[Federal Register Volume 84, Number 250 (Tuesday, December 31, 2019)]
[Rules and Regulations]
[Pages 72227-72230]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-27885]
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Rules and Regulations
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains regulatory documents
having general applicability and legal effect, most of which are keyed
to and codified in the Code of Federal Regulations, which is published
under 50 titles pursuant to 44 U.S.C. 1510.
The Code of Federal Regulations is sold by the Superintendent of Documents.
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Federal Register / Vol. 84, No. 250 / Tuesday, December 31, 2019 /
Rules and Regulations
[[Page 72227]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2016-9072; Product Identifier 2015-NM-110-AD; Amendment
39-19797; AD 2019-23-04]
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 727 airplanes. This AD was prompted by
the FAA's analysis of the Model 727 fuel system review conducted by the
manufacturer. This AD requires modifying the fuel quantity indicating
system (FQIS) to prevent development of an ignition source inside the
body-mounted auxiliary fuel tanks due to electrical fault conditions.
As an alternative to the modification, this AD allows deactivating the
body-mounted auxiliary fuel tanks. The FAA is issuing this AD to
address the unsafe condition on these products.
DATES: This AD is effective February 4, 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-
9072; or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
this final rule, the regulatory evaluation, any comments received, and
other information. The address for Docket Operations 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:
[email protected].
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain Boeing Model
727 airplanes equipped with Boeing body-mounted auxiliary fuel tanks.
The NPRM published in the Federal Register on September 23, 2016 (81 FR
65579). The NPRM was prompted by the FAA's analysis of the Model 727
fuel system review conducted by the manufacturer. The NPRM proposed to
require modifying the FQIS to prevent development of an ignition source
inside the body-mounted auxiliary fuel tanks due to electrical fault
conditions. As an alternative to the modification, the NPRM proposed to
allow deactivating the body-mounted auxiliary fuel tanks.
The FAA is issuing this AD to address ignition sources inside the
body-mounted auxiliary fuel tanks, 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.
Request To Withdraw NPRM: No Unsafe Condition
Boeing requested that the FAA withdraw the NPRM. Boeing reported
that its system safety assessment determined that the FQIS on the Model
727 airplane does not have an unsafe condition.
The FAA disagrees with the request. Boeing did not provide specific
details about the type of assessment that was performed (total fleet
risk, average risk per flight hour, peak individual flight risk, etc.).
Based on Boeing's fuel system safety assessment submitted in response
to Special Federal Aviation Regulation No. 88 (``SFAR 88'') of 14 CFR
part 21, the FAA has determined that there is an unsafe condition due
to the potential for a fuel tank ignition source to occur from the FQIS
due to its design architecture, component design details, and
installation design details. The FAA's determination was made in
accordance with the guidance contained in FAA Policy Memorandum ANM100-
2003-112-15, ``SFAR 88--Mandatory Action Decision Criteria,'' dated
February 25, 2003.\1\ Under that policy, an ignition source that can
occur in a high-flammability fuel tank, due to a combination of a
preexisting failure that can exist undetected for multiple flights and
one additional failure, is an unsafe condition requiring corrective
action. High-flammability fuel tanks are defined in the policy as fuel
tanks with a fleet average flammability greater than 7 percent as
calculated in accordance with 14 CFR Appendix N of part 25. At the time
of the unsafe condition determination in April 2003, Boeing
acknowledged that the Model 727 body-mounted auxiliary fuel tanks are
high-flammability fuel tanks. The Boeing SFAR 88 report for the Model
727 showed that a combination of an in-tank wire fault or contamination
condition (which can remain latent for multiple flights) and a hot
short outside of the tank between the affected FQIS tank circuit and
other aircraft power wiring cobundled with FQIS tank circuit wiring
could result in an ignition source in the fuel tank. That combination
of failures was classified by the FAA as a ``known combination of
failures'' under the criteria in the policy memo due to the similarity
of the Model 727 FQIS system architecture and design details to those
of the Boeing Model 747 airplane involved in the TWA Flight 800
catastrophic fuel tank explosion accident in 1996. The National
Transportation Safety Board (NTSB) concluded that an FQIS failure
combination as described above was the most likely cause of that
accident.\2\ The FAA has therefore 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.
\2\ NTSB Aviation Accident Report AAR-00-03 https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0003.pdf.
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[[Page 72228]]
Request To Withdraw NPRM: Limited Vulnerability to Unsafe Condition
Boeing requested that the FAA withdraw the NPRM. Boeing stated that
272 airplanes were manufactured with body-mounted auxiliary fuel tanks,
but only six were operated under FAA jurisdiction when the comment was
submitted, and that the fleet exposure continues to decrease due to
airplane aging and retirements. Boeing stated that its safety
assessment, using methodologies ``recognized by the FAA,'' shows that
the vulnerability of the Model 727 FQIS latent failure plus single
failure does not present an unsafe condition. Boeing concluded that
requiring the proposed actions will not promote air safety and instead
will add unnecessary cost to operators.
The FAA disagrees with the request. The FAA has determined that an
unsafe condition exists. The FAA assumes that, in citing assessment
methodologies recognized by the FAA, Boeing is referring to having
performed its assessment of the total fleet risk for the Model 727
fleet that showed a very low likelihood of a fuel tank ignition event
in the remaining life of that fleet. Boeing mentioned the number of
airplanes operated under U.S. jurisdiction. The FAA, as the civil
aviation authority of the state of design, is obligated, under the
Convention on International Civil Aviation (the Treaty), to inform all
affected aircraft of continuing safety issues regardless of where they
are operated. Issuance of airworthiness directives is the accepted
method by which the FAA notifies aviation authorities of other
countries of an unsafe condition as required by Annex 8 of the Treaty.
The FAA's unsafe condition determination was made using the
decision criteria in FAA Policy Memorandum ANM100-2003-112-15. This
determination was not driven by a fleet risk assessment. A latent in-
tank failure that provides a conductive path or reduces dielectric
strength of the tank wiring or components, combined with an external
wiring system failure that conducts power onto the tank wiring, could
create an ignition source in the fuel tank of the Boeing Model 727
airplane. That combination of failures was classified as a ``known
combination of failures'' under the criteria in the policy memorandum
due to the similarity of the Model 727 FQIS system architecture and
design details to those of the Model 747 airplane involved in the
catastrophic fuel tank explosion. The NTSB concluded that an FQIS
failure combination as described above was the most likely cause of
that accident. The FAA therefore considers it necessary to address this
unsafe condition. The per-airplane cost for modification is expected to
be approximately the same as the cost of the similar actions required
for Model 737 and 747 airplanes specified in AD 99-03-04, Amendment 39-
11018 (64 FR 4959, February 2, 1999) (``AD 99-03-04''); and AD 98-20-
40, Amendment 39-10808 (63 FR 52147, September 30, 1998) (``AD 98-20-
40''). If an operator chooses to deactivate or remove the auxiliary
tanks as allowed by the AD, the cost would be significantly lower.
Therefore, the FAA made no changes in this final rule as a result of
this comment.
Request To Withdraw NPRM: Extremely Remote Likelihood of Unsafe
Condition
Boeing requested that the FAA withdraw the NPRM. Boeing considered
the likelihood of an undetected latent electrical fault condition of
the FQIS to be extremely remote, due to the FQIS architecture. Boeing
added that the existing Model 727 FQIS design uses a three-wire system
that goes directly from the fuel tank to the flight deck indication.
Boeing stated that an electrical fault of an in-tank component causes
the FQIS to provide a fault indication to the flight crew, so the
failure is not latent.
The FAA disagrees with the request. The agency contacted Boeing to
resolve the apparent conflict between this comment and the company's
previously submitted SFAR 88 reports. In the SFAR 88 reports for Model
727 airplanes, Boeing stated that a latent in-tank failure condition
could not be claimed to be extremely remote, and acknowledged that the
system does not comply with the requirements of 14 CFR 25.981(a)(3)
related to a latent failure plus a single failure. (Extremely remote
qualitatively means that the condition would occur no more than a few
times in the total fleet life. In numerical probability analysis, a
condition that has a probability on the order of 1 in 10 million flight
hours or less is considered extremely remote.) However, the comment
that Boeing submitted to the NPRM stated that a latent in-tank failure
was extremely remote.
A meeting with representatives from the FAA and Boeing was held
February 15, 2019, to clarify Boeing's position. (A record of that
meeting has been posted to the AD docket.) Boeing explained that it had
intended to convey in its comment that the estimated probability for
the initial failure that creates a latent in-tank loss of dielectric
strength, resistive current path, or short condition is extremely
remote. Boeing acknowledged that when the estimated probability of that
failure initiation is multiplied by the average latency period, the
probability of a latent in-tank failure existing in any given flight
hour is not extremely remote.
Given this clarification, Boeing's comment was consistent with the
conclusions of its SFAR 88 reviews. The FQIS does not provide a fault
indication to the flight crew other than unusual readings or a zero
reading provided by a tank gage if a hard short to ground or power
occurs. In addition, even if such a fault is noted by the flight crew,
the approved Master Minimum Equipment List for the Model 727 airplane
allows operators to fly for up to ten days in that condition, without
disconnecting the FQIS for the affected tank, with provisions for
extending beyond the ten days. The FAA therefore does not agree that a
latent failure of in-tank wiring or components, such that an ignition
source could occur if an external hot short occurs, is extremely
remote. No changes were made to this final rule as a result of this
comment.
Request To Extend Compliance Time
Boeing requested that the FAA revise the proposed 12-month
compliance time, which it asserts will require Model 727 operators to
``develop the solution on their own (under 14 CFR part 121).'' Boeing
stated that it had no plans to create service action to modify the FQIS
or deactivate the auxiliary tank(s), as no operators have contacted
Boeing requesting this support.
The FAA disagrees with the request. Boeing did not propose a
specific compliance time, and after consideration, the agency still
considers 12 months to be adequate to allow operators to deactivate
their auxiliary tanks using existing information in the airplane
maintenance manual to develop alteration data and obtain FAA approval
of an alternative method of compliance (AMOC). A compliance time of 12
months or less is required for the deactivation of other after-market
body-mounted auxiliary fuel tanks on Model 727 airplanes in other ADs:
AD 2008-07-07, Amendment 39-15448 (73 FR 15880, March 26, 2008); AD
2008-07-09, Amendment 39-15450 (73 FR 16515, March 28, 2008); AD 2008-
12-03, Amendment 39-15546 (73 FR 31749, June 4, 2008); and AD 2009-20-
01, Amendment 39-16024 (74 FR 48007, September 21, 2009). The FAA has
not changed this AD regarding this issue. Under the provisions of
paragraph (h) of this AD, however, the FAA will consider requests for
approval of an extension to the compliance time if
[[Page 72229]]
sufficient data are submitted to substantiate that the new compliance
time would provide an acceptable level of safety.
Request To Revise Cost Estimate
Boeing requested that if the NPRM is not withdrawn, the FAA revise
the cost estimate to reflect the cost of developing an FQIS design
solution for the body-mounted auxiliary tanks. Boeing expected that
only six airplanes would actually be modified, so the cost of
developing a design solution would be spread over a small number of
airplanes, resulting in a significant per-airplane cost. Boeing did not
provide any specific cost information or describe the modifications for
which they provided cost comments.
The FAA disagrees with the request to revise the cost estimate
based on this comment. The agency based its cost estimate for Model 727
passenger airplanes on the inflation-adjusted estimated costs for
installation of transient suppression devices on the Model 747 airplane
as required by AD 98-20-40. The FAA considers that the transient
suppression design solutions, if not the actual parts, developed for
Model 737 and 747 airplanes in response to AD 99-03-04 and AD 98-20-40
will be applicable to the Model 727 airplane due to the similarity of
those models' FQIS designs. The FAA agrees that the nonrecurring design
development costs associated with any necessary model-specific design
activity will be spread over fewer airplanes, resulting in higher per-
airplane costs if the operator decides not to deactivate the subject
tanks. However, the FAA increased the cost estimate in the NPRM to
reflect that increased cost to the existing fleet. Boeing did not
propose any specific alternative cost figures to be substituted for the
FAA estimate. The FAA did not change this final rule as a result of
this comment.
Conclusion
The FAA reviewed the relevant data as previously discussed,
considered the comments received, and determined that air safety and
the public interest require adopting this final rule as proposed,
except for 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.
Costs of Compliance
The FAA estimates that this AD affects 6 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:
Estimated Costs: Required Actions
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Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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Modification........................ 300 work-hours x $85 $100,000 $125,500 $753,000
per hour = $25,500.
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Estimated Costs: Alternative Actions
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Cost per
Action Labor cost Parts cost product
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Tank deactivation............................ 10 work-hours x $85 per hour = $0 $850
$850.
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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.
This AD is issued in accordance with authority delegated by the
Executive Director, Aircraft Certification Service, as authorized by
FAA Order 8000.51C. In accordance with that order, issuance of ADs is
normally a function of the Compliance and Airworthiness Division, but
during this transition period, the Executive Director has delegated the
authority to issue ADs applicable to transport category airplanes and
associated appliances to the Director of the System Oversight Division.
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.
Sec. 39.13 [Amended]
0
2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):
2019-23-04 The Boeing Company: Amendment 39-19797; Docket No.
[[Page 72230]]
FAA-2016-9072; Product Identifier 2015-NM-110-AD.
(a) Effective Date
This AD is effective February 4, 2020.
(b) Affected ADs
None.
(c) Applicability
This AD applies to The Boeing Company Model 727, 727-100, 727C,
727-100C, 727-200, and 727-200F series airplanes; certificated in
any category; equipped with Boeing body-mounted auxiliary fuel
tanks.
(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 727 fuel
system review conducted by the manufacturer. The FAA is issuing this
AD to address ignition sources inside the body-mounted auxiliary
fuel tanks, 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 12 months after the effective date of this AD, do the
actions specified in either paragraph (g)(1) or (2) of this AD,
using a method approved in accordance with the procedures specified
in paragraph (h) of this AD.
(1) Modify the fuel quantity indicating system (FQIS) to prevent
development of an ignition source inside the body-mounted auxiliary
fuel tanks due to electrical fault conditions.
(2) Deactivate the body-mounted auxiliary fuel tanks.
(h) 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 (i) of this AD. Information may be
emailed to: [email protected].
(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, FAA, 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.
(i) 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: [email protected].
(j) Material Incorporated by Reference
None.
Issued in Des Moines, Washington, on November 27, 2019.
Michael Kaszycki,
Acting Director, System Oversight Division, Aircraft Certification
Service.
[FR Doc. 2019-27885 Filed 12-30-19; 8:45 am]
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