Document ID: FAA-2016-6140-0018
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: The Boeing Company Airplanes
Posted Date: 2020-09-21T04:00Z

[Federal Register Volume 85, Number 183 (Monday, September 21, 2020)]
[Rules and Regulations]
[Pages 59180-59187]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-19584]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-6140; Product Identifier 2015-NM-059-AD; Amendment 
39-21233; AD 2020-18-12]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain The Boeing Company Model 777-200, -200LR, and -300 series 
airplanes. This AD was prompted by the FAA's analysis of the Model 777 
fuel system reviews conducted by the manufacturer. This AD requires 
modifying the fuel quantity indicating system (FQIS) to prevent 
development of an ignition source inside the center fuel tank due to 
electrical fault conditions. This AD also provides alternative actions 
for cargo airplanes. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective October 26, 2020.

ADDRESSES: 

Examining the AD Docket

    You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2016-
6140; 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, any comments received, and other information. The 
address for Docket Operations 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: Jon Regimbal, Aerospace Engineer, 
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3557; email: 
Jon.Regimbal@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to certain The Boeing 
Company Model 777 airplanes. The NPRM published in the Federal Register 
on

[[Page 59181]]

May 4, 2016 (81 FR 26750). The NPRM was prompted by the FAA's analysis 
of the Model 777 fuel system reviews conducted by the manufacturer. The 
NPRM proposed to require modifying the FQIS to prevent development of 
an ignition source inside the center fuel tank due to electrical fault 
conditions. The NPRM also proposed to provide alternative actions for 
cargo airplanes. The FAA is issuing this AD to address ignition sources 
inside the center fuel tank, which, in combination with flammable fuel 
vapors, could result in a fuel tank explosion and consequent loss of 
the airplane.

Comments

    The FAA gave the public the opportunity to participate in 
developing this final rule. The following presents the comments 
received on the NPRM and the FAA's response to each comment.

Support for the NPRM

    The Air Line Pilots Association, International (ALPA) and National 
Air Traffic Controllers Association (NATCA) supported the intent of the 
NPRM. Additional comments from NATCA are addressed below.

Request To Withdraw NPRM: No Unsafe Condition

    Boeing requested that the FAA withdraw the NPRM. Boeing suggested 
that, by requiring center fuel tank FQIS wire separation for passenger 
airplanes that have not incorporated a nitrogen generating system 
(NGS), the NPRM specifically addresses airplanes regulated by the 
European Union Aviation Safety Agency (EASA) and other civil aviation 
authorities and the lack of a flammability reduction means (FRM) rule. 
Boeing stated that because it considered the use of FRM (NGS) to 
address unknown ignition sources as the final corrective action, Boeing 
has not developed center tank FQIS wire separation service instructions 
for passenger aircraft. Boeing stated that it believes no unsafe 
condition exists and does not feel that the lack of FRM rule 
harmonization should cause additional work and expense for airlines.
    The FAA disagrees with the commenter's request. The FAA determined 
that an unsafe condition exists using the criteria in FAA Policy 
Memorandum ANM100-2003-112-15, ``SFAR 88--Mandatory Action Decision 
Criteria,'' dated February 25, 2003.\1\ That policy was used to 
evaluate the noncompliant design areas identified in the manufacturer's 
fuel system reviews and to determine which noncompliance issues were 
unsafe conditions that required corrective action under 14 CFR part 39. 
The FAA's unsafe condition determination was not based on an assessment 
of average risk or total fleet risk, but rather was driven by the 
qualitative identification of an unacceptable level of individual risk 
that exists on flights that are anticipated to occur with a preexisting 
latent in-tank failure condition and with a flammable center fuel tank. 
For these reasons, and based on further detailed responses to similar 
comments in the supplemental NPRM (SNPRM) for Docket No. FAA-2012-0187 
(80 FR 9400, February 23, 2015), and in the subsequently issued final 
rule, AD 2016-07-07, Amendment 39-18452 (81 FR 19472, April 5, 2016) 
(``AD 2016-07-07''), which addressed the same unsafe condition for 
Boeing Model 757 airplanes, the FAA has determined that it is necessary 
to issue this final rule.
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    \1\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/
rgPolicy.nsf/0/dc94c3a46396950386256d5e006aed11/$FILE/Feb2503.pdf.
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Request To Withdraw NPRM: Unjustified by Risk

    KLM Royal Dutch Airlines (KLM), Cathay Pacific (Cathay), and 
Emirates requested that the FAA withdraw the NPRM. KLM stated that it 
understands that Boeing is not able to explain or substantiate the 
rationale behind the NPRM. Singapore Airlines (SIA) suggested that the 
FAA should consider the Special Federal Aviation Regulation (SFAR) No. 
88 (in 14 CFR part 21) modifications that have already been implemented 
to mitigate ignition risks and the resultant reduced risk exposure. SIA 
added that the determination of the risk level should also consider the 
remaining operating life of the Model 777 fleet. The FAA infers that 
SIA is also requesting that the NPRM be withdrawn. Cathay noted that 
operators have already accomplished numerous SFAR 88-related service 
bulletins, which have increased the level of fuel system safety. KLM 
and Emirates stated that the NPRM does not clarify the necessity of 
additional actions beyond the currently mandated SFAR 88-related 
service bulletins, airworthiness limitations, and critical design 
configuration control limitations (CDCCLs).
    The FAA disagrees with the commenters' request. The FAA notes that 
similar comments were addressed in the SNPRM for Docket No. FAA-2012-
0187 in the comment response for ``Request To Withdraw NPRM (77 FR 
12506, March 1, 2012): Unjustified by Risk.'' As explained in that 
comment response, in addition to examining average risk and total fleet 
risk, the FAA examines the individual flight risk on the worst 
reasonably anticipated flights. In general, the FAA issues ADs in cases 
where reasonably anticipated flights with preexisting failures (either 
due to latent failure conditions or allowable dispatch configurations) 
are vulnerable to a catastrophic event due to an additional foreseeable 
single failure condition. This is because the FAA considers operation 
of flights vulnerable to a potentially catastrophic single failure 
condition to be an excessive safety risk to the passengers on those 
flights. The FAA has determined that the currently mandated SFAR 88 
service bulletins, airworthiness limitations, and critical design 
configuration control limitations do not adequately address the unsafe 
condition identified in this AD and therefore it is necessary to issue 
this final rule. The FAA has not changed this AD regarding this issue.

Request To Withdraw NPRM: Inadequate Fleet Exposure and Cost Estimates

    Boeing requested that the FAA withdraw the NPRM. Boeing stated that 
the fleet exposure for the affected fleet continues to decrease due to 
aging airplanes. Boeing added that the estimated costs in the NPRM do 
not take into account the costs of compliance for passenger airplanes 
without FRM installed.
    The FAA disagrees with the commenter's request. The FAA did not 
base its unsafe condition determination on fleet risk but instead on 
individual risk. This is discussed in detail in the response to 
comments in the SNPRM for Docket No. FAA-2012-0187, under the heading 
``Request To Withdraw NPRM (77 FR 12506, March 1, 2012): Unjustified by 
Risk.'' Therefore, the age of the airplane does not affect the 
determination that an unsafe condition still exists on an individual 
airplane.
    The NPRM for this final rule did contain a cost estimate for 
passenger airplanes that was based on the estimate provided by Boeing 
for the Model 757 and Model 767 airplanes, which have an FQIS of 
similar design. The FAA notes that Boeing asserted that the cost to 
operators of modifying an airplane's FQIS to be fully compliant with 
the airworthiness standards would be similar to the cost of installing 
Boeing's NGS flammability reduction system. Based on that, Boeing 
requested that the FAA agree to not require Boeing to develop service 
information for a fully compliant FQIS modification. However, the FAA 
used Boeing's estimate of the cost to modify the Model 757 and Model 
767 FQIS to a fully part-25-compliant

[[Page 59182]]

configuration to provide the estimated costs in the NPRM, based on an 
assumption that the cost for Model 747 airplanes would be similar. At 
the time, Boeing concurred with this estimate. This is discussed in 
detail in the response to comments in the SNPRM for Docket No. FAA-
2012-0187. The FAA has not changed this AD regarding this issue.

Request To Cancel Any Retroactive Modification Requirements

    Cathay and KLM requested that any plans to require retroactive 
modification to install FRM on in-service airplanes be cancelled. 
Cathay stated that EASA does not plan to require retroactive 
modification to install FRM on in-service airplanes registered in the 
EASA member states. Cathay noted that Hong Kong Airworthiness Notice 
No. 103 states that FRM is non-mandatory on aircraft manufactured 
before February 1, 2012. Cathay added that if the NPRM is not 
withdrawn, it should be limited to U.S.-registered airplanes. KLM noted 
that the proposed AD would create a huge financial burden. KLM also 
noted that EASA only adopted the requirement to equip an FRM on newly 
delivered airplanes.
    The FAA does not agree. First, the FAA has already issued a final 
rule, Reduction of Fuel Tank Flammability in Transport Category 
Airplanes (73 FR 42444, July 21, 2008), the Fuel Tank Flammability 
Reduction (FTFR) rule, which requires retrofitting of FRM or ignition 
mitigation means (IMM) on passenger airplanes. The FAA has no plans to 
rescind that action, which was intended to increase the level of fuel 
tank safety on transport airplanes. Separately from that rulemaking, 
the FAA has determined that an unsafe condition exists in several 
Boeing and Airbus models, including early versions of the Model 777 
airplanes. The reasons behind that determination are detailed in the 
response to comments in the SNPRM for Docket No. FAA-2012-0187, under 
the heading ``Request To Withdraw NPRM (77 FR 12506, March 1, 2012): 
Unjustified by Risk.'' The FAA acknowledges that the cost of this 
retrofitting may be high, but has determined that the unsafe condition 
must be addressed.

Request To Record Only Certain Codes

    Boeing requested that paragraph (h)(1) of the proposed AD be 
revised to only require corrective actions if a nondispatchable fault 
code pertaining to the center wing tank is recorded (as opposed to any 
nondispatchable fault code being recorded). Boeing stated that all FQIS 
wire separation changes in the proposed AD are limited to the center 
wing tank, therefore only built-in test equipment (BITE) check messages 
pertaining to the center wing tank are applicable to the proposed AD. 
In addition, Boeing stated that a final rule should be postponed until 
the FAA develops a list of ``nondispatchable fault codes'' in 
conjunction with Boeing.
    The FAA agrees that the unsafe condition addressed by this AD is 
limited to the center wing tank. However, the FAA does not agree that 
the AD should be changed as proposed by Boeing. It is not clear to the 
FAA whether there may be FQIS BITE fault codes that are not clearly 
identified as related to the center wing tank but that may impact 
center tank circuits. Therefore, the FAA has determined that all 
nondispatchable fault codes recorded prior to the BITE check or as a 
result of the BITE check required by paragraph (h)(1) of this AD must 
be addressed. Operators or Boeing may request an alternative method of 
compliance (AMOC) under the provisions of paragraph (i) of this AD if 
they can provide sufficient data that a particular fault code does not 
pertain to the unsafe condition addressed by this AD.
    Regarding the requirement to record and address fault codes read 
immediately prior to running the BITE check procedure, the FAA notes 
that the normal Boeing procedure for performing an FQIS BITE check is 
to first erase all of the existing fault codes, then perform the BITE 
check and troubleshoot any resulting new fault codes. For this AD, the 
FAA did not want any already stored fault codes to be potentially 
ignored due to erasure at the first step because some of the failures 
of concern can be intermittent. This AD therefore requires operators to 
record the existing codes before doing the BITE check, then do the BITE 
check and record the new codes that result from that BITE check, and 
then do the appropriate troubleshooting and corrective action for both 
sets of codes per the manufacturer's guidance. The FAA has not changed 
this AD regarding this issue.
    Finally, the FAA does not agree to delay the final rule while 
Boeing proposes and obtains FAA agreement on a list of nondispatchable 
fault codes. The FAA requested service information from Boeing in 2016 
to support the option for all-cargo airplanes on all of the Boeing 
models for which similar FQIS ADs were planned. Boeing chose at that 
time to develop service information only for the Model 747-400, 757, 
and 767 airplanes because at that time only those airplanes had 
affected cargo configuration for which Boeing was the design approval 
holder. The FAA agreed at that time to not require Boeing to develop a 
BITE check service bulletin for the Model 777 airplanes because Boeing 
had not yet developed a cargo conversion service bulletin or 
supplemental type certificate (STC) for the Model 777 airplanes. The 
FAA also considered that, because the BITE check instructions already 
existed in the Model 777 AMM, a BITE check service bulletin could be 
developed quickly at a later date if needed. In addition, the process 
for obtaining FAA agreement on a list of nondispatchable fault codes 
for the models Boeing chose to support took less than 30 days. If any 
service information is developed to support compliance with paragraph 
(h) of this AD it will be evaluated for approval using the AMOC process 
specified in paragraph (i) of this AD.

Request To Exclude Certain Airplanes From the Applicability

    Boeing requested that the proposed AD be revised to exclude all 
Model 777-300ER and 777F airplanes, as well as all airplanes having 
line numbers 562 and subsequent. Boeing explained that all Model 777-
300ER and 777F airplanes were produced with FQIS center wing tank wire 
separation that has been shown to be compliant with 14 CFR 25.981(a)(3) 
as amended by amendment 25-102 (66 FR 23086, May 7, 2001) (``amendment 
25-102''). Boeing added that all Model 777 passenger airplanes after 
line number 562 were also produced with FQIS center wing tank wire 
separation that has been shown to be compliant with 14 CFR 
25.981(a)(3), as amended by amendment 25-102.
    KLM also requested that the proposed AD be revised to exclude line 
numbers 562 and subsequent because those airplanes have an improved 
FQIS wire separation, removing any potential for the unsafe condition 
to occur.
    The FAA agrees for the reasons provided. The FAA has revised 
paragraph (c) of this AD to remove the requested airplanes from the 
applicability. The FAA has also revised the Costs of Compliance section 
of this AD accordingly.

Request To Exclude Airplanes Based on Prior Incorporation of Certain 
Service Information

    Air France requested that the applicability of the proposed AD be 
revised to exclude airplanes on which certain service information has 
been incorporated.
    The FAA disagrees with the commenter's request (which the commenter 
inadvertently posted to docket FAA-2016-6141). The service

[[Page 59183]]

information mentioned by the commenter does not address the unsafe 
condition identified in this AD. The FAA has not changed this AD 
regarding this issue.

Request To Remove Inspection Requirement for Cargo Airplanes

    Air France noted that paragraph (h)(1) of the proposed AD requires 
an inspection (BITE check) on cargo airplanes. Air France asked why 
this action is required on cargo airplanes but not passenger airplanes.
    The FAA infers that the commenter is requesting that the FAA remove 
paragraph (h)(1) of this AD. The FAA disagrees with the commenter's 
request (which the commenter inadvertently posted to docket FAA-2016-
6141). The FAA has determined that the changes required for passenger 
airplanes--either compliance with the FTFR regulations or modification 
of the FQIS to make it fully compliant with the airworthiness 
regulations--are adequate to address the unsafe condition without the 
periodic BITE check required under the optional method of compliance 
for cargo airplanes. The optional method of compliance for cargo 
airplanes does not require compliance with the FTFR regulations or a 
fully compliant FQIS modification so the additional checks are 
necessary. The FAA has not changed the AD regarding this issue.

Request To Change Compliance Time

    Japan Airlines (JAL) requested that the FAA extend the compliance 
time for the modifications specified in paragraphs (g) and (h)(2) of 
the proposed AD to 72 months. JAL stated that Boeing anticipates that 
the installation of NGS will be an AMOC for the actions specified in 
the proposed AD. JAL added that some Model 777 airplanes are already 
being retired and that non-U.S. operators have not been mandated to 
install NGS. SIA requested that the compliance timeline take into 
consideration the lack of availability of a specific modification for 
operators to comply with, but did not request a specific change to the 
proposed compliance time.
    Conversely, NATCA recommended that the FAA reject requests for a 
compliance time longer than 5 years as proposed in the NPRM. Assuming 
final rule issuance in 2016, NATCA stated that a 5-year compliance time 
would result in required compliance by 2021--25 years after the TWA 
Flight 800 fuel tank explosion that led to the requirements in SFAR 88, 
and 20 years after issuance of SFAR 88.
    The FAA agrees with JAL's request to extend the compliance time, 
and disagrees with NATCA's request. The FAA received similar requests 
to extend the compliance time from several commenters regarding the 
NPRMs for the FQIS modification on other airplanes. The FAA has 
determined that a 72-month compliance time is appropriate and will 
provide operators adequate time to prepare for and perform the required 
modifications without excessive disruption of operations. The FAA has 
determined that the requested moderate increase in compliance time will 
continue to provide an acceptable level of safety. The FAA has revised 
paragraphs (g) and (h)(2) of this AD accordingly.

Request To Exclude Airplanes To Be Retired

    British Airways (BA) requested that the proposed AD be revised to 
provide dispensation for aircraft to be retired, which would not be 
prohibitive for operators.
    The FAA infers that the commenter is requesting an extension of the 
compliance time for airplanes that will be retired by a certain date or 
for the AD to exclude those airplanes from this AD. The FAA notes that 
the commenter did not propose a specific period of additional time for 
operation without addressing the unsafe condition, and did not propose 
any specific alternative corrective actions. In addition, it is the 
FAA's understanding that BA no longer operates any of the affected 
airplanes. As previously mentioned, the FAA has revised this AD to 
provide 72 months from the effective date of this AD for incorporation 
of the required modification, which should allow adequate time to plan 
for retiring aircraft if needed. If an operator wishes to make a 
specific proposal, they can submit that proposal using the AMOC 
process. The FAA has not changed this AD regarding this issue.

Request To Address Unsafe Condition on All Fuel Tanks

    NATCA recommended that the FAA require design changes that 
eliminate unsafe FQIS failure conditions on all fuel tanks on the 
affected models, regardless of fuel tank location or the percentage of 
time the fuel tank is flammable. NATCA referred to four fuel tank 
explosions in low-flammability exposure time fuel tanks identified by 
the FAA during FTFR rulemaking. NATCA stated that neither FRM nor 
alternative actions for cargo airplanes (e.g., BITE checks (checks of 
built-in test equipment) followed by applicable repairs before further 
flight and modification of the center fuel tank FQIS wiring within 60 
months) would bring the airplane into full regulatory compliance. NATCA 
added that the combination of failures described in the NPRM meets the 
criteria for ``known combinations'' of failures that require corrective 
action in FAA Policy Memorandum ANM100-2003-112-15.
    The FAA disagrees with the commenter's request. The FAA has 
determined that, according to FAA Policy Memorandum ANM100-2003-112-15, 
the failure condition for the airplanes affected by this AD should not 
be classified as a ``known combination.'' While the FQIS design 
architecture is similar to that of the early Boeing Model 747 
configuration that is suspected of contributing to the TWA Flight 800 
fuel tank explosion, significant differences exist in the design of 
FQIS components and wire installations between the affected Boeing 
airplane models and the early Model 747 airplanes such that the intent 
of the ``known combinations'' provision for low-flammability fuel tanks 
in the policy memorandum is not applicable. Therefore, this AD affects 
only the identified Boeing airplanes with high-flammability exposure 
time fuel tanks, as specified in paragraph (c) of this AD. The FAA 
provided a detailed response to similar comments in the preamble of the 
final rule for AD 2016-07-07. The FAA has not changed this final rule 
regarding this issue.

Request To Require Cargo Airplane Option for All Airplanes

    Boeing requested that the NPRM be revised to make the alternative 
actions for cargo airplanes specified in paragraph (h) of the proposed 
AD applicable to all airplanes, including passenger airplanes with FRM 
not installed due to differences in foreign regulations. In addition, 
Boeing requested that the actions specified in paragraph (h) of the 
proposed AD become the primary means of compliance for all airplanes, 
not an alternative method of compliance for some airplanes.
    The FAA disagrees with the commenter's request. As discussed in the 
comment response in the SNPRM for Docket No. FAA-2012-0187, under the 
heading ``Requests To Withdraw NPRM (77 FR 12506, March 1, 2012) Based 
on Applicability'' the FAA does not consider the alternative action for 
cargo airplanes allowed by this AD to provide an adequate level of 
safety for passenger airplanes. The FAA is willing to accept a higher 
level of individual flight risk exposure for cargo flights that are not 
fail-safe due to the absence of passengers and the resulting 
significant reduction in occupant exposure on a cargo airplane versus a 
passenger

[[Page 59184]]

airplane, and due to relatively low estimated individual flight risk 
that would exist on a cargo airplane after the corrective actions are 
taken. The FAA has not changed this AD regarding this issue.

Request To Exclude Certain Airplanes

    United Airlines (UAL) noted that 14 CFR 121.1117 requires that an 
FRM will have been installed on all affected airplanes in passenger 
configuration by December 26, 2018, well ahead of the compliance 
deadline of the proposed AD. UAL further suggested that the FAA either 
delete paragraph (g) of the proposed AD or make paragraph (g) of the 
proposed AD applicable only to airplanes in a cargo configuration that 
do not have an FRM installed and non-U.S.-registered airplanes that do 
not have to comply with FRM requirements.
    The FAA disagrees with the commenter's request. There are other 
passenger-carrying airplanes operated under 14 CFR part 91 that are not 
required to install FRM. (The requirement to install FRM on all 
passenger-carrying airplanes operated by air carriers is in 14 CFR 
121.1117.) The FAA notes that foreign air carriers may not have to 
comply with that requirement or similar requirements of their own civil 
aviation authority. EASA, for example, has chosen not to require FRM to 
be retrofitted to in-service airplanes. This AD is intended to require 
any Model 777 series passenger airplane that does not have FRM, 
regardless of the rules under which it is operated, to address the FQIS 
latent-plus-one unsafe condition with a corrective action that fully 
complies with the FAA airworthiness standards. This requirement 
fulfills the FAA's International Civil Aviation Organization (ICAO) 
obligation to address unsafe conditions on all of the aircraft 
manufactured by the state of design, not just those aircraft whose 
operation is under the jurisdiction of the state of design. The FAA has 
not changed this AD regarding this issue.

Request To Clarify Certification Basis for Modification Requirements

    NATCA recommended that the FAA revise paragraph (g) of the proposed 
AD to clearly state that the required FQIS design changes must comply 
with the fail-safe requirements of 14 CFR 25.901(c), as amended by 
amendment 25-46 (43 FR 50597, October 30, 1978); and 14 CFR 25.981(a) 
and (b), as amended by amendment 25-102; NATCA added that these 
provisions are required by SFAR 88.
    The FAA does not agree to change paragraph (g) of this AD. While 
the FAA agrees that modifications to comply with paragraph (g) of this 
AD should be required to comply with the referenced regulations, that 
requirement already exists in 14 CFR part 21. No change to this AD is 
necessary.

Request To Require Modification on All Production Airplanes

    NATCA recommended that the FAA require designs that comply with 14 
CFR 25.901(c) and 25.981(a)(3) on all newly produced transport 
airplanes. NATCA stated that continuing to grant exemptions to 14 CFR 
25.901(c), as amended by amendment 25-40 (42 FR 15042, March 17, 1977); 
and 14 CFR 25.981(a)(3), as amended by amendment 25-102; has allowed 
continued production of thousands of airplanes with this known unsafe 
condition.
    The FAA disagrees with the commenter's request. The recommendation 
to require production airplanes to fully comply with 14 CFR 25.901(c) 
and 14 CFR 25.981(a)(3) is outside the scope of this rulemaking. In 
addition, the FAA has implemented requirements for all large transport 
airplanes produced after September 2010 to include flammability 
reduction methods for tanks that would otherwise be high-flammability 
fuel tanks. Boeing incorporated this change into the Model 777 series 
airplanes that are still in production and the FAA has excluded those 
models from the applicability of this AD. The FAA has not changed this 
final rule regarding this issue.

Request To State That an Exemption Is Required

    Boeing requested that paragraph (h) of the proposed AD be revised 
to state that an exemption is required to accomplish the specified 
actions. Boeing stated that the FAA has identified that the BITE 
procedure and wire separation design changes specified in the proposed 
AD are not sufficient for compliance to 14 CFR 25.981(a) at the FQIS 
level. Boeing stated that an exemption is therefore needed prior to 
approval of the related design change.
    The FAA agrees to clarify. The BITE check is not a type design 
change or alteration, so no exemption from the airworthiness standards 
is required for that action. The design data approval of any partial 
wire separation modification would require an exemption. That exemption 
would be obtained by the party seeking approval of the alteration data, 
and no further exemption would be required for the party using that 
data to alter an aircraft. Obtaining such an exemption would be part of 
the certification process for such a change, so the FAA does not find 
it necessary to include such information in paragraph (h) of this AD. 
In addition, some parties may choose to comply with the AD using a 
design change that fully complies with the airworthiness standards. The 
FAA also notes that the commenter appears to misunderstand why an 
exemption is needed for the required modification. The exemption is 
needed because, even with the modification, the FQIS does not comply 
with 14 CFR 25.901(c) and 14 CFR 25.981(a). The exemption does not 
authorize evaluation of a partial system for compliance with the system 
level requirement. The FAA has not changed this AD regarding this 
issue.

Request To Change Compliance Time Relative to Receipt of Exemption

    Boeing requested that the FAA revise the compliance time for the 
proposed AD to ``60 months after an exemption from [14 CFR 
25.981(a)(3)] is FAA-approved.'' Boeing suggested that it would take 6 
months to develop an exemption petition and 6 months for the FAA to 
approve that exemption. Boeing added that the FAA has previously 
identified that the BITE checks procedure and wire separation design 
were not sufficient for compliance with 14 CFR 25.981(a)(3).
    The FAA disagrees with the commenter's request. An AD typically 
does not include a compliance time that is based on an optional action 
that an operator or manufacturer might choose to take. In addition, the 
FAA notes that Boeing has already received exemptions for Model 747-
400, 757, and 767 airplanes, and could quickly petition for and obtain 
approval of a similar exemption for the Model 777 airplanes using an 
almost identical petition. The FAA's flow time to disposition such a 
petition would be approximately 90 days, during which time Boeing could 
still proceed with development of the modification. In addition, as 
noted above, the compliance time for the actions specified in paragraph 
(h)(2) of this AD has been extended to 72 months, giving additional 
time for operators or manufacturers to obtain an exemption.

Request To Extend Repetitive BITE Check Interval

    Boeing requested that paragraph (h)(1) of the proposed AD be 
revised to extend the repetitive check interval for the BITE checks. 
Boeing requested that the repetitive interval be extended to 750 flight 
hours to match the repetitive intervals specified in service 
information for other airplane models.
    The FAA agrees to extend the repetitive check interval to 750 
flight

[[Page 59185]]

hours. The FAA intended to propose a 750 flight hour interval, but 
inadvertently specified 650 flight hour intervals in the proposed AD. 
The FAA has revised paragraph (h)(1) of this AD to specify repetitive 
intervals of 750 flight hours.

Request To Provide Cost-Effective Method of Compliance

    SIA, Emirates, JAL, Korean Air Lines (KAL), KLM, Cathay, and BA 
requested that the FAA provide a cost-effective method of compliance 
for passenger airplanes. Emirates and KAL noted that the proposed AD 
does not provide a clear means of compliance for the modification, such 
as a Boeing service bulletin. SIA stated that Boeing should develop a 
modification to specifically address the unsafe condition in the 
proposed AD and that operators should have the opportunity to assess 
compliance options. Emirates suggested that the only method of 
compliance for non-U.S. operators will be installation of an NGS. KAL 
noted that the majority of non-FAA operators are not required to 
retrofit the NGS system. JAL, KAL, KLM, and BA requested that the FAA 
encourage Boeing to develop an acceptable cost-effective method of 
compliance that does not require installation of an NGS. Cathay also 
urged Boeing to develop a cost-effective solution as method of 
compliance for the proposed actions.
    The FAA agrees that the lack of service information for FQIS 
modifications makes it difficult to assess the required work to modify 
the FQIS, and acknowledges the high cost of NGS. However, the FAA 
disagrees with the commenters' requests. For passenger-carrying 
airplanes, the cost per airplane of providing a modification of the 
FQIS that fully complies with the airworthiness standards was estimated 
by Boeing and their FQIS vendor (Goodrich) prior to the issuance of the 
NPRM to be comparable to the cost of installing NGS. Based on that cost 
estimate, Boeing proposed that they not be required to develop a fully 
compliant FQIS modification for passenger airplanes because it would 
not provide significant savings to operators and NGS would provide a 
greater safety benefit. The FAA agreed.
    The FAA's understanding is that Boeing's current position is the 
same, and that they do not plan to develop a fully compliant FQIS 
modification for passenger airplanes to address paragraph (g) of this 
AD. However, if service information is developed, approved, and 
available in the future, operators may request approval under the 
provisions of paragraph (i) of this AD to use approved service 
instructions as an AMOC for the requirements of this AD, or the FAA may 
approve the service information as a global AMOC for this AD.

Request To Clarify Applicability

    China Eastern Airlines (CEA) asked for clarification regarding the 
airplanes affected by the proposed AD. CEA asked if airplanes equipped 
with NGS satisfy the requirements of paragraph (c)(2) of the proposed 
AD.
    The FAA agrees to clarify. This AD applies to the listed airplane 
models listed in paragraph (c) of this AD, except for those that meet 
one of the exceptions listed in paragraphs (c)(1) through (3) of this 
AD. Paragraph (c)(2) of this AD provides an exception for airplanes 
that already have a flammability reduction means (such as an NGS 
installed in production or using a service bulletin) that meets the 
current airworthiness standards. Therefore, airplanes that are equipped 
with an NGS that meets current FAA airworthiness standards meet the 
requirements of paragraph (c)(2) of this AD and are compliant with the 
AD.

Request To Clarify if a Reference Document Exists for the Modification

    CEA asked if a document exists for operators to reference when 
incorporating the modification specified in paragraph (g) of the 
proposed AD. SIA stated it understands that Boeing intends to propose 
Boeing Service Bulletin 777-47-0002 as an AMOC to the proposed AD.
    The FAA agrees to clarify. This AD requires modifying the FQIS 
using a method approved in accordance with the procedures specified in 
paragraph (i) of this AD. For airplanes identified in the applicability 
of this AD, which excludes airplanes identified in paragraphs (c)(1) 
through (3) of this AD, there currently is no service information for 
accomplishing the FQIS modification. However, Boeing has issued an NGS 
installation service bulletin (Boeing Service Bulletin 777-47-0002, 
Revision 4, dated September 27, 2016) that addresses the unsafe 
condition. For airplanes on which that service bulletin modification is 
installed, the modified airplane would no longer be subject to the 
actions in this AD due to the exception in paragraph (c)(2) of this AD.

Request To Clarify Intent of Different Requirements in Paragraphs (g) 
and (h) of the Proposed AD

    Boeing asked that the FAA clarify the intent of the differences 
between the requirements in paragraphs (g) and (h) of the proposed AD. 
Boeing stated that it is unclear what change is expected for compliance 
with paragraph (g) of the proposed AD versus paragraph (h) of the 
proposed AD. Boeing suggested that one possibility is that paragraph 
(g) of the proposed AD is intended to cover development of transient 
suppression, while paragraph (h) of the proposed AD is intended to 
cover compliance via FQIS wire separation and BITE checks.
    The FAA agrees to clarify. Paragraph (g) of this AD is intended to 
require, for passenger airplanes that are subject to this AD, a 
modification to the FQIS that makes it fully compliant with 14 CFR 
25.981(a), as amended by amendment 25-102. A fully compliant FQIS 
modification might include wire separation or transient suppression 
devices, but due to the system design, either option would likely 
require changes to the FQIS processor.
    Paragraph (h) of this AD is intended to allow, as an optional 
method of compliance for all-cargo airplanes only, a change that 
isolates the center fuel tank circuit wiring between the FQIS processor 
and the fuel tanks from other wiring that is connected to a sufficient 
power source to create an ignition source in the event of a hot short 
between the wiring. Such a change would not be fully compliant with the 
airworthiness regulations (hence the requirement to obtain a partial 
exemption from 14 CFR 25.901(c) and 14 CFR 25.981(a) for any such 
design change), but would provide a level of risk reduction that the 
FAA considers acceptable for all-cargo airplanes and would 
significantly reduce the costs relative to a fully compliant 
modification.

Request To Require Design Changes From Manufacturers

    NATCA recommended that the FAA follow the agency's compliance and 
enforcement policy to require manufacturers to develop the necessary 
design changes soon enough to support operators' ability to comply with 
the proposed requirements. NATCA noted that SFAR 88 required 
manufacturers to develop all design changes for unsafe conditions 
identified by their SFAR 88 design reviews by December 2002, or within 
an additional 18 months if the FAA granted an extension.
    The FAA acknowledges the commenter's concerns. However, any 
enforcement action is outside the scope of this rulemaking. The FAA has 
not changed this final rule regarding this issue.

[[Page 59186]]

Clarification of BITE Check Compliance Time

    The FAA has revised paragraph (h)(1) of this AD to clarify the 
compliance time for the BITE check relative to the requirement to 
record the fault codes. The FAA recognized that operators might 
interpret the proposed requirements for alternative actions for cargo 
airplanes as allowing additional flights prior to performing the BITE 
check after first recording the fault codes. The FAA intended for 
operators to perform the BITE check immediately after recording the 
fault codes to address both the fault codes that exist prior to 
performing the BITE check and any new codes that are identified during 
the BITE check.

Clarification of Applicability

    The FAA has added paragraph (c)(3) of this AD to clarify that 
airplanes equipped with an IMM approved by the FAA as compliant with 
certain regulations are excluded from this AD. The FAA intended for 
airplanes with compliant IMM to be excluded from the actions required 
by this AD. The FAA has determined that the installation of an approved 
IMM provides a level of risk reduction at least as great as that 
provided by FRM and adequately addresses the unsafe condition.

Clarification of Costs of Compliance

    The FAA had previously determined, as specified in the NPRM, that 
the work involved for the cargo airplane wire separation modification 
would take 230 work-hours. Boeing has since provided an updated 
estimate of 74 work-hours for the alternative modification for cargo 
airplanes. The FAA has revised the cost estimate for the modification 
accordingly in this final rule.

Conclusion

    The FAA reviewed the relevant data, considered the comments 
received, and determined that air safety and the public interest 
require adopting this final rule with the changes described previously 
and minor editorial changes. The FAA has determined that these minor 
changes:
     Are consistent with the intent that was proposed in the 
NPRM for addressing the unsafe condition; and
     Do not add any additional burden upon the public than was 
already proposed in the NPRM.
    The FAA also determined that these changes will not increase the 
economic burden on any operator or increase the scope of this final 
rule.

Costs of Compliance

    The FAA estimates that this AD affects 180 airplanes of U.S. 
registry. Currently, there are no experimental, private, business/
corporate/executive, or government aircraft registered in the United 
States that would be affected by this AD. The affected U.S. air-carrier 
passenger airplanes are already required by applicable FAA operating 
regulations to be modified to include FRM, so this AD would not apply 
to those airplanes. However, to address the potential for those 
airplanes to be converted to cargo airplanes before the compliance 
deadline for the operating rule FRM requirement, the FAA provides the 
following cost estimates to comply with this AD:

                                        Estimated Costs: Required Actions
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Modification..................................  600 work-hours x $85 per hour =         $150,000        $201,000
                                                 $51,000.
----------------------------------------------------------------------------------------------------------------

                                      Estimated Costs: Alternative Actions
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
BITE check....................................  1 work-hours x $85 per hour =                 $0   $85 per check
                                                 $85 per check.
Wire separation...............................  74 work-hours x $85 per hour =            10,000          16,290
                                                 $6,290.
----------------------------------------------------------------------------------------------------------------

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII: Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

    This AD will not have federalism implications under Executive Order 
13132. This AD will not have a substantial direct effect on the States, 
on the relationship between the national government and the States, or 
on the distribution of power and responsibilities among the various 
levels of government.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Will not affect intrastate aviation in Alaska, and
    (3) Will not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

    Authority:  49 U.S.C. 106(g), 40113, 44701.

[[Page 59187]]

Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive (AD):

2020-18-12 The Boeing Company: Amendment 39-21233; Docket No. FAA-
2016-6140; Product Identifier 2015-NM-059-AD.

(a) Effective Date

    This AD is effective October 26, 2020.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 777-200, 777-200LR, 
and 777-300 series airplanes, certificated in any category, line 
numbers 1 through 561 inclusive, excluding airplanes identified in 
paragraphs (c)(1) through (3) of this AD.
    (1) Airplanes on which the center tank consists only of the 
inboard structural box of the left and right wings (i.e., the wing 
center structural box is a dry bay and is not part of the fuel 
tank).
    (2) Airplanes equipped with a flammability reduction means (FRM) 
approved by the FAA as compliant with the fuel tank flammability 
reduction (FTFR) requirements of 14 CFR 25.981(b) or 26.33(c)(1).
    (3) Airplanes equipped with an ignition mitigation means (IMM) 
approved by the FAA as compliant with the FTFR requirements of 14 
CFR 25.981(c) or 26.33(c)(2).

(d) Subject

    Air Transport Association (ATA) of America Code 28, Fuel.

(e) Unsafe Condition

    This AD was prompted by the FAA's analysis of the Model 777 fuel 
system reviews conducted by the manufacturer. The FAA is issuing 
this AD to prevent ignition sources inside the center fuel tank, 
which, in combination with flammable fuel vapors, could result in a 
fuel tank explosion and consequent loss of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Modification

    Within 72 months after the effective date of this AD, modify the 
fuel quantity indicating system (FQIS) to prevent development of an 
ignition source inside the center fuel tank due to electrical fault 
conditions, using a method approved in accordance with the 
procedures specified in paragraph (i) of this AD.

(h) Alternative Actions for Cargo Airplanes

    For airplanes used exclusively for cargo operations: As an 
alternative to the requirements of paragraph (g) of this AD, do the 
actions specified in paragraphs (h)(1) and (2) of this AD, using 
methods approved in accordance with the procedures specified in 
paragraph (i) of this AD. To exercise this alternative, operators 
must perform the first inspection required under paragraph (h)(1) of 
this AD within 6 months after the effective date of this AD. To 
exercise this alternative for airplanes returned to service after 
conversion of the airplane from a passenger configuration to an all-
cargo configuration more than 6 months after the effective date of 
this AD, operators must perform the first inspection required under 
paragraph (h)(1) of this AD prior to further flight after the 
conversion.
    (1) Within 6 months after the effective date of this AD, record 
the existing fault codes stored in the FQIS processor and before 
further flight thereafter do a BITE check (check of built-in test 
equipment) of the FQIS. If any nondispatchable fault code is 
recorded prior to the BITE check or as a result of the BITE check, 
before further flight, do all applicable repairs and repeat the BITE 
check until a successful test is performed with no nondispatchable 
faults found, using a method approved in accordance with the 
procedures specified in paragraph (i) of this AD. Repeat these 
actions thereafter at intervals not to exceed 750 flight hours. 
Modification as specified in paragraph (h)(2) of this AD does not 
terminate the repetitive BITE check requirement of this paragraph.
    (2) Within 72 months after the effective date of this AD, modify 
the airplane by separating FQIS wiring that runs between the FQIS 
processor and the center tank wing spar penetrations, including any 
circuits that might pass through a main fuel tank, from other 
airplane wiring that is not intrinsically safe, using methods 
approved in accordance with the procedures specified in paragraph 
(i) of this AD.

(i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Seattle ACO Branch, FAA, has the authority to 
approve AMOCs for this AD, if requested using the procedures found 
in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request 
to your principal inspector or local Flight Standards District 
Office, as appropriate. If sending information directly to the 
manager of the certification office, send it to the attention of the 
person identified in paragraph (j) of this AD. Information may be 
emailed to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration required by this AD 
if it is approved by The Boeing Company Organization Designation 
Authorization (ODA) that has been authorized by the Manager, Seattle 
ACO Branch, to make those findings. To be approved, the repair 
method, modification deviation, or alteration deviation must meet 
the certification basis of the airplane, and the approval must 
specifically refer to this AD.

(j) Related Information

    For more information about this AD, contact Jon Regimbal, 
Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 
2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-
3557; email: Jon.Regimbal@faa.gov.

(k) Material Incorporated by Reference

    None.

    Issued on August 26, 2020.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2020-19584 Filed 9-18-20; 8:45 am]
BILLING CODE 4910-13-P