DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2020-0341; Product Identifier 2020-NM-017-AD]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to adopt a new airworthiness directive
(AD)
for certain The Boeing Company Model 737-600, -700, -700C, -800, -900,
and -900ER series airplanes. This proposed AD was prompted by
significant changes made to the airworthiness limitations (AWLs)
related to fuel tank ignition prevention and the nitrogen generation
system. This proposed AD would require revising the existing
maintenance or inspection program, as applicable, to incorporate the
latest revision of the AWLs. The FAA is proposing this AD to address
the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by June
22, 2020.
ADDRESSES: You may send comments, using the procedures found in
14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
the
instructions for submitting comments.
Fax: 202-493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
For service information identified in this NPRM, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; internet https://www.myboeingfleet.com. You may
view this service information at the FAA, Airworthiness Products
Section, Operational Safety Branch, 2200 South 216th St., Des Moines,
WA. For information on the availability of this material at the FAA,
call 206-231-3195.
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-2020-0341;
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 NPRM, any comments received, and other information. The street
address for Docket Operations is listed above. Comments will be
available in the AD docket shortly after receipt.
FOR FURTHER INFORMATION CONTACT: Christopher Baker, Aerospace Engineer,
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3556; email:
Christopher.R.Baker@faa.gov.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include "Docket No. FAA-2020-0341;
Product Identifier 2020-NM-017-AD" at the beginning of your comments.
The FAA specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The FAA will
consider all comments received by the closing date and may amend this
NPRM because of those comments.
The FAA will post all comments received, without change, to https://www.
regulations.gov, including any personal information you provide.
The FAA will also post a report summarizing each substantive verbal
contact received about this NPRM.
Discussion
The FAA has examined the underlying safety issues involved in fuel
tank explosions on several large transport airplanes, including the
adequacy of existing regulations, the service history of airplanes
subject to those regulations, and existing maintenance practices for
fuel tank systems. As a result of those findings, the FAA issued a
final rule titled "Transport Airplane Fuel Tank System Design Review,
Flammability Reduction and Maintenance and Inspection Requirements"
(66 FR 23086, May 7, 2001). In addition to new airworthiness standards
for transport airplanes and new maintenance requirements that rule
included Amendment 21-78, which established Special Federal Aviation
Regulation No. 88 ("SFAR 88") at 14 CFR part 21. Subsequently, SFAR
88 was amended by Amendment 21-82 (67 FR 57490, September 10, 2002;
corrected at 67 FR 70809, November 26, 2002), Amendment 21-83 (67 FR
72830, December 9, 2002; corrected at 68 FR 37735, June 25, 2003, to
change "21-82" to "21-83"), and Amendment 21-101 (83 FR 9162, March
5, 2018).
Among other actions, SFAR 88 requires certain type design (i.e.,
type certificate (TC) and supplemental type certificate (STC)) holders
to substantiate that their fuel tank systems can prevent ignition
sources in the fuel tanks. This requirement applies to type design
holders for large turbine-powered transport airplanes and for
subsequent modifications to those airplanes. It requires them to
perform design reviews and to develop design changes and maintenance
procedures if their designs do not meet the new fuel tank safety
standards. As explained in the preamble to the final rule published on
May 7, 2001, the FAA intended to adopt airworthiness directives to
mandate any changes found necessary to address unsafe conditions
identified as a result of these reviews.
In evaluating these design reviews, the FAA has established four
criteria intended to define the unsafe conditions associated with fuel
tank systems that require corrective actions. The percentage of
operating time during which fuel tanks are exposed to flammable
conditions is one of these criteria. The other three criteria address
the failure types under evaluation: single failures, single failures in
combination with another latent condition(s), and in-service failure
experience. For all four criteria, the evaluations included
consideration of previous actions taken that may mitigate the need for
further action.
The FAA has determined that the actions identified in this proposed
AD are necessary to reduce the potential of ignition sources inside
fuel tanks, which, in combination with flammable fuel vapors, could
result in fuel tank explosions and consequent loss of the airplane.
The FAA issued AD 2008-10-10 R1, Amendment 39-16164 (75 FR 1529,
January 12, 2010) ("AD 2008-10-10 R1") and AD 2018-20-24, Amendment
39-19458 (83 FR 51815, October 15, 2018) ("AD 2018-20-24"), which
apply to certain The Boeing Company Model 737-600, -700, -700C, -800,
and -900 series airplanes. AD 2008-10-10 R1 and AD 2018-20-24 require
incorporation of fuel system AWLs and also require an initial
inspection to phase in certain repetitive inspections, and repair if
necessary. The fuel system AWLs were developed to satisfy SFAR 88
requirements and included in the Airworthiness Limitations Section
(ALS) of the manufacturer's Instructions for Continued Airworthiness.
Since AD 2008-10-10 R1 and AD 2018-20-24 were issued, the ALS has been
significantly revised by the manufacturer to correct technical and
editorial errors and also to add new requirements. Those changes affect
the fuel system and nitrogen generation system AWLs.
The FAA proposes to adopt this new AD to require revising the
maintenance or inspection program, as applicable, to incorporate the
latest revision of the AWLs. The FAA is proposing this AD to prevent
the potential for ignition sources inside the fuel tanks and also to
prevent increasing the flammability exposure of the center fuel tank
caused by latent failures, alterations, repairs, or maintenance
actions, which could result in a fuel tank explosion and consequent
loss of an airplane.
The FAA has determined that accomplishing the revision required by
paragraph (g) of this proposed AD would terminate the following
requirements for that airplane:
All requirements of AD 2008-10-10 R1.
The revision required by paragraphs (h) and (h)(1) of AD
2008-06-03, Amendment 39-15415 (73 FR 13081, March 12, 2008).
The revision required by paragraph (g) of AD 2008-17-15,
Amendment 39-15653 (73 FR 50714, August 28, 2008).
The revision required by paragraph (k) of AD 2011-18-03,
Amendment 39-16785 (76 FR 53317, August 26, 2011).
All requirements of AD 2013-15-17, Amendment 39-17533 (78
FR 52838, August 27, 2013).
All requirements of AD 2018-20-24.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Boeing 737-600/700/700C/800/900/900ER Special
Compliance Items/Airworthiness Limitations, D626A001-9-04, dated April
2019. This service information describes AWLs that include
airworthiness limitation instructions (ALIs) and critical design
configuration control limitations (CDCCLs) tasks related to fuel tank
ignition prevention and the nitrogen generation system. 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.
FAA's Determination
The FAA is proposing this AD because the agency evaluated all the
relevant information and determined the unsafe condition described
previously is likely to exist or develop in other products of the same
type design.
Proposed AD Requirements
This proposed AD would require revising the existing maintenance or
inspection program, as applicable, to incorporate new or more
restrictive airworthiness limitations.
This proposed AD would require revisions to certain operator
maintenance documents to include new actions (e.g., inspections) and
CDCCLs. Compliance with these actions and CDCCLs is required by 14 CFR
91.403(c). For airplanes that have been previously modified, altered,
or repaired in the areas addressed by this proposed AD, the operator
may not be able to accomplish the actions described in the revisions.
In this situation, to comply with 14 CFR 91.403(c), the operator must
request approval for an alternative method of compliance according to
paragraph (k) of this proposed AD.
Differences Between This Proposed AD and the Service Information
The "description" column of AWL No. 28-AWL-20 identifies certain
operational tests. However, airplanes on which the actions specified in
paragraph (g)(2)(ii) of AD 2011-20-07, Amendment 39-16818 (76 FR 60710,
September 30, 2011), have been done are not required to do the
operational test for left center tank fuel boost pump relay R54 and
right center tank fuel boost pump relay R55.
Paragraph (g) of this proposed AD would require operators to revise
their existing maintenance or inspection program by incorporating, in
part, AWL No. 28-AWL-05, "Wire Separation Requirements for New Wiring
Installed in Proximity to Wiring That Goes Into the Fuel Tanks" in
Boeing 737-600/700/700C/800/900/900ER Special Compliance Items/
Airworthiness Limitations, D626A001-9-04, dated April 2019. Paragraph
(h) of this proposed AD would allow certain changes to be made to the
requirements specified in AWL No. 28-AWL-05 as an option.
Clarification of the Service Information
The "applicability" column of AWL No. 28-AWL-19 identifies
affected airplanes. For airplanes on which the actions specified in
paragraph (s) of AD 2011-18-03 have been done, incorporation of Boeing
Service Bulletin 737-28A1206 is not required. Therefore, those
airplanes are not affected by AWL No. 28-AWL-19 and are not required to
do the functional test.
The "applicability" column of AWL No. 28-AWL-23 identifies
affected airplanes. For airplanes on which the actions specified in
paragraph (s) of AD 2011-18-03 have been done, incorporation of Boeing
Service Bulletin 737-28A1248 is not required. Therefore, those
airplanes are not affected by AWL No. 28-AWL-23 and are not required to
do the functional test.
Costs of Compliance
The FAA estimates that this proposed AD affects 2,057 airplanes of
U.S. registry. The FAA estimates the following costs to comply with
this proposed AD:
The FAA determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although the agency recognizes that this number may vary from operator
to operator. In the past, the FAA estimated that this action takes 1
work-hour per airplane. Since operators incorporate maintenance or
inspection program changes for their affected fleet(s), the FAA
determined that a per-operator estimate is more accurate than a per-
airplane estimate. Therefore, the FAA estimates the average total cost
per operator to be $7,650 (90 work-hours x $85 per work-hour).
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
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
regulation:
(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.
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
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]
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):
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