AD 2016-07-07

[Federal Register Volume 81, Number 65 (Tuesday, April 5, 2016)]
[Rules and Regulations]
[Pages 19472-19482]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2016-07150]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0187; Directorate Identifier 2011-NM-094-AD; 
Amendment 39-18452; AD 2016-07-07]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain 
The Boeing Company Model 757 airplanes. This AD was prompted by fuel 
system reviews conducted by the manufacturer. This AD requires 
modifying the fuel quantity indication system (FQIS) wiring to prevent 
development of an ignition source inside the center fuel tank. We are 
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.

DATES: This AD is effective May 10, 2016.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of May 10, 
2016.

[[Page 19473]]


ADDRESSES: For service information identified in this final rule, 
contact Boeing Commercial Airplanes, Attention: Data & Services 
Management, P. O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 
206-544-5000, extension 1; fax 206-766-5680; Internet <a href="https://www.myboeingfleet.com">https://www.myboeingfleet.com</a>. You may view this referenced service information 
at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., 
Renton, WA. For information on the availability of this material at the 
FAA, call 425-227-1221. It is also available on the Internet at <a href="http://www.regulations.gov">http://www.regulations.gov</a> by searching for and locating Docket No. FAA-2012-
0187.

Examining the AD Docket

    You may examine the AD docket on the Internet at <a href="http://www.regulations.gov">http://www.regulations.gov</a> by searching for and locating Docket No. FAA-2012-
0187; or in person at the Docket Management Facility between 9 a.m. and 
5 p.m., Monday through Friday, except Federal holidays. The AD docket 
contains this AD, the regulatory evaluation, any comments received, and 
other information. The address for the Docket Office (phone: 800-647-
5527) is Docket Management Facility, 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 Branch, ANM-140S, FAA, Seattle Aircraft Certification Office 
(ACO), 1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-
6506; fax: 425-917-6590; email: <a href="/cdn-cgi/l/email-protection#e18b8e8fcf938486888c83808da1878080cf868e97"><span class="__cf_email__" data-cfemail="ef858081c19d8a8886828d8e83af898e8ec1888099">[email&#160;protected]</span></a>.

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a supplemental notice of proposed rulemaking (SNPRM) to 
amend 14 CFR part 39 by adding an AD that would apply to certain The 
Boeing Company Model 757 airplanes. The SNPRM published in the Federal 
Register on February 23, 2015 (80 FR 9400) (``the SNPRM''). We preceded 
the SNPRM with a notice of proposed rulemaking (NPRM) that published in 
the Federal Register on March 1, 2012 (77 FR 12506). The NPRM proposed 
to require modifying the fuel quantity indication system (FQIS) wiring 
or fuel tank systems to prevent development of an ignition source 
inside the center fuel tank. The NPRM was prompted by fuel system 
reviews conducted by the manufacturer. The SNPRM proposed to revise the 
applicability, including alternative actions for cargo airplanes, and 
extend the compliance time. We are issuing this AD to prevent ignition 
sources inside the center fuel tank, which, in combination with 
flammable fuel vapors, could result in fuel tank explosions and 
consequent loss of the airplane.

Record of Ex Parte Communication

    In preparation of AD actions such as NPRMs and immediately adopted 
rules, it is the practice of the FAA to obtain technical information 
and information on the operational and economic impact from design 
approval holders and aircraft operators. We discussed certain issues 
related to this final rule in a meeting held December 1, 2015, with 
Airlines for America (A4A) and other members of the aviation industry. 
This final rule addresses the issues discussed during that meeting that 
are relevant to this final rule. A summary of this meeting can be found 
in the rulemaking docket at <a href="http://www.regulations.gov">http://www.regulations.gov</a> by searching for 
and locating Docket No. FAA-2012-0187.

Comments

    We gave the public the opportunity to participate in developing 
this AD. The following presents the comments received on the SNPRM and 
the FAA's response to each comment.

Request To Withdraw SNPRM: New Certification Requirements for 
Flammability Reduction Means (FRM) Unwarranted

    A4A, representing U.S. cargo operators, stated that the FAA intends 
to issue rulemaking requiring U.S. cargo operators to do additional 
fuel safety modifications to meet the latest aircraft certification 
requirements.
    We infer that A4A considers that requiring airplanes to meet the 
latest certification requirements is not warranted and that the SNPRM 
should therefore be withdrawn. We assume that by ``the latest aircraft 
certification requirements,'' A4A is referring to the relatively new 
requirements for FRM contained in 14 CFR part 125.
    We do not agree that the SNPRM should be withdrawn. This AD is not 
specifically intended to require that the affected airplanes meet the 
flammability requirements of 14 CFR part 125. It is instead intended to 
address an unsafe condition as required by 14 CFR part 39 identified by 
the FAA under the policy contained in the FAA's Special Federal 
Aviation Regulation No. 88 (14 CFR part 21, SFAR 88) AD decision policy 
(Policy Memorandum ANM-100-2003-112-15) (<a href="http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/DC94C3A46396950386256D5E006AED11?OpenDocument&Highlight=anm-100-2003-112-15">http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/DC94C3A46396950386256D5E006AED11?OpenDocument&Highlight=anm-100-2003-112-15</a>), dated February 25, 2003, and the FAA's Transport Airplane Risk 
Assessment Methodology (TARAM) (Policy Statement PS-ANM-25-05) (<a href="http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/4E5AE8707164674A862579510061F96B?OpenDocument&Highlight=ps-anm-25-05">http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/4E5AE8707164674A862579510061F96B?OpenDocument&Highlight=ps-anm-25-05</a>). 
The FAA determined that installing FRM that meets 14 CFR part 125 would 
be one acceptable way to address the identified unsafe condition, so 
airplanes on which such a modification was incorporated were excluded 
from the applicability of the SNPRM. Other modifications identified 
later in this discussion are available as alternative actions to 
installing FRM for certain operations. We have determined it is 
necessary to proceed with issuance of this final rule.

Request To Withdraw SNPRM: Intrusive, Expensive, Unnecessary

    A4A stated that Airbus and Boeing have indicated to them that the 
service bulletins for the wire separation modification that is part of 
the cargo airplane alternative actions will be intrusive and expensive 
and will not significantly improve safety. A4A stated that the safety 
analyses performed by the aircraft manufacturers do not classify the 
proposed modifications as safety critical. A4A noted that those service 
bulletins will not be issued as ``Alert'' service bulletins. 
Additionally, A4A stated that foreign regulatory authorities, aircraft 
manufacturers, and airlines do not support that a safety issue remains.
    We infer that A4A is requesting that we withdraw the SNPRM because 
the airplane manufacturers have determined that an unsafe condition 
does not exist and the SNPRM will not significantly improve safety. We 
do not agree that the SNPRM should be withdrawn. We acknowledge that 
Boeing does not consider the condition associated with FQIS on these 
airplanes to be unsafe. We disagree with Boeing's assertions, for the 
reasons discussed extensively in our response to Boeing's similar 
comment in the SNPRM, under ``Request to Withdraw NPRM (77 FR 12506, 
March 1, 2012): Unjustified by Risk.'' We have determined that it is 
necessary to proceed with issuance of this final rule.

[[Page 19474]]

Request To Withdraw SNPRM: Global Economic Disadvantage to U.S. 
Operators

    A4A does not expect that foreign regulators will require 
modification of affected foreign-registered aircraft, and stated that 
the competitive position of U.S. cargo operators will be harmed as a 
result. A4A stated that foreign regulatory agencies did not mandate 
retrofit of FRM for cargo airplanes, and therefore A4A did not expect 
that those authorities will mandate FQIS changes for their operators. 
A4A's comment made reference to documents published by the European 
Aviation Safety Agency (EASA), the Civil Aviation Authority of China 
(CAAC), and the Japan Civil Aviation Bureau (JCAB) as evidence that 
those agencies are not planning action to address any unsafe condition 
associated with FQIS.
    We infer that A4A is requesting that we withdraw the NPRM because 
other foreign regulatory agencies have determined that an unsafe 
condition does not exist with regard to FQIS as addressed by the 
proposed AD.
    We were unable to examine the EASA document A4A attempted to 
reference because the reference number was incomplete. We do not agree 
that the CAAC and JCAB documents indicate a position on the unsafe 
condition addressed by the SNPRM. Both of those documents simply state 
a requirement for existing type certificate holders to review fuel tank 
designs that is similar to the FAA's SFAR 88. Those documents do not 
state positions on any unsafe conditions or AD proposals identified by 
the FAA, the CAAC, or the JCAB.
    A4A stated that the U.S. air cargo industry is currently in an 
extremely competitive global market. Additional lower deck capacity on 
passenger aircraft, especially through Middle East hubs, has 
significantly increased the need for cargo industry capacity. Several 
cargo carriers have ceased operations, and many others have parked some 
aircraft. U.S. carriers compete directly with foreign cargo operators. 
A4A stated that any additional costs on U.S. cargo operators that are 
not incurred by foreign operators will make U.S. operators less 
competitive and will lead to the loss of jobs in the U.S.
    We infer that A4A is requesting that we withdraw the proposal to 
require corrective action on cargo airplanes because non-U.S. cargo 
operators will not be required to make similar modifications, and the 
FAA AD action would harm the competitive position of U.S. cargo 
operators, resulting in the loss of U.S. jobs.
    We do not agree to withdraw the SNPRM for corrective action on 
cargo airplanes. As part of the AD development process, the FAA works 
with the affected manufacturer to develop a cost estimate for the 
corrective actions in a proposed AD. The FAA considers all possible 
corrective actions proposed by a manufacturer in an attempt to minimize 
the cost burden on operators. In some cases the FAA even makes a 
specific suggestion to a manufacturer for a less costly alternative. In 
the end, the manufacturer is responsible for development of an 
appropriate corrective action.
    While the FAA attempts to minimize the costs associated with a 
required corrective action for a U.S. product, ultimately the FAA has 
the responsibility as the civil aviation authority (CAA) of the state 
of design to address unsafe conditions through AD action. Other CAAs 
overseeing foreign operators will typically apply the FAA AD or develop 
a similar AD for U.S. products operated under each CAA's jurisdiction. 
Other CAAs rely heavily on the knowledge and judgment of the CAA of the 
state of design to identify unsafe conditions and appropriate 
corrective actions for products of that state. The FAA is not aware at 
this time of any affected CAAs that do not plan to issue a 
corresponding mandate to address the unsafe condition associated with 
FQIS identified in the proposed AD. Even if such a situation occurs, 
the FAA would not use a foreign CAA's position as a justification for 
not addressing an unsafe condition identified by the FAA. While we 
acknowledge such a situation could harm the competitive position of a 
U.S. operator, we are still obligated by U.S. law and by international 
treaties to address the identified unsafe condition. We have determined 
that it is necessary to proceed with issuance of this final rule.

Request To Withdraw SNPRM: Costs of Compliance

    A4A stated that the proposed modifications are very costly, and 
noted that United Parcel Service (UPS) has estimated a total cost of 
$16 million for its fleet of four aircraft types that are potentially 
affected by the SNPRM and other similar planned ADs. A4A pointed out 
that U.S. cargo operators have already spent tens of millions of 
dollars on fuel tank safety improvements. UPS alone has spent $35.5 
million to comply with 51 SFAR 88 ADs on the four fleet types 
potentially affected. A4A noted that cargo operators already have 
recurring expenses for Enhanced Airworthiness Program for Airplane 
Safety (EAPAS) maintenance program tasks that continue to help ensure 
fuel tank safety. A4A added that cargo operators have already invested 
in improved and more expensive fuel tank component repair and overhaul 
processes.
    We infer that A4A is requesting that we withdraw the SNPRM because 
the costs of addressing previously identified fuel tank unsafe 
conditions has been high, and that the additional cost to address the 
FQIS latent-plus-one issue will also be high, with very little safety 
benefit.
    We do not agree to withdraw the SNPRM. We acknowledge that the 
total industry cost to address other fuel tank system unsafe conditions 
has been high. The SFAR 88 studies for Boeing airplanes identified 
several basic design deficiencies in lightning protection that could 
cause an ignition source in a fuel tank in the event of a lightning 
strike, and several issues with fuel pump systems and fuel valve 
systems where a single failure could result in an ignition source in a 
fuel tank. Fuel pump issues are suspected to have caused several fuel 
tank ignition events, so these issues were considered to be the highest 
priority for the development of corrective actions and related AD 
actions. The FAA considers the cost of addressing those issues to be 
clearly justified. Deficiencies in maintenance programs and 
inappropriate component repair actions that could lead to inadvertent 
significant increases in the risk of an ignition source in a fuel tank 
were also identified, and the cost of airworthiness limitations to 
address those issues is also considered to be justified.
    The SFAR 88 studies and the FAA's subsequent decision-making 
process identified FQIS vulnerability of Model 707, 727, 737, 747, 757, 
767, and 777 airplanes as an unsafe condition requiring corrective 
action. While the more recently designed of these airplane models have 
significant improvements in FQIS design details, they all have similar 
FQIS design architecture with respect to the identified failure 
scenario. That architecture is vulnerable to a combination of a latent 
in-tank wiring failure and a subsequent wiring failure outside of the 
tank that connects a high power source to the FQIS tank circuit 
creating an ignition source in a fuel tank. This failure combination 
was determined by the National Transportation Safety Board (NTSB) to 
have been the most likely cause of the Model 747 fuel tank explosion 
accident

[[Page 19475]]

off Long Island in 1996. NTSB Safety Recommendation A-98-038 (<a href="http://www.ntsb.gov/about/employment/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-98-038">http://www.ntsb.gov/about/employment/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-98-038</a>) recommended that the FAA require that 
FQIS wiring on all airplane models that have similar wiring 
installations be separated and shielded to the maximum extent possible.
    The FAA issued AD 98-20-40, Amendment 39-10808 (63 FR 52147, 
September 30, 1998); and AD 99-03-04, Amendment 39-11018 (64 FR 4959, 
February 2, 1999); to address this issue on early Model 747 and Model 
737 airplanes, respectively, which used the same FQIS as the accident 
airplane. The FAA subsequently (in 2003) determined that this same 
architectural vulnerability was an unsafe condition for high 
flammability fuel tanks on all Boeing jet transports existing at that 
time. This determination was consistent with the published FAA policy 
for SFAR 88 corrective actions and with the current FAA TARAM 
guidelines for identification of unsafe conditions on transport 
airplanes.
    The FAA deferred acting on this unsafe condition until after the 
FRM rulemaking activity was complete because introduction of FRM had 
the potential to change the classification of many of the affected fuel 
tanks to low flammability. When the final decision for the FRM rule did 
not include a requirement for FRM on all airplanes, the FAA resumed the 
planned actions to address the identified FQIS unsafe condition on the 
airplanes that were not required to have FRM.
    The FAA considers the safety benefit of the SNPRM to be significant 
for both passenger and cargo airplanes. We estimate that the 
installation of compliant FRM will provide approximately an order of 
magnitude reduction in the risk of a fuel tank explosion on anticipated 
flights with a latent failure of an FQIS circuit in the center fuel 
tank. We estimate that the periodic BITE checks in the cargo airplane 
alternative actions will result in a 75- to 90-percent reduction in the 
number of flights that operate with a latent in-tank failure that makes 
them vulnerable to a single additional wiring hot short failure 
creating an ignition source in the center fuel tank. We estimate that 
the proposed wire separation modification in the cargo airplane 
alternative actions will reduce the risk of a hot short (and a 
resultant ignition source) on flights that have a latent in-tank 
failure by 50 to 75 percent. This estimated reduction in the risk on 
anticipated flights with a latent in-tank failure is sufficient to 
reduce the risk below the FAA's TARAM individual flight risk guideline 
level for urgent action. As discussed below in our response to 
``Request to Remove Alternative Actions for Cargo Airplanes,'' we 
determined that further changes to further reduce the risk below the 
TARAM individual flight risk corrective action guideline of 1 in 10 
million per flight hour would significantly increase the costs of 
compliance and are not necessary to adequately address the unsafe 
condition. We have determined that it is necessary to proceed with 
issuance of this final rule.

Request To Withdraw SNPRM: Unsafe Condition Addressed by Previous 
Requirements

    A4A stated that there have been no fuel tank ignition incidents 
since the previously issued fuel tank safety ADs were implemented. A4A 
stated that this provides direct evidence that FAA projections for 
additional incidents were overstated and that SFAR 88 changes have 
worked. They further stated that no unsafe condition exists, asserting 
that service experience has shown that the fuel tank safety issues have 
been sufficiently addressed with significant previous modifications, 
recurring maintenance, controlled overhaul processes and repair 
processes, and maintenance program tasks.
    We infer that A4A is requesting that we withdraw the SNPRM because 
previously required actions have adequately addressed the need for 
improvements in fuel tank safety.
    We do not agree to withdraw the SNPRM. Until recently, fuel tank 
ignition incidents on U.S.- and European-manufactured transport 
airplanes have occurred roughly once every five to six years, with the 
most recent event in May 2006 (a Model 727 airplane in India in 2006, a 
Model 737 airplane in Thailand in 2001, a Model 747 airplane near New 
York in 1996, and a Model 737 airplane in the Philippines in 1991). It 
has now been ten years since the most recent event.
    We agree that a significant improvement in fuel tank safety has 
occurred due to actions that have reduced the potential for ignition 
sources associated with single failures of fuel pumps and fuel pump 
power systems. That improvement alone would be expected to increase the 
average interval between fuel tank ignition incidents to more than ten 
years. However, the fact that no incidents have occurred since 2006 is 
not statistically significant, and is not sufficient to predict that 
additional events will not occur. In addition, even assuming the 
average interval between events is significantly improved to the extent 
that the overall fleet risk is considered acceptable, we would still 
address unsafe conditions identified based on the published FAA policy 
for SFAR 88 corrective actions and the current FAA guidelines for 
identification of unsafe conditions on transport airplanes when the 
individual flight safety risk exceeds our guidelines, as in this case. 
We have determined that it is necessary to proceed with issuance of 
this final rule.

Request To Withdraw SNPRM: All Related NTSB Safety Recommendations 
Closed

    A4A stated that the NTSB previously issued the following safety 
recommendations related to flammability, wiring, and wiring 
maintenance:
    <bullet> A-96-174--Preclude flammable fuel air mixtures in fuel 
tanks. Closed--Acceptable Action: FRM Rulemaking. Safety Recommendation 
A-96-174 can be found at <a href="http://www.ntsb.gov/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-96-174">http://www.ntsb.gov/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-96-174</a>.
    <bullet> A-98-038--Separation of FQIS wires to the max extent 
possible. Closed--Acceptable Action: SFAR 88 Rulemaking.
    <bullet> A-98-039--Require surge protection systems for FQIS wires. 
Closed--Acceptable Action: SFAR 88 Rulemaking. Safety Recommendation A-
98-039 can be found at <a href="http://www.ntsb.gov/about/employment/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-98-039">http://www.ntsb.gov/about/employment/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-98-039</a>.
    <bullet> A-00-106--Assess wiring criticality and separation. 
Closed--Acceptable Action: EAPAS/FTS Rulemaking. Safety Recommendation 
A-00-106 can be found at (<a href="http://www.ntsb.gov/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-00-106">http://www.ntsb.gov/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-00-106</a>.
    <bullet> A-00-108--Repair of potentially unsafe wiring conditions. 
Closed--Acceptable Action: EAPAS/FTS Rulemaking. Safety Recommendation 
A-00-108 can be found at <a href="http://www.ntsb.gov/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-00-108">http://www.ntsb.gov/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-00-108</a>.
    A4A noted that all applicable NTSB safety recommendations are 
closed with acceptable actions taken by the FAA. A4A stated that none 
of the NTSB safety recommendations called for the FAA to address wire 
separation for the FQIS.
    We infer that A4A is requesting that we withdraw the SNPRM because 
the NTSB considers the overall fuel tank safety issue to be adequately 
addressed by previous actions.
    We do not agree to withdraw the SNPRM. A4A appears to have

[[Page 19476]]

misunderstood NTSB Safety Recommendation A-98-038 and the NTSB's 
acceptance of the FAA's response to that safety recommendation. NTSB 
Safety Recommendation A-98-038 specifically called for the FAA to 
require, in ``airplanes with fuel quantity indication system (FQIS) 
wire installations that are co-routed with wires that may be powered, 
the physical separation and electrical shielding of FQIS wires to the 
maximum extent possible.'' The NTSB classified that recommendation as 
``closed, acceptable action'' after the FAA stated that it would issue 
ADs to mandate FQIS protection on the high flammability tanks of 
aircraft on which the installation of FRM is not required by the Fuel 
Tank Flammability Reduction (FTFR) rule (73 FR 42444, July 21, 2008). 
The communications between the NTSB and the FAA on Safety 
Recommendation A-98-038 can be viewed at <a href="http://www.ntsb.gov/about/employment/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-98-038">http://www.ntsb.gov/about/employment/_layouts/ntsb.recsearch/Recommendation.aspx?Rec=A-98-038</a>. We 
have determined that it is necessary to proceed with issuance of this 
final rule.

Request To Withdraw SNPRM: Unjustified by Risk Assessment

    A4A stated that the original equipment manufacturers (OEMs) and 
other regulatory agencies are having difficulty calculating the true 
safety value associated with the proposed FQIS AD. A4A stated that its 
position is that all the unsafe conditions have been mitigated, 
operationally and across industry, and all previous rules have been 
effective. A4A added that, in light of the operators' financial and 
technical investment to mitigate the unsafe conditions in all areas, 
the SNPRM is difficult to understand technically relative to the amount 
of mitigation that would be required, in light of a true risk 
assessment. A4A stated that the FAA is alone in believing that a safety 
issue still exists.
    We infer that A4A is requesting that we withdraw the SNPRM because 
it has not been justified by a risk assessment and because previously 
required actions have adequately addressed the need for improvements in 
fuel tank safety.
    We do not agree to withdraw the SNPRM. We provided a detailed 
response to similar comments and described the FAA's risk assessment in 
the SNPRM in the sections ``Request to Withdraw NPRM (77 FR 12506, 
March 1, 2012): Unjustified by Risk,'' ``Request to Withdraw NPRM (77 
FR 12506, March 1, 2012): Not Supported by Risk Analysis,'' and 
``Request to Withdraw NPRM (77 FR 12506, March 1, 2012): No Unsafe 
Condition,'' as well as in earlier paragraphs in this discussion. We 
have determined that it is necessary to proceed with issuance of this 
final rule.

Request To Remove Requirement for Corrective Actions for Cargo 
Airplanes

    A4A stated that the alternative wire separation modifications 
allowed for cargo airplanes would not meet the ``new design criteria.'' 
(We assume that A4A is referring to the wire separation requirements 
for repairs and modifications that are included in the fuel tank system 
airworthiness limitations required by recent ADs for the various Boeing 
models.) A4A stated that in the Model 757 service bulletin under 
development by Boeing, only about ``5 percent'' of FQIS wires can be 
separated from other systems by a distance of 2 inches, and that the 
majority of the wire bundle relocation will achieve only up to 0.5-inch 
spacing. A4A stated that because the wire separation requirements are 
not met, partial exemptions from the requirements of 14 CFR 25.981 are 
required to allow approval of these wire separation service bulletins. 
Based on the reduced separation distance and the need for exemptions, 
A4A considered the proposed wire separation requirements included in 
the cargo airplane alternative actions to be a symbolic gesture with no 
significant safety benefit, while at the same time being expensive and 
intrusive. A4A further stated that operators have reviewed the 
associated draft service bulletins and are concerned about the lack of 
a design target or adequate rationale for the actions proposed by the 
FAA. Finally, A4A stated that Boeing had stated to them that Boeing 
does not understand what design changes the FAA wants or why the FAA 
considers there to be a safety issue.
    We infer that A4A is requesting that we remove the alternative 
actions for a wire separation modification on cargo airplanes because 
A4A believes the wire separation actions associated with the cargo 
airplane alternative actions in the SNPRM would have no significant 
safety benefit since inadequate physical wire separation is provided.
    We do not agree to withdraw the SNPRM. A4A appears to have 
misunderstood the intent of the FQIS wire separation requirements added 
to the airworthiness limitations as a critical design configuration 
control limitation (CDCCL). The FQIS wire separation CDCCL provides a 
set of wire separation requirements that are intended to be used as a 
default when modifying or repairing an aircraft to ensure that the 
intended level of separation of the FQIS wiring from other wiring is 
maintained. The Model 757 CDCCL (28-AWL-05) contains a simple 2-inch 
separation requirement as originally proposed by Boeing. While Boeing 
has not proposed changes to the Model 757 FQIS wire separation CDCCL, 
the corresponding CDCCL (28-AWL-05) for Model 737-700, -800, and -900 
airplanes has numerous additional provisions approving other design 
approaches (typically combinations of wire sleeving and smaller 
separation distances) that Boeing or operators proposed and that the 
FAA approved. Each time wire separation configuration options were 
approved for Boeing, alternative CDCCL wording was approved as an AMOC 
with the AD that required the addition of the CDCCLs to operators' 
maintenance programs. A similar AMOC will be granted for the approved 
modifications to the FQIS for Model 757 airplanes.
    A4A also appears to have misunderstood the reason that exemptions 
would be required to allow approval of the cargo airplane wire 
separation modification. Lack of a full 2 inches of wire separation in 
all of the changed areas is not the reason an exemption is required. 
Rather, an exemption is required because the overall FQIS will not 
comply with 14 CFR 25.901(c) and 25.981(a)(3) due to the existing 
noncompliance of the unchanged areas of the system. Because those rules 
require a system-level safety analysis, we cannot find the changes to 
the system compliant if a noncompliance exists in the unchanged areas 
of the system.
    The proposed Boeing design uses sleeving over the wire bundles and 
extensive retention features to provide a level of wire protection 
similar to the protection that would be provided by a greater 
separation distance. The design measures are consistent with those 
previously approved by the FAA in the Model 737-700/800/900 CDCCL 
mentioned previously.
    We consider the safety benefit provided by the proposed cargo 
airplane alternative actions to be significant. The unsafe condition 
determination and the rationale and estimated safety benefit for the 
cargo airplane alternative actions were discussed extensively with 
Boeing in several meetings, and we consider that Boeing fully 
understands the FAA's position on each of those aspects of the 
proposal. The proposed requirement for a periodic check through the 
built-in test equipment (BITE) of the FQIS processor is intended to 
identify and result in corrective actions for the detectable fault 
conditions in the FQIS in-tank wiring. We estimated that this

[[Page 19477]]

proposed requirement will result in a 75- to 90-percent reduction in 
the number of flights that operate with a latent in-tank failure that 
makes them vulnerable to a single additional wiring hot short failure 
creating an ignition source in the center fuel tank. The proposed FQIS 
wire separation modification is intended to reduce the risk of a hot 
short of power onto center tank FQIS circuits by physically isolating 
the portions of those circuits that are outside of the tank in the 
areas where those circuits are most vulnerable to damage and most 
easily separated. We did not propose to require modifications of the 
wiring in the electrical racks or in the cockpit areas because of the 
difficulty involved in accessing and achieving additional wire 
separation in those areas, and in recognition that the FQIS processor 
provides some beneficial circuit isolation to protect against hot 
shorts in those areas. We estimated that the proposed wire separation 
modification would reduce the risk of a hot short on flights that have 
a latent in-tank failure by 50 to 75 percent. Those estimates were 
reviewed with Boeing, and Boeing did not disagree with those estimates. 
We have determined it is necessary to proceed with issuance of this 
final rule.

Request To Remove Alternative Actions for Cargo Airplanes

    Colin Edwards and an anonymous commenter made no explicit request 
to change the SNPRM, but objected to the proposed addition of 
alternative actions for cargo airplanes that would allow a design 
change that does not fully comply with the fuel tank system safety 
requirements of 14 CFR part 25 (14 CFR 25.981(a)(3)) to be used to 
address the unsafe condition. The commenters stated that it should not 
be acceptable to allow greater risk to exist on cargo airplanes than 
that allowed for passenger airplanes.
    We infer that the commenters propose the elimination of the 
proposed alternative corrective action for cargo airplanes. We disagree 
with this request. We determined that an acceptable level of safety 
would be provided for the affected cargo airplanes, and explained our 
position in depth in response to similar comments in the SNPRM. 
However, we will attempt to address the commenters' concerns by 
expanding on the explanation of our safety determination.
    When assessing potential unsafe conditions on transport airplanes 
to determine if corrective action is necessary, the FAA assesses the 
total risk to the affected fleet of airplanes exposed to the condition, 
and assesses the level of risk on individual airplanes within the 
fleet. The FAA's guidelines for assessing the total fleet risk related 
to the unsafe condition are slightly different for cargo and passenger 
airplanes due to operational usage differences. In this case, however, 
the total risk to the affected fleet is lower than the unsafe condition 
risk guidelines for both passenger and cargo airplanes. Total fleet 
risk is therefore not the risk assessment element driving the proposed 
actions.
    When assessing the level of risk on individual airplanes, the FAA 
considers the risk on the worst reasonably anticipated flights to 
ensure that the level of safety on each flight is acceptable. Our 
individual flight risk unsafe condition threshold is 1 x 10E-7 events 
(or a 1-in-10-million chance of a catastrophic event) per flight hour. 
In addition, the worst reasonably anticipated flights should not be 
vulnerable to a single failure that causes a fatal event, regardless of 
probability. There is no difference in the individual flight risk 
unsafe condition criteria for cargo airplanes and passenger airplanes 
because the operational differences are not considered in this risk 
calculation.
    In this case, we are concerned about a latent failure inside the 
fuel tank that, in combination with an electrical short circuit in FQIS 
wiring outside of the tank, could result in an electrical spark or arc 
in the tank. An electrical arc or spark in the fuel tank combined with 
flammable conditions in the fuel tank could result in a fuel tank 
explosion. The worst reasonably anticipated flights in this case are 
those that have both the latent failure and flammable conditions in the 
tank. The manufacturer's analysis indicates that a significant number 
of flights would be expected to occur with these conditions in the life 
of the affected fleet if no corrective action is taken. For those 
flights, one additional failure--a short circuit between FQIS wiring 
and power wiring--could cause a fuel tank explosion. Also, the 
probability of an explosion is between 1 in a million and 1 in 10 
million, per flight hour, which slightly exceeds the numerical unsafe 
condition guideline for individual flight risk discussed above.
    An issue that violates one or more of the individual flight risk 
guidelines would normally require corrective action that reduces the 
risk to a level that is below the unsafe condition guidelines. However, 
in this case the FAA acknowledged that the cost of corrective action is 
high, and that the available corrective action (fuel tank FRM systems) 
would reduce, but not eliminate, the number of expected flights with 
the condition we are concerned about (a latent failure plus flammable 
conditions inside the tank). The alternative actions for cargo 
airplanes would also reduce the number of expected flights with the 
condition we are concerned about, but to a lesser degree. The FAA has 
determined that allowing a moderate number of cargo flights per year 
(on average) with this condition provides an acceptable level of 
safety. As part of making this determination, we noted that the level 
of risk on the worst reasonably anticipated flights is similar to the 
level of risk for private and commercial pilots flying normal category 
airplanes.
    We have not changed the final rule regarding this issue.

Request To Require FQIS Modification in all Fuel Tanks

    National Air Traffic Controllers Association (NATCA) requested that 
we require changes to the FQIS to address the potential ``latent-plus-
one-failure scenario'' in all fuel tanks, not just in the center fuel 
tank.
    NATCA stated that the failure condition that is the subject of the 
SNPRM should be classified as a ``known'' latent-plus-one-failure 
condition when applying the FAA Transport Airplane Directorate Policy 
Memorandum 2003-112-15, ``SFAR 88--Mandatory Action Decision 
Criteria,'' dated February 25, 2015 (http://rgl.faa.gov/
Regulatory_and_Guidance_Library/rgPolicy.nsf/0/
dc94c3a46396950386256d5e006aed11/$FILE/Feb2503.pdf). NATCA stated that 
this would have the effect of classifying the failure condition as an 
unsafe condition requiring corrective action in all affected fuel tanks 
regardless of flammability level.
    NATCA considered the combination of a latent in-tank failure with 
electrical energy transmitted into the fuel tank via the FQIS wiring 
due to an additional failure outside of the tank to be a ``known'' 
failure condition because that failure condition was considered to be 
the most likely cause of the TWA Flight 800 Model 747 accident. (That 
accident occurred on July 17, 1996, shortly after takeoff from John F. 
Kennedy International Airport in Jamaica, New York.) NATCA concluded 
that because the Model 757 FQIS is similar to that of the Model 747, 
both models are vulnerable to the same failure scenario. NATCA cited 
the unsafe condition statement for the SNPRM as evidence that the 
scenario should be classified as ``known.'' NATCA pointed out that the 
FAA issued AD 98-20-40, Amendment 39-10808 (63 FR 52147, September 30, 
1998), to address this issue for Model

[[Page 19478]]

747 airplanes, and pointed out that the FAA TARAM Handbook specifically 
states that Policy Memorandum 2003-112-15 should be followed in 
determining whether corrective action should be required for fuel tank 
safety concerns identified through SFAR 88.
    We disagree with the request to require modification of the FQIS in 
all fuel tanks. We have determined that, under the policy contained in 
the policy memorandum, this failure condition for the Model 757 FQIS 
should not be classified as ``known.'' The memo defines ``known'' 
failure conditions as follows:

    [T]hose conditions which have occurred in-service and are likely 
to occur on other products of the same or similar type design, and 
conditions which have been subject to mandatory corrective actions, 
following in-service findings, on products with a similar design of 
fuel system.

    We agree that the Model 757 FQIS has the same high-level system 
architecture and operating principles as those of the Model 747 FQIS, 
resulting in vulnerability to the same theoretical latent-plus-one-
failure scenario. There are, however, significant differences in the 
details of the Model 757 FQIS design that reduce the likelihood of the 
individual contributing failures. Those differences include the 
following:
    <bullet> Improved FQIS probe terminal connector block design;
    <bullet> The use of wiring that is not silver plated and therefore 
does not create silver sulfide deposits on the terminal blocks;
    <bullet> The use of improved wire types and wiring installation 
practices outside of the fuel tanks; and
    <bullet> The use of a system processor that provides significant 
isolation of the tank probe circuits from the indication and power 
circuits of the FQIS.
    We therefore did not consider that the FQIS designs for the Model 
747 and Model 757 were so similar that the Model 757 FQIS design should 
be considered to have a ``known'' latent-plus-one-failure condition 
vulnerability as defined in the policy memorandum. The provisions in 
the above definition for classifying a failure condition as ``known'' 
based on the existence of a similar design were intended to allow the 
FAA to evaluate the degree of similarity in the design, and to make 
discretionary judgments in determining that a failure condition that is 
believed to have occurred (and/or was addressed by AD action) in one 
specific design should be classified as ``known'' in a different 
specific design. The application of that discretion would be expected 
to involve evaluation of design detail differences and the effects of 
those differences on failure modes and failure probability. Based on 
our determination that sufficient design differences exist between the 
Model 757 and Model 747 FQIS designs to not classify the Model 757 FQIS 
latent-plus-one-failure condition as ``known,'' under the direction 
contained in the policy memorandum, this AD addresses that failure 
condition vulnerability only for the center fuel tank, which is the 
only high-flammability fuel tank on the Model 757.
    NATCA expressed a concern that the FAA did not understand NATCA's 
previous comment on this matter, and stated that the FAA had not 
considered the requirements of ``Element 2.a)'' from Policy Memorandum 
2003-112-15, dated February 25, 2015. In fact, we had addressed the 
requirements of ``Element 2.a)'' in the response to the comments under 
``Request to Revise Proposed AD Requirements to Apply to All Fuel 
Tanks'' of the SNPRM. The FAA understood the earlier comment and 
understands the more recent comment, but has reached a different 
conclusion about the classification of the failure condition under the 
guidance in the policy memorandum. We classified the Model 757 FQIS 
latent-plus-one-failure scenario as a theoretical vulnerability rather 
than a ``known'' combination of failures. Policy Memorandum 2003-112-
15, dated February 25, 2015, calls for corrective action for 
theoretical latent-plus-one-failure conditions only in high-
flammability fuel tanks. Contrary to the assertion in the NATCA 
comment, the acknowledgement of the scenario as theoretically possible 
and the consequent AD proposal to address the scenario in the high 
flammability center fuel tank do not automatically drive classification 
of the failure as ``known'' under the policy memorandum. We have not 
changed this final rule regarding this issue.

Request To Address Unsafe Condition in All Fuel Tanks, With or Without 
FRM

    NATCA requested that we require design changes to the FQIS to 
address the potential latent-plus-one-failure scenario in all fuel 
tanks of all Model 757 airplanes, regardless whether FRM is installed. 
NATCA stated that the minimum performance standards for FRM contained 
in 14 CFR part 25 allow flights to occur with flammable conditions in 
tanks that are required to incorporate FRM due to system performance as 
designed and due to system failures. In addition, time-limited dispatch 
with an inoperative FRM has been allowed in the master minimum 
equipment list (MMEL) for affected airplanes. Flights with flammable 
conditions and a pre-existing latent in-tank FQIS failure are 
reasonably anticipated to occur in the life of the affected fleet. For 
those flights, a fuel tank explosion could occur due to a single 
additional failure (hot short of power onto FQIS tank probe circuits). 
NATCA notes that four fuel tank explosion events have occurred in fuel 
tanks that are classified as low flammability.
    We disagree with the request. We have determined that the proposed 
corrective actions (either installation of FRM or specific FQIS changes 
limited to the center fuel tank) represent a reasonable, cost-effective 
method to achieve a meaningful reduction in the risk of an accident due 
to potential FQIS fuel tank ignition sources.
    The service history of conventional unheated aluminum wing tanks 
that contain Jet A fuel indicates that there would be little safety 
benefit by further limiting the flammability of these tanks. While 
NATCA expressed concern because fuel vapor ignition events have 
occurred in wing fuel tanks, NATCA did not differentiate service 
experience based on fuel type used (JP-4 versus Jet A fuel).
    Our review of the nine wing tank ignition events we know to have 
occurred on turbine-engine-powered transport airplanes shows that five 
of the nine airplanes were using JP-4 fuel, and this type of fuel is no 
longer used except on an emergency basis in the U.S. Use of JP-4 fuel 
in other parts of the world is also relatively rare, and is normally 
limited to areas with extremely cold airport conditions. Three of the 
remaining four events were caused by external heating of the wing by 
engine fires, and the remaining event occurred on the ground during 
maintenance. To date, there have been no fuel tank explosions in 
conventional unheated aluminum wing tanks fueled with Jet A fuel that 
have resulted in any fatalities.
    The flammability characteristics of JP-4 fuel results in the fuel 
tanks being flammable a significant portion of the time when an 
airplane is in flight. This is not the case for wing tanks containing 
Jet A fuel. Therefore, based on the low fleet average flammability of 
the Model 757 wing fuel tanks and on the specific features of the Model 
757 FQIS design, we have determined that the latent-plus-one 
vulnerability that exists in the Model 757 wing tank FQIS is not an 
unsafe condition requiring corrective action on in-service airplanes.
    We have not changed this final rule regarding this issue.

[[Page 19479]]

Request To Require Design Changes for Full Compliance with 
Airworthiness Regulations

    NATCA requested that we require design changes to the FQIS that 
would bring that system into full compliance with the applicable 
airworthiness regulations. NATCA stated that the failure condition that 
is the subject of the SNPRM represents a noncompliance of the type 
design with the requirements of 14 CFR 25.901(c) and 25.981(a)(3), even 
for low-flammability fuel tanks. NATCA stated that the proposed 
corrective actions would not bring the airplane design into compliance 
with those regulations ``as required by SFAR 88 and SFAR 88 Policy 
published by the FAA as Mandatory Corrective Action criteria in FAA 
Policy Statement No. 2003-112-15.'' NATCA added that the proposed 
alternative corrective actions for cargo airplanes do not comply with 
those regulations because the alternative actions do not fully 
eliminate the potential for the failure condition that is addressed by 
the SNPRM.
    We disagree with the request. SFAR 88, as modified by Amendment 21-
82, and Policy Memorandum 2003-112-15, dated February 25, 2003, do not 
specifically require noncompliant designs discovered through SFAR 88 to 
be brought into compliance. As originally issued, SFAR 88 required 
design approval holders to develop the corrective actions necessary to 
bring any noncompliant design fuel system features into compliance. 
However, SFAR 88 did not dictate that the FAA require a given 
corrective action. In fact, the FAA later published Amendment 21-82, 
``Equivalent Safety Provisions for Fuel Tank System Fault Tolerance 
Evaluations (SFAR 88),'' to clarify that the FAA would accept SFAR 88 
reports that do not provide corrective actions that directly comply 
with 14 CFR 25.981(a)(3) provided any aspects that do not comply are 
compensated for by factors that provide an equivalent level of safety. 
The FAA used the introduction of flammability reduction in place of 
corrective action for a specific ignition source as an example of a 
potentially acceptable compensating factor.
    Also, while the normal certification process requires proposed 
design changes to be compliant with the applicable regulations, 
applicants are permitted under 14 CFR part 11 to petition for an 
exemption from any FAA regulatory requirement. Policy Memorandum 2003-
112-15, dated February 25, 2003, did not state that the FAA would not 
consider a petition for exemption from an airworthiness requirement for 
a proposed design intended as corrective action for an SFAR 88 issue. 
We therefore consider that the applicant may petition for an exemption 
and propose a noncompliant design change, and the FAA may approve and 
issue an AD to require a noncompliant design change. Boeing's FRM 
design change for the Model 757 was approved some time ago. We have 
determined that for Model 757 airplanes, installation of FRM, instead 
of FQIS design changes, represents a reasonable, cost-effective method 
to achieve a meaningful overall reduction in the risk of an accident 
due to fuel tank ignition events. We therefore excluded airplanes with 
FRM installed from the applicability of this AD.

Request To Mandate Compliance with Airworthiness Regulations for Newly 
Produced Airplanes

    NATCA requested that we require newly produced airplanes to be in 
compliance with 14 CFR 25.901, 25.981(a), and 25.981(b). NATCA 
expressed concern that nearly 20 years after the TWA Flight 800 
accident, manufacturers have been allowed to continue production of 
airplanes without making changes to eliminate the FQIS latent-plus-one-
failure scenario, and that the FAA has granted exemptions to approve 
certain design changes without fully addressing the issue.
    We disagree with the request. This AD applies only to certain Model 
757 series airplanes, and the Model 757 is out of production. The 
comment is therefore outside of the scope of this AD. We have not 
changed the final rule regarding this issue.

Request To Allow Alternative Procedure for BITE Check

    FedEx proposed that we revise paragraph (h)(1) of the SNPRM to 
allow use of the FQIS BITE check procedure in its airplane maintenance 
manual (AMM) as an alternative to the procedure in Boeing Service 
Bulletin 757-28-0136, dated June 5, 2014, which does not apply to 
FedEx's fleet. We assume this is because FedEx operates some airplanes 
that were converted to a cargo configuration using a non-Boeing 
supplemental type certificate.
    We disagree with the request. FedEx's comment did not provide 
adequate information to show that its AMM procedure is equivalent to 
the procedure described in Boeing Service Bulletin 757-28-0136, dated 
June 5, 2014. FedEx's comment also did not identify the fault 
conditions for which dispatch would be prohibited. We therefore do not 
have sufficient information at this time to allow FedEx's proposed 
alternative procedure. However, under the provisions of paragraph (i) 
of this AD, we will consider requests for approval of alternative 
procedures, if sufficient data are submitted to substantiate that the 
change would provide an acceptable level of safety. We have not changed 
this final rule regarding this request.

Request To Reduce Compliance Time

    NATCA requested that we reduce the compliance time to 5 years or 
less. NATCA noted that the proposed 72-month compliance time would 
result in a corrective action deadline that is approximately 27 years 
after the TWA Flight 800 accident. NATCA stated that such a long delay 
in action is not in the public interest.
    We disagree with the request to reduce the compliance time, which 
we have determined is necessary to give operators adequate time to 
prepare for and perform the required modifications without excessive 
disruption of operations. We had initially proposed 60 months, but 
extended that to 72 months in response to operator comments, which 
included extension requests of up to 108 months. NATCA made a similar 
comment to the NPRM (77 FR 12506, March 1, 2012), requesting a 
reduction in the compliance time to 36 months, and the FAA provided its 
response in the SNPRM under ``Request to Reduce Compliance Time.'' We 
have not changed this final rule regarding this issue.

Statement Regarding Compliance Time for Wire Separation

    FedEx stated that without service information for the wire 
separation, it cannot effectively determine whether the proposed 72-
month compliance time is acceptable.
    We had previously determined, as specified in the SNPRM, that the 
work involved for the cargo airplane wire separation modification would 
take 230 work-hours, and a compliance time of 72 months would be 
adequate for operators to perform the modification on their affected 
fleets. Boeing has since provided an updated estimate of 74 work-hours 
for the alternative modification for cargo airplanes. We have revised 
the cost estimate accordingly in this final rule, but since this change 
reduces the work-hour estimate, it is not necessary to adjust the 
compliance time to accommodate the workload for this action for cargo 
operators.

[[Page 19480]]

Request To Remove Reference to ``Fuel Tank Systems''

    Paragraph (g) of the SNPRM would have required modification of 
``the FQIS wiring or fuel tank systems.'' Boeing asked that we remove 
reference to ``fuel tank systems'' in this proposed requirement because 
a fuel tank system modification could be done as an AMOC.
    We agree with the commenter's request and rationale. We have 
removed the references to ``fuel tank systems'' throughout the preamble 
and in paragraph (g) of this AD.

Request To Clarify Condition Requiring Repair

    Boeing requested that we revise paragraph (h)(1) of the SNPRM to 
specify that repair is required for any ``nondispatchable'' fault code 
recorded before or as a result of the BITE check. (The SNPRM would have 
required repair for any fault code.) Boeing requested this change to 
make the repair requirement consistent with the BITE check service 
information referenced in the SNPRM (Boeing Service Bulletin 757-28-
0136, dated June 5, 2014).
    We agree with the request. The intent of the SNPRM was to require 
correction only of faults identified as ``nondispatchable.'' The SNPRM 
used the terminology ``as applicable'' to indicate this intent, but we 
agree that further clarification is appropriate. We have revised 
paragraph (h)(1) in this AD as requested by the commenter.

Request To Clarify End Point for FQIS Wire Separation

    Paragraph (h)(2) of the SNPRM specified that the FQIS wiring 
separation was to be done on the wiring that runs between the FQIS 
processor and the center fuel tank. Boeing requested that we change 
``the center fuel tank'' to ``the center fuel tank wall penetrations.'' 
Boeing requested this change to clarify the end point for the FQIS wire 
separation.
    We agree with the request. Boeing's suggestion is consistent with 
the intent of this AD, and improves the clarity of the requirement. We 
have revised paragraph (h)(2) in this AD to incorporate Boeing's 
request.

Request To Delay Final Rule Pending New Service Information

    Boeing requested that we delay issuance of the final rule pending 
issuance of new service information that would specifically define an 
acceptable wiring configuration that complies with the proposed 
requirements.
    We disagree with the request because the referenced service 
information was not available at the time we were ready to publish the 
final rule, and we cannot reliably predict the time that service 
information will be issued by Boeing. We do not consider it in the 
public interest to further delay this rulemaking. We have determined 
that it is necessary to proceed with issuing the final rule as 
proposed. Operators may, however, request approval under the provisions 
of paragraph (i) of this AD to use a future approved service bulletin, 
if developed, as an AMOC with the requirements of this AD, or we may 
approve the service bulletin as a global AMOC.

Statement Regarding Unsafe Condition

    Boeing stated that it has accepted the FAA's requirement to provide 
service information defining an acceptable wire separation 
modification, but, based on previously provided analysis, maintained 
that the risk level is less than extremely improbable. As asserted in 
earlier comments, Boeing considers the design of the affected airplanes 
safe and the proposed requirements therefore unnecessary.
    We disagree with Boeing's assertions for the reasons discussed 
extensively in our response to Boeing's similar comment in the SNPRM. 
The FAA's response to Boeing's assertion is covered in the response to 
comments in the SNPRM under ``Request to Withdraw NPRM (77 FR 12506, 
March 1, 2012): Unjustified by Risk.''

Additional Change Made to This AD

    We have revised the introductory text to paragraph (h) of this AD 
to clarify that the alternative modification for cargo airplanes must 
be accompanied by periodic BITE checks started within 6 months after 
the effective date of this AD. And, for airplanes converted to an all-
cargo configuration more than 6 months after the effective date of this 
AD, operators must perform the first BITE check before flight after the 
conversion. In reviewing the proposed requirements after publication of 
the SNPRM, we recognized that operators might interpret the 
requirements as allowing a delay in the decision to exercise the cargo 
airplane alternative until late in the compliance period. That is not 
the literal meaning of the proposed language of the requirement, and 
was not the FAA's intent. However, we determined that we should clarify 
the language of paragraph (h) of this AD regarding the required timing 
for the first BITE check if an operator chooses to exercise the cargo 
airplane alternative.

Conclusion

    We reviewed the relevant data, considered the comments received, 
and determined that air safety and the public interest require adopting 
this AD with the changes described previously and minor editorial 
changes. We have determined that these minor changes:
    <bullet> Are consistent with the intent that was proposed in the 
SNPRM for correcting the unsafe condition; and
    <bullet> Do not add any additional burden upon the public than was 
already proposed in the SNPRM.
    We also determined that these changes will not increase the 
economic burden on any operator or increase the scope of this AD.

Related Service Information Under 1 CFR Part 51

    We have reviewed Boeing Service Bulletin 757-28-0136, dated June 5, 
2014, which describes procedures for a BITE check (check of built-in 
test equipment). This service information is reasonably available 
because the interested parties have access to it through their normal 
course of business or by the means identified in the ADDRESSES section.

Costs of Compliance

    We estimate that this AD affects 167 airplanes of U.S. registry. 
This estimate includes 148 cargo airplanes and 19 non-air-carrier 
passenger airplanes. We estimate the following costs to comply with 
this AD:

                              Estimated Costs: Basic Requirement for All Airplanes
----------------------------------------------------------------------------------------------------------------
                Action                          Labor cost             Parts cost          Cost per product
----------------------------------------------------------------------------------------------------------------
Fully correct FQIS vulnerability to     1,200 work-hours x $85              $200,000  $302,000
 latent-plus-one-failure conditions.     per hour = $102,000.
----------------------------------------------------------------------------------------------------------------

[[Page 19481]]

 
                             Estimated Costs: Alternative Actions for All Airplanes
----------------------------------------------------------------------------------------------------------------
Install FRM...........................  720 work-hours x $85 per             323,000  $384,200.
                                         hour = $61,200.
----------------------------------------------------------------------------------------------------------------
                            Estimated Costs: Alternative Actions for Cargo Airplanes
----------------------------------------------------------------------------------------------------------------
Wire separation.......................  74 work-hours x $85 per               10,000  $16,290.
                                         hour = $6,290.
----------------------------------------------------------------------------------------------------------------
FQIS BITE check (required with wire     1 work-hour x $85 per                      0  $85 per check (4 checks
 separation alternative actions).        hour = $85.                                   per year).
----------------------------------------------------------------------------------------------------------------

    Existing regulations already require that air-carrier passenger 
airplanes be equipped with FRM by December 26, 2017. We therefore 
assume that the FRM installation specified in paragraph (g) of this AD 
will be done on only the 19 affected non-air-carrier passenger 
airplanes, for an estimated passenger fleet cost of $7,299,800. We also 
assume that the operators of the 148 affected cargo airplanes would 
choose the less costly actions specified in paragraph (h) of this AD, 
at an estimated cost of $2,410,920 for the wire separation 
modification, plus $50,320 annually for the BITE checks.

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.
    We are 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) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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.


Sec.  39.13  [Amended]

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


2016-07-07 The Boeing Company: Amendment 39-18452; Docket No. FAA-
2012-0187; Directorate Identifier 2011-NM-094-AD.

(a) Effective Date

    This AD is effective May 10, 2016.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 757-200, -200PF, -
200CB, and -300 series airplanes; certificated in any category; 
except airplanes equipped with a flammability reduction means (FRM) 
approved by the FAA as compliant with the Fuel Tank Flammability 
Reduction (FTFR) rule (73 FR 42444, July 21, 2008) requirements of 
14 CFR 25.981(b) or 14 CFR 26.33(c)(1).

(d) Subject

    Joint Aircraft System Component (JASC) Code 7397: Engine fuel 
system wiring.

(e) Unsafe Condition

    This AD was prompted by fuel system reviews conducted by the 
manufacturer. We are 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 indication system (FQIS) wiring to prevent development 
of an ignition source inside the center fuel tank, 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 (h)(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 then do a 
BITE check (check of built-in test equipment) of the FQIS, in 
accordance with the

[[Page 19482]]

Accomplishment Instructions of Boeing Service Bulletin 757-28-0136, 
dated June 5, 2014. 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 fault 
found, in accordance with the Accomplishment Instructions of Boeing 
Service Bulletin 757-28-0136, dated June 5, 2014. Repeat these 
actions thereafter at intervals not to exceed 750 flight hours.
    (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 fuel tank wall penetrations, including any 
circuits that pass through a main fuel tank, from other airplane 
wiring that is not intrinsically safe.

(i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Seattle Aircraft Certification Office (ACO), 
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 ACO, send it to the 
attention of the person identified in paragraph (j) of this AD. 
Information may be emailed to: <a href="/cdn-cgi/l/email-protection#d3eafe929d9efe80b6b2a7a7bfb6fe92909cfe929e9c90fe81b6a2a6b6a0a7a093b5b2b2fdb4bca5"><span class="__cf_email__" data-cfemail="7f46523e3132522c1a1e0b0b131a523e3c30523e32303c522d1a0e0a1a0c0b0c3f191e1e51181009">[email&#160;protected]</span></a>.
    (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 Commercial Airplanes Organization 
Designation Authorization (ODA) that has been authorized by the 
Manager, Seattle ACO, 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 Branch, ANM-140S, FAA, Seattle ACO, 
1601 Lind Avenue SW., Renton, WA 98057-3356; phone: 425-917-6506; 
fax: 425-917-6590; email: <a href="/cdn-cgi/l/email-protection#90fafffebee2f5f7f9fdf2f1fcd0f6f1f1bef7ffe6"><span class="__cf_email__" data-cfemail="bdd7d2d393cfd8dad4d0dfdcd1fddbdcdc93dad2cb">[email&#160;protected]</span></a>.

(k) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (i) Boeing Service Bulletin 757-28-0136, dated June 5, 2014.
    (ii) Reserved.
    (3) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Data & Services Management, 
P. O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544-
5000, extension 1; fax 206-766-5680; Internet <a href="https://www.myboeingfleet.com">https://www.myboeingfleet.com</a>.
    (4) You may view this service information at FAA, Transport 
Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For 
information on the availability of this material at the FAA, call 
425-227-1221.
    (5) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, call 202-741-6030, or go to <a href="http://www.archives.gov/federal-register/cfr/ibr-locations.html">http://www.archives.gov/federal-register/cfr/ibr-locations.html</a>.

    Issued in Renton, Washington, on March 21, 2016.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2016-07150 Filed 4-4-16; 8:45 am]
 BILLING CODE 4910-13-P