Special Conditions: Boeing Model 777-9 Airplanes; Post-Crash Fire Survivability, Airplane Level of Safety Provided by Composite Fuel-Tank Structure, 6313-6315 [2019-03343]

Download as PDF 6313 Rules and Regulations Federal Register Vol. 84, No. 39 Wednesday, February 27, 2019 This section of the FEDERAL REGISTER contains regulatory documents having general applicability and legal effect, most of which are keyed to and codified in the Code of Federal Regulations, which is published under 50 titles pursuant to 44 U.S.C. 1510. The Code of Federal Regulations is sold by the Superintendent of Documents. DEPARTMENT OF THE TREASURY Office of the Comptroller of the Currency 12 CFR Parts 19 and 109 Notice of Inflation Adjustments for Civil Money Penalties Correction In rule document 2018–27784, appearing on pages 66599 through 66601, in the issue of Thursday, December 27, 2018, make the following corrections: 1. On page 66600, in the table, in the second column, on the tenth line, ‘‘Tier 322,013,399’’ should read, ‘‘Tier 3’’. ■ 2. On the same page, in the same table, in the third column, on the tenth line, the blank space should be replaced with, ‘‘2 2,013,399’’. ■ [FR Doc. C1–2018–27784 Filed 2–26–19; 8:45 am] BILLING CODE 1301–00–D DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 25 [Docket No. FAA–2018–1017; Special Conditions No. 25–741–SC] Special Conditions: Boeing Model 777– 9 Airplanes; Post-Crash Fire Survivability, Airplane Level of Safety Provided by Composite Fuel-Tank Structure Federal Aviation Administration (FAA), DOT. ACTION: Final special conditions; request for comments. amozie on DSK3GDR082PROD with RULES 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 SUMMARY: VerDate Sep<11>2014 16:10 Feb 26, 2019 Jkt 247001 airworthiness standards for transportcategory airplanes. This design feature is composite fuel-tank structure as it relates to post-crash fire survivability. 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: This action is effective on Boeing on February 27, 2019. Send comments on or before April 15, 2019. ADDRESSES: Send comments identified by Docket No. FAA–2018–1017 using any of the following methods: • Federal eRegulations Portal: Go to http://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 http://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 http://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, PO 00000 Frm 00001 Fmt 4700 Sfmt 4700 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 FAA has determined that notice of, and opportunity for prior public comment on, these special conditions is impracticable because 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 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 Model 777– 9 airplane meets the applicable E:\FR\FM\27FER1.SGM 27FER1 6314 Federal Register / Vol. 84, No. 39 / Wednesday, February 27, 2019 / Rules and Regulations 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 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. amozie on DSK3GDR082PROD with RULES Novel or Unusual Design Features The Boeing Model 777–9 airplane will incorporate the following novel or unusual design feature: Composite fuel-tank structure as it relates to post-crash fire survivability. Discussion As with previous applicant airplane designs with underwing-mounted engines, the wing tanks and center tanks are located in proximity to the passengers and near the engines. Experience indicates post-crash survivability is greatly influenced by the size and intensity of any fire that occurs. Tests conducted at the FAA Technical Center have shown the ability of aluminum wing surfaces to withstand post-crash fire conditions. These tests have verified adequate dissipation of heat across wetted aluminum fuel-tank surfaces so that localized hot spots do not occur, thus minimizing the threat of explosion. This inherent capability of aluminum to dissipate heat also allows the wing lower surface to retain its load- VerDate Sep<11>2014 16:10 Feb 26, 2019 Jkt 247001 carrying characteristics during a fuel-fed ground fire. These properties significantly delay wing collapse and burn-through for a time interval that usually exceeds evacuation times. In addition, as an aluminum fuel tank is heated with significant quantities of fuel inside, fuel vapor accumulates in the ullage space, exceeding the upper flammability limit relatively quickly, and thus reducing the threat of a fueltank explosion prior to fuel-tank burnthrough. The service history of conventional aluminum airplanes has shown that fuel-tank explosions caused by ground fires have been rare on airplanes configured with flame arrestors in the fuel-tank vent lines. Fuel tanks constructed with composite materials, a new technology, may or may not have equivalent capability. Current regulations were developed and have evolved under the assumption that wing construction would be of aluminum materials, which provide inherent properties. Current regulations may not be adequate when applied to airplanes constructed of different materials. Aluminum has the following properties with respect to fuel tanks and fuel-fed external fires. Aluminum is highly thermally conductive. It readily transmits the heat of a fuel-fed external fire to fuel in the tank. This has the benefit of rapidly driving the fuel-tank ullage to exceed the upper flammability limit prior to burn-through of the fuel-tank skin, or heating of the wing upper surface above the auto-ignition temperature. This greatly reduces the threat of fuel-tank explosion. Aluminum panels at thicknesses previously used in wing lower surfaces of large transport-category airplanes have been fire resistant as defined in 14 CFR part 1, and Advisory Circular (AC) 20–135, ‘‘Powerplant Installation and Propulsion System Component Fire Protection Test Methods, Standards and Criteria.’’ The heat-absorption capacity of both aluminum and fuel prevent burnthrough and wing collapse for a time interval that generally exceeds the passenger evacuation time. The extensive use of composite materials in the design of the Boeing Model 777–9 airplane wing and fueltank structure is considered a major change from conventional and traditional methods of construction. The applicable airworthiness regulations do not contain specific standards for postcrash fire-safety performance of wing and fuel-tank skin or structure. To provide the same level of safety as exists with conventional airplane PO 00000 Frm 00002 Fmt 4700 Sfmt 4700 construction, the applicant must demonstrate that the airplane has sufficient post-crash survivability to enable occupants to safely evacuate in the event that the wings are exposed to a large fuel-fed fire. Factors in fuel-tank survivability are the structural integrity of the wing and tank, flammability of the tank, burn-through resistance of the wing skin, and the presence of autoignition threats during exposure to a fire. The FAA assessed post-crash survival time during the adoption of Amendment 25–111 for fuselage burnthrough protection. Studies conducted by and on behalf of the FAA indicated that, following a survivable accident, prevention of fuselage burn-through for approximately 5 minutes can significantly enhance survivability. (See report numbers DOT/FAA/AR–99/57 and DOT/FAA/AR–02/49.) Research reveals little benefit in requiring wingskin design to prevent wing-skin burnthrough beyond five minutes, due to the effects of the fuel fire itself on the rest of the airplane. That assessment was carried out based on accidents involving airplanes with conventional fuel tanks, and considering the ability of ground personnel to rescue occupants. In addition, AC 20–135 indicates that, when aluminum is used for fuel tanks, the tank should withstand the effects of fire for 5 minutes without failure. Therefore, to be consistent with existing capability and related requirements, the applicant airplane fuel tanks must be capable of resisting a post-crash fire for at least 5 minutes. In demonstrating compliance, the applicant must address a range of fuel loads from minimum to maximum, as well as any other critical fuel load. 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. E:\FR\FM\27FER1.SGM 27FER1 Federal Register / Vol. 84, No. 39 / Wednesday, February 27, 2019 / Rules and Regulations 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. In addition to complying with 14 CFR part 25 regulations governing the firesafety performance of the fuel tanks, wings, and nacelle, the Boeing Model 777–9 airplane must demonstrate acceptable post-crash survivability in the event the wings are exposed to a large fuel-fed ground fire. Boeing must demonstrate that the wing and fuel-tank design can endure an external fuel-fed pool fire for at least 5 minutes. This must be demonstrated for minimum fuel loads (not less than reserve fuel levels) and maximum fuel loads (maximumrange fuel quantities), and other identified critical fuel loads. Considerations must include fuel-tank flammability, burn-through resistance, wing structural-strength-retention properties, and auto-ignition threats during a ground-fire event for the required duration. Issued in Des Moines, Washington, on February 19, 2019. Victor Wicklund, Manager, Transport Standards Branch, Policy and Innovation Division, Aircraft Certification Service. [FR Doc. 2019–03343 Filed 2–26–19; 8:45 am] BILLING CODE 4910–13–P DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA–2018–0554; Product Identifier 2018–NM–064–AD; Amendment 39–19569; AD 2019–03–17] amozie on DSK3GDR082PROD with RULES RIN 2120–AA64 Airworthiness Directives; Airbus SAS Airplanes Federal Aviation Administration (FAA), Department of Transportation (DOT). ACTION: Final rule. AGENCY: VerDate Sep<11>2014 16:10 Feb 26, 2019 Jkt 247001 We are adopting a new airworthiness directive (AD) for certain Airbus SAS Model A318 series airplanes; Model A319 series airplanes; Model A320 series airplanes; and Model A321 series airplanes. This AD was prompted by a revision of an airworthiness limitation item (ALI) document, which requires more restrictive maintenance requirements and airworthiness limitations. This AD requires revising the operator’s maintenance or inspection program, as applicable, to incorporate new maintenance requirements and airworthiness limitations. We are issuing this AD to address the unsafe condition on these products. DATES: This AD is effective April 3, 2019. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of April 3, 2019. ADDRESSES: For service information identified in this final rule, contact Airbus SAS, Airworthiness Office— EIAS, Rond-Point Emile Dewoitine No: 2, 31700 Blagnac Cedex, France; telephone +33 5 61 93 36 96; fax +33 5 61 93 44 51; email account.airwortheas@airbus.com; internet http:// www.airbus.com. You may view this service information at the FAA, Transport Standards Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206–231–3195. It is also available on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA–2018– 0554. SUMMARY: Examining the AD Docket You may examine the AD docket on the internet at http:// www.regulations.gov by searching for and locating Docket No. FAA–2018– 0554; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, the regulatory evaluation, any comments received, and other information. The address for Docket Operations (phone: 800–647–5527) is U.S. Department of Transportation, Docket Operations, M–30, West Building Ground Floor, Room W12–140, 1200 New Jersey Avenue SE, Washington, DC 20590. FOR FURTHER INFORMATION CONTACT: Sanjay Ralhan, Aerospace Engineer, International Section, Transport Standards Branch, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone and fax 206–231–3223. SUPPLEMENTARY INFORMATION: PO 00000 Frm 00003 Fmt 4700 Sfmt 4700 6315 Discussion We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Airbus SAS Model A318 series airplanes; Model A319 series airplanes; Model A320 series airplanes; and Model A321–111, –112, –131, –211, –212, –213, –231, –232, –251N, –253N, and –271N airplanes. The NPRM published in the Federal Register on July 17, 2018 (83 FR 33159). The NPRM was prompted by a revision of an ALI document, which requires more restrictive maintenance requirements and airworthiness limitations. The NPRM proposed to require revising the operator’s maintenance or inspection program, as applicable, to incorporate new maintenance requirements and airworthiness limitations. We issued a supplemental NPRM (SNPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Airbus SAS Model A318 series airplanes; Model A319 series airplanes; Model A320 series airplanes; and Model A321 series airplanes. The SNPRM published in the Federal Register on November 8, 2018 (83 FR 55830). We issued the SNPRM to include revised restrictive requirements and add airplanes to the applicability. We are issuing this AD to address a safety-significant latent failure (that is not annunciated), which, in combination with one or more other specific failures or events, could result in a hazardous or catastrophic failure condition. The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2018–0180, dated August 27, 2018 (referred to after this as the Mandatory Continuing Airworthiness Information, or ‘‘the MCAI’’), to correct an unsafe condition for certain Airbus SAS Model A318 series airplanes; Model A319 series airplanes; Model A320 series airplanes; and Model A321 series airplanes. The MCAI states: The airworthiness limitations for the Airbus A320 family aeroplanes, which are approved by EASA, are currently defined and published in the A318/A319/A320/A321 ALS [Airworthiness Limitations Section] document(s). The airworthiness limitations applicable to the Certification Maintenance Requirements (CMR), which are approved by EASA, are published in ALS Part 3. Failure to accomplish these instructions could result in an unsafe condition. Previously, EASA issued AD 2017–0168 to require accomplishment of all maintenance tasks as described in ALS Part 3 at Revision 05. E:\FR\FM\27FER1.SGM 27FER1

Agencies

[Federal Register Volume 84, Number 39 (Wednesday, February 27, 2019)]
[Rules and Regulations]
[Pages 6313-6315]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-03343]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2018-1017; Special Conditions No. 25-741-SC]


Special Conditions: Boeing Model 777-9 Airplanes; Post-Crash Fire 
Survivability, Airplane Level of Safety Provided by Composite 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-tank structure as it 
relates to post-crash fire survivability. 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: This action is effective on Boeing on February 27, 2019. Send 
comments on or before April 15, 2019.

ADDRESSES: Send comments identified by Docket No. FAA-2018-1017 using 
any of the following methods:
     Federal eRegulations Portal: Go to http://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 http://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 
http://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 FAA has determined that notice of, and 
opportunity for prior public comment on, these special conditions is 
impracticable because 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 Model 777-9 airplane meets the 
applicable

[[Page 6314]]

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-tank structure as it relates to post-crash fire 
survivability.

Discussion

    As with previous applicant airplane designs with underwing-mounted 
engines, the wing tanks and center tanks are located in proximity to 
the passengers and near the engines. Experience indicates post-crash 
survivability is greatly influenced by the size and intensity of any 
fire that occurs. Tests conducted at the FAA Technical Center have 
shown the ability of aluminum wing surfaces to withstand post-crash 
fire conditions. These tests have verified adequate dissipation of heat 
across wetted aluminum fuel-tank surfaces so that localized hot spots 
do not occur, thus minimizing the threat of explosion. This inherent 
capability of aluminum to dissipate heat also allows the wing lower 
surface to retain its load-carrying characteristics during a fuel-fed 
ground fire. These properties significantly delay wing collapse and 
burn-through for a time interval that usually exceeds evacuation times. 
In addition, as an aluminum fuel tank is heated with significant 
quantities of fuel inside, fuel vapor accumulates in the ullage space, 
exceeding the upper flammability limit relatively quickly, and thus 
reducing the threat of a fuel-tank explosion prior to fuel-tank burn-
through. The service history of conventional aluminum airplanes has 
shown that fuel-tank explosions caused by ground fires have been rare 
on airplanes configured with flame arrestors in the fuel-tank vent 
lines. Fuel tanks constructed with composite materials, a new 
technology, may or may not have equivalent capability.
    Current regulations were developed and have evolved under the 
assumption that wing construction would be of aluminum materials, which 
provide inherent properties. Current regulations may not be adequate 
when applied to airplanes constructed of different materials.
    Aluminum has the following properties with respect to fuel tanks 
and fuel-fed external fires.
    Aluminum is highly thermally conductive. It readily transmits the 
heat of a fuel-fed external fire to fuel in the tank. This has the 
benefit of rapidly driving the fuel-tank ullage to exceed the upper 
flammability limit prior to burn-through of the fuel-tank skin, or 
heating of the wing upper surface above the auto-ignition temperature. 
This greatly reduces the threat of fuel-tank explosion.
    Aluminum panels at thicknesses previously used in wing lower 
surfaces of large transport-category airplanes have been fire resistant 
as defined in 14 CFR part 1, and Advisory Circular (AC) 20-135, 
``Powerplant Installation and Propulsion System Component Fire 
Protection Test Methods, Standards and Criteria.''
    The heat-absorption capacity of both aluminum and fuel prevent 
burn-through and wing collapse for a time interval that generally 
exceeds the passenger evacuation time.
    The extensive use of composite materials in the design of the 
Boeing Model 777-9 airplane wing and fuel-tank structure is considered 
a major change from conventional and traditional methods of 
construction. The applicable airworthiness regulations do not contain 
specific standards for post-crash fire-safety performance of wing and 
fuel-tank skin or structure.
    To provide the same level of safety as exists with conventional 
airplane construction, the applicant must demonstrate that the airplane 
has sufficient post-crash survivability to enable occupants to safely 
evacuate in the event that the wings are exposed to a large fuel-fed 
fire. Factors in fuel-tank survivability are the structural integrity 
of the wing and tank, flammability of the tank, burn-through resistance 
of the wing skin, and the presence of auto-ignition threats during 
exposure to a fire. The FAA assessed post-crash survival time during 
the adoption of Amendment 25-111 for fuselage burn-through protection. 
Studies conducted by and on behalf of the FAA indicated that, following 
a survivable accident, prevention of fuselage burn-through for 
approximately 5 minutes can significantly enhance survivability. (See 
report numbers DOT/FAA/AR-99/57 and DOT/FAA/AR-02/49.) Research reveals 
little benefit in requiring wing-skin design to prevent wing-skin burn-
through beyond five minutes, due to the effects of the fuel fire itself 
on the rest of the airplane. That assessment was carried out based on 
accidents involving airplanes with conventional fuel tanks, and 
considering the ability of ground personnel to rescue occupants. In 
addition, AC 20-135 indicates that, when aluminum is used for fuel 
tanks, the tank should withstand the effects of fire for 5 minutes 
without failure. Therefore, to be consistent with existing capability 
and related requirements, the applicant airplane fuel tanks must be 
capable of resisting a post-crash fire for at least 5 minutes. In 
demonstrating compliance, the applicant must address a range of fuel 
loads from minimum to maximum, as well as any other critical fuel load.
    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.

[[Page 6315]]

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.
    In addition to complying with 14 CFR part 25 regulations governing 
the fire-safety performance of the fuel tanks, wings, and nacelle, the 
Boeing Model 777-9 airplane must demonstrate acceptable post-crash 
survivability in the event the wings are exposed to a large fuel-fed 
ground fire. Boeing must demonstrate that the wing and fuel-tank design 
can endure an external fuel-fed pool fire for at least 5 minutes. This 
must be demonstrated for minimum fuel loads (not less than reserve fuel 
levels) and maximum fuel loads (maximum-range fuel quantities), and 
other identified critical fuel loads. Considerations must include fuel-
tank flammability, burn-through resistance, wing structural-strength-
retention properties, and auto-ignition threats during a ground-fire 
event for the required duration.

    Issued in Des Moines, Washington, on February 19, 2019.
Victor Wicklund,
Manager, Transport Standards Branch, Policy and Innovation Division, 
Aircraft Certification Service.
[FR Doc. 2019-03343 Filed 2-26-19; 8:45 am]
 BILLING CODE 4910-13-P