Special Conditions: Airbus Model A350-900 Airplanes; High-Speed Protection System, 49427-49429 [2014-19824]
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Federal Register / Vol. 79, No. 162 / Thursday, August 21, 2014 / Rules and Regulations
the anonymous comment is beyond the
scope of this special condition, and is
already accounted for and considered in
the basic regulatory-compliance process.
Applicability
As discussed above, these special
conditions apply to Airbus Model
A350–900 airplanes. Should Airbus
apply later for a change to the type
certificate to include another model
incorporating the same novel or unusual
design feature, the special conditions
would apply to that model as well.
Conclusion
This action affects only certain novel
or unusual design features on Airbus
Model A350–900 series airplanes. It is
not a rule of general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements.
The authority citation for these
special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701,
44702, 44704.
The Special Conditions
Accordingly, pursuant to the authority
delegated to me by the Administrator,
the following special conditions are
issued as part of the type-certification
basis for Airbus Model A350–900 series
airplanes.
In addition to § 25.143, the following
requirements apply: Operation of the
high-speed limiter during all routine
and descent-procedure flight must not
impede normal attainment of speeds up
to overspeed warning.
■
Issued in Renton, Washington, on August
15, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. 2014–19822 Filed 8–20–14; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
tkelley on DSK3SPTVN1PROD with RULES
[Docket No. FAA–2013–1001; Special
Conditions No. 25–535–SC]
Special Conditions: Airbus Model
A350–900 Airplanes; High-Speed
Protection System
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions.
AGENCY:
These special conditions are
issued for Airbus Model A350–900
SUMMARY:
VerDate Mar<15>2010
18:53 Aug 20, 2014
Jkt 232001
airplanes. These airplanes will have a
novel or unusual design feature
associated with a high-speed protection
system that limits nose-down pilot
authority at speeds above VC/MC, and
prevents the airplane from performing
the maneuver required under the Code
of Federal Regulations. The applicable
airworthiness regulations do not contain
adequate or appropriate safety standards
for this design feature. These special
conditions contain the additional safety
standards that the Administrator
considers necessary to establish a level
of safety equivalent to that established
by the existing airworthiness standards.
DATES: Effective date: September 22,
2014.
FOR FURTHER INFORMATION CONTACT:
Todd Martin, FAA, Airframe/Cabin
Safety, ANM–115, Transport Airplane
Directorate, Aircraft Certification
Service, 1601 Lind Avenue SW.,
Renton, Washington 98057–3356;
telephone (425) 227–1178; facsimile
(425) 227–1322.
SUPPLEMENTARY INFORMATION:
Background
On August 25, 2008, Airbus applied
for a type certificate for their new Model
A350–900 airplane. Later, Airbus
requested, and the FAA approved, an
extension to the application for FAA
type certification to November 15, 2009.
The Model A350–900 airplane has a
conventional layout with twin wingmounted Rolls-Royce Trent XWB
engines. It features a twin-aisle, 9abreast, economy-class layout, and
accommodates side-by-side placement
of LD–3 containers in the cargo
compartment. The basic Model A350–
900 airplane configuration
accommodates 315 passengers in a
standard two-class arrangement. The
design cruise speed is Mach 0.85 with
a maximum take-off weight of 602,000
lbs.
The Model A350–900 airplane, like
Airbus Model A320, A330, A340 and
A380 series airplanes, has a high-speed
protection system that limits nose-down
pilot authority at speeds above VC/MC,
and prevents the airplane from actually
performing the maneuver required
under § 25.335(b)(1). Special conditions
are necessary to address the Model
A350–900 airplane high-speed
protection system. These special
conditions identify various symmetric
and non-symmetric maneuvers that will
ensure that an appropriate design dive
speed, VD/MD, is established.
Type Certification Basis
Under Title 14, Code of Federal
Regulations (14 CFR) 21.17, Airbus must
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Fmt 4700
Sfmt 4700
49427
show that the Model A350–900 airplane
meets the applicable provisions of part
25, as amended by Amendments 25–1
through 25–129.
If the Administrator finds that the
applicable airworthiness regulations
(i.e., 14 CFR part 25) do not contain
adequate or appropriate safety standards
for the Model A350–900 airplane
because of a novel or unusual design
feature, special conditions are
prescribed under the provisions of
§ 21.16.
Special conditions are initially
applicable to the model for which they
are issued. Should the type certificate
for that model be amended later to
include any other model that
incorporates the same or similar novel
or unusual design feature, the special
conditions would also apply to the other
model under § 21.101.
In addition to the applicable
airworthiness regulations and special
conditions, the Model A350–900
airplane must comply with the fuel-vent
and exhaust-emission requirements of
14 CFR part 34, and the noisecertification requirements of 14 CFR
part 36. The FAA must issue a finding
of regulatory adequacy under section
611 of Public Law 92–574, the ‘‘Noise
Control Act of 1972.’’
The FAA issues special conditions, as
defined in 14 CFR 11.19, under § 11.38,
and they become part of the typecertification basis under § 21.17(a)(2).
Novel or Unusual Design Features
In addition to the applicable
airworthiness regulations and special
conditions, the Model A350–900
airplane must comply with the fuel-vent
and exhaust-emission requirements of
14 CFR part 34, and the noisecertification requirements of 14 CFR
part 36. The FAA must issue a finding
of regulatory adequacy under § 611 of
Public Law 92–574, the ‘‘Noise Control
Act of 1972.’’
The Airbus Model A350–900 airplane
will incorporate the following novel or
unusual design features:
A high-speed protection system that
limits nose-down pilot authority at
speeds above VC/MC, and prevents the
airplane from actually performing the
maneuver required under § 25.335(b)(1).
The special conditions identify various
symmetric and non-symmetric
maneuvers that will ensure that an
appropriate design dive speed, VD/MD,
is established.
Discussion
Section 25.335(b)(1) is an analytical
envelope condition originally adopted
in Part 4b of the Civil Air Regulations
to provide an acceptable speed margin
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21AUR1
tkelley on DSK3SPTVN1PROD with RULES
49428
Federal Register / Vol. 79, No. 162 / Thursday, August 21, 2014 / Rules and Regulations
between design cruise speed and design
dive speed. Flutter-clearance design
speeds and airframe design loads are
impacted by the design dive speed.
While the initial condition for the upset
specified in the rule is 1g level flight,
protection is afforded for other
inadvertent overspeed conditions as
well. Section 25.335(b)(1) is intended as
a conservative enveloping condition for
potential overspeed conditions,
including non-symmetric conditions.
To establish that potential overspeed
conditions are enveloped, Airbus
should demonstrate that any reduced
speed margin, based on the high-speed
protection system in the Model A350–
900 airplane, will not be exceeded in
inadvertent, or gust-induced, upsets
resulting in initiation of the dive from
non-symmetric attitudes; or that the
airplane is protected, by the flightcontrol laws, from getting into nonsymmetric upset conditions. The special
conditions identify various symmetric
and non-symmetric maneuvers that will
ensure that an appropriate design dive
speed, VD/MD, is established.
These special conditions are in lieu of
§ 25.335(b)(1). Section 25.335(b)(2),
which also addresses the design dive
speed, is applied separately (Advisory
Circular (AC) 25.335–1A provides an
acceptable means of compliance to
§ 25.335(b)(2)). The applicant should
conduct a demonstration that includes a
comprehensive set of conditions, as
described below.
Special conditions (3) and (4) indicate
that failures of the high-speed
protection system must be improbable
and must be annunciated to the pilots.
If these two criteria are not met, then the
probability that the established dive
speed will be exceeded, and the
resulting risk to the airplane, is too
great. On the other hand, if the highspeed protection system is known to be
inoperative, then dispatch of the
airplane could be acceptable under an
approved minimum-equipment list
(MEL) containing language similar to
special condition (5). Dispatch under an
MEL would require that appropriate
reduced operating speeds, VMO/MMO,
are provided in the airplane flight
manual (AFM), and the cockpit display
of those reduced speeds, as well as the
overspeed warning for exceeding those
speeds, are equivalent to that of the
normal airplane with the high-speed
protection system operative.
We do not believe that application of
the Interaction of Systems and
Structures special conditions (docket
no. FAA–2013–0894), or the European
Aviation Safety Agency (EASA)
Certification Specification (CS) 25.302,
is appropriate in this case because
VerDate Mar<15>2010
18:53 Aug 20, 2014
Jkt 232001
design dive speed is, in and of itself,
part of the design criteria. Stability and
control, flight loads, and flutter
evaluations all depend on the design
dive speed. Therefore, a single design
dive speed should be established that
will not be exceeded, taking into
account the performance of the highspeed protection system as well as its
failure modes, failure indications, and
accompanying AFM instructions.
These special conditions contain the
additional safety standards that the
Administrator considers necessary to
establish a level of safety equivalent to
that established by the existing
airworthiness standards.
Discussion of Comments
Notice of proposed special conditions
No. 25–13–35–SC for Airbus Model
A350–900 airplanes was published in
the Federal Register on December 24,
2013 (78 FR 77611). No comments were
received and the special conditions are
adopted as proposed.
Applicability
As discussed above, these special
conditions apply to Airbus Model
A350–900 airplanes. Should Airbus
apply at a later date for a change to the
type certificate to include another
airplane series incorporating the same
novel or unusual design feature, the
special conditions would apply to that
series as well.
Conclusion
This action affects only certain novel
or unusual design features on the Airbus
Model A350–900 series airplanes. It is
not a rule of general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements.
The authority citation for these
special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701,
44702 and 44704.
The Special Conditions
Accordingly, pursuant to the
authority delegated to me by the
Administrator, the following special
conditions are issued as part of the typecertification basis for Airbus Model
A350–900 series airplanes.
1. In lieu of compliance with
§ 25.335(b)(1), if the flight-control
system includes functions that act
automatically to initiate recovery before
the end of the 20-second period
specified in § 25.335(b)(1), VD/MD must
be determined from the greater of the
speeds resulting from conditions (a) and
(b), below. The speed increase occurring
in these maneuvers may be calculated if
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Frm 00006
Fmt 4700
Sfmt 4700
reliable or conservative aerodynamic
data are used.
a. From an initial condition of
stabilized flight at VC/MC, the airplane
is upset so as to travel a new flight path
7.5 degrees below the initial path.
Control application, up to full authority,
is made to try to maintain this new
flight path. Twenty seconds after
initiating the upset, manual recovery is
made at a load factor of 1.5 g (0.5
acceleration increment), or such greater
load factor that is automatically applied
by the system with the pilot’s pitch
control set to neutral. Power, as
specified in § 25.175(b)(1)(iv), is
assumed until recovery is initiated, at
which time power reduction and the use
of pilot-controlled drag devices may be
used.
b. From a speed below VC/MC, with
power to maintain stabilized level flight
at this speed, the airplane is upset so as
to accelerate through VC/MC at a flight
path 15 degrees below the initial path
(or at the steepest nose-down attitude
that the system will permit with full
control authority, if less than 15
degrees). The pilot’s controls may be in
the neutral position after reaching VC/
MC and before recovery is initiated.
Recovery may be initiated three seconds
after operation of the high-speed
warning system by application of a load
of 1.5g (0.5 acceleration increment), or
such greater load factor that is
automatically applied by the system
with the pilot’s pitch control set to
neutral. Power may be reduced
simultaneously. All other means of
decelerating the airplane, the use of
which is authorized up to the highest
speed reached in the maneuver, may be
used. The interval between successive
pilot actions must not be less than one
second.
2. The applicant must also
demonstrate that the speed margin,
established as above, will not be
exceeded in inadvertent, or gustinduced, upsets resulting in initiation of
the dive from non-symmetric attitudes,
unless the airplane is protected by the
flight-control laws from getting into
non-symmetric upset conditions. The
upset maneuvers described in AC 25–
7C, Chapter 2, Section 8, Paragraph
32c.(3)(a) and (c), may be used to
comply with this requirement.
3. Detected loss of the high-speed
protection function must be less than
10¥3 per flight hour.
4. Failures of the system must be
annunciated to the pilots. The
Operating Limitations Section of the
AFM must contain instructions that
reduce the maximum operating speeds,
Vmax/Mmax, to a value that maintains a
speed margin between these speeds and
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Federal Register / Vol. 79, No. 162 / Thursday, August 21, 2014 / Rules and Regulations
VD/MD that is consistent with showing
compliance to § 25.335(b), without the
benefit of the high-speed protection
system.
5. Dispatch of the airplane with the
high-speed protection system
inoperative is prohibited except under
an approved MEL that requires AFM
instructions to indicate reduced
maximum operating speeds, as
described in special condition (4),
above. In addition, the cockpit display
of the reduced operating speeds, as well
as the overspeed warning for exceeding
those speeds, must be equivalent to that
of the normal airplane with the highspeed protection system operative. Also,
it must be shown that no additional
hazards are introduced with the highspeed protection system inoperative.
Issued in Renton, Washington, on July 30,
2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. 2014–19824 Filed 8–20–14; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA–2013–0908; Special
Conditions No. 25–538–SC]
Special Conditions: Airbus Model
A350–900 Series Airplane; Airplane
Level of Safety Provided by Composite
Fuel-Tank Structure: Post-Crash Fire
Survivability
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions.
AGENCY:
These special conditions are
issued for Airbus Model A350–900
series airplanes. These airplanes will
have a novel or unusual design feature
associated with the post-crash fire
survivability of composite fuel tanks.
The applicable airworthiness
regulations do not contain adequate or
appropriate safety standards for this
design feature. These special conditions
contain the additional safety standards
that the Administrator considers
necessary to establish a level of safety
equivalent to that established by the
existing airworthiness standards.
DATES: Effective date: September 22,
2014.
tkelley on DSK3SPTVN1PROD with RULES
SUMMARY:
FOR FURTHER INFORMATION CONTACT:
Doug Bryant, Propulsion and
Mechanical Systems, ANM–112,
Transport Airplane Directorate, Aircraft
VerDate Mar<15>2010
18:53 Aug 20, 2014
Jkt 232001
Certification Service, 1601 Lind Avenue
SW., Renton, Washington 98057–3356;
telephone (425) 227–2384; facsimile
(425) 227–1320.
SUPPLEMENTARY INFORMATION:
Background
On August 25, 2008, Airbus applied
for a type certificate for their new Model
A350–900 series airplane. Later, Airbus
requested, and the FAA approved, an
extension to the application for FAA
type certification to November 15, 2009.
The Model A350–900 series airplane
has a conventional layout with twin
wing-mounted Rolls-Royce Trent XWB
engines. It features a twin-aisle, 9abreast, economy-class layout, and
accommodates side-by-side placement
of LD–3 containers in the cargo
compartment. The basic Model A350–
900 series airplane configuration
accommodates 315 passengers in a
standard two-class arrangement. The
design cruise speed is Mach 0.85 with
a maximum take-off weight of 602,000
lbs.
The Model A350–900 series airplane
will be the second large, transportcategory airplane certificated with
composite wing and fuel-tank structure
that may be exposed to the direct effects
of post-crash ground, or under-wing,
fuel-fed fires. Although the FAA has
previously approved fuel tanks made of
composite materials located in the
horizontal stabilizer of some airplanes,
the composite wing structure of the
Model A350–900 series airplane will
incorporate a new fuel-tank
construction into service.
Advisory Circular (AC) 20–107A,
Composite Aircraft Structure, under the
topic of flammability, states:
The existing requirements for
flammability and fire protection of
aircraft structure attempt to minimize
the hazard to the occupants in the event
ignition of flammable fluids or vapors
occurs. The use of composite structure
should not decrease this existing level
of safety.
Pertinent to the wing structure, postcrash-fire passenger survivability is
dependent on the time available for
passenger evacuation prior to fuel-tank
breach or structural failure. Structural
failure can be a result of degradation in
load-carrying capability in the upper or
lower wing surface caused by a fuel-fed
ground fire. Structural failure can also
be a result of over-pressurization caused
by ignition of fuel vapors inside the fuel
tank.
The inherent capability of aluminum
to resist fire has been considered by the
FAA in development of the current
regulations. Title 14, Code of Federal
Regulations (14 CFR) part 25 Chapter 1,
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Fmt 4700
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49429
Section 1.1, General Definitions, defines
‘‘fire resistant’’ to mean, with respect to
sheet or structural members, the
capacity to withstand heat associated
with fire at least as well as aluminum
alloy does in dimensions appropriate for
the purpose for which those materials
are used.
Note that aluminum alloy is identified
as the performance standard for fire
resistance, although no thickness or heat
intensities are defined. Based on the
performance of aluminum alloy, the
definition of ‘‘fire resistance’’ was later
defined, for testing of other materials in
AC 20–135, as the capability to
withstand a 2000 °F flame for five
minutes.
The FAA has historically issued rules
with the assumption that the material of
construction for wing and fuselage
would be aluminum. As a representative
case, 14 CFR 25.963 was issued as a
result of a large, fuel-fed fire following
the failures of fuel-tank access doors
caused by uncontained engine failures.
During the subsequent Aviation
Rulemaking Advisory Committee
(ARAC) harmonization process, the
structures group attempted to
harmonize § 25.963 regarding the
impact-and-fire resistance of the fueltank access panels. Discussions between
the FAA and the European Aviation
Safety Agency (EASA), formerly the
European Joint Aviation Authorities
(JAA), ensued regarding the need for fire
resistance of the fuel-tank access panels.
The EASA position was that the FAA
requirement for the access panels to be
fire resistant, when the surrounding
wing structure was not required to be
fire resistant, was inconsistent, and that
the access panels only needed to be as
fire resistant as the surrounding tank
structure. The FAA position stated that
the fuel-tank access-panel fire-resistance
requirement should be retained, and
that, long-term, a minimum requirement
should be created for the wing skin
itself. Both authorities recognized that
existing aluminum wing structure
provided an acceptable level of safety.
Further rulemaking has not yet been
pursued.
As with previous Airbus airplane
designs with under-wing-mounted
engines, the wing tanks and center tanks
are located in proximity to the
passengers and near the engines. Past
experience indicates that post-crash
survivability is greatly influenced by the
size and intensity of any fire that occurs.
The ability of aluminum wing surfaces,
wetted by fuel on their interior surface,
to withstand post-crash fire conditions,
has been demonstrated by tests
conducted at the FAA William J.
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]]>Agencies
[Federal Register Volume 79, Number 162 (Thursday, August 21, 2014)]
[Rules and Regulations]
[Pages 49427-49429]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-19824]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2013-1001; Special Conditions No. 25-535-SC]
Special Conditions: Airbus Model A350-900 Airplanes; High-Speed
Protection System
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
-----------------------------------------------------------------------
SUMMARY: These special conditions are issued for Airbus Model A350-900
airplanes. These airplanes will have a novel or unusual design feature
associated with a high-speed protection system that limits nose-down
pilot authority at speeds above VC/MC, and
prevents the airplane from performing the maneuver required under the
Code of Federal Regulations. The applicable airworthiness regulations
do not contain adequate or appropriate safety standards for this design
feature. These special conditions contain the additional safety
standards that the Administrator considers necessary to establish a
level of safety equivalent to that established by the existing
airworthiness standards.
DATES: Effective date: September 22, 2014.
FOR FURTHER INFORMATION CONTACT: Todd Martin, FAA, Airframe/Cabin
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone
(425) 227-1178; facsimile (425) 227-1322.
SUPPLEMENTARY INFORMATION:
Background
On August 25, 2008, Airbus applied for a type certificate for their
new Model A350-900 airplane. Later, Airbus requested, and the FAA
approved, an extension to the application for FAA type certification to
November 15, 2009. The Model A350-900 airplane has a conventional
layout with twin wing-mounted Rolls-Royce Trent XWB engines. It
features a twin-aisle, 9-abreast, economy-class layout, and
accommodates side-by-side placement of LD-3 containers in the cargo
compartment. The basic Model A350-900 airplane configuration
accommodates 315 passengers in a standard two-class arrangement. The
design cruise speed is Mach 0.85 with a maximum take-off weight of
602,000 lbs.
The Model A350-900 airplane, like Airbus Model A320, A330, A340 and
A380 series airplanes, has a high-speed protection system that limits
nose-down pilot authority at speeds above VC/MC,
and prevents the airplane from actually performing the maneuver
required under Sec. 25.335(b)(1). Special conditions are necessary to
address the Model A350-900 airplane high-speed protection system. These
special conditions identify various symmetric and non-symmetric
maneuvers that will ensure that an appropriate design dive speed,
VD/MD, is established.
Type Certification Basis
Under Title 14, Code of Federal Regulations (14 CFR) 21.17, Airbus
must show that the Model A350-900 airplane meets the applicable
provisions of part 25, as amended by Amendments 25-1 through 25-129.
If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the Model A350-900 airplane because of
a novel or unusual design feature, special conditions are prescribed
under the provisions of Sec. 21.16.
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same or similar
novel or unusual design feature, the special conditions would also
apply to the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Model A350-900 airplane must comply with the fuel-vent
and exhaust-emission requirements of 14 CFR part 34, and the noise-
certification requirements of 14 CFR part 36. The FAA must issue a
finding of regulatory adequacy under section 611 of Public Law 92-574,
the ``Noise Control Act of 1972.''
The FAA issues special conditions, as defined in 14 CFR 11.19,
under Sec. 11.38, and they become part of the type-certification basis
under Sec. 21.17(a)(2).
Novel or Unusual Design Features
In addition to the applicable airworthiness regulations and special
conditions, the Model A350-900 airplane must comply with the fuel-vent
and exhaust-emission requirements of 14 CFR part 34, and the noise-
certification requirements of 14 CFR part 36. The FAA must issue a
finding of regulatory adequacy under Sec. 611 of Public Law 92-574,
the ``Noise Control Act of 1972.''
The Airbus Model A350-900 airplane will incorporate the following
novel or unusual design features:
A high-speed protection system that limits nose-down pilot
authority at speeds above VC/MC, and prevents the
airplane from actually performing the maneuver required under Sec.
25.335(b)(1). The special conditions identify various symmetric and
non-symmetric maneuvers that will ensure that an appropriate design
dive speed, VD/MD, is established.
Discussion
Section 25.335(b)(1) is an analytical envelope condition originally
adopted in Part 4b of the Civil Air Regulations to provide an
acceptable speed margin
[[Page 49428]]
between design cruise speed and design dive speed. Flutter-clearance
design speeds and airframe design loads are impacted by the design dive
speed. While the initial condition for the upset specified in the rule
is 1g level flight, protection is afforded for other inadvertent
overspeed conditions as well. Section 25.335(b)(1) is intended as a
conservative enveloping condition for potential overspeed conditions,
including non-symmetric conditions.
To establish that potential overspeed conditions are enveloped,
Airbus should demonstrate that any reduced speed margin, based on the
high-speed protection system in the Model A350-900 airplane, will not
be exceeded in inadvertent, or gust-induced, upsets resulting in
initiation of the dive from non-symmetric attitudes; or that the
airplane is protected, by the flight-control laws, from getting into
non-symmetric upset conditions. The special conditions identify various
symmetric and non-symmetric maneuvers that will ensure that an
appropriate design dive speed, VD/MD, is
established.
These special conditions are in lieu of Sec. 25.335(b)(1). Section
25.335(b)(2), which also addresses the design dive speed, is applied
separately (Advisory Circular (AC) 25.335-1A provides an acceptable
means of compliance to Sec. 25.335(b)(2)). The applicant should
conduct a demonstration that includes a comprehensive set of
conditions, as described below.
Special conditions (3) and (4) indicate that failures of the high-
speed protection system must be improbable and must be annunciated to
the pilots. If these two criteria are not met, then the probability
that the established dive speed will be exceeded, and the resulting
risk to the airplane, is too great. On the other hand, if the high-
speed protection system is known to be inoperative, then dispatch of
the airplane could be acceptable under an approved minimum-equipment
list (MEL) containing language similar to special condition (5).
Dispatch under an MEL would require that appropriate reduced operating
speeds, VMO/MMO, are provided in the airplane
flight manual (AFM), and the cockpit display of those reduced speeds,
as well as the overspeed warning for exceeding those speeds, are
equivalent to that of the normal airplane with the high-speed
protection system operative.
We do not believe that application of the Interaction of Systems
and Structures special conditions (docket no. FAA-2013-0894), or the
European Aviation Safety Agency (EASA) Certification Specification (CS)
25.302, is appropriate in this case because design dive speed is, in
and of itself, part of the design criteria. Stability and control,
flight loads, and flutter evaluations all depend on the design dive
speed. Therefore, a single design dive speed should be established that
will not be exceeded, taking into account the performance of the high-
speed protection system as well as its failure modes, failure
indications, and accompanying AFM instructions.
These special conditions contain the additional safety standards
that the Administrator considers necessary to establish a level of
safety equivalent to that established by the existing airworthiness
standards.
Discussion of Comments
Notice of proposed special conditions No. 25-13-35-SC for Airbus
Model A350-900 airplanes was published in the Federal Register on
December 24, 2013 (78 FR 77611). No comments were received and the
special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions apply to Airbus Model
A350-900 airplanes. Should Airbus apply at a later date for a change to
the type certificate to include another airplane series incorporating
the same novel or unusual design feature, the special conditions would
apply to that series as well.
Conclusion
This action affects only certain novel or unusual design features
on the Airbus Model A350-900 series airplanes. It is not a rule of
general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702 and 44704.
The Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type-certification basis for Airbus Model A350-900 series
airplanes.
1. In lieu of compliance with Sec. 25.335(b)(1), if the flight-
control system includes functions that act automatically to initiate
recovery before the end of the 20-second period specified in Sec.
25.335(b)(1), VD/MD must be determined from the
greater of the speeds resulting from conditions (a) and (b), below. The
speed increase occurring in these maneuvers may be calculated if
reliable or conservative aerodynamic data are used.
a. From an initial condition of stabilized flight at VC/
MC, the airplane is upset so as to travel a new flight path
7.5 degrees below the initial path. Control application, up to full
authority, is made to try to maintain this new flight path. Twenty
seconds after initiating the upset, manual recovery is made at a load
factor of 1.5 g (0.5 acceleration increment), or such greater load
factor that is automatically applied by the system with the pilot's
pitch control set to neutral. Power, as specified in Sec.
25.175(b)(1)(iv), is assumed until recovery is initiated, at which time
power reduction and the use of pilot-controlled drag devices may be
used.
b. From a speed below VC/MC, with power to
maintain stabilized level flight at this speed, the airplane is upset
so as to accelerate through VC/MC at a flight
path 15 degrees below the initial path (or at the steepest nose-down
attitude that the system will permit with full control authority, if
less than 15 degrees). The pilot's controls may be in the neutral
position after reaching VC/MC and before recovery
is initiated. Recovery may be initiated three seconds after operation
of the high-speed warning system by application of a load of 1.5g (0.5
acceleration increment), or such greater load factor that is
automatically applied by the system with the pilot's pitch control set
to neutral. Power may be reduced simultaneously. All other means of
decelerating the airplane, the use of which is authorized up to the
highest speed reached in the maneuver, may be used. The interval
between successive pilot actions must not be less than one second.
2. The applicant must also demonstrate that the speed margin,
established as above, will not be exceeded in inadvertent, or gust-
induced, upsets resulting in initiation of the dive from non-symmetric
attitudes, unless the airplane is protected by the flight-control laws
from getting into non-symmetric upset conditions. The upset maneuvers
described in AC 25-7C, Chapter 2, Section 8, Paragraph 32c.(3)(a) and
(c), may be used to comply with this requirement.
3. Detected loss of the high-speed protection function must be less
than 10-3 per flight hour.
4. Failures of the system must be annunciated to the pilots. The
Operating Limitations Section of the AFM must contain instructions that
reduce the maximum operating speeds, Vmax/Mmax,
to a value that maintains a speed margin between these speeds and
[[Page 49429]]
VD/MD that is consistent with showing compliance
to Sec. 25.335(b), without the benefit of the high-speed protection
system.
5. Dispatch of the airplane with the high-speed protection system
inoperative is prohibited except under an approved MEL that requires
AFM instructions to indicate reduced maximum operating speeds, as
described in special condition (4), above. In addition, the cockpit
display of the reduced operating speeds, as well as the overspeed
warning for exceeding those speeds, must be equivalent to that of the
normal airplane with the high-speed protection system operative. Also,
it must be shown that no additional hazards are introduced with the
high-speed protection system inoperative.
Issued in Renton, Washington, on July 30, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2014-19824 Filed 8-20-14; 8:45 am]
BILLING CODE 4910-13-P
