operating in icing
conditions. The recommendations
would:
• Address when ice protection
systems must be activated.
8 NTSB recommendation A–96–54; available in
the Docket and on the Internet at: https://
www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
9 NTSB recommendation A–96–56; available in
the Docket and on the Internet at: https://
www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
E:\FR\FM\29JNP1.SGM
29JNP1
37314
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
• Require some airplanes to exit all
icing conditions after encountering large
drop icing conditions conducive to ice
accretions aft of the airframe’s protected
area.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
D. Advisory Material
The proposed new AC and revisions
to existing ACs would provide guidance
material for one acceptable means, but
not the only means, of demonstrating
compliance with the proposed
regulations contained in this NPRM.
The guidance provided in these
documents is directed at airplane
manufacturers, modifiers, foreign
regulatory authorities, and FAA
transport airplane type certification
engineers, flight test pilots, and their
designees. The proposed ACs will be
posted on the ‘‘Aircraft Certification
Draft Documents Open for Comment’’
Web site, https://www.faa.gov/aircraft/
draft_docs, after this NPRM is published
in the Federal Register
For advisory material related to this
NPRM, the FAA is:
• Developing a new AC 25–xx,
Compliance of Transport Category
Airplanes with Certification
Requirements for Flight in Icing
Conditions.
• Revising AC 20–147, Turbojet,
Turboprop, and Turbofan Engine
Induction System Icing and Ice
Ingestion.
• Revising AC 25–25, Performance
and Handling Characteristics in the
Icing Conditions Specified in Part 25,
Appendix C.
• Revising AC 25.629–1A, Aeroelastic
Stability Substantiation of Transport
Category Airplanes.
• Revising AC 25.1329–1B, Approval
of Flight Guidance Systems.
General Discussion of the Proposal
The FAA proposes to revise certain
regulations in parts 25 and 33 related to
the certification of transport category
airplanes and turbine aircraft engines in
icing conditions.
We also propose to create a new:
§ 25.1324—Angle of attack systems;
§ 25.1420—Supercooled large drop icing
conditions; part 25, appendix O
(supercooled large drop icing
conditions; part 33, appendix C
(intentionally left blank); and part 33,
appendix D (Mixed phase and ice
crystal icing conditions). Part 33,
appendix C, is intentionally left blank
and retained as a placeholder for nonicing related regulations so that part 33,
appendix C, would not be confused
with the icing conditions defined in part
25, appendix C.
To improve the safety of transport
category airplanes operating in SLD,
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
mixed phase, and ice crystal icing
conditions, the proposed regulations
would:
• Expand the certification icing
environment to include freezing rain
and freezing drizzle.
• Require airplanes most affected by
SLD icing conditions (transport category
airplanes with a maximum takeoff
weight less than 60,000 pounds or with
reversible flight controls) to meet certain
safety standards in the expanded
certification icing environment,
including additional airplane
performance and handling qualities
requirements.
• Expand the engine and engine
installation certification, and some
airplane component certification
regulations (for example, angle of attack
and airspeed indicating systems) to
include freezing rain, freezing drizzle,
ice crystal, and mixed phase icing
conditions. For certain cases, a subset of
these icing conditions is proposed.
A. Safety Concern
The ARAC’s IPHWG reviewed icing
events involving transport category
airplanes and found accidents and
incidents that are believed to have
occurred in icing conditions that are not
addressed by the current regulations.
The icing conditions resulted in
flightcrews losing control of their
aircraft and, in some cases, engine
power loss. The review found hull
losses and fatalities associated with SLD
conditions, but not for ice crystal and
mixed phase conditions. However, there
have been 14 documented cases of ice
crystal and mixed phase engine power
loss events between 1988 through 2009.
Of those events, there were 13
occurrences of multi-engine power loss
events. Fifty percent of those events
were defined as ‘‘aircraft level events,’’
since they occurred on multiple engines
installed on the same airplane. Two of
these aircraft level events resulted in
diversions.
The incident history also indicates
that flightcrews have experienced
temporary loss of or misleading airspeed
indications in icing. Airspeed
indications on transport category
airplanes are derived from the
difference between two air pressures—
the total pressure, as measured by a
pitot tube mounted somewhere on the
fuselage, and the ambient or static
pressure, as measured by a static port.
The static port may be flush mounted on
the airplane fuselage or co-located on
the pitot tube. When the static and pitot
systems are co-located, the
configuration is referred to as a pitotstatic tube. Static ports are not prone to
collecting ice crystals, either because of
PO 00000
Frm 00004
Fmt 4702
Sfmt 4702
their flush mounted locations or their
overall shape.
Due to the way pitot or pitot-static
tubes are usually mounted, they are
prone to collecting ice crystals.
Encountering high concentrations of ice
crystals may lead to blocked pitot or
pitot-static tubes because the energy
necessary to melt the ice crystals can
exceed the tubes’ design requirements.
Pitot or pitot-static tube blockage can
lead to errors in measuring airspeed.
The regulatory changes which add ice
crystal conditions for airspeed
indicating systems are intended to apply
to either a pitot tube or pitot-static tube
configuration.
The IPHWG did not identify any
events due to ice accumulations on
probes that are used to measure angle of
attack, or other angle of attack sensors.
However, the IPHWG determined there
are angle of attack probe designs that are
susceptible to mixed phase conditions.
The IPHWG concluded that the
current regulations do not adequately
address SLD, mixed phase, and ice
crystal conditions. The concerns
regarding mixed phase and ice crystal
conditions were limited to engines,
propulsion installations, airspeed
indications, and angle of attack systems.
The FAA concurs with the IPHWG’s
conclusions.
B. Prior FAA Actions To Address the
Safety Concern
The FAA has issued airworthiness
directives (ADs) to address the unsafe
conditions associated with operating
certain airplanes in severe icing
conditions, which can include SLD
icing conditions. These ADs are
applicable to airplanes equipped with
both reversible flight controls in the roll
axis and pneumatic deicing boots. The
ADs require the flightcrews to exit icing
when visual cues are observed that
indicate the conditions exceed the
capabilities of the ice protection
equipment. In addition, for new
certifications of airplanes equipped with
unpowered roll axis controls and
pneumatic deicing boots, the airplanes
are evaluated to ensure the roll control
forces are acceptable if the airplane
operates in certain SLD conditions.
However, the scope of these actions is
limited because they do not address all
transport category airplanes and do not
address the underlying safety concern of
the unknown performance and handling
qualities safety margins for airplanes
and engines operating in freezing
drizzle, freezing rain, mixed phase, and
ice crystal conditions. The IPHWG
concluded there is a need to improve
the regulations to ensure safe operation
E:\FR\FM\29JNP1.SGM
29JNP1
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
of airplanes and engines in these
conditions.
C. Alternatives to Rulemaking
Before proposing new rulemaking, the
FAA considers alternative ways to solve
the safety issue under consideration.
Following is a brief discussion of two of
the alternatives we considered during
deliberations on this proposed rule.
1. Alternative 1: Terminal Area Radar
and Sensors
The IPHWG considered the use of
terminal area radar and ground-based
sensors to identify areas of SLDs so they
can be avoided, rather than require
certification for operations in SLD.
Equipment for detecting and
characterizing icing conditions in
holding areas is being developed.
However, the equipment would have
limited coverage area. For areas not
covered by terminal area radar and
ground-based sensors, airborne radars
and sensors are being developed that
would identify SLD conditions in
sufficient time for avoidance. These
ground-based and airborne systems are
not mature enough to provide sufficient
protection for all flight operations
affected by SLD. Even if the equipment
was mature, rulemaking would still be
necessary to establish safety margins for
inadvertent flight into such conditions
and to provide an option for applicants
to substantiate that the airplane is
capable of safe operation in SLD
conditions.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
2. Alternative 2: Icing Diagnostic and
Predictive Weather Tools
The IPHWG considered the use of
icing diagnostic and predictive weather
tools to avoid SLD rather than certify an
airplane to operate in SLD conditions.
Tools have been developed that can
provide information on icing and SLD
potential, but may not report all
occurrences of SLD. These experimental
tools are available on the Internet and
can be used to provide flight planning
information guidance for avoidance of
SLD conditions. However, rulemaking
would still be necessary to establish
safety margins for inadvertent flight into
such conditions and to provide an
option for applicants to substantiate that
the airplane is capable of safe operation
in SLD conditions.
Discussion of the Proposed Regulatory
Requirements
Appendix O to Part 25
The proposed appendix O is
structured like part 25, appendix C, one
part defining icing conditions and one
defining ice accretions. Appendix O,
part I, would define SLD icing
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
conditions and part II would define the
ice accretions that a manufacturer must
consider when designing an airplane.
Supercooled Large Drop Icing
Conditions
Proposed § 25.1420 would add safety
requirements that must be met in SLD
icing conditions for certain transport
category airplanes to be certified for
flight in icing conditions. This change
would require evaluating the operation
of these airplanes in the SLD icing
environment; developing a means to
differentiate between different SLD
icing conditions, if necessary; and
developing procedures to exit all icing
conditions.
The proposed regulation would
require consideration of the SLD icing
conditions (freezing drizzle and freezing
rain) defined in a proposed new part 25,
appendix O, part I, in addition to the
existing part 25, appendix C, icing
conditions. Proposed appendix O would
include drop sizes larger than those
considered by current icing regulations.
These larger drops impinge and freeze
farther aft on airplane surfaces than the
drops defined in appendix C and may
affect the airplane’s performance,
handling qualities, flutter
characteristics, and engine and systems
operations. The appendix O icing
conditions, if adopted, may affect the
design of airplane ice protection
systems.
The SLD icing conditions described in
the proposed appendix O would be
those in which the airplane must be able
to either safely exit following the
detection of any or specifically
identified appendix O icing conditions,
or safely operate without restrictions.
Specifically, the proposed § 25.1420
would allow three options:
• Detect appendix O conditions and
then operate safely while exiting all
icing conditions (§ 25.1420(a)(1)).
• Safely operate in a selected portion
of appendix O conditions, detect when
the airplane is operating in conditions
that exceed the selected portion, and
then operate safely while exiting all
icing conditions (§ 25.1420(a)(2)).
• Operate safely in all of the
appendix O conditions (§ 25.1420(a)(3)).
As discussed below in the section
titled ‘‘Differences from the ARAC
Recommendations,’’ the proposed
§ 25.1420 would apply to airplanes with
either: (1) a takeoff maximum gross
weight of less than 60,000 pounds, or (2)
reversible flight controls.
To establish that an airplane could
operate safely in the proposed appendix
O conditions described above, proposed
§ 25.1420(b) would require both analysis
and one test, or more as found
PO 00000
Frm 00005
Fmt 4702
Sfmt 4702
37315
necessary, to establish that the ice
protection for the various components
of the airplane is adequate. The words
‘‘as found necessary’’ would be applied
in the same way as they are applied in
§ 25.1419(b). During the certification
process, the applicant would
demonstrate compliance with the rule
using a combination of analyses and
test(s). The applicant’s means of
compliance would consist of analyses
and the amount and types of testing it
finds necessary to demonstrate
compliance with the regulation. The
applicant would choose to use one or
more of the tests identified in
paragraphs § 25.1420(b)(1) through
(b)(5). Although the applicant may
choose the means of compliance, it is
ultimately the FAA that determines
whether the applicant has performed
sufficient test(s) and analyses to
substantiate compliance with the
regulation. Similarly, the words ‘‘as
necessary,’’ which appear in
§ 25.1420(b)(3) and (b)(5), would result
in the applicant choosing the means of
compliance that is needed to support
the analysis, but the FAA would make
a finding whether the means of
compliance is acceptable. If an
applicant has adequate data a similarity
analysis may be used in lieu of the
testing required by § 25.1420(b). For an
airplane certified to operate in at least
a portion of proposed appendix O icing
conditions, proposed § 25.1420(c)
would extend the requirements of
§ 25.1419(e), (f), (g), and (h) 10 to include
activation and operation of airframe ice
protection systems in the appendix O
icing conditions for which the airplane
is certified. Proposed § 25.1420(c)
would not apply to airplanes certified to
proposed § 25.1420(a)(1) because
proposed § 25.1420(a)(1) would require
a method to identify and safely exit all
appendix O conditions.
The proposed appendix O defines
SLD conditions. It was developed by the
ARAC IPHWG, which included
meteorologists and icing research
specialists from industry, FAA/FAA
Tech Center, Meteorological Services of
Canada, National Aeronautics and
Space Administration (NASA), and
Transport Canada/Transport
Development Center. The IPHWG
collected and analyzed airborne
measurements of pertinent SLD
variables, developed an engineering
standard to be used in aircraft
certification, and recommended that
10 These requirements were recently adopted in
Amendment 25–129 (74 FR 38328, August 3, 2009).
Generally, that amendment requires methods to
detect airframe icing and to activate and operate ice
protection systems.
E:\FR\FM\29JNP1.SGM
29JNP1
37316
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
standard to the FAA. The FAA concurs
with the recommendation.
The SLD conditions defined in
appendix O, part I, include freezing
drizzle and freezing rain conditions.
The freezing drizzle and freezing rain
environments are further divided into
conditions in which the drop median
volume diameters are either less than or
greater than the 40 microns. Appendix
O consists of measured data that was
divided into drop distributions within
these four icing conditions. These
distributions were averaged to produce
the representative distributions for each
condition.
The distributions of drop sizes are
defined as part of appendix O. The need
to include the distributions comes from
the larger amount of mass in the larger
drop diameters of appendix O. The
water mass of the larger drops affects
the amount of water that impinges on
airplane components, the drop
impingement, icing limits, and the ice
buildup shape.
Appendix O provides a liquid water
content scale factor that would be used
to adjust the liquid water content for
freezing drizzle and freezing rain. The
scale factor is based on the liquid water
contents of continuous freezing drizzle
and freezing rain conditions decreasing
with increasing horizontal extents.
Performance and Handling Qualities
The ice accretion definitions in
proposed appendix O, part II, and the
proposed revisions to the performance
and handling qualities requirements for
flight in icing conditions are similar to
those required for flight in appendix C
icing conditions. The proposals address
the three options allowed by proposed
§ 25.1420(a). Proposed appendix O, part
II, would contain definitions of the ice
accretions appropriate to each phase of
flight. The proposed appendix O, part
II(b), would define the ice accretions
used to show compliance with the
performance and handling qualities
requirements for any portion of
appendix O in which the airplane is not
certified to operate. The proposed
appendix O, part II(c), would define the
ice accretions for any portion of
appendix O in which the airplane is
certified to operate.
Proposed appendix O, part II(d),
would define the ice accretion in
appendix O conditions before the
airframe ice protection system is
activated and is performing its intended
function to reduce or eliminate ice
accretions on protected surfaces. This
ice accretion would be used in showing
compliance with the controllability and
stall warning margin requirements of
§§ 25.143(j) and 25.207(h), respectively,
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
that apply before the airframe ice
protection system has been activated
and is performing its intended function.
Even if the airplane is certified to
operate only in a portion of the
appendix O icing conditions, the ice
accretion used to show compliance with
§§ 25.143(j) and 25.207(h) must consider
all appendix O icing conditions since
the initial entry into icing conditions
may be into appendix O icing
conditions in which the airplane is not
certified to operate.
To reduce the number of ice
accretions needed to show compliance
with § 25.21(g), the proposed appendix
O, part II(e), would allow the option of
using an ice accretion defined for one
flight phase for any other flight phase if
it is shown to be more critical than the
ice accretion defined for that other flight
phase.
Existing § 25.21(g)(1) 11 requires that
the performance and handling qualities
requirements of part 25, subpart B, with
certain exceptions,12 be met in appendix
C icing conditions.13 Proposed
§ 25.21(g)(3) would identify the
performance and handling qualities
requirements that must be met to ensure
that an airplane certified to either the
proposed § 25.1420(a)(1) or (a)(2) could
safely exit icing if the icing conditions
of proposed appendix O, for which
certification is not sought, are
encountered. Such an airplane would
not be approved to take off in proposed
appendix O icing conditions and would
only need to be able to detect and safely
exit those icing conditions encountered
en route. Therefore, it is proposed that,
in addition to the exceptions identified
in the existing § 25.21(g)(1), such an
airplane would not need to meet certain
requirements 14 for appendix O icing
conditions.
With one exception, for an airplane
certified under proposed § 25.1420(a)(1)
or (a)(2), the same handling qualities
requirements that must currently be met
for flight in appendix C icing conditions
are proposed for flight in appendix O
icing conditions for which certification
is not sought. That exception is
§ 25.143(c)(1), which addresses
controllability following engine failure
during takeoff at V2. Compliance with
that rule would not be necessary since
11 14 CFR 25.21(g)(1) is proposed to be
redesignated as § 25.21(g)(2).
12 The exceptions listed in this requirement are
§§ 25.121(a), 25.123(c), 25.143(b)(1) and (b)(2),
25.149, 25.201(c)(2), 25.207(c) and (d), 25.239, and
25.251(b) through (e).
13 For a complete discussion of these
requirements, see Amendment 25–121 (72 FR
44665, August 8, 2007).
14 14 CFR 25.105, 25.107, 25.109, 25.111, 25.113,
25.121, and 25.123.
PO 00000
Frm 00006
Fmt 4702
Sfmt 4702
the airplane would not be approved for
takeoff in appendix O icing conditions.
No justification for a relaxation of other
handling qualities requirements could
be identified.
The requirements for safe operation in
all or any portion of proposed appendix
O icing conditions under proposed
§ 25.21(g)(4) are similar to those
currently required for appendix C icing
conditions. With one exception, the list
of part 25, subpart B requirements that
currently do not have to be met for flight
in appendix C icing conditions would
not have to be met in proposed
appendix O icing conditions. The
exception is that compliance with
§ 25.121(a), Climb: One-engineinoperative would be required for
appendix O icing conditions because,
unlike for appendix C icing conditions,
the FAA cannot justify an assumption
that the ice accretion in this flight phase
can be assumed insignificant. In
practice, it is expected that some
applicants may use an operating
limitation to prohibit takeoff in
appendix O icing conditions. Otherwise,
the same rationales behind the
requirements are used for both appendix
C and appendix O icing conditions. For
continued operation in appendix O
icing conditions, there should
effectively be no degradation in
handling qualities, and any degradation
in performance should be no greater
than that allowed by the regulations for
appendix C icing conditions.
Component Requirements for All Part
25 Transport Category Airplanes
In certification programs, both the
airplane as a whole and its individual
components are evaluated for flight in
icing conditions. There are several rules
in part 25 15 that contain icing related
requirements for specific components.
We propose to revise those rules to
ensure the airplane can safely operate in
the new icing conditions established in
this proposed rule.
Section 25.1419 requires that an
airplane be able to safely operate in all
of the conditions specified in appendix
C, whereas the proposed § 25.1420
would not require an airplane to safely
operate in all of the appendix O icing
conditions. Proposed § 25.1420(a)(1)
and (a)(2) only require an airplane to be
capable of safely exiting icing
conditions after encountering an
appendix O icing condition for which
that airplane will not be certified. The
existing regulations for pilot
compartment view, airspeed indication
15 14 CFR 25.773, 25.929, 25.1093, 25.1323, and
25.1325.
E:\FR\FM\29JNP1.SGM
29JNP1
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
system, and static pressure system 16
contain requirements for operation in
icing conditions. These sections would
be revised to add requirements for
operation in appendix O icing
conditions. Section 25.1323, Airspeed
indicating system, would also be revised
to include and define mixed phase and
ice crystal conditions. New proposed
§ 25.1324 includes an icing requirement
for angle of attack systems. This would
be similar to the icing requirements for
airspeed indication systems. The
proposed section would require the
angle of attack system to be heated to
prevent malfunction in appendices C
and O icing conditions and in the mixed
phase and ice crystal conditions defined
in § 25.1323.
In the proposed revisions to the
requirements for pilot compartment
view, airspeed indication system, and
static pressure system,17 and the new
proposed requirements for angle of
attack systems, an airplane certified in
accordance with § 25.1420(a)(1) or (a)(2)
would not be required to be evaluated
for all of appendix O. For airplanes
certified in accordance with
§ 25.1420(a)(1), the icing conditions that
the airplane is certified to safely exit
following detection must be considered.
For airplanes certified in accordance
with § 25.1420(a)(2), the icing
conditions that the airplane is certified
to safely operate in, and to safely exit
following detection, must be
considered. For airplanes certified in
accordance with § 25.1420(a)(3) and for
airplanes not subject to § 25.1420, all
icing conditions must be considered.
Airplanes not certified for flight in icing
need not consider appendix O.
The engine induction system icing
section (§ 25.1093) and propeller
deicing section (§ 25.929) contain
requirements for operation in icing
conditions. As a conservative approach
to ensure safe operation of an airplane
in an inadvertent encounter with icing,
the existing language in § 25.1093
contains requirements for operation in
icing conditions, even for an airplane
that is not approved for flight in icing.
Since proposed appendix O defines
icing conditions that also may be
inadvertently encountered, § 25.1093
would be revised to reference appendix
O in its entirety. This would maintain
the FAA’s conservative approach for
this section. Section 25.929 (propeller
deicing) would also be revised to
reference appendix O in its entirety.
Sections 25.929 and 25.1323
generically reference icing instead of
specifically mentioning appendix C.
16 14
CFR 25.773, 25.1323, and 25.1325.
17 Ibid.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
Historically, the icing conditions
specified in appendix C have been
applied to these rules. For clarity, we
are revising §§ 25.929 and 25.1323 so
they specifically reference appendix C,
as well as appendix O. The proposed
revisions to icing regulations for pilot
compartment view, propellers, engine
induction system icing protection,
airspeed indication system, static
pressure system, and angle of attack
system would be applicable to all
transport category airplanes to ensure
safe operation during operations in icing
conditions.
The proposed revisions to § 25.903
would retain the existing regulations
and add new subparagraphs to be
consistent with the proposed part 33
changes in § 33.68. These revisions
would allow for approving new aircraft
type certification programs with engines
certified to earlier amendment levels.
The proposed revisions would make it
clear that the proposed part 33 changes
would not be retroactively imposed on
an already type certified engine design,
unless service history indicated that an
unsafe condition was present.
The proposed revision to § 25.929
clarifies the meaning of the words ‘‘for
airplanes intended for use where icing
may be expected.’’ The intent has been
for the rule to be applicable to airplanes
certified for flight in icing.
Engine and Engine Installation
Requirements
The proposed revisions to §§ 25.1093,
33.68, and 33.77 would change the icing
environmental requirements used to
evaluate engine protection and
operation in icing conditions. The
reason for these changes is that the
incident history of some airplanes has
shown that the current icing
environmental requirements are
inadequate. The effect of the change
would be to require an evaluation of
safe operation in the revised icing
environment. The proposed revision to
§ 25.1093 restructures paragraph (b) and
adds a new Table 1—Icing Conditions
for Ground Tests. The proposed rules
would require engines and engine
installations to operate safely
throughout the SLD conditions defined
in proposed new part 25, appendix O,
and the newly defined mixed phase and
ice crystal conditions defined in
proposed new part 33, appendix D.18
The proposed appendix D was
developed by the ARAC Engine
Harmonization Working Group and the
18 See
FAA report DOT/FAA/AR–09/13,
Technical Compendium from Meetings of the
Engine Harmonization Working Group, March 2009
for details on appendix D and its development.
PO 00000
Frm 00007
Fmt 4702
Sfmt 4702
37317
Power Plant Installation Harmonization
Working Group, which included
meteorologists and icing research
specialists from industry, FAA/FAA
Tech Center, Meteorological Services of
Canada, National Aeronautics and
Space Administration (NASA), and
Transport Canada/Transport
Development Center. The ARAC
recommended appendix D and the FAA
concurs with the recommendation.
The proposed revision to § 25.1521
would retain the existing regulations
and add a new subparagraph that would
require an additional operating
limitation for turbine engine
installations during ground operation in
icing conditions defined in
§ 25.1093(b)(2). That operating
limitation would address the maximum
time interval between any engine runups from idle and the minimum
ambient temperature associated with
that run-up interval. This limitation is
necessary because we do not currently
have any specific requirements for runup procedures for engine ground
operation in icing conditions. The
engine run-up procedure, including the
maximum time interval between runups from idle, run-up power setting,
duration at power, and the minimum
ambient temperature demonstrated for
that run-up interval proposed in
§ 25.1521, would be included in the
Airplane Flight Manual in accordance
with existing § 25.1581(a)(1) and
§ 25.1583(b)(1).
The engine run-up procedure from
ground idle to a moderate power or
thrust setting is necessary to shed ice
build-up on the fan blades before the
quantity of ice reaches a level that could
adversely affect engine operation if ice
is shed into the engine. The proposed
revision to § 25.1521 would not require
additional testing. The ice shedding
demonstration may be included as part
of the § 33.68 engine icing testing.
Operating Limitations
The proposed revision to § 25.1533
would establish an operating limitation
applicable to airplanes that are not
certified in accordance with proposed
§ 25.1420(a)(1) or (a)(2). The flightcrews
of these airplanes would be required to
exit all icing conditions if they
encounter appendix O icing conditions
that the airplane has not been certified
to operate in.
Expansion of Proposed Icing
Requirements
The proposed regulations 19 for the
airspeed indicating system and angle of
19 14
E:\FR\FM\29JNP1.SGM
CFR 25.1323, and 25.1324.
29JNP1
37318
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
attack system would address the
operation of those systems in specific
mixed phase and ice crystal conditions,
as defined in proposed Appendix O.
During the drafting of this NPRM the
FAA became aware of airspeed
indicating system malfunctions in
environmental conditions that may not
be addressed by these proposed
regulations. The FAA is reviewing the
malfunctions and is considering the
need to change the proposed mixed
phase and ice crystal parameters to
include freezing rain. The maximum
mixed phase and ice crystal parameters
that we are considering are those
Static air temperature
Altitude range
(°C)
(ft)
¥2 to 0 .........................................................................................................................
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
We consider the mixed phase and ice
crystal parameters defined in the
proposed part 33, appendix D, plus the
freezing rain parameters defined above
to be adequate to prevent potential
airspeed indicating system malfunctions
in these newly defined environmental
conditions. We request technical and
economic comments on whether the
proposed airspeed indicating system
and angle of attack system regulations
should include these expanded
parameters. Based on comments we
receive, we may add these parameters to
the final rule.
Differences From the ARAC
Recommendations
The IPHWG recommended changes to
parts 25 and 33 to ensure the safe
operation of airplanes and engines in
icing conditions. The FAA concurs with
the recommendations, but has
determined it is necessary to revise to
which airplanes the new airplane icing
certification requirements in the
proposed § 25.1420 would apply. The
proposed § 25.1420 in this NPRM would
apply to airplanes with either: (1) a
takeoff maximum gross weight of less
than 60,000 lbs (27,000 kg), or (2)
reversible flight controls. An airplane
with reversible flight controls in any
axis (pitch, roll, or yaw), even if these
flight controls are aerodynamically
boosted and/or power-assisted, would
be considered to have reversible flight
controls under this proposed rule. An
airplane with flight controls that are
irreversible under normal operating
conditions, but are reversible following
a failure, would not be considered to
have reversible flight controls under this
proposed rule. Reversible,
aerodynamically boosted, and powerassisted flight controls are defined in
Appendix 1 to the preamble of this
NPRM. The ADs described above in
section B. ‘‘Prior FAA Actions to address
the Safety Concern’’ are only applicable
to airplanes equipped with both
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
defined in the proposed part 33,
appendix D. The freezing rain
parameters that we are considering are
based on standards some manufacturers
have used for airdata probes. The
maximum freezing rain parameters that
we are considering are:
(m)
0 to 10 000
Frm 00008
Fmt 4702
Sfmt 4702
(g/m3)
0 to 3000
reversible flight controls in the roll axis
and pneumatic deicing boots.
A group of IPHWG members (Boeing,
Airbus, and Embraer, supported by
Cessna) held a minority position in their
belief that the applicability of the
proposed § 25.1420 should exclude
airplanes with certain design features.
Their rationale for the position is that
large transport airplanes still in
production have not experienced any
accidents or serious incidents as a result
of flying in SLD icing conditions. These
manufacturers proposed that airplanes
having all three of the following design
features should be excluded from
compliance with § 25.1420:
(1) Gross weight in excess of 60,000
lbs (27,000 kg);
(2) Irreversible powered flight
controls; and
(3) Wing leading-edge high-lift
devices.
These manufacturers included the
gross weight criterion in this list, in
part, because size has a direct bearing
on an airplane’s susceptibility to the
adverse effects of ice accretion. The size
of an airplane determines the sensitivity
of its flight characteristics to ice
thickness and roughness. The relative
effect of a given ice height (or ice
roughness height) decreases as airplane
size increases.
The irreversible powered flight
controls design feature was chosen, in
part, because using irreversible powered
flight controls reduces an airplane’s
susceptibility to SLD conditions. The
concern that SLD accretions can
produce hinge moment or other
anomalous control force/trim effects is
not applicable to those systems.
The wing leading-edge high-lift
devices design feature was chosen, in
part, because, for wings without ice
contamination, those devices provide a
considerable increase in the maximum
lift coefficient (CLmax) compared to
fixed leading edges. When wings
equipped with those devices are
PO 00000
Liquid water
content
Horizontal extent
(km)
1
6
15
100
5
1
(nmiles)
50
3
0.5
Droplet
MVD
(μm)
1000
2000
2000
contaminated with ice, they have
smaller relative CLmax losses due to ice
accretion than wings with fixed leading
edges.
The IPHWG majority (Air Line Pilots
Association, International (ALPA), Civil
Aviation Authority for the United
Kingdom (CAA/UK), FAA/FAA Tech
Center, Meteorological Services of
Canada, National Aeronautics and
Space Administration (NASA), SAAB,
Transport Canada/Transport
Development Center) did not accept the
exclusion of airplanes with the three
aforementioned design features because
one cannot predict with confidence that
the past service experience of airplanes
with these specific design features will
be applicable to future designs. The
IPHWG majority recommended
applying the new SLD airplane
certification requirements proposed in
the new § 25.1420 to all future transport
category airplane type designs.
The IPHWG majority opposed
limiting the applicability of the rule
based on airplane gross weight, in part,
because the ratio of wing and control
surface sizes to airplane weight varies
between airplane designs. Therefore,
airplane takeoff weight is not a
consistent indicator of lifting and
control surface size or chord, which are
the important parameters affecting
sensitivity to a given ice accretion.
Excluding airplanes with irreversible
flight controls was opposed, in part,
because hinge moment and other
anomalous control forces are not the
only concern in SLD icing conditions.
An irreversible control surface may not
be deflected by the SLD accumulation
but the aerodynamic efficiency of the
control is likely to be degraded by the
presence of SLD icing in front of the
control surface.
Excluding airplanes with wing
leading edge high-lift devices was
opposed, in part, because there are
many different designs for such devices,
which may not all be equally effective
E:\FR\FM\29JNP1.SGM
29JNP1
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
in mitigating the negative effects of SLD
ice accretions. The designs for those
devices include:
• Slats that may be slotted or sealed
to the basic wing leading edge, over or
under deflected, with deflection and
slotting that may be automated as a
function of stall warning or airplane
angle of attack;
• Krueger flaps that may be slotted or
sealed to the wing leading edge, flexed
to optimum curvature or conformed to
the wing’s leading edge lower surface;
and
• Vortilons or some other vortex
creating devices.
In addition, for transport category
airplanes with leading edge high-lift
devices, the spanwise extent of ice
protection varies from 100 percent for
some early turbo-jet airplane slats, to the
span of two slats for later airplane
designs, to none for Krueger flaps. The
variations in the designs lead to varying
degrees of aerodynamic benefit. Without
defining the specific performance
benefits associated with the above
designs, the potential safety margins for
SLD conditions cannot be determined.
The complete minority and majority
positions are discussed in the working
group report, which is available in the
public docket.20
In order to propose a rule with the
estimated costs commensurate with the
estimated benefits, the FAA determined
the applicability of the proposed rule
should be limited based on service
histories of certified airplanes, and the
assumption that similar future designs
will continue to not experience the
safety problems addressed by this
proposal. Therefore, the FAA decided to
revise the IPHWG rulemaking
recommendation by incorporating, in
part, the IPHWG minority position to
exclude airplanes with certain design
features.
The FAA continues to agree with the
IPHWG majority position that the
presence (or conversely, the absence) of
leading edge high lift devices should not
be used as a basis for determining the
applicability of the proposed § 25.1420.
There is insufficient data to conclude
either that every type of leading edge
high lift device, or that a specific
leading edge high lift device design will
affect (positively or negatively) an
airplane’s ability to operate in SLD
atmospheric icing conditions. Also,
leading edge high lift devices are only
deployed in certain phases of flight (for
example, takeoff and landing), and their
20 The complete IPHWG working group report is
available on the Internet at https://regulations.gov. A
copy will also be placed in the docket (FAA–2010–
0636).
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
deployment may differ for different flap
configurations. For example, a leading
edge slat may be sealed in one flap
configuration, but slotted (that is, with
a gap opened up between the trailing
edge of the slat and the wing) in others.
Therefore, the applicability of the
proposed § 25.1420 is not affected by
the presence or absence of leading edge
high lift devices.
We request comment on whether this
proposed rule, if adopted, should be
applied to airplanes larger than 60,000
pounds MTOW or airplanes with other
design features whose presence or
absence would result in the airplane
being susceptible to safety problems
while operating in the SLD icing
conditions defined in the proposed
appendix O, as well as the economic
analysis associated with these
decisions.21
This NPRM also differs from the
ARAC recommendation by proposing a
revision to § 25.1533 for airplanes not
certified to operate in all of the SLD
atmospheric icing conditions specified
in the proposed new appendix O (that
is, airplanes certified in accordance
with proposed § 25.1420(a)(1) or (a)(2)).
The proposal would establish an
operating limitation that requires the
flightcrews to exit all icing conditions if
they encounter appendix O icing
conditions in which the airplane has not
been certified to operate.
Another difference between this
NPRM and the ARAC recommendation
concerns an ARAC recommendation to
establish separate stall warning margin
and controllability requirements using
the ice accretion associated with
detection of appendix O icing
conditions that require exiting all icing
conditions. For airplanes that require
exiting all icing conditions after
encountering certain appendix O icing
conditions, the ARAC recommended
(and the FAA proposes in this NPRM)
stall warning margin and controllability
requirements that must be met with the
ice accretion existing at the time the
airplane exits all icing conditions. The
ARAC was concerned that some future
airplanes would be incapable of
complying with these recommended
requirements without including some
means to increase the stall warning
margin and airplane controllability
upon detection of appendix O icing
conditions. The ARAC recommended
applying less stringent stall warning and
controllability requirements with the ice
accretion existing at the time appendix
O icing conditions are detected, before
21 A copy of the Initial Regulatory Evaluation
(dated October 5, 2009) can be found in the docket
(FAA–2010–0636).
PO 00000
Frm 00009
Fmt 4702
Sfmt 4702
37319
the means to increase the stall warning
margin and airplane controllability
becomes effective.
The FAA considers these ARAC
recommended requirements to add
significant complexity to the proposed
rule to address an issue that may not
arise. The FAA considers it unlikely
that future airplane designs will include
means to increase the stall warning
margin and airplane controllability
upon detection of appendix O icing
conditions in addition to the means that
are incorporated in many current
transport category airplane designs to
change the stall warning device
activation point upon activation of the
ice protection system. Therefore, these
ARAC recommendations are not
included in this NPRM. If needed, the
FAA can issue special conditions, in
accordance with § 21.16, to provide
adequate safety standards in the
unlikely event that such design features
are included in a future transport
category airplane.
Another difference between this
NPRM and the ARAC recommendation
concerns the requirements for pilot
compartment view, airspeed indication
system, angle of attack system and static
pressure system.22 For these rules the
ARAC recommendation would have
required airplanes certified in
accordance with § 25.1420(a)(1) or (a)(2)
to consider all appendix O icing
conditions. However, the ARAC
recommended advisory circular material
allowed these airplanes to consider less
than the full appendix O icing
conditions. The FAA is not proposing
that these airplanes must meet the
performance and handling qualities
requirements for all of the icing
conditions specified in appendix O.
Therefore, for pilot compartment view,
airspeed indication system, angle of
attack system and static pressure
system,23 the agency concurs that it
would only be necessary to show
compliance under the applicable
conditions in appendix O.
Discussion of Working Group NonConsensus Issues
One goal of the ARAC process is to
have a working group achieve
consensus on all of the
recommendations. The IPHWG did not
unanimously agree on the following
issues:
1. Whether it is necessary to flight test
in natural SLD icing conditions.
2. Whether airplanes with certain
design features should be exempt from
the recommendation for § 25.1420.
22 14
CFR 25.773, 25.1323, 25.1324, and 25.1325.
23 Ibid.
E:\FR\FM\29JNP1.SGM
29JNP1
37320
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
3. Whether it is acceptable to
certificate an airplane to a portion of
appendix O, as proposed in the
recommendation for § 25.1420(a)(2).
4. Whether certain icing related
accidents might have been prevented if
an accident airplane had complied with
the recommendations in the IPHWG
report.
A detailed discussion of the IPHWG’s
minority and majority opinions on these
issues is included in the working group
report. A copy of the working group
report is in the public docket.24
The FAA predominantly concurred
with the ARAC’s recommendations, but
determined it was necessary to revise
the applicability of the recommendation
for § 25.1420, as discussed previously.
Paperwork Reduction Act
The Paperwork Reduction Act of 1995
(44 U.S.C. 3507(d)) requires that the
FAA consider the impact of paperwork
and other information collection
burdens imposed on the public. The
information collection requirements
associated with this NPRM have been
previously approved by the Office of
Management and Budget (OMB) under
the provisions of the Paperwork
Reduction Act of 1995 (44 U.S.C.
3507(d)) and have been assigned OMB
Control Number 2120–0018.
International Compatibility
In keeping with U.S. obligations
under the Convention on International
Civil Aviation, it is FAA policy to
comply with International Civil
Aviation Organization (ICAO) Standards
and Recommended Practices to the
maximum extent practicable. The FAA
has determined that there are no ICAO
Standards and Recommended Practices
that correspond to these proposed
regulations.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
European Aviation Safety Agency
The European Aviation Safety Agency
(EASA) was established by the
European Community to develop
standards to ensure safety and
environmental protection, oversee
uniform application of those standards,
and promote them internationally.
EASA formally became responsible for
certification of aircraft, engines, parts,
and appliances on September 28, 2003.
EASA has a project similar to SLD on
its rulemaking inventory and our intent
is to harmonize these regulations.
24 The complete IPHWG working group report is
available on the Internet at https://regulations.gov.
The docket number is FAA–2010–0636.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
Regulatory Evaluation, Regulatory
Flexibility Determination, International
Trade Analysis, and Unfunded
Mandates
Changes to Federal regulations must
undergo several economic analyses.
First, Executive Order 12866 directs that
each Federal agency shall propose or
adopt a regulation only upon a reasoned
determination that the benefits of the
intended regulation justify its costs.
Second, the Regulatory Flexibility Act
of 1980 (Pub. L. 96–354) requires
agencies to analyze the economic
impact of regulatory changes on small
entities. Third, the Trade Agreements
Act (Pub. L. 96–39) prohibits agencies
from setting standards that create
unnecessary obstacles to the foreign
commerce of the United States. In
developing U.S. standards, this Trade
Act requires agencies to consider
international standards and, where
appropriate, that they be the basis of
U.S. standards. Fourth, the Unfunded
Mandates Reform Act of 1995 (Pub. L.
104–4) requires agencies to prepare a
written assessment of the costs, benefits,
and other effects of proposed or final
rules that include a Federal mandate
likely to result in the expenditure by
State, local, or tribal governments, in the
aggregate, or by the private sector, of
$100 million or more annually (adjusted
for inflation with base year of 1995).
This portion of the preamble
summarizes the FAA’s analysis of the
economic impacts of this proposed rule.
We suggest readers seeking greater
detail read the full regulatory
evaluation, a copy of which we have
placed in the docket for this rulemaking.
In conducting these analyses, FAA
has determined that this proposed rule:
(1) Has benefits that justify its costs; (2)
is not an economically ‘‘significant
regulatory action’’ as defined in section
3(f) of Executive Order 12866; (3) is
‘‘significant’’ as defined in DOT’s
Regulatory Policies and Procedures; (4)
would not have a significant economic
impact on a substantial number of small
entities; (5) would not create
unnecessary obstacles to the foreign
commerce of the United States; and (6)
would not impose an unfunded
mandate on State, local, or tribal
governments, or on the private sector by
exceeding the threshold identified
above. These analyses are summarized
below.
Total Benefits and Costs of This Rule
This NPRM would amend the
airworthiness standards applicable to
certain transport category airplanes
certified for flight in icing conditions
and the icing airworthiness standards
PO 00000
Frm 00010
Fmt 4702
Sfmt 4702
applicable to certain aircraft engines.
The affected fleet and categories of
benefits and costs are customized to the
requirements contained in this proposal.
So, depending on the category and type
of airplane, the benefits and costs are
analyzed over different time periods. It
is important for the reader to focus on
present value benefits and costs. The
total estimated benefits are $405.6
million ($99.5 million present value).
The total estimated costs are $71.0
million ($54.0 million present value).
On an annualized basis, for the time
period 2012–2064, the benefits are $7.0
million, and the costs are $3.8 million.
Therefore, the benefits of the proposed
rule justify the costs, and the proposed
rule is cost beneficial.
Persons Potentially Affected by This
Rule
• Part 25 airplane manufacturers.
• Engine manufacturers.
• Operators of Affected Equipment.
Assumptions
• Discount rate—7%.
• Costs and benefits are expressed in
2009 dollars and that both costs and
benefits start to occur in 2011. We
conservatively assume that all
certifications are approved one year
after the rule is codified (2011), and that
production/deliveries begin to occur the
following year (2012). Airplane
deliveries continue to accumulate until
the airplane is out of production and
then begin to retire in the 25th year of
service. We have customized different
fleet types (smaller, medium, larger)
based upon the actual historical
production cycles and deliveries. The
varying periods are based on all the
historical data that we have available.
The production cycles for smaller
airplanes are shorter than the
production cycles of larger airplanes,
thus the differing time periods.
• Value of an Averted Fatality—$6.0
million.
• Fuel Cost per gallon—$1.92.
Benefits of This Proposed Rule
The industry, with the FAA, analyzed
the SLD events for part 25 certified
airplanes. We evaluated the events for
applicability and preventability in
context with the requirements contained
in this proposed rule.
First, we develop an annual risk of a
catastrophic SLD event per aircraft and
assume a uniform annual likelihood.
Next, we multiply the total annual
affected aircraft by the annual risk per
aircraft. Lastly, we multiply the total
annual risk by the estimated cost of an
average SLD event. When summed over
time, the total estimated benefits are
E:\FR\FM\29JNP1.SGM
29JNP1
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
$405.6 million ($99.5 million present
value).
Costs of This Proposed Rule
The total estimated costs are $71.0
million ($54.0 million present value).
We obtained the basis of our cost
estimates from the industry. The
manufacturers used accompanying
advisory circulars (AC) describing
acceptable means for showing
compliance. The compliance costs are
analyzed in context of the part 25 and
part 33 certification requirements.
The FAA originally asked ARAC to
estimate other operational costs beyond
the additional hardware and fuel
consumption costs. The additional
hardware costs would be for SLD ice
detectors that manufacturers would
install to be in compliance with the
proposed requirements. The additional
hardware costs would be accompanied
by additional fuel consumption costs
from the accompanying weight changes
due to the SLD ice detectors.
Accordingly, ARAC provided this data
to the FAA. However, as we neared
completion of our cost analysis for these
37321
requirements, we queried individual
operators and they informed us that
they were already in compliance and
there were no additional operational
costs beyond fuel and hardware.
As summarized below, the cost
categories in the regulatory evaluation
incorporate both certification and
operational costs. We analyze each cost
category separately. The cost categories
in this evaluation are the same as those
provided by industry to comply with
the requirements contained in this
proposal. For this analysis, the
estimated costs were:
Nominal Cost
PV Cost
Engine Cert Cost .........................................................................................................................................
Engine Capital Cost .....................................................................................................................................
Total Engine .................................................................................................................................................
Small Aircraft Certification Cost ...................................................................................................................
New Large Aircraft Certification Cost ..........................................................................................................
Amended Type Certificate Large Airplane Certification Cost .....................................................................
Hardware Costs ...........................................................................................................................................
Fuel Burn All ................................................................................................................................................
$7,936,000
6,000,000
13,936,000
24,999,039
3,154,600
10,438,800
10,390,000
8,046,676
$6,931,610
5,240,632
12,172,242
21,835,129
2,755,350
9,117,652
5,842,024
2,261,941
Total ......................................................................................................................................................
70,965,115
53,984,338
Alternatives Considered
Alternative 1—Make all sizes of
aircraft applicable to the proposal. Not
all the requirements in this proposal
extend to larger transport category
aircraft (those with a maximum takeoff
weight greater than 60,000 pounds).
Under this alternative, the proposed
design requirements would extend to all
transport category aircraft. This
alternative was rejected because this
alternative would add significant cost
without a commensurate increase in
benefits.
Alternative 2—Limit the scope of
applicability to small aircraft. Although
this alternative would decrease the
estimated cost, the FAA believes that
medium airplanes have the same risk as
small airplanes. The FAA does not want
a significant proportion of the future
fleet to be disproportionately at risk.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980
(Pub. L. 96–354) (RFA) establishes ‘‘as a
principle of regulatory issuance that
agencies shall endeavor, consistent with
the objectives of the rule and of
applicable statutes, to fit regulatory and
informational requirements to the scale
of the businesses, organizations, and
governmental jurisdictions subject to
regulation. To achieve this principle,
agencies are required to solicit and
consider flexible regulatory proposals
and to explain the rationale for their
actions to assure that such proposals are
given serious consideration.’’ The RFA
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
covers a wide-range of small entities,
including small businesses, not-forprofit organizations, and small
governmental jurisdictions.
Agencies must perform a review to
determine whether a rule will have a
significant economic impact on a
substantial number of small entities. If
the agency determines that it will, the
agency must prepare a regulatory
flexibility analysis as described in the
RFA.
However, if an agency determines that
a rule is not expected to have a
significant economic impact on a
substantial number of small entities,
section 605(b) of the RFA provides that
the head of the agency may so certify
and a regulatory flexibility analysis is
not required. The certification must
include a statement providing the
factual basis for this determination, and
the reasoning should be clear. Based on
the analysis presented below, we
determined there would not be a
significant impact on a substantial
number of small entities.
Airplane and Engine Manufacturers
Aircraft and Engine Manufacturers
would be affected by the requirements
contained in this proposal.
For aircraft manufacturers, we use the
size standards from the Small Business
Administration for Air Transportation
and Aircraft Manufacturing specifying
companies having less than 1,500
employees as small entities. The current
United States part 25 airplane
manufacturers include: Boeing, Cessna
PO 00000
Frm 00011
Fmt 4702
Sfmt 4702
Aircraft, Gulfstream Aerospace, Learjet
(owned by Bombardier), Lockheed
Martin, McDonnell Douglas (a whollyowned subsidiary of The Boeing
Company), Raytheon Aircraft, and
Sabreliner Corporation. Because all U.S.
transport-aircraft category
manufacturers have more than 1,500
employees, none are considered small
entities.
United States aircraft engine
manufacturers include: General Electric,
CFM International, Pratt & Whitney,
International Aero Engines, Rolls-Royce
Corporation, Honeywell, and Williams
International. All but one exceeds the
Small Business Administration smallentity criteria for aircraft engine
manufacturers. Williams International is
the only one of these manufacturers that
is a U.S. small business. One small
entity is not a substantial number.
Operators
In addition to the certification cost
incurred by manufacturers, operators
would incur fuel costs due to the
estimated additional impact of weight
changes from equipment on affected
airplanes. On average, an affected
airplane would incur additional fuel
costs of roughly $525 per year.
Because this proposed rule would
apply to airplanes that have yet to be
designed, there would be no immediate
cost to small entities. However, as of
2007, there are at least 54 small entity
operators with 1,500 or fewer employees
who would qualify as small entities.
E:\FR\FM\29JNP1.SGM
29JNP1
37322
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
According to the ‘‘Airliner Price
Guide,’’ the average cost of a new
aircraft that would incur such expenses
is approximately $17 million. The
corresponding 3-year average total
aircraft operating expenses on an
affected per airplane basis was
$758,000. The estimated additional cost
of $525 would add only 0.07% to the
total annual operating expenses. We do
not consider this a significant economic
impact.
Because this proposed rule would not
have a significant economic impact on
a substantial number of airplane
manufacturers, engine manufacturers or
operators, the FAA certifies that this
proposed rule would not have a
significant economic impact on a
substantial number of small entities.
The FAA solicits comments regarding
this determination.
International Trade Analysis
The Trade Agreements Act of 1979
(Pub. L. 96–39), as amended by the
Uruguay Round Agreements Act (Pub.
L. 103–465), prohibits Federal agencies
from establishing standards or engaging
in related activities that create
unnecessary obstacles to the foreign
commerce of the United States.
Pursuant to these Acts, the
establishment of standards is not
considered an unnecessary obstacle to
the foreign commerce of the United
States, so long as the standard has a
legitimate domestic objective, such the
protection of safety, and does not
operate in a manner that excludes
imports that meet this objective. The
statute also requires consideration of
international standards and, where
appropriate, that they be the basis for
U.S. standards.
The FAA has assessed the potential
effect of this proposed rule and
determined that it would impose the
same costs on domestic and
international entities and thus has a
neutral trade impact.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Unfunded Mandates Assessment
Title II of the Unfunded Mandates
Reform Act of 1995 (Pub. L. 104–4)
requires each Federal agency to prepare
a written statement assessing the effects
of any Federal mandate in a proposed or
final agency rule that may result in an
expenditure of $100 million or more (in
1995 dollars) in any one year by State,
local, and tribal governments, in the
aggregate, or by the private sector; such
a mandate is deemed to be a ‘‘significant
regulatory action.’’ The FAA currently
uses an inflation-adjusted value of
$143.1 million in lieu of $100 million.
This proposed rule does not contain
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
such a mandate; therefore, the
requirements of Title II do not apply.
Executive Order 13132, Federalism
The FAA has analyzed this proposed
rule under the principles and criteria of
Executive Order 13132, Federalism. We
determined that this action would not
have a substantial direct effect on the
States, on the relationship between the
national Government and the States, or
on the distribution of power and
responsibilities among the various
levels of government, and, therefore,
would not have federalism implications.
Regulations Affecting Intrastate
Aviation in Alaska
Section 1205 of the FAA
Reauthorization Act of 1996 (110 Stat.
3213) requires the Administrator, when
modifying regulations in Title 14 of the
CFR in a manner affecting intrastate
aviation in Alaska, to consider the
extent to which Alaska is not served by
transportation modes other than
aviation, and to establish appropriate
regulatory distinctions. Because this
proposed rule would apply to the
certification of future designs of
transport category airplanes and their
subsequent operation, it could, if
adopted, affect intrastate aviation in
Alaska. The FAA, therefore, specifically
requests comments on whether there is
justification for applying the proposed
rule differently in intrastate operations
in Alaska.
Environmental Analysis
FAA Order 1050.1E identifies FAA
actions that are categorically excluded
from preparation of an environmental
assessment or environmental impact
statement under the National
Environmental Policy Act in the
absence of extraordinary circumstances.
The FAA has determined this proposed
rulemaking action qualifies for the
categorical exclusion identified in
paragraph 4(j) and involves no
extraordinary circumstances.
Regulations That Significantly Affect
Energy Supply, Distribution, or Use
The FAA has analyzed this NPRM
under Executive Order 13211, Actions
Concerning Regulations that
Significantly Affect Energy Supply,
Distribution, or Use (May 18, 2001). We
have determined that it is not a
‘‘significant energy action’’ under the
executive order because, while it is a
‘‘significant regulatory action,’’ it is not
likely to have a significant adverse effect
on the supply, distribution, or use of
energy.
PO 00000
Frm 00012
Fmt 4702
Sfmt 4702
Plain English
Executive Order 12866 (58 FR 51735,
Oct. 4, 1993) requires each agency to
write regulations that are simple and
easy to understand. We invite your
comments on how to make these
proposed regulations easier to
understand, including answers to
questions such as the following:
• Are the requirements in the
proposed regulations clearly stated?
• Do the proposed regulations contain
unnecessary technical language or
jargon that interferes with their clarity?
• Would the regulations be easier to
understand if they were divided into
more (but shorter) sections?
• Is the description in the preamble
helpful in understanding the proposed
regulations?
Please send your comments to the
address specified in the ADDRESSES
section of this preamble.
Additional Information
Comments Invited
The FAA invites interested persons to
participate in this rulemaking by
submitting written comments, data, or
views. We also invite comments relating
to the economic, environmental, energy,
or federalism impacts that might result
from adopting the proposals in this
document. The most helpful comments
reference a specific portion of the
proposal, explain the reason for any
recommended change, and include
supporting data. To ensure the docket
does not contain duplicate comments,
please send only one copy of written
comments, or if you are filing comments
electronically, please submit your
comments only one time.
We will file in the docket all
comments we receive, as well as a
report summarizing each substantive
public contact with FAA personnel
concerning this proposed rulemaking.
Before acting on this proposal, we will
consider all comments we receive on or
before the closing date for comments.
We will consider comments filed after
the comment period has closed if it is
possible to do so without incurring
expense or delay. We may change this
proposal in light of the comments we
receive.
Proprietary or Confidential Business
Information
Do not file in the docket information
that you consider to be proprietary or
confidential business information. Send
or deliver this information directly to
the person identified in the FOR FURTHER
INFORMATION CONTACT section of this
document. You must mark the
information that you consider
E:\FR\FM\29JNP1.SGM
29JNP1
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
proprietary or confidential. If you send
the information on a disk or CD ROM,
mark the outside of the disk or CD ROM
and also identify electronically within
the disk or CD ROM the specific
information that is proprietary or
confidential.
Under 14 CFR 11.35(b), when we are
aware of proprietary information filed
with a comment, we do not place it in
the docket. We hold it in a separate file
to which the public does not have
access, and we place a note in the
docket that we have received it. If we
receive a request to examine or copy
this information, we treat it as any other
request under the Freedom of
Information Act (5 U.S.C. 552). We
process such a request under the DOT
procedures found in 49 CFR part 7.
Availability of Rulemaking Documents
You can get an electronic copy of
rulemaking documents using the
Internet by—
1. Searching the Federal eRulemaking
Portal (https://www.regulations.gov);
2. Visiting the FAA’s Regulations and
Policies web page at https://
www.faa.gov/regulations_policies/; or
3. Accessing the Government Printing
Office’s web page at https://
www.gpoaccess.gov/fr/.
You can also get a copy by sending a
request to the Federal Aviation
Administration, Office of Rulemaking,
ARM–1, 800 Independence Avenue,
SW., Washington, DC 20591, or by
calling (202) 267–9680. Make sure to
identify the docket number or notice
number of this rulemaking.
You may access all documents the
FAA considered in developing this
proposed rule, including economic
analyses and technical reports, from the
internet through the Federal
eRulemaking Portal referenced in
paragraph (1).
The following appendix will not
appear in the Code of Federal
Regulations.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Appendix 1 to the Preamble—Definition
of Terms Used in This Preamble
For the purposes of this preamble, the
following definitions are applicable.
These definitions of terms are intended
for use only with this preamble:
a. Appendix C Icing Conditions: The
environmental conditions defined in
appendix C of 14 CFR part 25.
b. Appendix O Icing Conditions: The
environmental conditions defined in
appendix O of 14 CFR part 25.
c. Drizzle Drop: A drop of water
measuring 100 μm to 500 μm (0.1–0.5
mm) in diameter.
d. Freezing Drizzle (FZDZ):
Supercooled drizzle drops that remain
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
in liquid form and freeze upon contact
with objects colder than 0°C.
e. Freezing Rain (FZRA): Supercooled
rain drops that remain in liquid form
and freeze upon contact with objects
colder than 0°C.
f. Icing Conditions: The presence of
atmospheric moisture and temperature
conducive to airplane icing.
g. Icing Conditions Detector: A device
that detects the presence of atmospheric
moisture and temperature conducive to
airplane icing.
h. Irreversible Flight Controls: Flight
controls in the normal operating
configuration that have loads generated
at the control surfaces of an airplane
which are reacted against the actuator
and its mounting and cannot be
transmitted directly back to the flight
deck controls. This term refers to flight
controls in which all of the force
necessary to move the pitch, roll, or yaw
control surfaces is provided by
hydraulic or electric actuators, the
motion of which is controlled by signals
from the flight deck controls.
i. Liquid Water Content (LWC): The
total mass of water contained in liquid
drops within a unit volume or mass of
air, usually given in units of grams of
water per cubic meter (g/m3).
j. Mean Effective Diameter (MED): The
calculated drop diameter that divides
the total liquid water content present in
the drop size distribution in half. Half
the water volume will be in larger drops
and half the volume in smaller drops.
This value is calculated, as opposed to
being arrived at by measuring actual
drop size. The MED is based on an
assumed Langmuir drop size
distribution. The fact that it is a
calculated measurement is how it differs
from median volume diameter, which is
based on actual drop size.
k. Median Volume Diameter (MVD):
The drop diameter that divides the total
liquid water content present in the drop
distribution in half. Half the water
volume will be in larger drops and half
the volume in smaller drops. The value
is obtained by actual drop size
measurements.
l. Mixed Phase Icing Environment: A
combination of supercooled liquid and
ice crystals.
m. Rain Drop: A drop of water greater
than 500 μm (0.5 mm) in diameter.
n. Reversible Flight Controls: Flight
controls in the normal operating
configuration that have force or motion
originating at the airplane’s control
surface (for example, through
aerodynamic loads, static imbalance, or
trim tab inputs) that is transmitted back
to flight deck controls. This term refers
to flight deck controls connected to the
pitch, roll, or yaw control surfaces by
PO 00000
Frm 00013
Fmt 4702
Sfmt 4702
37323
direct mechanical linkages, cables, or
push-pull rods in such a way that pilot
effort produces motion or force about
the hinge line.
(1) Aerodynamically boosted flight
controls: Reversible flight control
systems that employ a movable tab on
the trailing edge of the main control
surface linked to the pilot’s controls or
to the structure in such a way as to
produce aerodynamic forces that move,
or help to move, the surface. Among the
various forms are flying tabs, geared or
servo tabs, and spring tabs.
(2) Power-assisted flight controls:
Reversible flight control systems in
which some means is provided, usually
a hydraulic actuator, to apply force to a
control surface in addition to that
supplied by the pilot to enable large
surface deflections to be obtained at
high speeds.
o. Supercooled Large Drops (SLD):
Supercooled liquid water that includes
freezing rain or freezing drizzle.
p. Supercooled Water: Liquid water at
a temperature below the freezing point
of 0°C.
List of Subjects
14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements, Safety,
Transportation.
14 CFR Part 33
Aircraft, Aviation safety.
The Proposed Amendment
In consideration of the foregoing, the
Federal Aviation Administration
proposes to amend Chapter I of Title 14,
Code of Federal Regulations parts 25
and 33 as follows:
PART 25—AIRWORTHINESS
STANDARDS: TRANSPORT
CATEGORY AIRPLANES
1. The authority citation for part 25
continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701,
44702 and 44704.
2. Amend § 25.21 by revising
paragraphs (g)(1) and (g)(2) and adding
paragraphs (g)(3) and (g)(4) to read as
follows:
§ 25.21
Proof of compliance.
*
*
*
*
*
(g) * * *
(1) Paragraphs (g)(3) and (g)(4) of this
section apply only to airplanes with one
or both of the following attributes:
(i) Takeoff maximum gross weight is
less than 60,000 lbs; or
(ii) The airplane is equipped with
reversible flight controls.
E:\FR\FM\29JNP1.SGM
29JNP1
37324
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
(2) Each requirement of this subpart,
except §§ 25.121(a), 25.123(c),
25.143(b)(1) and (2), 25.149,
25.201(c)(2), 25.207(c) and (d), 25.239,
and 25.251(b) through (e), must be met
in the icing conditions specified in
appendix C of this part. Compliance
must be shown using the ice accretions
defined in part II of appendix C of this
part, assuming normal operation of the
airplane and its ice protection system in
accordance with the operating
limitations and operating procedures
established by the applicant and
provided in the Airplane Flight Manual.
(3) If the applicant does not seek
certification for flight in all icing
conditions defined in appendix O of
this part, each requirement of this
subpart, except §§ 25.105, 25.107,
25.109, 25.111, 25.113, 25.115, 25.121,
25.123, 25.143(b)(1), (b)(2), and (c)(1),
25.149, 25.201(c)(2), 25.207(c) and (d),
25.239, and 25.251(b) through (e), must
be met in the appendix O icing
conditions for which certification is not
sought in order to allow a safe exit from
those conditions. Compliance must be
shown using the ice accretions defined
in part II, paragraphs (b) and (d) of
appendix O of this part, assuming
normal operation of the airplane and its
ice protection system in accordance
with the operating limitations and
operating procedures established by the
applicant and provided in the Airplane
Flight Manual.
(4) If the applicant seeks certification
for flight in any portion of the icing
conditions of appendix O of this part,
each requirement of this subpart, except
§§ 25.123(c), 25.143(b)(1) and (2),
25.149, 25.201(c)(2), 25.207(c) and (d),
25.239, and 25.251(b) through (e), must
be met in the appendix O icing
conditions for which certification is
sought. Compliance must be shown
using the ice accretions defined in part
II, paragraphs (c) and (d) of appendix O
of this part, assuming normal operation
of the airplane and its ice protection
system in accordance with the operating
limitations and operating procedures
established by the applicant and
provided in the Airplane Flight Manual.
3. Amend § 25.105 by revising
paragraph (a)(2) introductory text to
read as follows:
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
§ 25.105
Takeoff.
(a) * * *
(2) In icing conditions, if in the
configuration used to show compliance
with § 25.121(b), and with the most
critical of the takeoff ice accretion(s)
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g):
*
*
*
*
*
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
4. Amend § 25.111 by revising
paragraphs (c)(5)(i) and (c)(5)(ii) to read
as follows:
§ 25.111
Takeoff path.
*
*
*
*
*
(c) * * *
(5) * * *
(i) With the most critical of the takeoff
ice accretion(s) defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g), from a
height of 35 feet above the takeoff
surface up to the point where the
airplane is 400 feet above the takeoff
surface; and
(ii) With the most critical of the final
takeoff ice accretion(s) defined in
appendices C and O of this part, as
applicable, in accordance with
§ 25.21(g), from the point where the
airplane is 400 feet above the takeoff
surface to the end of the takeoff path.
*
*
*
*
*
5. Amend § 25.119 by revising
paragraph (b) to read as follows:
§ 25.119 Landing climb: All-enginesoperating.
*
*
*
*
*
(b) In icing conditions with the most
critical of the landing ice accretion(s)
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g), and with a climb speed of
VREF determined in accordance with
§ 25.125(b)(2)(ii).
6. Amend § 25.121 by revising
paragraphs (b)(2)(ii) introductory text,
(c)(2)(ii) introductory text, and (d)(2)(ii)
to read as follows:
§ 25.121
Climb: One-engine-inoperative.
*
*
*
*
*
(b) * * *
(2) * * *
(ii) In icing conditions with the most
critical of the takeoff ice accretion(s)
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g), if in the configuration used to
show compliance with § 25.121(b) with
this takeoff ice accretion:
*
*
*
*
*
(c) * * *
(2) * * *
(ii) In icing conditions with the most
critical of the final takeoff ice
accretion(s) defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g), if in the
configuration used to show compliance
with § 25.121(b) with the takeoff ice
accretion used to show compliance with
§ 25.111(c)(5)(i):
*
*
*
*
*
(d) * * *
(2) * * *
(ii) In icing conditions with the most
critical of the approach ice accretion(s)
PO 00000
Frm 00014
Fmt 4702
Sfmt 4702
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g). The climb speed selected for
non-icing conditions may be used if the
climb speed for icing conditions,
computed in accordance with paragraph
(d)(1)(iii) of this section, does not
exceed that for non-icing conditions by
more than the greater of 3 knots CAS or
3 percent.
7. Amend § 25.123 by revising
paragraph (b)(2) introductory text to
read as follows:
§ 25.123
En-route flight paths.
*
*
*
*
*
(b) * * *
(2) In icing conditions with the most
critical of the en route ice accretion(s)
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g), if:
*
*
*
*
*
8. Amend § 25.125 by revising
paragraphs (a)(2), (b)(2)(ii)(B), and
(b)(2)(ii)(C) to read as follows:
§ 25.125
Landing.
(a) * * *
(2) In icing conditions with the most
critical of the landing ice accretion(s)
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g), if VREF for icing conditions
exceeds VREF for non-icing conditions
by more than 5 knots CAS at the
maximum landing weight.
(b) * * *
(2) * * *
(ii) * * *
(B) 1.23 VSR0 with the most critical of
the landing ice accretion(s) defined in
appendices C and O of this part, as
applicable, in accordance with
§ 25.21(g), if that speed exceeds VREF
selected for non-icing conditions by
more than 5 knots CAS; and
(C) A speed that provides the
maneuvering capability specified in
§ 25.143(h) with the most critical of the
landing ice accretion(s) defined in
appendices C and O of this part, as
applicable, in accordance with
§ 25.21(g).
*
*
*
*
*
9. Amend § 25.143 by revising
paragraphs (c) introductory text, (i)(1),
and (j) introductory text to read as
follows:
§ 25.143 Controllability and
maneuverability—General.
*
*
*
*
*
(c) The airplane must be shown to be
safely controllable and maneuverable
with the most critical of the ice
accretion(s) appropriate to the phase of
flight as defined in appendices C and O
of this part, as applicable, in accordance
E:\FR\FM\29JNP1.SGM
29JNP1
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
with § 25.21(g), and with the critical
engine inoperative and its propeller (if
applicable) in the minimum drag
position:
*
*
*
*
*
(i) * * *
(1) Controllability must be
demonstrated with the most critical of
the ice accretion(s) for the particular
flight phase as defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g);
*
*
*
*
*
(j) For flight in icing conditions before
the ice protection system has been
activated and is performing its intended
function, it must be demonstrated in
flight with the most critical of the ice
accretion(s) defined in appendix C, part
II, paragraph (e) of this part and
appendix O, part II, paragraph (d) of this
part, as applicable, in accordance with
§ 25.21(g), that:
*
*
*
*
*
10. Amend § 25.207 by revising
paragraphs (b), (e)(1) through (5), and
(h) introductory text to read as follows:
§ 25.207
Stall warning.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
*
*
*
*
*
(b) The warning must be furnished
either through the inherent aerodynamic
qualities of the airplane or by a device
that will give clearly distinguishable
indications under expected conditions
of flight. However, a visual stall warning
device that requires the attention of the
crew within the cockpit is not
acceptable by itself. If a warning device
is used, it must provide a warning in
each of the airplane configurations
prescribed in paragraph (a) of this
section at the speed prescribed in
paragraphs (c) and (d) of this section.
Except for the stall warning prescribed
in paragraph (h)(3)(ii) of this section, the
stall warning for flight in icing
conditions must be provided by the
same means as the stall warning for
flight in non-icing conditions.
*
*
*
*
*
(e) * * *
(1) The most critical of the takeoff ice
and final takeoff ice accretions defined
in appendices C and O of this part, as
applicable, in accordance with
§ 25.21(g), for each configuration used
in the takeoff phase of flight;
(2) The most critical of the en route
ice accretion(s) defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g), for the en
route configuration;
(3) The most critical of the holding ice
accretion(s) defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g), for the
holding configuration(s);
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
(4) The most critical of the approach
ice accretion(s) defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g), for the
approach configuration(s); and
(5) The most critical of the landing ice
accretion(s) defined in appendices C
and O of this part, as applicable, in
accordance with § 25.21(g), for the
landing and go-around configuration(s).
*
*
*
*
*
(h) The following stall warning
margin is required for flight in icing
conditions before the ice protection
system has been activated and is
performing its intended function.
Compliance must be shown using the
most critical of the ice accretion(s)
defined in appendix C, part II,
paragraph (e) of this part and appendix
O, part II, paragraph (d) of this part, as
applicable, in accordance with
§ 25.21(g). The stall warning margin in
straight and turning flight must be
sufficient to allow the pilot to prevent
stalling without encountering any
adverse flight characteristics when:
*
*
*
*
*
11. Amend § 25.237 by revising
paragraph (a)(3)(ii) to read as follows:
§ 25.237
Wind velocities.
(a) * * *
(3) * * *
(ii) Icing conditions with the most
critical of the landing ice accretion(s)
defined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g).
*
*
*
*
*
12. Amend § 25.253 by revising
paragraph (c) introductory text to read
as follows:
§ 25.253
High-speed characteristics.
*
*
*
*
*
(c) Maximum speed for stability
characteristics in icing conditions. The
maximum speed for stability
characteristics with the most critical of
the ice accretions defined in appendices
C and O of this part, as applicable, in
accordance with § 25.21(g), at which the
requirements of §§ 25.143(g), 25.147(e),
25.175(b)(1), 25.177 and 25.181 must be
met, is the lower of:
*
*
*
*
*
13. Amend § 25.773 by revising
paragraph (b)(1)(ii) to read as follows:
§ 25.773
Pilot compartment view.
*
*
*
*
*
(b) * * *
(1) * * *
(ii) The icing conditions specified in
appendix C and the following icing
conditions specified in appendix O of
this part, if certification for flight in
icing conditions is sought:
PO 00000
Frm 00015
Fmt 4702
Sfmt 4702
37325
(A) For airplanes certificated in
accordance with § 25.1420(a)(1), the
icing conditions that the airplane is
certified to safely exit following
detection.
(B) For airplanes certificated in
accordance with § 25.1420(a)(2), the
icing conditions that the airplane is
certified to safely operate in and the
icing conditions that the airplane is
certified to safely exit following
detection.
(C) For airplanes certificated in
accordance with § 25.1420(a)(3) and for
airplanes not subject to § 25.1420, all
icing conditions.
*
*
*
*
*
14. Amend § 25.903 by adding
paragraph (a)(3) to read as follows:
§ 25.903
Engines.
(a) * * *
(3) Each turbine engine must comply
with one of the following paragraphs:
(i) Section 33.68 of this chapter in
effect on [effective date of final rule], or
as subsequently amended; or
(ii) Section 33.68 of this chapter in
effect on February 23, 1984, or as
subsequently amended before [effective
date of final rule], unless that engine’s
ice accumulation service history has
resulted in an unsafe condition; or
(iii) Section 33.68 of this chapter in
effect on October 1, 1974, or as
subsequently amended prior to February
23, 1984, unless that engine’s ice
accumulation service history has
resulted in an unsafe condition; or
(iv) Be shown to have an ice
accumulation service history in similar
installation locations which has not
resulted in any unsafe conditions.
*
*
*
*
*
15. Amend § 25.929 by revising
paragraph (a) to read as follows:
§ 25.929
Propeller deicing.
(a) If certification for flight in icing is
sought there must be a means to prevent
or remove hazardous ice accumulations
that could form in the icing conditions
defined in appendices C and O of this
part on propellers or on accessories
where ice accumulation would
jeopardize engine performance.
*
*
*
*
*
16. Amend § 25.1093 by revising
paragraph (b) to read as follows:
§ 25.1093 Induction system icing
protection.
*
*
*
*
*
(b) Turbine engines. Each engine, with
all icing protection systems operating,
must:
(1) Operate throughout its flight
power range, including the minimum
descent idling speeds, in the icing
E:\FR\FM\29JNP1.SGM
29JNP1
37326
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
conditions defined in appendices C and
O of this part, and appendix D of part
33 of this chapter, and in falling and
blowing snow within the limitations
established for the airplane for such
operation, without the accumulation of
ice on the engine, inlet system
components or airframe components
that would do any of the following:
(i) Adversely affect installed engine
operation or cause a sustained loss of
power or thrust; or an unacceptable
increase in gas path operating
temperature; or an airframe/engine
incompatibility; or
operation the engine may be run up
periodically to a moderate power or
thrust setting in a manner acceptable to
the Administrator. The applicant must
document the engine run-up procedure
(including the maximum time interval
between run-ups from idle, run-up
power setting, and duration at power)
and associated minimum ambient
temperature demonstrated for the
maximum time interval, and these
conditions must be used in establishing
the airplane operating limitations in
accordance with § 25.1521.
(ii) Result in unacceptable temporary
power loss or engine damage; or
(iii) Cause a stall, surge, or flameout
or loss of engine controllability (for
example, rollback).
(2) Idle for a minimum of 30 minutes
on the ground in the following icing
conditions shown in Table 1, unless
replaced by similar test conditions that
are more critical. These conditions must
be demonstrated with the available air
bleed for icing protection at its critical
condition, without adverse effect,
followed by an acceleration to takeoff
power or thrust. During the idle
TABLE 1—ICING CONDITIONS FOR GROUND TESTS
Condition
(i) Rime ice condition .....
(ii) Glaze ice condition ...
(iii) Large drop condition
0 to 15 °F (¥18 to ¥9
°C).
20 to 30 °F (¥7 to ¥1
°C).
15 to 30 °F (¥9 to ¥1
°C).
*
*
*
*
*
17. Amend § 25.1323 by revising
paragraph (i) to read as follows:
§ 25.1323
Water concentration
(minimum)
Mean effective particle
diameter
Demonstration
Liquid—0.3 g/m3 ............
15–25 microns ...............
Liquid—0.3 g/m3 ............
15–25 microns ...............
Liquid—0.3 g/m3 ............
100 microns (minimum)
By test, analysis or combination of
the two.
By test, analysis or combination of
the two.
By test, analysis or combination of
the two.
Total air temperature
Airspeed indicating system.
*
*
*
*
*
(i) Each system must have a heated
pitot tube or an equivalent means of
preventing malfunction in mixed phase
and ice crystal conditions as defined in
Table 1 of this section, the icing
icing conditions that the airplane is
certified to safely operate in and the
icing conditions that the airplane is
certified to safely exit following
detection.
(3) For airplanes certificated in
accordance with § 25.1420(a)(3) and for
airplanes not subject to § 25.1420, all
icing conditions.
conditions defined in appendix C of this
part, and the following icing conditions
specified in appendix O of this part:
(1) For airplanes certificated in
accordance with § 25.1420(a)(1), the
icing conditions that the airplane is
certified to safely exit following
detection.
(2) For airplanes certificated in
accordance with § 25.1420(a)(2), the
TABLE 1—ICING CONDITIONS FOR AIRSPEED INDICATING SYSTEM TESTS
Air temperature
Altitude range
Ice water
content
(°C)
(ft)
(m)
0 to ¥20 .....................
10,000 to 30,000 .......
15,000 to 40,000 .......
g/m3
4,500 to 12,000 .........
*
*
*
*
*
18. Add § 25.1324 to read as follows:
§ 25.1324
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
g/m3
3,000 to 9,000 ...........
¥20 to ¥40 ................
Liquid
water
content
Angle of attack system.
Each angle of attack system sensor
must be heated or have an equivalent
means of preventing malfunction in the
mixed phase and ice crystal conditions
as defined in § 25.1323, the icing
conditions defined in appendix C of this
part, and the following icing conditions
specified in appendix O of this part:
(a) For airplanes certificated in
accordance with § 25.1420(a)(1), the
icing conditions that the airplane is
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
4
1
0.5
5
2
1
0.5
Horizontal extent
(km)
1
1
0.5
0
0
0
0
certified to safely exit following
detection.
(b) For airplanes certificated in
accordance with § 25.1420(a)(2), the
icing conditions that the airplane is
certified to safely operate in and the
icing conditions that the airplane is
certified to safely exit following
detection.
(c) For airplanes certificated in
accordance with § 25.1420(a)(3) and for
airplanes not subject to § 25.1420, all
icing conditions.
PO 00000
Frm 00016
Fmt 4702
Sfmt 4702
Ice median mass
dimension
(n miles)
5
100
500
5
20
100
500
3
50
300
3
10
50
300
Liquid
water MVD
(μm)
(μm)
100 to 1,000 ..............
20
19. Amend § 25.1325 by revising
paragraph (b) to read as follows:
§ 25.1325
Static pressure systems.
*
*
*
*
*
(b) Each static port must be designed
and located so that:
(1) The static pressure system
performance is least affected by airflow
variation, or by moisture or other
foreign matter, and
(2) The correlation between air
pressure in the static pressure system
and true ambient atmospheric static
pressure is not changed when the
E:\FR\FM\29JNP1.SGM
29JNP1
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
airplane is exposed to the icing
conditions defined in appendix C of this
part, and the following icing conditions
specified in appendix O of this part:
(i) For airplanes certificated in
accordance with § 25.1420(a)(1), the
icing conditions that the airplane is
certified to safely exit following
detection.
(ii) For airplanes certificated in
accordance with § 25.1420(a)(2), the
icing conditions that the airplane is
certified to safely operate in and the
icing conditions that the airplane is
certified to safely exit following
detection.
(iii) For airplanes certificated in
accordance with § 25.1420(a)(3) and for
airplanes not subject to § 25.1420, all
icing conditions.
*
*
*
*
*
20. Add § 25.1420 to read as follows:
§ 25.1420 Supercooled large drop icing
conditions.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(a) If certification for flight in icing
conditions is sought, in addition to the
requirements of § 25.1419, an airplane
with a maximum takeoff weight less
than 60,000 pounds or with reversible
flight controls must be capable of
operating in accordance with
paragraphs (a)(1), (2), or (3), of this
section.
(1) Operating safely after encountering
the icing conditions defined in
appendix O of this part:
(i) There must be a means provided to
detect that the airplane is operating in
appendix O icing conditions; and
(ii) Following detection of appendix O
icing conditions, the airplane must be
capable of operating safely while exiting
all icing conditions.
(2) Operating safely in a portion of the
icing conditions defined in appendix O
of this part as selected by the applicant.
(i) There must be a means provided to
detect that the airplane is operating in
conditions that exceed the selected
portion of appendix O icing conditions;
and
(ii) Following detection, the airplane
must be capable of operating safely
while exiting all icing conditions.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
(3) Operating safely in the icing
conditions defined in appendix O of
this part.
(b) To establish that the airplane can
operate safely as required in paragraph
(a) of this section, an analysis must be
performed to establish that the ice
protection for the various components
of the airplane is adequate, taking into
account the various airplane operational
configurations. To verify the analysis,
one, or more as found necessary, of the
following methods must be used:
(1) Laboratory dry air or simulated
icing tests, or a combination of both, of
the components or models of the
components.
(2) Laboratory dry air or simulated
icing tests, or a combination of both, of
models of the airplane.
(3) Flight tests of the airplane or its
components in simulated icing
conditions, measured as necessary to
support the analysis.
(4) Flight tests of the airplane with
simulated ice shapes.
(5) Flight tests of the airplane in
natural icing conditions, measured as
necessary to support the analysis.
(c) For an airplane certified in
accordance with paragraph (a)(2) or
(a)(3) of this section, the requirements of
§ 25.1419 (e), (f), (g), and (h) must be
met for the icing conditions defined in
appendix O of this part in which the
airplane is certified to operate.
21. Amend § 25.1521 by redesignating
paragraph (c)(3) as (c)(4) and revising it,
and by adding new paragraph (c)(3) to
read as follows:
§ 25.1521
Powerplant limitations.
*
*
*
*
*
(c) * * *
(3) Maximum time interval between
engine run-ups from idle, run-up power
setting, duration at power, and the
associated minimum ambient
temperature demonstrated for the
maximum time interval, for ground
operation in icing conditions, as defined
in § 25.1093(b)(2).
(4) Any other parameter for which a
limitation has been established as part
of the engine type certificate except that
a limitation need not be established for
a parameter that cannot be exceeded
PO 00000
Frm 00017
Fmt 4702
Sfmt 4702
37327
during normal operation due to the
design of the installation or to another
established limitation.
*
*
*
*
*
22. Amend § 25.1533 by adding
paragraph (c) to read as follows:
§ 25.1533
Additional operating limitations.
*
*
*
*
*
(c) For airplanes certified in
accordance with § 25.1420(a)(1) or
(a)(2), an operating limitation must be
established to require exiting all icing
conditions if icing conditions defined in
appendix O of this part are encountered
for which the airplane has not been
certified to safely operate.
23. Amend part 25 by adding
Appendix O to part 25 to read as
follows:
Appendix O to Part 25—Supercooled
Large Drop Icing Conditions
Appendix O consists of two parts. Part I
defines appendix O as a description of
supercooled large drop (SLD) icing
conditions in which the drop median volume
diameter (MVD) is less than or greater than
40 μm, the maximum mean effective drop
diameter (MED) of appendix C continuous
maximum (stratiform clouds) icing
conditions. For appendix O, SLD icing
conditions consist of freezing drizzle and
freezing rain occurring in and/or below
stratiform clouds. Part II defines ice
accretions used to show compliance with
part 25, subpart B, airplane performance and
handling qualities requirements.
Part I—Meteorology
Appendix O icing conditions are defined
by the parameters of altitude, vertical and
horizontal extent, temperature, liquid water
content, and water mass distribution as a
function of drop diameter distribution.
(a) Freezing Drizzle (Conditions with
spectra maximum drop diameters from 100
μm to 500 μm):
(1) Pressure altitude range: 0 to 22,000 feet
MSL.
(2) Maximum vertical extent: 12,000 feet.
(3) Horizontal extent: standard distance of
17.4 nautical miles.
(4) Total liquid water content.
Note: Liquid water content (LWC) in grams
per cubic meter (g/m3) based on horizontal
extent standard distance of 17.4 nautical
miles.
BILLING CODE 4910–13–P
E:\FR\FM\29JNP1.SGM
29JNP1
37328
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
PO 00000
Frm 00018
Fmt 4702
Sfmt 4702
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.051</GPH>
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(5) Drop diameter distribution:
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
37329
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
PO 00000
Frm 00019
Fmt 4702
Sfmt 4702
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.052</GPH>
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(6) Altitude and temperature envelope:
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(b) Freezing Rain (Conditions with spectra
maximum drop diameters greater than 500
μm):
(1) Pressure altitude range: 0 to 12,000 ft
MSL.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
(2) Maximum vertical extent: 7,000 ft.
(3) Horizontal extent: standard distance of
17.4 nautical miles.
(4) Total liquid water content.
PO 00000
Frm 00020
Fmt 4702
Sfmt 4702
Note: LWC in grams per cubic meter (g/m3)
based on horizontal extent standard distance
of 17.4 nautical miles.
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.053</GPH>
37330
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
37331
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
PO 00000
Frm 00021
Fmt 4702
Sfmt 4702
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.054</GPH>
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(5) Drop Diameter Distribution
37332
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
PO 00000
Frm 00022
Fmt 4702
Sfmt 4702
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.055</GPH>
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(6) Altitude and temperature envelope:
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
horizontal extents other than the standard
17.4 nautical miles can be determined by the
value of the liquid water content determined
PO 00000
Frm 00023
Fmt 4702
Sfmt 4702
from Figure 1 or Figure 4, multiplied by the
factor provided in Figure 7.
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.056</GPH>
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(c) Horizontal extent.
The liquid water content for freezing
drizzle and freezing rain conditions for
37333
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Part II—Airframe Ice Accretions for
Showing Compliance With Subpart B
(a) General.
The most critical ice accretion in terms of
airplane performance and handling qualities
for each flight phase must be used to show
compliance with the applicable airplane
performance and handling qualities
requirements for icing conditions contained
in subpart B of this part. Applicants must
demonstrate that the full range of
atmospheric icing conditions specified in
part I of this appendix have been considered,
including drop diameter distributions, liquid
water content, and temperature appropriate
to the flight conditions (for example,
configuration, speed, angle-of-attack, and
altitude).
(1) For an airplane certified in accordance
with § 25.1420(a)(1), the ice accretions for
each flight phase are defined in part II,
paragraph (b) of this appendix.
(2) For an airplane certified in accordance
with § 25.1420(a)(2), the most critical ice
accretion for each flight phase defined in part
II, paragraphs (b) and (c) of this appendix,
must be used. For the ice accretions defined
in part II, paragraph (c) of this appendix, only
the portion of part I of this appendix in
which the airplane is capable of operating
safely must be considered.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
(3) For an airplane certified in accordance
with § 25.1420(a)(3), the ice accretions for
each flight phase are defined in part II,
paragraph (c) of this appendix.
(b) Ice accretions for airplanes certified in
accordance with § 25.1420(a)(1) or (a)(2).
(1) En route ice is the en route ice as
defined by part II, paragraph (c)(3), of this
appendix, for an airplane certified in
accordance with § 25.1420(a)(2), or defined
by part II, paragraph (a)(3), of appendix C of
this part, for an airplane certified in
accordance with § 25.1420(a)(1), plus:
(i) Pre-detection ice as defined by part II
paragraph (b)(5) of this appendix; and
(ii) The ice accumulated during the transit
of one cloud with a horizontal extent of 17.4
nautical miles in the most critical of the icing
conditions defined in part I of this appendix
and one cloud with a horizontal extent of
17.4 nautical miles in the continuous
maximum icing conditions defined in
appendix C of this part.
(2) Holding ice is the holding ice defined
by part II, paragraph (c)(4), of this appendix,
for an airplane certified in accordance with
§ 25.1420(a)(2), or defined by part II,
paragraph (a)(4) of appendix C of this part,
for an airplane certified in accordance with
§ 25.1420(a)(1), plus:
(i) Pre-detection ice as defined by part II,
paragraph (b)(5) of this appendix; and
PO 00000
Frm 00024
Fmt 4702
Sfmt 4702
(ii) The ice accumulated during the transit
of one cloud with a 17.4 nautical miles
horizontal extent in the most critical of the
icing conditions defined in part I of this
appendix and one cloud with a horizontal
extent of 17.4 nautical miles in the
continuous maximum icing conditions
defined in appendix C of this part. The total
exposure to the icing conditions need not
exceed 45 minutes.
(3) Approach ice is the more critical of the
holding ice defined by part II, paragraph
(b)(2) of this appendix, or the ice calculated
in the applicable paragraph (b)(3)(i) or (ii) of
part II of this appendix:
(i) For an airplane certified in accordance
with § 25.1420(a)(2), the ice accumulated
during descent from the maximum vertical
extent of the icing conditions defined in part
I of this appendix to 2,000 feet above the
landing surface in the cruise configuration,
plus transition to the approach configuration,
plus:
(A) Pre-detection ice, as defined by part II,
paragraph (b)(5) of this appendix; and
(B) The ice accumulated during the transit
at 2,000 feet above the landing surface of one
cloud with a horizontal extent of 17.4
nautical miles in the most critical of the icing
conditions defined in part I of this appendix
and one cloud with a horizontal extent of
17.4 nautical miles in the continuous
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.057</GPH>
37334
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
maximum icing conditions defined in
appendix C of this part.
(ii) For an airplane certified in accordance
with § 25.1420(a)(1), the ice accumulated
during descent from the maximum vertical
extent of the maximum continuous icing
conditions defined in part I of appendix C to
2,000 feet above the landing surface in the
cruise configuration, plus transition to the
approach configuration, plus:
(A) Pre-detection ice, as defined by part II,
paragraph (b)(5) of this appendix; and
(B) The ice accumulated during the transit
at 2,000 feet above the landing surface of one
cloud with a horizontal extent of 17.4
nautical miles in the most critical of the icing
conditions defined in part I of this appendix
and one cloud with a horizontal extent of
17.4 nautical miles in the continuous
maximum icing conditions defined in
appendix C of this part.
(4) Landing ice is the more critical of the
holding ice as defined by part II, paragraph
(b)(2) of this appendix, or the ice calculated
in the applicable paragraph (b)(4)(i) or (ii) of
part II of this appendix:
(i) For an airplane certified in accordance
with § 25.1420(a)(2), the ice accretion defined
by part II, paragraph (c)(5)(i) of this
appendix, plus a descent from 2,000 feet
above the landing surface to a height of 200
feet above the landing surface with a
transition to the landing configuration in the
icing conditions defined in part I of this
appendix, plus:
(A) Pre-detection ice, as defined in part II,
paragraph (b)(5) of this appendix; and
(B) The ice accumulated during an exit
maneuver, beginning with the minimum
climb gradient required by § 25.119, from a
height of 200 feet above the landing surface
through one cloud with a horizontal extent
of 17.4 nautical miles in the most critical of
the icing conditions defined in part I of this
appendix and one cloud with a horizontal
extent of 17.4 nautical miles in the
continuous maximum icing conditions
defined in appendix C of this part.
(ii) For an airplane certified in accordance
with § 25.1420(a)(1), the ice accumulated in
the maximum continuous icing conditions
defined in appendix C of this part, during a
descent from the maximum vertical extent of
the icing conditions defined in appendix C
of this part, to 2,000 feet above the landing
surface in the cruise configuration, plus
transition to the approach configuration and
flying for 15 minutes at 2,000 feet above the
landing surface, plus a descent from 2,000
feet above the landing surface to a height of
200 feet above the landing surface with a
transition to the landing configuration, plus:
(A) Pre-detection ice, as described by part
II, paragraph (b)(5) of this appendix; and
(B) The ice accumulated during an exit
maneuver, beginning with the minimum
climb gradient required by § 25.119, from a
height of 200 feet above the landing surface
through one cloud with a horizontal extent
of 17.4 nautical miles in the most critical of
the icing conditions defined in part I of this
appendix and one cloud with a horizontal
extent of 17.4 nautical miles in the
continuous maximum icing conditions
defined in appendix C of this part.
(5) Pre-detection ice is the ice accretion
before detection of appendix O conditions
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
that require exiting per § 25.1420(a)(1) and
(a)(2). It is the pre-existing ice accretion that
may exist from operating in icing conditions
in which the airplane is approved to operate
prior to encountering the icing conditions
requiring an exit, plus the ice accumulated
during the time needed to detect the icing
conditions, followed by two minutes of
further ice accumulation to take into account
the time for the flight crew to take action to
exit the icing conditions, including
coordination with air traffic control.
(i) For an airplane certified in accordance
with § 25.1420(a)(1), the pre-existing ice
accretion must be based on the icing
conditions defined in appendix C of this part.
(ii) For an airplane certified in accordance
with § 25.1420(a)(2), the pre-existing ice
accretion must be based on the more critical
of the icing conditions defined in appendix
C of this part, or the icing conditions defined
in part I of this appendix in which the
airplane is capable of safely operating. The
pre-detection ice accretion applies in
showing compliance with §§ 25.143(k) and
25.207(k), and as part of the ice accretion
definitions of part II, paragraph (b)(1) through
(b)(4) of this appendix.
(c) Ice accretions for airplanes certified in
accordance with §§ 25.1420(a)(2) or
25.1420(a)(3). For an airplane certified in
accordance with § 25.1420(a)(2), only the
portion of the icing conditions of part I of
this appendix in which the airplane is
capable of operating safely must be
considered.
(1) Takeoff ice is the most critical ice
accretion on unprotected surfaces, and any
ice accretion on the protected surfaces
appropriate to normal ice protection system
operation, occurring between liftoff and 400
feet above the takeoff surface, assuming
accretion starts at liftoff in the icing
conditions defined in part I of this appendix.
(2) Final takeoff ice is the most critical ice
accretion on unprotected surfaces, and any
ice accretion on the protected surfaces
appropriate to normal ice protection system
operation, between 400 feet and either 1,500
feet above the takeoff surface, or the height
at which the transition from the takeoff to the
en route configuration is completed and VFTO
is reached, whichever is higher. Ice accretion
is assumed to start at liftoff in the icing
conditions defined in part I of this appendix.
(3) En route ice is the most critical ice
accretion on the unprotected surfaces, and
any ice accretion on the protected surfaces
appropriate to normal ice protection system
operation, during the en route flight phase in
the icing conditions defined in part I of this
appendix.
(4) Holding ice is the most critical ice
accretion on the unprotected surfaces, and
any ice accretion on the protected surfaces
appropriate to normal ice protection system
operation, resulting from 45 minutes of flight
within a cloud with a 17.4 nautical miles
horizontal extent in the icing conditions
defined in part I of this appendix, during the
holding phase of flight.
(5) Approach ice is the ice accretion on the
unprotected surfaces, and any ice accretion
on the protected surfaces appropriate to
normal ice protection system operation,
resulting from the more critical of the:
PO 00000
Frm 00025
Fmt 4702
Sfmt 4702
37335
(i) Ice accumulated in the icing conditions
defined in part I of this appendix during a
descent from the maximum vertical extent of
the icing conditions defined in part I of this
appendix, to 2,000 feet above the landing
surface in the cruise configuration, plus
transition to the approach configuration and
flying for 15 minutes at 2,000 feet above the
landing surface; or
(ii) Holding ice as defined by part II,
paragraph (c)(4) of this appendix.
(6) Landing ice is the ice accretion on the
unprotected surfaces, and any ice accretion
on the protected surfaces appropriate to
normal ice protection system operation,
resulting from the more critical of the:
(i) Ice accretion defined by part II,
paragraph (c)(5)(i), of this appendix, plus ice
accumulated in the icing conditions defined
in part I of this appendix during a descent
from 2,000 feet above the landing surface to
a height of 200 feet above the landing surface
with a transition to the landing configuration,
followed by a go-around at the minimum
climb gradient required by § 25.119, from a
height of 200 feet above the landing surface
to 2,000 feet above the landing surface, flying
for 15 minutes at 2,000 feet above the landing
surface in the approach configuration, and a
descent to the landing surface (touchdown)
in the landing configuration; or
(ii) Holding ice as defined by part II
paragraph (c)(4) of this appendix.
(7) For both unprotected and protected
parts, the ice accretion for the takeoff phase
must be determined for the icing conditions
defined in part I of this appendix, using the
following assumptions:
(i) The airfoils, control surfaces, and, if
applicable, propellers are free from frost,
snow, or ice at the start of takeoff;
(ii) The ice accretion begins at liftoff;
(iii) The critical ratio of thrust/power-toweight;
(iv) Failure of the critical engine occurs at
VEF; and
(v) Crew activation of the ice protection
system is in accordance with a normal
operating procedure provided in the Airplane
Flight Manual, except that after beginning the
takeoff roll, it must be assumed that the crew
takes no action to activate the ice protection
system until the airplane is at least 400 feet
above the takeoff surface.
(d) The ice accretion before the ice
protection system has been activated and is
performing its intended function is the
critical ice accretion formed on the
unprotected and normally protected surfaces
before activation and effective operation of
the ice protection system in the icing
conditions defined in part I of this appendix.
This ice accretion only applies in showing
compliance to §§ 25.143(j) and 25.207(h).
(e) In order to reduce the number of ice
accretions to be considered when
demonstrating compliance with the
requirements of § 25.21(g), any of the ice
accretions defined in this appendix may be
used for any other flight phase if it is shown
to be more critical than the specific ice
accretion defined for that flight phase.
Configuration differences and their effects on
ice accretions must be taken into account.
(f) The ice accretion that has the most
adverse effect on handling qualities may be
E:\FR\FM\29JNP1.SGM
29JNP1
37336
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
used for airplane performance tests provided
any difference in performance is
conservatively taken into account.
PART 33—AIRWORTHINESS
STANDARDS: AIRCRAFT ENGINES
24. The authority citation for part 33
continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701,
44702, 44704.
25. Revise § 33.68 to read as follows:
§ 33.68
Induction system icing.
Each engine, with all icing protection
systems operating, must:
(a) Operate throughout its flight
power range, including the minimum
descent idle rotor speeds achievable in
flight, in the icing conditions defined in
appendices C and O of part 25 of this
chapter, and appendix D of this part 33,
without the accumulation of ice on the
engine components that:
(1) Adversely affects engine operation
or that causes an unacceptable
permanent loss of power or thrust or
unacceptable increase in engine
operating temperature; or
(2) Results in unacceptable temporary
power loss or engine damage; or
(3) Causes a stall, surge, or flameout
or loss of engine controllability (for
example, rollback). The applicant must
account for in-flight ram effects (for
example; scoop factor amplification,
water temperature, air density) in any
critical point analysis or test
demonstration of these flight conditions.
(b) Operate throughout its flight
power range, including minimum
descent idle rotor speeds achievable in
flight, in the icing conditions defined in
appendices C and O of part 25 of this
chapter. In addition,
(1) It must be shown through Critical
Point Analysis (CPA) that the complete
ice envelope has been analyzed, and
that the most critical points must be
demonstrated by engine test, analysis or
a combination of the two to operate
acceptably. Extended flight in critical
flight conditions such as hold, descent,
approach, climb, and cruise, must be
addressed, for the ice conditions
defined in these appendices.
(2) It must be shown by engine test,
analysis or a combination of the two
that the engine can operate acceptably
for the following durations:
(i) At engine powers that can sustain
level flight: A duration that achieves
repetitive, stabilized operation in the
icing conditions defined in appendices
C and O of part 25 of this chapter.
(ii) At engine power below that which
can sustain level flight:
(A) Demonstration in altitude flight
simulation test facility: A duration of 10
minutes consistent with a simulated
flight descent of 10,000 ft (3 km) in
altitude while operating in Continuous
Maximum icing conditions defined in
appendix C of part 25 of this chapter,
plus 40 percent liquid water content
margin, at the critical level of airspeed
and air temperature, or
(B) Demonstration in ground test
facility: A duration of 3 cycles of
alternating icing exposure
corresponding to the liquid water
content levels and standard cloud
lengths in Intermittent Maximum and
Continuous Maximum icing conditions
defined in appendix C of part 25 of this
chapter, at the critical level of air
temperature.
(c) In addition to complying with
§ 33.68(b), the following conditions
shown in Table 1 of this section unless
replaced by similar CPA test conditions
that are more critical or produce an
equivalent level of severity, must be
demonstrated by an engine test:
TABLE 1—CONDITIONS THAT MUST BE DEMONSTRATED BY AN ENGINE TEST
Condition
Total air
temperature
Supercooled water
concentrations
(minimum)
Median volume
drop diameter
(±3 microns)
1. Glaze ice conditions.
21 to 25 °F (¥6 to
¥4 °C).
2 g/m3 ...................
25 microns ............
2. Rime ice conditions.
¥10 to 0 °F (¥23
to ¥18 °C).
1 g/m3 ...................
15 microns ............
3. Glaze ice holding
conditions (Turboprop and turbofan, only).
Turbofan, only: 10
to 18 °F (¥12 to
¥8 °C).
Turboprop, only: 2
to 10 °F (¥17 to
¥12 °C).
Turbofan, only:
¥10 to 0 °F
(¥23 to ¥18
°C)
Turboprop, only: 2
to 10 °F (¥17 to
¥12 °C).
Alternating cycle:
0.3 g/m3 (6
minute) 1.7 g/m3
(1 minute).
20 microns ............
0.25 g/m3 ..............
20 microns ............
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
4. Rime ice holding
conditions (Turboprop and turbofan, only).
(d) The engine should be run at
ground idle speed for a minimum of 30
minutes at each of the following icing
conditions shown in Table 2 of this
section with the available air bleed for
icing protection at its critical condition,
without adverse effect, followed by
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
Duration
(a) 10 minutes for power below sustainable level flight
(idle descent).
(b) Must show repetitive, stabilized operation for higher
powers (50%, 75%, 100% MC).
(a) 10 minutes for power below sustainable level flight
(idle descent).
(b) Must show repetitive, stabilized operation for higher
powers (50%, 75%, 100% MC).
Must show repetitive, stabilized operation (or 45 minutes
max).
Must show repetitive, stabilized operation (or 45 minutes
max).
acceleration to takeoff power or thrust.
During the idle operation the engine
may be run up periodically to a
moderate power or thrust setting in a
manner acceptable to the Administrator.
The applicant must document any
demonstrated run ups and minimum
PO 00000
Frm 00026
Fmt 4702
Sfmt 4702
ambient temperature capability during
the conduct of icing testing in the
engine operating manual as mandatory
in icing conditions. The applicant must
demonstrate, with consideration of
expected airport elevations, the
following:
E:\FR\FM\29JNP1.SGM
29JNP1
37337
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
TABLE 2—DEMONSTRATION METHODS FOR SPECIFIC ICING CONDITIONS
Supercooled water
concentrations
(minimum)
Mean effective particle
diameter
Liquid—0.3 g/m3 ............
15–25 microns ...............
By engine test.
Liquid—0.3 g/m3 ............
15–25 microns ...............
By engine test.
3. Snow ice condition ....
0 to 15 °F (¥8 to ¥9
°C).
20 to 30 °F (¥7 to ¥1
°C).
26 to 32 °F (¥3 to 0 °C)
Ice—0.9 g/m3 ................
100 microns (minimum)
4. Large drop glaze ice
condition.
15 to 30 °F (¥9 to ¥1
°C).
Liquid—0.3 g/m3 ............
100 microns (minimum);
3000 microns (maximum).
By test, analysis or combination of
the two.
By test, analysis or combination of
the two.
Condition
Total air temperature
1. Rime ice condition .....
2. Glaze ice condition ....
(e) The applicant must demonstrate
by test, analysis, or combination of the
two, acceptable operation in ice crystals
and mixed phase icing conditions
throughout part 33, appendix D, icing
envelope throughout its flight power
range, including minimum descent
idling speeds.
26. Amend § 33.77 by adding
paragraph (a) and by revising
paragraphs (c) introductory text, (c)(1),
(d), and (e)(1) through (4) to read as
follows:
§ 33.77
Foreign object ingestion—ice.
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
(a) Compliance with the requirements
of this paragraph shall be demonstrated
by engine ice ingestion test or by
validated analysis showing equivalence
of other means for demonstrating soft
body damage tolerance.
*
*
*
*
*
(c) Ingestion of ice under the
conditions of this section may not —
(1) Cause an immediate or ultimate
unacceptable sustained power or thrust
loss; or
*
*
*
*
*
(d) For an engine that incorporates a
protection device, compliance with this
section need not be demonstrated with
respect to ice formed forward of the
protection device if it is shown that—
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
(1) Such ice is of a size that will not
pass through the protective device;
(2) The protective device will
withstand the impact of the ice; and
(3) The ice stopped by the protective
device will not obstruct the flow of
induction air into the engine with a
resultant sustained reduction in power
or thrust greater than those values
defined by paragraph (c) of this section.
(e) * * *
(1) The minimum ice quantity and
dimensions will be established by the
engine size as defined in Table 1 of this
section.
(2) The ingested ice dimensions are
determined by linear interpolation
between table values, and are based on
the actual engine’s inlet hilite area.
(3) The ingestion velocity will
simulate ice from the inlet being sucked
into the engine.
(4) Engine operation will be at the
maximum cruise power or thrust unless
lower power is more critical.
PO 00000
Frm 00027
Fmt 4702
Sfmt 4700
Demonstration
TABLE 1—MINIMUM ICE SLAB DIMENSIONS BASED ON ENGINE INLET SIZE
Engine
inlet hilite
area
(sq inch)
0 ..............
80 ............
300 ..........
700 ..........
2800 ........
5000 ........
7000 ........
7900 ........
9500 ........
11300 ......
13300 ......
16500 ......
20000 ......
Thickness
(inch)
0.25
0.25
0.25
0.25
0.35
0.43
0.50
0.50
0.50
0.50
0.50
0.5
0.5
Width
(inch)
0
6
12
12
12
12
12
12
12
12
12
12
12
Length
(inch)
3.6
3.6
3.6
4.8
8.5
11.0
12.7
13.4
14.6
15.9
17.1
18.9
20.0
27. Amend part 33 by adding
appendix D to read as follows:
Appendix D to Part 33—Mixed Phase
And Ice Crystal Icing Envelope (Deep
Convective Clouds)
Ice crystal conditions associated with
convective storm cloud formations exist
within the part 25, appendix C, Intermittent
Maximum Icing envelope (including the
extension to ¥40 deg C) and the Mil
Standard 210 Hot Day envelope. This ice
crystal icing envelope is depicted in Figure
D1, below.
E:\FR\FM\29JNP1.SGM
29JNP1
37338
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
temperature within the boundaries of the ice
crystal envelope specified in Figure D1.
EP29JN10.059</GPH>
from sea level to higher altitudes and scaled
by a factor of 0.65 to a standard cloud length
of 17.4 nautical miles. Figure D2 displays
TWC for this distance over a range of ambient
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
PO 00000
Frm 00028
Fmt 4702
Sfmt 4725
E:\FR\FM\29JNP1.SGM
29JNP1
EP29JN10.058</GPH>
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
Within the envelope, total water content
(TWC) in g/m3 has been determined based
upon the adiabatic lapse defined by the
convective rise of 90% relative humidity air
37339
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 / Proposed Rules
Ice crystal size median mass dimension
(MMD) range is 50–200 microns (equivalent
spherical size) based upon measurements
near convective storm cores.
The TWC can be treated as completely
glaciated (ice crystal) except as noted in the
Table 1.
TABLE 1—SUPERCOOLED LIQUID PORTION OF TWC
Temperature
range—deg C
Horizontal cloud length
0 to ¥20 ......................................................................................
0 to ¥20 ......................................................................................
<¥20 ...........................................................................................
</= 50 miles ................................................................................
Indefinite ......................................................................................
.....................................................................................................
LWC—g/m3
</=1.0
</=0.5
0
The TWC levels displayed in Figure D2
represent TWC values for a standard
exposure distance (horizontal cloud length)
of 17.4 nautical miles that must be adjusted
with length of icing exposure. The
assessment from data measurements in
Reference 1 supports the reduction factor
with exposure length shown in Figure D3.
Issued in Washington, DC, on June 23,
2010.
KC Yanamura,
Acting Director, Aircraft Certification Service.
DEPARTMENT OF TRANSPORTATION
ACTION: Notice of Proposed Rulemaking
(NPRM).
14 CFR Part 39
[Docket No. FAA–2010–0640; Directorate
Identifier 2009–NM–142–AD]
BILLING CODE 4910–13–P
wwoods2 on DSK1DXX6B1PROD with PROPOSALS
RIN 2120–AA64
Airworthiness Directives; EADS CASA
(Type Certificate Previously Held by
Construcciones Aeronauticas, S.A.)
Model CN–235, CN–235–100, CN–235–
200, and CN–235–300 Airplanes, and
Model C–295 Airplanes
AGENCY: Federal Aviation
Administration (FAA), DOT.
VerDate Mar<15>2010
15:07 Jun 28, 2010
Jkt 220001
PO 00000
Frm 00029
Fmt 4702
Sfmt 4702
SUMMARY: We propose to adopt a new
airworthiness directive (AD) for the
products listed above that would
supersede an existing AD. This
proposed AD results from mandatory
continuing airworthiness information
(MCAI) originated by an aviation
authority of another country to identify
and correct an unsafe condition on an
aviation product. The MCAI describes
the unsafe condition as:
Prompted by [an] accident * * * the FAA
published SFAR 88 (Special Federal Aviation
Regulation 88) * * *.
*
E:\FR\FM\29JNP1.SGM
*
*
29JNP1
*
*
EP29JN10.060</GPH>
[FR Doc. 2010–15726 Filed 6–28–10; 8:45 am]
Federal Aviation Administration
]]>Agencies
[Federal Register Volume 75, Number 124 (Tuesday, June 29, 2010)]
[Proposed Rules]
[Pages 37311-37339]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-15726]
========================================================================
Proposed Rules
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
========================================================================
Federal Register / Vol. 75, No. 124 / Tuesday, June 29, 2010 /
Proposed Rules
[[Page 37311]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 25 and 33
[Docket No. FAA-2010-0636; Notice No. 10-10]
RIN 2120-AJ34
Airplane and Engine Certification Requirements in Supercooled
Large Drop, Mixed Phase, and Ice Crystal Icing Conditions
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of Proposed Rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: The Federal Aviation Administration proposes to amend the
airworthiness standards applicable to certain transport category
airplanes certified for flight in icing conditions and the icing
airworthiness standards applicable to certain aircraft engines. The
proposed regulations would improve safety by addressing supercooled
large drop icing conditions for transport category airplanes most
affected by these icing conditions, mixed phase and ice crystal
conditions for all transport category airplanes, and supercooled large
drop, mixed phase, and ice crystal icing conditions for all turbine
engines. These proposed regulations are the result of information
gathered from a review of icing accidents and incidents.
DATES: Send your comments on or before August 30, 2010.
ADDRESSES: You may send comments identified by Docket Number FAA-2010-
0636 using any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov and follow the online instructions for sending your
comments electronically.
Mail: Send comments to Docket Operations, M-30; U.S.
Department of Transportation, 1200 New Jersey Avenue, SE., Room W12-
140, West Building Ground Floor, Washington, DC 20590-0001.
Hand Delivery or Courier: Bring comments to Docket
Operations in Room W12-140 of the West Building Ground Floor at 1200
New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.
Fax: Fax comments to Docket Operations at 202-493-2251.
For more information on the rulemaking process, see the
SUPPLEMENTARY INFORMATION section of this document.
Privacy: The FAA will post all comments we receive, without change,
to https://www.regulations.gov, including any personal information you
provide. Using the search function of our docket Web site, anyone can
find and read the electronic form of all comments received into any of
our dockets, including the name of the individual sending the comment
(or signing the comment for an association, business, labor union,
etc.). You may review DOT's complete Privacy Act Statement in the
Federal Register published on April 11, 2000 (65 FR 19477-78) or you
may visit https://DocketsInfo.dot.gov.
Docket: To read background documents or comments received, go to
https://www.regulations.gov at any time and follow the online
instructions for accessing the docket. Or, go to Docket Operations in
Room W12-140 of the West Building Ground Floor at 1200 New Jersey
Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Monday through
Friday, except Federal holidays.
FOR FURTHER INFORMATION CONTACT: For part 25 technical questions
contact Robert Hettman, FAA, Propulsion/Mechanical Systems Branch, ANM-
112, Transport Airplane Directorate, Aircraft Certification Service,
1601 Lind Avenue, SW., Renton, WA 98057-3356; telephone (425) 227-2683;
facsimile (425) 227-1320, e-mail robert.hettman@faa.gov.
For part 33 technical questions contact John Fisher, FAA,
Rulemaking and Policy Branch, ANE-111, Engine and Propeller Directorate
Standards Staff, Aircraft Certification Service, 12 New England
Executive Park, Burlington, MA 01803; telephone (781) 238-7149,
facsimile (781) 238-7199, e-mail john.fisher@faa.gov.
For part 25 legal questions contact Douglas Anderson, FAA, Office
of the Regional Counsel, ANM-7, Northwest Mountain Region, 1601 Lind
Avenue, SW., Renton, WA 98057-3356; telephone (425) 227-2166; facsimile
(425) 227-1007, e-mail douglas.anderson@faa.gov.
For part 33 legal questions contact Vince Bennett, FAA, Office of
the Regional Counsel, ANE-007, New England Region, 12 New England
Executive Park, Burlington, MA 01803; telephone (781) 238-7044;
facsimile (781) 238-7055, e-mail vincent.bennett@faa.gov.
SUPPLEMENTARY INFORMATION: Later in this preamble under the Additional
Information section, the FAA discusses how you can comment on this
proposal and how the agency will handle your comments. Included in this
discussion is related information about the docket, privacy, and the
handling of proprietary or confidential business information. The FAA
also discusses how you can get a copy of this proposal and related
rulemaking documents.
Authority for This Rulemaking
The FAA's authority to issue rules on aviation safety is found in
Title 49 of the United States Code. Subtitle I, section 106 describes
the authority of the FAA Administrator. Subtitle VII, Aviation
Programs, describes in more detail the scope of the agency's authority.
This rulemaking is proposed under the authority described in
subtitle VII, part A, subpart III, section 44701, ``General
requirements.'' Under that section, the FAA is charged with promoting
safe flight of civil aircraft in air commerce by prescribing minimum
standards required in the interest of safety for the design and
performance of aircraft; regulations and minimum standards in the
interest of safety for inspecting, servicing, and overhauling aircraft;
and regulations for other practices, methods, and procedures the
Administrator finds necessary for safety in air commerce. This
regulation is within the scope of that authority because it would
prescribe--
New safety standards for the design and performance of
certain transport category airplanes and aircraft engines; and
New safety requirements that are necessary for the design,
production, and operation of those airplanes, and for other practices,
methods, and
[[Page 37312]]
procedures relating to those airplanes and engines.
Summary of the Proposal
The FAA proposes to revise certain regulations in Title 14, Code of
Federal Regulations (14 CFR) part 25 (Airworthiness Standards:
Transport Category Airplanes) and part 33 (Airworthiness Standards:
Aircraft Engines) related to the certification of transport category
airplanes and turbine aircraft engines in icing conditions. We also
propose to create new regulations: Sec. 25.1324--Angle of attack
systems; Sec. 25.1420 SLD icing conditions; part 25, appendix O (SLD
icing conditions); part 33, appendix C (this will be intentionally left
blank as a placeholder); and part 33, appendix D (Mixed phase and ice
crystal icing conditions). To improve the safety of transport category
airplanes operating in SLD, mixed phase, and ice crystal icing
conditions, the proposed regulations would:
Expand the certification icing environment to include
freezing rain and freezing drizzle.
Require airplanes most affected by SLD icing conditions to
meet certain safety standards in the expanded certification icing
environment, including additional airplane performance and handling
qualities requirements.
Expand the engine and engine installation certification,
and some airplane component certification regulations (for example,
angle of attack and airspeed indicating systems), to include freezing
rain, freezing drizzle, ice crystal, and mixed phase icing conditions.
For certain cases, a subset of these icing conditions is proposed.
The benefits and costs are summarized below. The estimated benefits
are $405.6 million ($99.5 million present value). The total estimated
costs are $71.0 million ($54.0 million present value). On an annualized
basis, for the time period 2012-2064, the benefits are $7.0 million,
and the costs are $3.8 million.
----------------------------------------------------------------------------------------------------------------
Nominal benefits PV benefits
----------------------------------------------------------------------------------------------------------------
Benefits
----------------------------------------------------------------------------------------------------------------
Smaller & Medium Airplanes................. $249,580,915 $69,994,259
Larger Airplanes........................... 156,004,884 29,498,469
Total Benefits......................... 405,585,799 99,492,728
��������������������������������������������
(7.0 million annually)
----------------------------------------------------------------------------------------------------------------
Costs
----------------------------------------------------------------------------------------------------------------
Nominal cost PV cost
----------------------------------------------------------------------------------------------------------------
Engine Cert Cost........................... 7,936,000 6,931,610
Engine Capital Cost........................ 6,000,000 5,240,632
--------------------------------------------------------------------
Total Engine........................... 13,936,000 12,172,242
================================================================================================================
Smaller Airplane Certification Cost........ 24,999,039 21,835,129
New Larger Airplane Certification Cost..... 3,154,600 2,755,350
Derivative Larger Airplane Certification 10,438,800 9,117,652
Cost.
Hardware Costs............................. 10,390,000 5,842,024
Fuel Burn All.............................. 8,046,676 2,261,941
================================================================================================================
Total Costs............................ 70,965,115 53,984,338
----------------------------------------------------------------------------------------------------------------
($3.8 million annually)
----------------------------------------------------------------------------------------------------------------
Background
In the 1990s, the FAA became aware that the types of icing
conditions considered during the certification of transport category
airplanes and turbine aircraft engines needed to be expanded to
increase the level of safety during flight in icing. The FAA determined
that the revised icing certification standards should include
supercooled large drops (SLD), mixed phase, and ice crystals.\1\
---------------------------------------------------------------------------
\1\ Appendix 1 of this preamble contains definitions of certain
terms used in this notice of proposed rulemaking (NPRM).
---------------------------------------------------------------------------
Safety concerns about the adequacy of the icing certification
standards were brought to the forefront of public and governmental
attention by a 1994 accident in Roselawn, Indiana, involving an Avions
de Transport Regional ATR 72 series airplane. The FAA, Aerospatiale,
the French Direction G[eacute]n[eacute]ral de l'Aviation Civile, Bureau
Enquete Accident, the National Aeronautics and Space Administration,
the National Transportation Safety Board (NTSB), and others conducted
an extensive investigation of this accident. These investigations led
to the conclusion that freezing drizzle conditions created a ridge of
ice on the wing's upper surface aft of the deicing boots and forward of
the ailerons. It was further concluded that this ridge of ice
contributed to an uncommanded roll of the airplane. Based on its
investigation, the NTSB recommended changes to the icing certification
requirements.
The certification requirements for icing conditions are specified
in part 25, appendix C. The atmospheric condition (freezing drizzle)
that contributed to the Roselawn accident is currently outside the
icing envelope for certifying transport category airplanes. The term
``icing envelope'' is used within part 25, appendix C, and this NPRM to
refer to the environmental icing conditions within which the airplane
must be shown to be able to safely operate. The term ``transport
category airplanes'' is used throughout this rulemaking document to
include all airplanes type certificated to part 25 regulations.
Another atmospheric icing condition that is currently outside the
icing envelope is freezing rain. The FAA has not required airplane
manufacturers to show that airplanes can operate safely in freezing
drizzle or freezing rain conditions. These conditions constitute an
icing environment known as supercooled large drops (SLDs).
As a result of this accident and consistent with related NTSB
[[Page 37313]]
recommendations \2\ the FAA tasked the Aviation Rulemaking Advisory
Committee (ARAC),\3\ through its Ice Protection Harmonization Working
Group (IPHWG), to do the following:
---------------------------------------------------------------------------
\2\ NTSB recommendations A-96-54 and A-96-56; available in the
Docket and on the Internet at: https://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
\3\ Published in the Federal Register, December 8, 1997 (62 FR
64621).
---------------------------------------------------------------------------
Define an icing environment that includes SLDs.
Consider the need to define a mixed phase icing
environment (supercooled liquid and ice crystals).
Devise requirements to assess the ability of an airplane
to either safely operate without restrictions in SLD and mixed phase
conditions or safely operate until it can exit these conditions.
Study the effects icing requirement changes could have on
Sec. Sec. 25.773, Pilot compartment view; 25.1323, Airspeed indicating
system; and 25.1325, Static pressure systems.
Consider the need for a regulation on ice protection for
angle of attack probes.
This proposed rule is based on the ARAC's recommendations to the
FAA. Terms used in this notice of proposed rulemaking (NPRM) are
defined in Appendix 1 of this preamble.
A. Existing Regulations for Flight in Icing Conditions
Currently, the certification regulations applicable to transport
category airplanes for flight in icing conditions require that: ``The
airplane must be able to operate safely in the continuous maximum and
intermittent maximum icing conditions of appendix C.'' \4\ The
certification regulations also require minimum performance and handling
qualities in these icing conditions and methods to detect airframe
icing and to activate and operate ice protection systems.\5\ Icing
regulations applicable to engines are in Sec. Sec. 33.68 and 33.77.
Operating regulations in parts 91 (General Operating and Flight Rules)
and 135 (Operating Requirements: Commuter and On Demand Operations)
address limitations in icing conditions for airplanes operated under
these parts.\6\ Part 121 (Operating Requirements: Domestic, Flag and
Supplemental Operations) addresses operations in icing conditions that
might adversely affect safety and requires installing certain types of
ice protection equipment and wing illumination equipment.\7\
---------------------------------------------------------------------------
\4\ 14 CFR 25.1419, Ice Protection.
\5\ For a complete discussion of the regulations see Amendment
25-121 (72 FR 44665, August 8, 2007), and Amendment 25-129 (74 FR
38328, August 3, 2009).
\6\ 14 CFR 91.527, Operating in icing conditions; and Sec.
135.227, Icing conditions: Operating limitations.
\7\ 14 CFR 121.629(a), Operation in icing conditions and Sec.
121.341, Equipment for operations in icing conditions.
---------------------------------------------------------------------------
Some of the part 25 and 33 regulations specify that the affected
equipment must be able to operate in some or all of the icing
conditions defined in part 25, appendix C. Other regulations within
these parts do not specify the icing conditions that must be considered
for airplane certification, but, historically, airplane certification
programs have only considered icing conditions that are defined in
appendix C.
Appendix C addresses continuous maximum and intermittent maximum
icing conditions within stratiform and cumuliform clouds ranging from
sea level up to 30,000 feet. Appendix C defines icing cloud
characteristics in terms of mean effective drop diameters, liquid water
content, temperature, horizontal and vertical extent, and altitude.
Icing conditions that contain drops with mean effective diameters that
are larger than the cloud mean effective drop diameters defined in
appendix C are typically referred to as freezing drizzle or freezing
rain. Icing conditions containing freezing drizzle and freezing rain
are not currently considered when certifying an airplane's ice
protection systems. Because the larger diameter drops typically impinge
farther aft on the airfoil, exposure to these conditions can result in
ice accretions aft of the ice protection area, which can negatively
affect airplane performance and handling qualities.
Likewise, mixed phase (supercooled liquid and ice crystals) and
100% ice crystal icing conditions are not currently considered when
certifying an airplane's ice protection systems. Exposing engines and
externally mounted probes to these conditions could result in hazardous
ice accumulations within the engine that may result in engine damage,
power loss, and loss of or misleading airspeed indications. The
certification regulations for transport category airplanes and engines
do not address the safe operation of airplanes in SLD, mixed phase, or
ice crystal icing conditions and the operating rules do not
specifically prohibit operations in these conditions.
B. National Transportation Safety Board Safety Recommendations
The NTSB issued NTSB Safety Recommendation Numbers A-96-54 \8\ and
A-96-56 \9\ as a result of the Roselawn accident previously discussed.
This rulemaking activity partially addresses the NTSB recommendations
because there are separate rulemaking activities associated with
revisions to 14 CFR part 23 regulations for small airplanes and 14 CFR
part 121 operational regulations. The NTSB recommendations are as
follows:
---------------------------------------------------------------------------
\8\ NTSB recommendation A-96-54; available in the Docket and on
the Internet at: https://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
\9\ NTSB recommendation A-96-56; available in the Docket and on
the Internet at: https://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
---------------------------------------------------------------------------
1. A-96-54
Revise the icing criteria published in 14 Code of Federal
Regulations (CFR), parts 23 and 25, in light of both recent research
into aircraft ice accretion under varying conditions of liquid water
content, drop size distribution, and temperature, and recent
developments in both the design and use of aircraft. Also, expand the
appendix C icing certification envelope to include freezing drizzle/
freezing rain and mixed water/ice crystal conditions, as necessary.
(Class II, Priority Action) (A-96-54) (Supersedes A-81-116 and--118)
2. A-96-56
Revise the icing certification testing regulation to ensure that
airplanes are properly tested for all conditions in which they are
authorized to operate, or are otherwise shown to be capable of safe
flight into such conditions. If safe operations can not be demonstrated
by the manufacturer, operational limitations should be imposed to
prohibit flight in such conditions and flightcrews should be provided
with the means to positively determine when they are in icing
conditions that exceed the limits for aircraft certification. (Class
II, Priority Action) (A-96-56)
C. Related Rulemaking Activity
The ARAC's Ice Protection Harmonization Working Group (IPHWG)
submitted additional part 121 icing rulemaking recommendations to the
FAA that may lead to future rulemaking, but do not directly impact this
NPRM. Those recommendations would improve airplane safety when
operating in icing conditions. The recommendations would:
Address when ice protection systems must be activated.
[[Page 37314]]
Require some airplanes to exit all icing conditions after
encountering large drop icing conditions conducive to ice accretions
aft of the airframe's protected area.
D. Advisory Material
The proposed new AC and revisions to existing ACs would provide
guidance material for one acceptable means, but not the only means, of
demonstrating compliance with the proposed regulations contained in
this NPRM. The guidance provided in these documents is directed at
airplane manufacturers, modifiers, foreign regulatory authorities, and
FAA transport airplane type certification engineers, flight test
pilots, and their designees. The proposed ACs will be posted on the
``Aircraft Certification Draft Documents Open for Comment'' Web site,
https://www.faa.gov/aircraft/draft_docs, after this NPRM is published
in the Federal Register
For advisory material related to this NPRM, the FAA is:
Developing a new AC 25-xx, Compliance of Transport
Category Airplanes with Certification Requirements for Flight in Icing
Conditions.
Revising AC 20-147, Turbojet, Turboprop, and Turbofan
Engine Induction System Icing and Ice Ingestion.
Revising AC 25-25, Performance and Handling
Characteristics in the Icing Conditions Specified in Part 25, Appendix
C.
Revising AC 25.629-1A, Aeroelastic Stability
Substantiation of Transport Category Airplanes.
Revising AC 25.1329-1B, Approval of Flight Guidance
Systems.
General Discussion of the Proposal
The FAA proposes to revise certain regulations in parts 25 and 33
related to the certification of transport category airplanes and
turbine aircraft engines in icing conditions.
We also propose to create a new: Sec. 25.1324--Angle of attack
systems; Sec. 25.1420--Supercooled large drop icing conditions; part
25, appendix O (supercooled large drop icing conditions; part 33,
appendix C (intentionally left blank); and part 33, appendix D (Mixed
phase and ice crystal icing conditions). Part 33, appendix C, is
intentionally left blank and retained as a placeholder for non-icing
related regulations so that part 33, appendix C, would not be confused
with the icing conditions defined in part 25, appendix C.
To improve the safety of transport category airplanes operating in
SLD, mixed phase, and ice crystal icing conditions, the proposed
regulations would:
Expand the certification icing environment to include
freezing rain and freezing drizzle.
Require airplanes most affected by SLD icing conditions
(transport category airplanes with a maximum takeoff weight less than
60,000 pounds or with reversible flight controls) to meet certain
safety standards in the expanded certification icing environment,
including additional airplane performance and handling qualities
requirements.
Expand the engine and engine installation certification,
and some airplane component certification regulations (for example,
angle of attack and airspeed indicating systems) to include freezing
rain, freezing drizzle, ice crystal, and mixed phase icing conditions.
For certain cases, a subset of these icing conditions is proposed.
A. Safety Concern
The ARAC's IPHWG reviewed icing events involving transport category
airplanes and found accidents and incidents that are believed to have
occurred in icing conditions that are not addressed by the current
regulations. The icing conditions resulted in flightcrews losing
control of their aircraft and, in some cases, engine power loss. The
review found hull losses and fatalities associated with SLD conditions,
but not for ice crystal and mixed phase conditions. However, there have
been 14 documented cases of ice crystal and mixed phase engine power
loss events between 1988 through 2009. Of those events, there were 13
occurrences of multi-engine power loss events. Fifty percent of those
events were defined as ``aircraft level events,'' since they occurred
on multiple engines installed on the same airplane. Two of these
aircraft level events resulted in diversions.
The incident history also indicates that flightcrews have
experienced temporary loss of or misleading airspeed indications in
icing. Airspeed indications on transport category airplanes are derived
from the difference between two air pressures--the total pressure, as
measured by a pitot tube mounted somewhere on the fuselage, and the
ambient or static pressure, as measured by a static port. The static
port may be flush mounted on the airplane fuselage or co-located on the
pitot tube. When the static and pitot systems are co-located, the
configuration is referred to as a pitot-static tube. Static ports are
not prone to collecting ice crystals, either because of their flush
mounted locations or their overall shape.
Due to the way pitot or pitot-static tubes are usually mounted,
they are prone to collecting ice crystals. Encountering high
concentrations of ice crystals may lead to blocked pitot or pitot-
static tubes because the energy necessary to melt the ice crystals can
exceed the tubes' design requirements. Pitot or pitot-static tube
blockage can lead to errors in measuring airspeed. The regulatory
changes which add ice crystal conditions for airspeed indicating
systems are intended to apply to either a pitot tube or pitot-static
tube configuration.
The IPHWG did not identify any events due to ice accumulations on
probes that are used to measure angle of attack, or other angle of
attack sensors. However, the IPHWG determined there are angle of attack
probe designs that are susceptible to mixed phase conditions.
The IPHWG concluded that the current regulations do not adequately
address SLD, mixed phase, and ice crystal conditions. The concerns
regarding mixed phase and ice crystal conditions were limited to
engines, propulsion installations, airspeed indications, and angle of
attack systems. The FAA concurs with the IPHWG's conclusions.
B. Prior FAA Actions To Address the Safety Concern
The FAA has issued airworthiness directives (ADs) to address the
unsafe conditions associated with operating certain airplanes in severe
icing conditions, which can include SLD icing conditions. These ADs are
applicable to airplanes equipped with both reversible flight controls
in the roll axis and pneumatic deicing boots. The ADs require the
flightcrews to exit icing when visual cues are observed that indicate
the conditions exceed the capabilities of the ice protection equipment.
In addition, for new certifications of airplanes equipped with
unpowered roll axis controls and pneumatic deicing boots, the airplanes
are evaluated to ensure the roll control forces are acceptable if the
airplane operates in certain SLD conditions. However, the scope of
these actions is limited because they do not address all transport
category airplanes and do not address the underlying safety concern of
the unknown performance and handling qualities safety margins for
airplanes and engines operating in freezing drizzle, freezing rain,
mixed phase, and ice crystal conditions. The IPHWG concluded there is a
need to improve the regulations to ensure safe operation
[[Page 37315]]
of airplanes and engines in these conditions.
C. Alternatives to Rulemaking
Before proposing new rulemaking, the FAA considers alternative ways
to solve the safety issue under consideration. Following is a brief
discussion of two of the alternatives we considered during
deliberations on this proposed rule.
1. Alternative 1: Terminal Area Radar and Sensors
The IPHWG considered the use of terminal area radar and ground-
based sensors to identify areas of SLDs so they can be avoided, rather
than require certification for operations in SLD. Equipment for
detecting and characterizing icing conditions in holding areas is being
developed. However, the equipment would have limited coverage area. For
areas not covered by terminal area radar and ground-based sensors,
airborne radars and sensors are being developed that would identify SLD
conditions in sufficient time for avoidance. These ground-based and
airborne systems are not mature enough to provide sufficient protection
for all flight operations affected by SLD. Even if the equipment was
mature, rulemaking would still be necessary to establish safety margins
for inadvertent flight into such conditions and to provide an option
for applicants to substantiate that the airplane is capable of safe
operation in SLD conditions.
2. Alternative 2: Icing Diagnostic and Predictive Weather Tools
The IPHWG considered the use of icing diagnostic and predictive
weather tools to avoid SLD rather than certify an airplane to operate
in SLD conditions. Tools have been developed that can provide
information on icing and SLD potential, but may not report all
occurrences of SLD. These experimental tools are available on the
Internet and can be used to provide flight planning information
guidance for avoidance of SLD conditions. However, rulemaking would
still be necessary to establish safety margins for inadvertent flight
into such conditions and to provide an option for applicants to
substantiate that the airplane is capable of safe operation in SLD
conditions.
Discussion of the Proposed Regulatory Requirements
Appendix O to Part 25
The proposed appendix O is structured like part 25, appendix C, one
part defining icing conditions and one defining ice accretions.
Appendix O, part I, would define SLD icing conditions and part II would
define the ice accretions that a manufacturer must consider when
designing an airplane.
Supercooled Large Drop Icing Conditions
Proposed Sec. 25.1420 would add safety requirements that must be
met in SLD icing conditions for certain transport category airplanes to
be certified for flight in icing conditions. This change would require
evaluating the operation of these airplanes in the SLD icing
environment; developing a means to differentiate between different SLD
icing conditions, if necessary; and developing procedures to exit all
icing conditions.
The proposed regulation would require consideration of the SLD
icing conditions (freezing drizzle and freezing rain) defined in a
proposed new part 25, appendix O, part I, in addition to the existing
part 25, appendix C, icing conditions. Proposed appendix O would
include drop sizes larger than those considered by current icing
regulations. These larger drops impinge and freeze farther aft on
airplane surfaces than the drops defined in appendix C and may affect
the airplane's performance, handling qualities, flutter
characteristics, and engine and systems operations. The appendix O
icing conditions, if adopted, may affect the design of airplane ice
protection systems.
The SLD icing conditions described in the proposed appendix O would
be those in which the airplane must be able to either safely exit
following the detection of any or specifically identified appendix O
icing conditions, or safely operate without restrictions. Specifically,
the proposed Sec. 25.1420 would allow three options:
Detect appendix O conditions and then operate safely while
exiting all icing conditions (Sec. 25.1420(a)(1)).
Safely operate in a selected portion of appendix O
conditions, detect when the airplane is operating in conditions that
exceed the selected portion, and then operate safely while exiting all
icing conditions (Sec. 25.1420(a)(2)).
Operate safely in all of the appendix O conditions (Sec.
25.1420(a)(3)).
As discussed below in the section titled ``Differences from the
ARAC Recommendations,'' the proposed Sec. 25.1420 would apply to
airplanes with either: (1) a takeoff maximum gross weight of less than
60,000 pounds, or (2) reversible flight controls.
To establish that an airplane could operate safely in the proposed
appendix O conditions described above, proposed Sec. 25.1420(b) would
require both analysis and one test, or more as found necessary, to
establish that the ice protection for the various components of the
airplane is adequate. The words ``as found necessary'' would be applied
in the same way as they are applied in Sec. 25.1419(b). During the
certification process, the applicant would demonstrate compliance with
the rule using a combination of analyses and test(s). The applicant's
means of compliance would consist of analyses and the amount and types
of testing it finds necessary to demonstrate compliance with the
regulation. The applicant would choose to use one or more of the tests
identified in paragraphs Sec. 25.1420(b)(1) through (b)(5). Although
the applicant may choose the means of compliance, it is ultimately the
FAA that determines whether the applicant has performed sufficient
test(s) and analyses to substantiate compliance with the regulation.
Similarly, the words ``as necessary,'' which appear in Sec.
25.1420(b)(3) and (b)(5), would result in the applicant choosing the
means of compliance that is needed to support the analysis, but the FAA
would make a finding whether the means of compliance is acceptable. If
an applicant has adequate data a similarity analysis may be used in
lieu of the testing required by Sec. 25.1420(b). For an airplane
certified to operate in at least a portion of proposed appendix O icing
conditions, proposed Sec. 25.1420(c) would extend the requirements of
Sec. 25.1419(e), (f), (g), and (h) \10\ to include activation and
operation of airframe ice protection systems in the appendix O icing
conditions for which the airplane is certified. Proposed Sec.
25.1420(c) would not apply to airplanes certified to proposed Sec.
25.1420(a)(1) because proposed Sec. 25.1420(a)(1) would require a
method to identify and safely exit all appendix O conditions.
---------------------------------------------------------------------------
\10\ These requirements were recently adopted in Amendment 25-
129 (74 FR 38328, August 3, 2009). Generally, that amendment
requires methods to detect airframe icing and to activate and
operate ice protection systems.
---------------------------------------------------------------------------
The proposed appendix O defines SLD conditions. It was developed by
the ARAC IPHWG, which included meteorologists and icing research
specialists from industry, FAA/FAA Tech Center, Meteorological Services
of Canada, National Aeronautics and Space Administration (NASA), and
Transport Canada/Transport Development Center. The IPHWG collected and
analyzed airborne measurements of pertinent SLD variables, developed an
engineering standard to be used in aircraft certification, and
recommended that
[[Page 37316]]
standard to the FAA. The FAA concurs with the recommendation.
The SLD conditions defined in appendix O, part I, include freezing
drizzle and freezing rain conditions. The freezing drizzle and freezing
rain environments are further divided into conditions in which the drop
median volume diameters are either less than or greater than the 40
microns. Appendix O consists of measured data that was divided into
drop distributions within these four icing conditions. These
distributions were averaged to produce the representative distributions
for each condition.
The distributions of drop sizes are defined as part of appendix O.
The need to include the distributions comes from the larger amount of
mass in the larger drop diameters of appendix O. The water mass of the
larger drops affects the amount of water that impinges on airplane
components, the drop impingement, icing limits, and the ice buildup
shape.
Appendix O provides a liquid water content scale factor that would
be used to adjust the liquid water content for freezing drizzle and
freezing rain. The scale factor is based on the liquid water contents
of continuous freezing drizzle and freezing rain conditions decreasing
with increasing horizontal extents.
Performance and Handling Qualities
The ice accretion definitions in proposed appendix O, part II, and
the proposed revisions to the performance and handling qualities
requirements for flight in icing conditions are similar to those
required for flight in appendix C icing conditions. The proposals
address the three options allowed by proposed Sec. 25.1420(a).
Proposed appendix O, part II, would contain definitions of the ice
accretions appropriate to each phase of flight. The proposed appendix
O, part II(b), would define the ice accretions used to show compliance
with the performance and handling qualities requirements for any
portion of appendix O in which the airplane is not certified to
operate. The proposed appendix O, part II(c), would define the ice
accretions for any portion of appendix O in which the airplane is
certified to operate.
Proposed appendix O, part II(d), would define the ice accretion in
appendix O conditions before the airframe ice protection system is
activated and is performing its intended function to reduce or
eliminate ice accretions on protected surfaces. This ice accretion
would be used in showing compliance with the controllability and stall
warning margin requirements of Sec. Sec. 25.143(j) and 25.207(h),
respectively, that apply before the airframe ice protection system has
been activated and is performing its intended function. Even if the
airplane is certified to operate only in a portion of the appendix O
icing conditions, the ice accretion used to show compliance with
Sec. Sec. 25.143(j) and 25.207(h) must consider all appendix O icing
conditions since the initial entry into icing conditions may be into
appendix O icing conditions in which the airplane is not certified to
operate.
To reduce the number of ice accretions needed to show compliance
with Sec. 25.21(g), the proposed appendix O, part II(e), would allow
the option of using an ice accretion defined for one flight phase for
any other flight phase if it is shown to be more critical than the ice
accretion defined for that other flight phase.
Existing Sec. 25.21(g)(1) \11\ requires that the performance and
handling qualities requirements of part 25, subpart B, with certain
exceptions,\12\ be met in appendix C icing conditions.\13\ Proposed
Sec. 25.21(g)(3) would identify the performance and handling qualities
requirements that must be met to ensure that an airplane certified to
either the proposed Sec. 25.1420(a)(1) or (a)(2) could safely exit
icing if the icing conditions of proposed appendix O, for which
certification is not sought, are encountered. Such an airplane would
not be approved to take off in proposed appendix O icing conditions and
would only need to be able to detect and safely exit those icing
conditions encountered en route. Therefore, it is proposed that, in
addition to the exceptions identified in the existing Sec.
25.21(g)(1), such an airplane would not need to meet certain
requirements \14\ for appendix O icing conditions.
---------------------------------------------------------------------------
\11\ 14 CFR 25.21(g)(1) is proposed to be redesignated as Sec.
25.21(g)(2).
\12\ The exceptions listed in this requirement are Sec. Sec.
25.121(a), 25.123(c), 25.143(b)(1) and (b)(2), 25.149, 25.201(c)(2),
25.207(c) and (d), 25.239, and 25.251(b) through (e).
\13\ For a complete discussion of these requirements, see
Amendment 25-121 (72 FR 44665, August 8, 2007).
\14\ 14 CFR 25.105, 25.107, 25.109, 25.111, 25.113, 25.121, and
25.123.
---------------------------------------------------------------------------
With one exception, for an airplane certified under proposed Sec.
25.1420(a)(1) or (a)(2), the same handling qualities requirements that
must currently be met for flight in appendix C icing conditions are
proposed for flight in appendix O icing conditions for which
certification is not sought. That exception is Sec. 25.143(c)(1),
which addresses controllability following engine failure during takeoff
at V2. Compliance with that rule would not be necessary
since the airplane would not be approved for takeoff in appendix O
icing conditions. No justification for a relaxation of other handling
qualities requirements could be identified.
The requirements for safe operation in all or any portion of
proposed appendix O icing conditions under proposed Sec. 25.21(g)(4)
are similar to those currently required for appendix C icing
conditions. With one exception, the list of part 25, subpart B
requirements that currently do not have to be met for flight in
appendix C icing conditions would not have to be met in proposed
appendix O icing conditions. The exception is that compliance with
Sec. 25.121(a), Climb: One-engine-inoperative would be required for
appendix O icing conditions because, unlike for appendix C icing
conditions, the FAA cannot justify an assumption that the ice accretion
in this flight phase can be assumed insignificant. In practice, it is
expected that some applicants may use an operating limitation to
prohibit takeoff in appendix O icing conditions. Otherwise, the same
rationales behind the requirements are used for both appendix C and
appendix O icing conditions. For continued operation in appendix O
icing conditions, there should effectively be no degradation in
handling qualities, and any degradation in performance should be no
greater than that allowed by the regulations for appendix C icing
conditions.
Component Requirements for All Part 25 Transport Category Airplanes
In certification programs, both the airplane as a whole and its
individual components are evaluated for flight in icing conditions.
There are several rules in part 25 \15\ that contain icing related
requirements for specific components. We propose to revise those rules
to ensure the airplane can safely operate in the new icing conditions
established in this proposed rule.
---------------------------------------------------------------------------
\15\ 14 CFR 25.773, 25.929, 25.1093, 25.1323, and 25.1325.
---------------------------------------------------------------------------
Section 25.1419 requires that an airplane be able to safely operate
in all of the conditions specified in appendix C, whereas the proposed
Sec. 25.1420 would not require an airplane to safely operate in all of
the appendix O icing conditions. Proposed Sec. 25.1420(a)(1) and
(a)(2) only require an airplane to be capable of safely exiting icing
conditions after encountering an appendix O icing condition for which
that airplane will not be certified. The existing regulations for pilot
compartment view, airspeed indication
[[Page 37317]]
system, and static pressure system \16\ contain requirements for
operation in icing conditions. These sections would be revised to add
requirements for operation in appendix O icing conditions. Section
25.1323, Airspeed indicating system, would also be revised to include
and define mixed phase and ice crystal conditions. New proposed Sec.
25.1324 includes an icing requirement for angle of attack systems. This
would be similar to the icing requirements for airspeed indication
systems. The proposed section would require the angle of attack system
to be heated to prevent malfunction in appendices C and O icing
conditions and in the mixed phase and ice crystal conditions defined in
Sec. 25.1323.
---------------------------------------------------------------------------
\16\ 14 CFR 25.773, 25.1323, and 25.1325.
---------------------------------------------------------------------------
In the proposed revisions to the requirements for pilot compartment
view, airspeed indication system, and static pressure system,\17\ and
the new proposed requirements for angle of attack systems, an airplane
certified in accordance with Sec. 25.1420(a)(1) or (a)(2) would not be
required to be evaluated for all of appendix O. For airplanes certified
in accordance with Sec. 25.1420(a)(1), the icing conditions that the
airplane is certified to safely exit following detection must be
considered. For airplanes certified in accordance with Sec.
25.1420(a)(2), the icing conditions that the airplane is certified to
safely operate in, and to safely exit following detection, must be
considered. For airplanes certified in accordance with Sec.
25.1420(a)(3) and for airplanes not subject to Sec. 25.1420, all icing
conditions must be considered. Airplanes not certified for flight in
icing need not consider appendix O.
---------------------------------------------------------------------------
\17\ Ibid.
---------------------------------------------------------------------------
The engine induction system icing section (Sec. 25.1093) and
propeller deicing section (Sec. 25.929) contain requirements for
operation in icing conditions. As a conservative approach to ensure
safe operation of an airplane in an inadvertent encounter with icing,
the existing language in Sec. 25.1093 contains requirements for
operation in icing conditions, even for an airplane that is not
approved for flight in icing. Since proposed appendix O defines icing
conditions that also may be inadvertently encountered, Sec. 25.1093
would be revised to reference appendix O in its entirety. This would
maintain the FAA's conservative approach for this section. Section
25.929 (propeller deicing) would also be revised to reference appendix
O in its entirety.
Sections 25.929 and 25.1323 generically reference icing instead of
specifically mentioning appendix C. Historically, the icing conditions
specified in appendix C have been applied to these rules. For clarity,
we are revising Sec. Sec. 25.929 and 25.1323 so they specifically
reference appendix C, as well as appendix O. The proposed revisions to
icing regulations for pilot compartment view, propellers, engine
induction system icing protection, airspeed indication system, static
pressure system, and angle of attack system would be applicable to all
transport category airplanes to ensure safe operation during operations
in icing conditions.
The proposed revisions to Sec. 25.903 would retain the existing
regulations and add new subparagraphs to be consistent with the
proposed part 33 changes in Sec. 33.68. These revisions would allow
for approving new aircraft type certification programs with engines
certified to earlier amendment levels. The proposed revisions would
make it clear that the proposed part 33 changes would not be
retroactively imposed on an already type certified engine design,
unless service history indicated that an unsafe condition was present.
The proposed revision to Sec. 25.929 clarifies the meaning of the
words ``for airplanes intended for use where icing may be expected.''
The intent has been for the rule to be applicable to airplanes
certified for flight in icing.
Engine and Engine Installation Requirements
The proposed revisions to Sec. Sec. 25.1093, 33.68, and 33.77
would change the icing environmental requirements used to evaluate
engine protection and operation in icing conditions. The reason for
these changes is that the incident history of some airplanes has shown
that the current icing environmental requirements are inadequate. The
effect of the change would be to require an evaluation of safe
operation in the revised icing environment. The proposed revision to
Sec. 25.1093 restructures paragraph (b) and adds a new Table 1--Icing
Conditions for Ground Tests. The proposed rules would require engines
and engine installations to operate safely throughout the SLD
conditions defined in proposed new part 25, appendix O, and the newly
defined mixed phase and ice crystal conditions defined in proposed new
part 33, appendix D.\18\ The proposed appendix D was developed by the
ARAC Engine Harmonization Working Group and the Power Plant
Installation Harmonization Working Group, which included meteorologists
and icing research specialists from industry, FAA/FAA Tech Center,
Meteorological Services of Canada, National Aeronautics and Space
Administration (NASA), and Transport Canada/Transport Development
Center. The ARAC recommended appendix D and the FAA concurs with the
recommendation.
---------------------------------------------------------------------------
\18\ See FAA report DOT/FAA/AR-09/13, Technical Compendium from
Meetings of the Engine Harmonization Working Group, March 2009 for
details on appendix D and its development.
---------------------------------------------------------------------------
The proposed revision to Sec. 25.1521 would retain the existing
regulations and add a new subparagraph that would require an additional
operating limitation for turbine engine installations during ground
operation in icing conditions defined in Sec. 25.1093(b)(2). That
operating limitation would address the maximum time interval between
any engine run-ups from idle and the minimum ambient temperature
associated with that run-up interval. This limitation is necessary
because we do not currently have any specific requirements for run-up
procedures for engine ground operation in icing conditions. The engine
run-up procedure, including the maximum time interval between run-ups
from idle, run-up power setting, duration at power, and the minimum
ambient temperature demonstrated for that run-up interval proposed in
Sec. 25.1521, would be included in the Airplane Flight Manual in
accordance with existing Sec. 25.1581(a)(1) and Sec. 25.1583(b)(1).
The engine run-up procedure from ground idle to a moderate power or
thrust setting is necessary to shed ice build-up on the fan blades
before the quantity of ice reaches a level that could adversely affect
engine operation if ice is shed into the engine. The proposed revision
to Sec. 25.1521 would not require additional testing. The ice shedding
demonstration may be included as part of the Sec. 33.68 engine icing
testing.
Operating Limitations
The proposed revision to Sec. 25.1533 would establish an operating
limitation applicable to airplanes that are not certified in accordance
with proposed Sec. 25.1420(a)(1) or (a)(2). The flightcrews of these
airplanes would be required to exit all icing conditions if they
encounter appendix O icing conditions that the airplane has not been
certified to operate in.
Expansion of Proposed Icing Requirements
The proposed regulations \19\ for the airspeed indicating system
and angle of
[[Page 37318]]
attack system would address the operation of those systems in specific
mixed phase and ice crystal conditions, as defined in proposed Appendix
O. During the drafting of this NPRM the FAA became aware of airspeed
indicating system malfunctions in environmental conditions that may not
be addressed by these proposed regulations. The FAA is reviewing the
malfunctions and is considering the need to change the proposed mixed
phase and ice crystal parameters to include freezing rain. The maximum
mixed phase and ice crystal parameters that we are considering are
those defined in the proposed part 33, appendix D. The freezing rain
parameters that we are considering are based on standards some
manufacturers have used for airdata probes. The maximum freezing rain
parameters that we are considering are:
---------------------------------------------------------------------------
\19\ 14 CFR 25.1323, and 25.1324.
----------------------------------------------------------------------------------------------------------------
Static air temperature Altitude range Liquid Droplet
water MVD
content Horizontal extent
----------------------------------------------------------------------------------------------------------------
([deg]C) (ft) (m) (g/m3) (km) (nmiles) ([micro]
m)
----------------------------------------------------------------------------------------------------------------
-2 to 0............................... 0 to 10 000 0 to 3000 1 100 50 1000
6 5 3 2000
15 1 0.5 2000
----------------------------------------------------------------------------------------------------------------
We consider the mixed phase and ice crystal parameters defined in
the proposed part 33, appendix D, plus the freezing rain parameters
defined above to be adequate to prevent potential airspeed indicating
system malfunctions in these newly defined environmental conditions. We
request technical and economic comments on whether the proposed
airspeed indicating system and angle of attack system regulations
should include these expanded parameters. Based on comments we receive,
we may add these parameters to the final rule.
Differences From the ARAC Recommendations
The IPHWG recommended changes to parts 25 and 33 to ensure the safe
operation of airplanes and engines in icing conditions. The FAA concurs
with the recommendations, but has determined it is necessary to revise
to which airplanes the new airplane icing certification requirements in
the proposed Sec. 25.1420 would apply. The proposed Sec. 25.1420 in
this NPRM would apply to airplanes with either: (1) a takeoff maximum
gross weight of less than 60,000 lbs (27,000 kg), or (2) reversible
flight controls. An airplane with reversible flight controls in any
axis (pitch, roll, or yaw), even if these flight controls are
aerodynamically boosted and/or power-assisted, would be considered to
have reversible flight controls under this proposed rule. An airplane
with flight controls that are irreversible under normal operating
conditions, but are reversible following a failure, would not be
considered to have reversible flight controls under this proposed rule.
Reversible, aerodynamically boosted, and power-assisted flight controls
are defined in Appendix 1 to the preamble of this NPRM. The ADs
described above in section B. ``Prior FAA Actions to address the Safety
Concern'' are only applicable to airplanes equipped with both
reversible flight controls in the roll axis and pneumatic deicing
boots.
A group of IPHWG members (Boeing, Airbus, and Embraer, supported by
Cessna) held a minority position in their belief that the applicability
of the proposed Sec. 25.1420 should exclude airplanes with certain
design features. Their rationale for the position is that large
transport airplanes still in production have not experienced any
accidents or serious incidents as a result of flying in SLD icing
conditions. These manufacturers proposed that airplanes having all
three of the following design features should be excluded from
compliance with Sec. 25.1420:
(1) Gross weight in excess of 60,000 lbs (27,000 kg);
(2) Irreversible powered flight controls; and
(3) Wing leading-edge high-lift devices.
These manufacturers included the gross weight criterion in this
list, in part, because size has a direct bearing on an airplane's
susceptibility to the adverse effects of ice accretion. The size of an
airplane determines the sensitivity of its flight characteristics to
ice thickness and roughness. The relative effect of a given ice height
(or ice roughness height) decreases as airplane size increases.
The irreversible powered flight controls design feature was chosen,
in part, because using irreversible powered flight controls reduces an
airplane's susceptibility to SLD conditions. The concern that SLD
accretions can produce hinge moment or other anomalous control force/
trim effects is not applicable to those systems.
The wing leading-edge high-lift devices design feature was chosen,
in part, because, for wings without ice contamination, those devices
provide a considerable increase in the maximum lift coefficient (CLmax)
compared to fixed leading edges. When wings equipped with those devices
are contaminated with ice, they have smaller relative CLmax losses due
to ice accretion than wings with fixed leading edges.
The IPHWG majority (Air Line Pilots Association, International
(ALPA), Civil Aviation Authority for the United Kingdom (CAA/UK), FAA/
FAA Tech Center, Meteorological Services of Canada, National
Aeronautics and Space Administration (NASA), SAAB, Transport Canada/
Transport Development Center) did not accept the exclusion of airplanes
with the three aforementioned design features because one cannot
predict with confidence that the past service experience of airplanes
with these specific design features will be applicable to future
designs. The IPHWG majority recommended applying the new SLD airplane
certification requirements proposed in the new Sec. 25.1420 to all
future transport category airplane type designs.
The IPHWG majority opposed limiting the applicability of the rule
based on airplane gross weight, in part, because the ratio of wing and
control surface sizes to airplane weight varies between airplane
designs. Therefore, airplane takeoff weight is not a consistent
indicator of lifting and control surface size or chord, which are the
important parameters affecting sensitivity to a given ice accretion.
Excluding airplanes with irreversible flight controls was opposed,
in part, because hinge moment and other anomalous control forces are
not the only concern in SLD icing conditions. An irreversible control
surface may not be deflected by the SLD accumulation but the
aerodynamic efficiency of the control is likely to be degraded by the
presence of SLD icing in front of the control surface.
Excluding airplanes with wing leading edge high-lift devices was
opposed, in part, because there are many different designs for such
devices, which may not all be equally effective
[[Page 37319]]
in mitigating the negative effects of SLD ice accretions. The designs
for those devices include:
Slats that may be slotted or sealed to the basic wing
leading edge, over or under deflected, with deflection and slotting
that may be automated as a function of stall warning or airplane angle
of attack;
Krueger flaps that may be slotted or sealed to the wing
leading edge, flexed to optimum curvature or conformed to the wing's
leading edge lower surface; and
Vortilons or some other vortex creating devices.
In addition, for transport category airplanes with leading edge
high-lift devices, the spanwise extent of ice protection varies from
100 percent for some early turbo-jet airplane slats, to the span of two
slats for later airplane designs, to none for Krueger flaps. The
variations in the designs lead to varying degrees of aerodynamic
benefit. Without defining the specific performance benefits associated
with the above designs, the potential safety margins for SLD conditions
cannot be determined.
The complete minority and majority positions are discussed in the
working group report, which is available in the public docket.\20\
---------------------------------------------------------------------------
\20\ The complete IPHWG working group report is available on the
Internet at https://regulations.gov. A copy will also be placed in
the docket (FAA-2010-0636).
---------------------------------------------------------------------------
In order to propose a rule with the estimated costs commensurate
with the estimated benefits, the FAA determined the applicability of
the proposed rule should be limited based on service histories of
certified airplanes, and the assumption that similar future designs
will continue to not experience the safety problems addressed by this
proposal. Therefore, the FAA decided to revise the IPHWG rulemaking
recommendation by incorporating, in part, the IPHWG minority position
to exclude airplanes with certain design features.
The FAA continues to agree with the IPHWG majority position that
the presence (or conversely, the absence) of leading edge high lift
devices should not be used as a basis for determining the applicability
of the proposed Sec. 25.1420. There is insufficient data to conclude
either that every type of leading edge high lift device, or that a
specific leading edge high lift device design will affect (positively
or negatively) an airplane's ability to operate in SLD atmospheric
icing conditions. Also, leading edge high lift devices are only
deployed in certain phases of flight (for example, takeoff and
landing), and their deployment may differ for different flap
configurations. For example, a leading edge slat may be sealed in one
flap configuration, but slotted (that is, with a gap opened up between
the trailing edge of the slat and the wing) in others. Therefore, the
applicability of the proposed Sec. 25.1420 is not affected by the
presence or absence of leading edge high lift devices.
We request comment on whether this proposed rule, if adopted,
should be applied to airplanes larger than 60,000 pounds MTOW or
airplanes with other design features whose presence or absence would
result in the airplane being susceptible to safety problems while
operating in the SLD icing conditions defined in the proposed appendix
O, as well as the economic analysis associated with these
decisions.\21\
---------------------------------------------------------------------------
\21\ A copy of the Initial Regulatory Evaluation (dated October
5, 2009) can be found in the docket (FAA-2010-0636).
---------------------------------------------------------------------------
This NPRM also differs from the ARAC recommendation by proposing a
revision to Sec. 25.1533 for airplanes not certified to operate in all
of the SLD atmospheric icing conditions specified in the proposed new
appendix O (that is, airplanes certified in accordance with proposed
Sec. 25.1420(a)(1) or (a)(2)). The pro
