Special Conditions: Boeing Model 777-9 Airplane; Tire Debris Penetration of Fuel Tank Structure, 23456-23458 [2019-10703]
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Federal Register / Vol. 84, No. 99 / Wednesday, May 22, 2019 / Rules and Regulations
paragraph VIII.B.5 of this appendix. Further,
the petition must demonstrate that the
change bears on an asserted noncompliance
with an ITAAC acceptance criterion in the
case of a § 52.103 preoperational hearing, or
that the change bears directly on the
amendment request in the case of a hearing
on a license amendment. Any other party
may file a response. If, on the basis of the
petition and any response, the presiding
officer determines that a sufficient showing
has been made, the presiding officer shall
certify the matter directly to the Commission
for determination of the admissibility of the
contention. The Commission may admit such
a contention if it determines the petition
raises a genuine issue of material fact
regarding compliance with paragraph VIII.B.5
of this appendix.
this appendix was approved, as set forth in
Section V of this appendix. Any other party
may file a response to the petition. If, on the
basis of the petition and any response, the
presiding officer determines that a sufficient
showing has been made, the presiding officer
shall certify the matter directly to the
Commission for determination of the
admissibility of the contention. All other
issues with respect to the plant-specific TS
or other operational requirements are subject
to a hearing as part of the licensing
proceeding.
6. After issuance of a license, the generic
TS have no further effect on the plantspecific TS. Changes to the plant-specific TS
will be treated as license amendments under
10 CFR 50.90.
C. Operational Requirements
1. Changes to APR1400 DC generic TS and
other operational requirements that were
completely reviewed and approved in the
design certification rulemaking and do not
require a change to a design feature in the
generic DCD are governed by the
requirements in 10 CFR 50.109. Changes that
require a change to a design feature in the
generic DCD are governed by the
requirements in paragraphs A or B of this
section.
2. Changes to APR1400 DC generic TS and
other operational requirements are applicable
to all applicants who reference this
appendix, except those for which the change
has been rendered technically irrelevant by
action taken under paragraphs C.3 or C.4 of
this section.
3. The Commission may require plantspecific departures on generic TS and other
operational requirements that were
completely reviewed and approved, provided
a change to a design feature in the generic
DCD is not required and special
circumstances, as defined in 10 CFR 2.335
are present. The Commission may modify or
supplement generic TS and other operational
requirements that were not completely
reviewed and approved or require additional
TS and other operational requirements on a
plant-specific basis, provided a change to a
design feature in the generic DCD is not
required.
4. An applicant who references this
appendix may request an exemption from the
generic TS or other operational requirements.
The Commission may grant such a request
only if it determines that the exemption will
comply with the requirements of § 52.7. The
granting of an exemption must be subject to
litigation in the same manner as other issues
material to the license hearing.
5. A party to an adjudicatory proceeding
for the issuance, amendment, or renewal of
a license, or for operation under § 52.103(a),
who believes that an operational requirement
approved in the DCD or a TS derived from
the generic TS must be changed, may petition
to admit such a contention into the
proceeding. The petition must comply with
the general requirements of 10 CFR 2.309 and
must demonstrate why special circumstances
as defined in 10 CFR 2.335 are present, or
demonstrate compliance with the
Commission’s regulations in effect at the time
X. Records and Reporting
VerDate Sep<11>2014
15:56 May 21, 2019
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IX. [Reserved]
A. Records
1. The applicant for this appendix shall
maintain a copy of the generic DCD that
includes all generic changes that are made to
Tier 1 and Tier 2, and the generic TS and
other operational requirements. The
applicant shall maintain the sensitive
unclassified non-safeguards information
(including proprietary information and
security-related information) and safeguards
information referenced in the generic DCD
for the period that this appendix may be
referenced, as specified in Section VII of this
appendix.
2. An applicant or licensee who references
this appendix shall maintain the plantspecific DCD to accurately reflect both
generic changes to the generic DCD and
plant-specific departures made under Section
VIII of this appendix throughout the period
of application and for the term of the license
(including any periods of renewal).
3. An applicant or licensee who references
this appendix shall prepare and maintain
written evaluations which provide the bases
for the determinations required by Section
VIII of this appendix. These evaluations must
be retained throughout the period of
application and for the term of the license
(including any periods of renewal).
4.a. The applicant for the APR1400 design
shall maintain a copy of the aircraft impact
assessment performed to comply with the
requirements of 10 CFR 50.150(a) for the term
of the certification (including any period of
renewal).
b. An applicant or licensee who references
this appendix shall maintain a copy of the
aircraft impact assessment performed to
comply with the requirements of 10 CFR
50.150(a) throughout the pendency of the
application and for the term of the license
(including any periods of renewal).
B. Reporting
1. An applicant or licensee who references
this appendix shall submit a report to the
NRC containing a brief description of any
plant-specific departures from the DCD,
including a summary of the evaluation of
each departure. This report must be filed in
accordance with the filing requirements
applicable to reports in § 52.3.
2. An applicant or licensee who references
this appendix shall submit updates to its
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plant-specific DCD, which reflect the generic
changes to and plant-specific departures from
the generic DCD made under Section VIII of
this appendix. These updates shall be filed
under the filing requirements applicable to
final safety analysis report updates in 10 CFR
50.71(e) and 52.3.
3. The reports and updates required by
paragraphs X.B.1 and X.B.2 of this appendix
must be submitted as follows:
a. On the date that an application for a
license referencing this appendix is
submitted, the application must include the
report and any updates to the generic DCD.
b. During the interval from the date of
application for a license to the date the
Commission makes its finding required by
§ 52.103(g), the report must be submitted
semi-annually. Updates to the plant-specific
DCD must be submitted annually and may be
submitted along with amendments to the
application.
c. After the Commission makes the finding
required by § 52.103(g), the reports and
updates to the plant-specific DCD must be
submitted, along with updates to the sitespecific portion of the final safety analysis
report for the facility, at the intervals
required by 10 CFR 50.59(d)(2) and
50.71(e)(4), respectively, or at shorter
intervals as specified in the license.
Dated at Rockville, Maryland, this 17th day
of May 2019.
For the Nuclear Regulatory Commission.
Annette Vietti-Cook,
Secretary of the Commission.
[FR Doc. 2019–10715 Filed 5–21–19; 8:45 am]
BILLING CODE 7590–01–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA–2018–1015; Special
Conditions No. 25–746–SC]
Special Conditions: Boeing Model 777–
9 Airplane; Tire Debris Penetration of
Fuel Tank Structure
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions; request
for comments.
AGENCY:
These special conditions are
issued for The Boeing Company
(Boeing) Model 777–9 airplane. This
airplane will have a novel or unusual
design feature when compared to the
state of technology envisioned in the
airworthiness standards for transport
category airplanes. This design feature
is composite fuel tanks that may be
subject to tire-debris penetration of the
fuel tanks. The applicable airworthiness
regulations do not contain adequate or
appropriate safety standards for this
design feature. These special conditions
SUMMARY:
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Federal Register / Vol. 84, No. 99 / Wednesday, May 22, 2019 / Rules and Regulations
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: This action is effective on Boeing
on May 22, 2019. Send comments on or
before July 8, 2019.
ADDRESSES: Send comments identified
by Docket No. FAA–2018–1015 using
any of the following methods:
• Federal eRegulations 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 (DOT), 1200 New Jersey
Avenue SE, Room W12–140, West
Building Ground Floor, Washington, DC
20590–0001.
• Hand Delivery or Courier: Take
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.
Privacy: The FAA will post all
comments it receives, without change,
to https://www.regulations.gov/,
including any personal information the
commenter provides. Using the search
function of the docket website, anyone
can find and read the electronic form of
all comments received into any FAA
docket, including the name of the
individual sending the comment (or
signing the comment for an association,
business, labor union, etc.). DOT’s
complete Privacy Act Statement can be
found in the Federal Register published
on April 11, 2000 (65 FR 19477–19478).
Docket: Background documents or
comments received may be read at
https://www.regulations.gov/ at any time.
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:
Suzanne Lucier, Propulsion and
Mechanical Systems Section, AIR–672,
Transport Standards Branch, Policy and
Innovation Division, Aircraft
Certification Service, Federal Aviation
Administration, 2200 South 216th
Street, Des Moines, Washington 98198;
telephone and fax 206–231–3173; email
suzanne.lucier@faa.gov.
SUPPLEMENTARY INFORMATION: The
substance of these special conditions
has been published in the Federal
VerDate Sep<11>2014
15:56 May 21, 2019
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Register for public comment in several
prior instances with no substantive
comments received. Therefore, the FAA
has determined that prior public notice
and comment are unnecessary, and
finds that, for the same reason, good
cause exists for adopting these special
conditions upon publication in the
Federal Register.
Comments Invited
We invite interested people to take
part in this rulemaking by sending
written comments, data, or views. The
most helpful comments reference a
specific portion of the special
conditions, explain the reason for any
recommended change, and include
supporting data.
We will consider all comments we
receive by the closing date for
comments. We may change these special
conditions based on the comments we
receive.
Background
On March 12, 2015, Boeing applied
for an amendment to Type Certificate
No. T00001SE to include the new 777–
9 airplane. This airplane, which is a
derivative of the Boeing Model 777
airplane currently approved under Type
Certificate No. T00001SE, is a twinengine, transport category airplane with
seating for 495 passengers and a
maximum takeoff weight of 775,000
pounds.
Type Certification Basis
Under the provisions of title 14, Code
of Federal Regulations (14 CFR) 21.101,
Boeing must show that the 777–9
airplane meets the applicable provisions
of the regulations listed in Type
Certificate No. T00001SE, or the
applicable regulations in effect on the
date of application for the change,
except for earlier amendments as agreed
upon by the FAA.
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 Boeing Model 777–9 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 novel or unusual
design feature, or should any other
model already included on the same
type certificate be modified to
incorporate the same novel or unusual
design feature, these special conditions
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23457
would also apply to the other model
under § 21.101.
In addition to the applicable
airworthiness regulations and special
conditions, the Boeing Model 777–9
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 issues special conditions, as
defined in 14 CFR 11.19, in accordance
with § 11.38, and they become part of
the type certification basis under
§ 21.101.
Novel or Unusual Design Features
The Boeing Model 777–9 airplane will
incorporate the following novel or
unusual design feature:
Composite fuel tanks that may be
subject to tire-debris penetration of the
fuel tanks.
Discussion
Accidents or incidents have resulted
from uncontrolled fires caused by fuel
leaks due to fragments of tires or
uncontained engine failure penetrating
or rupturing the undersides of airplane
wings. The effects of engine debris as a
result of uncontained engine failure are
not included in these special conditions
because, for the Boeing Model 777–9
airplane, this hazard is addressed under
the existing requirements of § 25.903(d),
which requires minimizing the hazards
from uncontained engine-failure debris.
In one incident in Honolulu, Hawaii,
a tire on a Boeing Model 747 airplane
burst, and tire debris penetrated a fueltank access panel, causing a substantial
fuel leak. Takeoff was aborted and
passengers were evacuated down the
emergency chutes into pools of fuel,
which fortunately had not ignited. This
accident highlighted deficiencies in the
then-existing 14 CFR part 25 regulations
pertaining to fuel-tank fuel retention
following tire fragments penetrating fuel
tanks.
After a subsequent Boeing Model 737
airplane accident in Manchester,
England, in which uncontained enginefailure debris penetrated a fuel-tank
access panel, the FAA amended
§ 25.963 to require that fuel-tank access
panels be resistant to penetration from
both tire-failure debris and uncontained
engine-failure debris. Section 25.963(e)
requires showing, by analysis or tests,
that fuel-tank access covers ‘‘. . .
minimize penetration and deformation
by tire fragments, low energy engine
debris, or other likely debris.’’ Advisory
Circular (AC) 25.963–1, ‘‘Fuel Tank
Access Covers,’’ defines the region of
the wing that is vulnerable to impact
damage from these sources, and
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Federal Register / Vol. 84, No. 99 / Wednesday, May 22, 2019 / Rules and Regulations
provides a method to substantiate that
the rule has been met for tire fragments.
No specific requirements were
established for the contiguous wing
areas into which the fuel-tank access
covers are installed, because of the
inherent ability of conventional
aluminum wing skins to resist tiredebris penetration. Advisory Circular
25.963–1 specifically notes, ‘‘The [fueltank] access covers, however, need not
be more impact resistant than the
contiguous tank structure,’’ highlighting
the assumption that the basic structures
of these wings meet some higher
standard. An additional amendment to
14 CFR part 121 required operators to
modify their existing fleets of airplanes
with impact-resistant fuel-tank access
panels. This amendment only addressed
fuel-tank access panels because service
experience at the time indicated that the
wing skin on the underside of a wing,
on conventional, subsonic airplanes,
provided adequate, inherent capability
to resist tire debris and engine debris
penetration.
However, after the adoption of the
amendments to § 25.963 in 2000, an
unanticipated failure mode occurred on
a Concorde airplane when tire debris
impacted the fuel tank. The initial
impact of the tire debris did not
penetrate the fuel tank, but a pressure
wave from the debris impact caused the
fuel tank to rupture. In September 2001,
both the French civil-aviation authority
(DGAC) and the United Kingdom Civil
Aviation Authority (CAA) issued
airworthiness directives requiring
modifications to Concorde airplanes, to
add a means to retain fuel if the primary
fuel retention means was damaged.
To maintain the level of safety
envisioned by § 25.963(e), these special
conditions establish a standard for
resistance to potential tire-debris
impacts to the contiguous wing surfaces,
and require consideration of possible
secondary effects of a tire impact, such
as the induced pressure wave that was
a factor in the Concorde accident. This
standard takes into account that new
construction methods and materials
may not necessarily provide the
resistance to debris impact that
historically has been shown as adequate
with conventional aluminum wings.
These special conditions are based on
the defined tire-impact areas and tirefragment characteristics described in AC
25.963–1.
In addition, despite practical design
considerations, some uncommon debris
larger than that defined in paragraph (b)
of these special conditions may cause a
fuel leak within the defined area, so
paragraph (c) of these special conditions
also takes into consideration possible
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15:56 May 21, 2019
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fuel-leak paths. Fuel-tank surfaces of
typical transport airplanes have thick
aluminum construction in the tiredebris impact areas that is tolerant to
tire debris larger than that defined in
paragraph (b) of these special
conditions. Consideration of leaks
caused by larger tire fragments is
needed to ensure that an adequate level
of safety is provided where composite
material is used.
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.
Applicability
As discussed above, these special
conditions are applicable to the Boeing
Model 777–9 airplane. Should Boeing
apply at a later date for a change to the
type certificate to include another
model incorporating the same novel or
unusual design feature, these special
conditions would apply to that model as
well.
Conclusion
This action affects only a certain
novel or unusual design feature on one
model of airplane. It is not a rule of
general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements.
Authority Citation
The authority citation for these
special conditions is as follows:
Authority: 49 U.S.C. 106(f), 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 Boeing Model
777–9 airplanes.
(a) Tire-debris impact to any fuel tank
or fuel-system component, located
within 30 degrees to either side of wheel
rotational planes, may not result in
penetration or otherwise induce fueltank deformation, rupture (e.g., through
propagation of pressure waves), or
cracking sufficient to allow a hazardous
fuel leak. A hazardous fuel leak results
if debris impact to a fuel-tank surface
causes—
1. A running leak,
2. A dripping leak, or
3. A leak that, 15 minutes after wiping
dry, results in a wetted airplane surface
exceeding 6 inches in length or
diameter.
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Fmt 4700
Sfmt 4700
The leak must be evaluated under
maximum fuel head pressure.
(b) Compliance with paragraph (a),
above, must be shown by analysis or
tests assuming all of the following. The
tire-debris fragment:
1. Size is 1 percent of the tire mass.
2. Is propelled at a tangential speed
that could be attained by a tire tread at
the airplane flight-manual airplane
rotational speed (VR at maximum gross
weight).
3. Load is distributed over an area on
the fuel-tank surface equal to 1.5
percent of the total tire tread area.
(c) Fuel leaks caused by impact from
tire debris larger than that specified in
paragraph (b), from any portion of a fuel
tank located within the tire-debris
impact area defined in paragraph (a),
may not result in hazardous quantities
of fuel entering any of the following
areas of the airplane:
1. Engine inlet,
2. APU inlet, or
3. Cabin-air inlet.
This must be shown by test or
analysis, or a combination of both, for
each approved engine forward-thrust
condition, and each approved reversethrust condition.
Issued in Des Moines, Washington, on May
13, 2019.
Victor Wicklund,
Manager, Transport Standards Branch, Policy
and Innovation Division, Aircraft
Certification Service.
[FR Doc. 2019–10703 Filed 5–21–19; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA–2018–0961; Product
Identifier 2018–NM–121–AD; Amendment
39–19635; AD 2019–09–01]
RIN 2120–AA64
Airworthiness Directives; The Boeing
Company Airplanes
Federal Aviation
Administration (FAA), DOT.
ACTION: Final rule.
AGENCY:
We are adopting a new
airworthiness directive (AD) for certain
The Boeing Company Model 737–100,
–200, –200C, –300, –400, and –500
series airplanes. This AD was prompted
by reports indicating that the pitot heat
switch is not always set to ON, which
could result in misleading air data. This
AD requires replacement of pitot antiicing system components, installation of
SUMMARY:
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]]>Agencies
[Federal Register Volume 84, Number 99 (Wednesday, May 22, 2019)]
[Rules and Regulations]
[Pages 23456-23458]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-10703]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2018-1015; Special Conditions No. 25-746-SC]
Special Conditions: Boeing Model 777-9 Airplane; Tire Debris
Penetration of Fuel Tank Structure
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions; request for comments.
-----------------------------------------------------------------------
SUMMARY: These special conditions are issued for The Boeing Company
(Boeing) Model 777-9 airplane. This airplane will have a novel or
unusual design feature when compared to the state of technology
envisioned in the airworthiness standards for transport category
airplanes. This design feature is composite fuel tanks that may be
subject to tire-debris penetration of the fuel tanks. The applicable
airworthiness regulations do not contain adequate or appropriate safety
standards for this design feature. These special conditions
[[Page 23457]]
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: This action is effective on Boeing on May 22, 2019. Send
comments on or before July 8, 2019.
ADDRESSES: Send comments identified by Docket No. FAA-2018-1015 using
any of the following methods:
Federal eRegulations 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 (DOT), 1200 New Jersey Avenue SE, Room
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
Hand Delivery or Courier: Take 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.
Privacy: The FAA will post all comments it receives, without
change, to https://www.regulations.gov/, including any personal
information the commenter provides. Using the search function of the
docket website, anyone can find and read the electronic form of all
comments received into any FAA docket, including the name of the
individual sending the comment (or signing the comment for an
association, business, labor union, etc.). DOT's complete Privacy Act
Statement can be found in the Federal Register published on April 11,
2000 (65 FR 19477-19478).
Docket: Background documents or comments received may be read at
https://www.regulations.gov/ at any time. 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: Suzanne Lucier, Propulsion and
Mechanical Systems Section, AIR-672, Transport Standards Branch, Policy
and Innovation Division, Aircraft Certification Service, Federal
Aviation Administration, 2200 South 216th Street, Des Moines,
Washington 98198; telephone and fax 206-231-3173; email
[email protected].
SUPPLEMENTARY INFORMATION: The substance of these special conditions
has been published in the Federal Register for public comment in
several prior instances with no substantive comments received.
Therefore, the FAA has determined that prior public notice and comment
are unnecessary, and finds that, for the same reason, good cause exists
for adopting these special conditions upon publication in the Federal
Register.
Comments Invited
We invite interested people to take part in this rulemaking by
sending written comments, data, or views. The most helpful comments
reference a specific portion of the special conditions, explain the
reason for any recommended change, and include supporting data.
We will consider all comments we receive by the closing date for
comments. We may change these special conditions based on the comments
we receive.
Background
On March 12, 2015, Boeing applied for an amendment to Type
Certificate No. T00001SE to include the new 777-9 airplane. This
airplane, which is a derivative of the Boeing Model 777 airplane
currently approved under Type Certificate No. T00001SE, is a twin-
engine, transport category airplane with seating for 495 passengers and
a maximum takeoff weight of 775,000 pounds.
Type Certification Basis
Under the provisions of title 14, Code of Federal Regulations (14
CFR) 21.101, Boeing must show that the 777-9 airplane meets the
applicable provisions of the regulations listed in Type Certificate No.
T00001SE, or the applicable regulations in effect on the date of
application for the change, except for earlier amendments as agreed
upon by the FAA.
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 Boeing Model 777-9 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 novel or
unusual design feature, or should any other model already included on
the same type certificate be modified to incorporate the same novel or
unusual design feature, these special conditions would also apply to
the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Boeing Model 777-9 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 issues special conditions, as defined in 14 CFR 11.19, in
accordance with Sec. 11.38, and they become part of the type
certification basis under Sec. 21.101.
Novel or Unusual Design Features
The Boeing Model 777-9 airplane will incorporate the following
novel or unusual design feature:
Composite fuel tanks that may be subject to tire-debris penetration
of the fuel tanks.
Discussion
Accidents or incidents have resulted from uncontrolled fires caused
by fuel leaks due to fragments of tires or uncontained engine failure
penetrating or rupturing the undersides of airplane wings. The effects
of engine debris as a result of uncontained engine failure are not
included in these special conditions because, for the Boeing Model 777-
9 airplane, this hazard is addressed under the existing requirements of
Sec. 25.903(d), which requires minimizing the hazards from uncontained
engine-failure debris.
In one incident in Honolulu, Hawaii, a tire on a Boeing Model 747
airplane burst, and tire debris penetrated a fuel-tank access panel,
causing a substantial fuel leak. Takeoff was aborted and passengers
were evacuated down the emergency chutes into pools of fuel, which
fortunately had not ignited. This accident highlighted deficiencies in
the then-existing 14 CFR part 25 regulations pertaining to fuel-tank
fuel retention following tire fragments penetrating fuel tanks.
After a subsequent Boeing Model 737 airplane accident in
Manchester, England, in which uncontained engine-failure debris
penetrated a fuel-tank access panel, the FAA amended Sec. 25.963 to
require that fuel-tank access panels be resistant to penetration from
both tire-failure debris and uncontained engine-failure debris. Section
25.963(e) requires showing, by analysis or tests, that fuel-tank access
covers ``. . . minimize penetration and deformation by tire fragments,
low energy engine debris, or other likely debris.'' Advisory Circular
(AC) 25.963-1, ``Fuel Tank Access Covers,'' defines the region of the
wing that is vulnerable to impact damage from these sources, and
[[Page 23458]]
provides a method to substantiate that the rule has been met for tire
fragments. No specific requirements were established for the contiguous
wing areas into which the fuel-tank access covers are installed,
because of the inherent ability of conventional aluminum wing skins to
resist tire-debris penetration. Advisory Circular 25.963-1 specifically
notes, ``The [fuel-tank] access covers, however, need not be more
impact resistant than the contiguous tank structure,'' highlighting the
assumption that the basic structures of these wings meet some higher
standard. An additional amendment to 14 CFR part 121 required operators
to modify their existing fleets of airplanes with impact-resistant
fuel-tank access panels. This amendment only addressed fuel-tank access
panels because service experience at the time indicated that the wing
skin on the underside of a wing, on conventional, subsonic airplanes,
provided adequate, inherent capability to resist tire debris and engine
debris penetration.
However, after the adoption of the amendments to Sec. 25.963 in
2000, an unanticipated failure mode occurred on a Concorde airplane
when tire debris impacted the fuel tank. The initial impact of the tire
debris did not penetrate the fuel tank, but a pressure wave from the
debris impact caused the fuel tank to rupture. In September 2001, both
the French civil-aviation authority (DGAC) and the United Kingdom Civil
Aviation Authority (CAA) issued airworthiness directives requiring
modifications to Concorde airplanes, to add a means to retain fuel if
the primary fuel retention means was damaged.
To maintain the level of safety envisioned by Sec. 25.963(e),
these special conditions establish a standard for resistance to
potential tire-debris impacts to the contiguous wing surfaces, and
require consideration of possible secondary effects of a tire impact,
such as the induced pressure wave that was a factor in the Concorde
accident. This standard takes into account that new construction
methods and materials may not necessarily provide the resistance to
debris impact that historically has been shown as adequate with
conventional aluminum wings. These special conditions are based on the
defined tire-impact areas and tire-fragment characteristics described
in AC 25.963-1.
In addition, despite practical design considerations, some uncommon
debris larger than that defined in paragraph (b) of these special
conditions may cause a fuel leak within the defined area, so paragraph
(c) of these special conditions also takes into consideration possible
fuel-leak paths. Fuel-tank surfaces of typical transport airplanes have
thick aluminum construction in the tire-debris impact areas that is
tolerant to tire debris larger than that defined in paragraph (b) of
these special conditions. Consideration of leaks caused by larger tire
fragments is needed to ensure that an adequate level of safety is
provided where composite material is used.
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.
Applicability
As discussed above, these special conditions are applicable to the
Boeing Model 777-9 airplane. Should Boeing apply at a later date for a
change to the type certificate to include another model incorporating
the same novel or unusual design feature, these special conditions
would apply to that model as well.
Conclusion
This action affects only a certain novel or unusual design feature
on one model of airplane. It is not a rule of general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
Authority Citation
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(f), 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 Boeing Model 777-9 airplanes.
(a) Tire-debris impact to any fuel tank or fuel-system component,
located within 30 degrees to either side of wheel rotational planes,
may not result in penetration or otherwise induce fuel-tank
deformation, rupture (e.g., through propagation of pressure waves), or
cracking sufficient to allow a hazardous fuel leak. A hazardous fuel
leak results if debris impact to a fuel-tank surface causes--
1. A running leak,
2. A dripping leak, or
3. A leak that, 15 minutes after wiping dry, results in a wetted
airplane surface exceeding 6 inches in length or diameter.
The leak must be evaluated under maximum fuel head pressure.
(b) Compliance with paragraph (a), above, must be shown by analysis
or tests assuming all of the following. The tire-debris fragment:
1. Size is 1 percent of the tire mass.
2. Is propelled at a tangential speed that could be attained by a
tire tread at the airplane flight-manual airplane rotational speed
(VR at maximum gross weight).
3. Load is distributed over an area on the fuel-tank surface equal
to 1.5 percent of the total tire tread area.
(c) Fuel leaks caused by impact from tire debris larger than that
specified in paragraph (b), from any portion of a fuel tank located
within the tire-debris impact area defined in paragraph (a), may not
result in hazardous quantities of fuel entering any of the following
areas of the airplane:
1. Engine inlet,
2. APU inlet, or
3. Cabin-air inlet.
This must be shown by test or analysis, or a combination of both,
for each approved engine forward-thrust condition, and each approved
reverse-thrust condition.
Issued in Des Moines, Washington, on May 13, 2019.
Victor Wicklund,
Manager, Transport Standards Branch, Policy and Innovation Division,
Aircraft Certification Service.
[FR Doc. 2019-10703 Filed 5-21-19; 8:45 am]
BILLING CODE 4910-13-P
