[Federal Register Volume 73, Number 222 (Monday, November 17, 2008)]
[Rules and Regulations]
[Pages 67722-67726]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-26480]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2007-0308; Directorate Identifier 2007-NM-160-AD;
Amendment 39-15731; AD 2008-23-10]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-
100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D,
747-400F, and 747SR Series 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
Boeing Model 747 airplanes identified above. This AD requires modifying
the outboard flap track and transmission attachments. This AD results
from a joint Boeing and FAA multi-model study (following in-service
trailing edge flap structure and drive system events) on the hazards
posed by skewing and failed flaps. This study identified the safety
concerns regarding the transmission attachment design and the potential
loss of an outboard trailing edge flap. We are issuing this AD to
prevent certain discrepancies associated with this design (for example,
a flap skew or lateral control asymmetry that can cause collateral
damage to adjacent hydraulic tubing and subsequent loss of a hydraulic
system), which could result in the asymmetric flight control limits
being exceeded, and could adversely affect the airplane's continued
safe flight and landing.
DATES: This AD is effective December 22, 2008.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of December 22,
2008.
ADDRESSES: For service information identified in this AD, contact
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-
2207.
Examining the AD Docket
You may examine the AD docket on the Internet at http://
[[Page 67723]]
www.regulations.gov; 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 (telephone 800-647-5527) is the Document 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: Doug Tsuji, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-
3356; telephone (425) 917-6487; fax (425) 917-6590.
SUPPLEMENTARY INFORMATION:
Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to include an airworthiness directive (AD) that would apply to
certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-
200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, and 747SR series
airplanes. That NPRM was published in the Federal Register on December
11, 2007 (72 FR 70247). That NPRM proposed to require modifying the
outboard flap track and transmission attachments.
Actions Since NPRM Was Issued
Since we issued the NPRM, Boeing has issued Service Bulletins 747-
27A2398, Revision 1, dated July 31, 2008; and 747-27A2421, Revision 1,
dated July 10, 2008; to add longer grip length bolts necessary to
install the new support housing and optional part numbers for the new
support housing. In the NPRM, we referred to the original issue of the
service bulletins, both dated April 19, 2007, as the sources of service
information for modifying the outboard trailing edge flaps. The
procedures in the original issue of the service bulletins are
essentially the same as those in Revision 1. Therefore, we have revised
paragraph (f) of this AD to refer to Revision 1 of the service
bulletins as the appropriate sources of service information for
modifying the outboard trailing edge flaps. We have also revised
paragraphs (c) and (g) of this AD to refer to Revision 1 of the service
bulletins. In addition, we have added a new paragraph (h) to the AD to
give credit for using the original issue of the service bulletins for
accomplishing the required actions before the effective date of the AD.
Comments
We gave the public the opportunity to participate in developing
this AD. We considered the comments received.
Request To Extend Compliance Period
All Nippon Airways Co. Ltd. (ANA) and KLM Royal Dutch Airlines--
Fleet Services request that the compliance period be extended from a
tiered 3 years and 6 years to 5 years and 8 years. The commenters cite
difficulties in accomplishing the proposed actions (difficulties
related to manpower and facility requirements) and claim that the
proposed actions are better suited to correspond to scheduled ``D''
check maintenance.
We disagree with the request to extend the compliance times. We
have determined that the tiered compliance times of 3 years and 6
years, as proposed, are commensurate with the unsafe condition
associated with the loss of the transmission. We have not changed the
final rule regarding this issue.
Request To Revise Cost Estimate
British Airways (BA) and Boeing state that the work-hour estimate
specified in the NPRM (150 work hours) is too low. Boeing reports that
its original work-hour estimate has been updated based on further
evaluation and the results of the service bulletin validation. (The
work hours specified in the NPRM are based on information provided in
the service bulletin.) Boeing's recalculation now estimates that the
actions will take 310 total hours (258 hours on the airplane and 52
hours for component work).
We agree, based on Boeing's explanation. We have revised the cost
estimates in this final rule.
Request to Allow Repetitive Maintenance Instead of Modification
Singapore Airlines Limited states that the intent of the proposed
AD can be achieved through regular replacement of the flap transmission
bolts (with non H-11 bolts) and regular nondestructive testing (NDT)
inspections on the Nos. 1, 2, 7, and 8 transmission housings. The
commenter notes that AD 2001-03-10 (amendment 39-12114, 66 FR 10951,
February 21, 2001) mandates replacing H-11 bolts (which failed
prematurely) with Inconel bolts. Service history has shown no bolt
failures after the bolts were replaced.
We infer that the commenter is requesting that we revise the NPRM
to allow repetitive inspections and replacements instead of the
modification. We do not agree. The intent of this AD is to remove an
identified single failure condition that can result in a catastrophic
event. Although AD 2001-03-10 requires replacing a known source of
failures on the same airplanes affected by this new AD, and service
history has shown no failures of the existing transmission attachment
fitting, the potential single failure condition would still exist if no
further action were taken. We have not changed the final rule regarding
this issue.
Request for Alternative Method
According to Lufthansa, the existing transmission attachment (solid
Inconel bolts) is a damage-tolerant design, and the new attachment with
a double load path bolt is a fail-safe design. A cracked hollow bolt
could go undetected, which Lufthansa claims is a disadvantage compared
to the existing design.
We partially agree with the commenter's assertions. We agree that a
cracked hollow bolt could go undetected. A planned inspection program
must be developed to detect a fractured hollow bolt before the nested
inner solid bolt fractures. For this reason, the FAA is considering
additional rulemaking to address this broader issue. We disagree,
however, that the solid Inconel bolt is a damage-tolerant design.
Neither the existing single bolt design nor the new double load path
bolt design would be classified as damage tolerant without planned
inspections to detect a fractured bolt. The single bolt design was
identified as a potential safety issue because a single bolt failure
could lead to overload failure of the two remaining transmission
mounting bolts, which is a static strength issue. A planned inspection
program of the double load path bolt design will provide a transmission
mount attachment design that is damage tolerant. While we might issue
additional rulemaking related to the broader issue of inspecting to
detect a fractured hollow bolt, we have not changed this final rule
regarding this issue.
Request To Clarify Relationship of NPRM to Existing ADs
We cited Boeing Alert Service Bulletin 747-27A2398, dated April 19,
2007, in the NPRM as an appropriate source of service information for
the modification. Japan Airlines (JAL) and ANA request that the actions
specified in that service bulletin be considered an alternative method
of compliance (AMOC) to paragraphs (a) and (b) of AD 2001-03-10 and
paragraph (a) of AD
[[Page 67724]]
2001-23-13 (amendment 39-12512, 66 FR 58918, November 26, 2001) (a
correction of that rule was published in the Federal Register on
February 14, 2002 (67 FR 6864)).
The commenters also request that we describe the relationship among
AD 2001-03-10, AD 2001-23-13, and the NPRM. We provide this summary
information in the table titled ``Breakdown of Actions.''
Breakdown of Actions
------------------------------------------------------------------------
Boeing Service
AD action Bulletin Actions
------------------------------------------------------------------------
AD 2001-03-10................. 747-27A2376, Replacing H-11 bolts
dated July 1, with Inconel bolts
1999. at the trailing edge
(TE) flap
transmission
attachment fitting.
AD 2001-23-13................. 747-27-2374, Replacing the TE flap
dated November transmission torque
18, 1999. brake and changing
the flap
transmission P/N,
after a torque brake
is replaced.
The NPRM...................... 747-27A2398, Replacing the bolts
dated April 19, with non-Inconel,
2007. dual load path
bolts; installing
new flap tracks; and
installing the new
transmission
attachment fitting.
------------------------------------------------------------------------
The commenters state that the NPRM and Boeing Service Bulletin 747-
27A2398 show part numbers for the No. 2 and No. 7 transmission
assemblies that are different from the part numbers specified in Boeing
Service Bulletin 747-27-2374.
We agree that the requirements of this AD may terminate certain
other requirements. This AD requires replacing the Inconel attach bolts
installed by AD 2001-03-10 used for the transmission attachment
fitting. Installation of the new bolts in accordance with Boeing
Service Bulletin 747-27A2398, dated April 19, 2007, was previously
approved as an AMOC to the requirements of paragraphs (a) and (b) of AD
2001-03-10 by FAA Letter 130S-08-47a, dated February 21, 2008. We have
revised the AD in newly added paragraph (i) to clarify the relationship
between the two ADs.
AD 2001-23-13 requires re-identifying the transmission assembly
after replacing a discrepant torque brake with a new, improved torque
brake. Before doing the requirements of this AD, operators should have
already done the requirements of AD 2001-23-13, so the ``new'' part
numbers created by AD 2001-23-13 are the ``existing'' part numbers in
this AD. The modification required by this AD creates ``new'' part
numbers. The ``new'' part numbers created by this AD were previously
approved as an AMOC to paragraph (a)(2)(ii) of AD 2001-23-13 by FAA
Letter 130S-08-48a, dated February 5, 2008. This final rule does not
terminate any requirement of AD 2001-23-13.
Request to Revise Compliance Time for Paragraph (h)
Paragraph (h) of the NPRM (paragraph (j) in this final rule) would
prohibit installing unmodified flap transmissions as of the effective
date of the AD. BA, ANA, KLM, and Boeing request that we revise this
provision to allow the continued use of unmodified hinge braces and
support assemblies during the proposed compliance period for the
modification. As written, paragraph (h) of the NPRM would require
modifying a flap transmission and associated flap track whenever a flap
transmission or hinge brace is replaced in service, regardless of the
reason. The modification requires removing the outboard flaps and
corresponding flap track, and is intended to be performed during
planned maintenance. The modification would require significant
manpower and use of proper facilities, equipment, tooling, etc. The
commenters state that, if a transmission or hinge brace would need to
be replaced outside of the planned schedule, such as for miscellaneous
damage or an oil leak, the airplane would have to be taken out of
service for modification, resulting in significant economic and
operational impact.
We agree with the request and the commenters' rationale. The intent
of this AD is to phase out a potential catastrophic failure mode that
currently exists on Model 747 airplanes; service history indicates that
immediate modification is not required. We have revised paragraph (j)
of this AD to correspond with the modification specified in paragraph
(f) of this AD.
Request to Clarify Compliance Times
Boeing requests that we revise the Relevant Service Information
section of the NPRM, which indicates that the compliance time is based
on flight cycles on the ``airplane,'' which, Boeing asserts, should
instead be on the flap ``transmission.'' Paragraph 1.E. of Boeing
Service Bulletins 747-27A2398 and 747-27A2421 explains that the
compliance time is 6 years for flap transmissions known to have fewer
than 20,000 total flight cycles, and 3 years for all other
transmissions.
We agree with the commenter's explanation. We intended that the
compliance times in this AD match the compliance times in the service
bulletins. Although the Relevant Service Information section is not
repeated in a final rule, the compliance time clarification provided by
the commenter applies to paragraphs (f) and (g) in this final rule.
Request To Allow Flowchart for Deriving Compliance Time
Boeing requests that we revise the NPRM to include matrices
(flowcharts) to help operators determine whether the 6-year or 3-year
compliance time applies to a specific transmission. Alternatively, the
commenter requests that flowcharts be considered for a future AMOC.
Boeing states that the FAA agreed that operators may use transmission
age and/or configuration to select the proper compliance time when the
number of flight cycles on the flap transmission is unknown. Boeing
reports that its flowcharts mirror the compliance time recommendations
agreed on by Boeing and the FAA.
We disagree with the request to include flowcharts in the AD,
although we generally agree that using transmission age and/or
configuration is acceptable for selecting the proper compliance time.
If the number of cycles is unknown, operators can estimate from the
flap transmission configuration the date it was put into service, and
can thus estimate the number of cycles on the transmission. But
flowcharts can be variously interpreted and are often subject to
misinterpretation, so they are generally not enforceable and therefore
cannot be included in ADs. However, according to the provisions of
paragraph (k) of the final rule, a request may be made to use a
specific flowchart if the derived compliance times would accurately
reflect the requirements of the AD.
Clarification of NPRM Discussion
In the Discussion section of the NPRM, we stated that we received a
report about a joint Boeing and FAA
[[Page 67725]]
multi-model study. Although the Discussion section is not repeated in a
final rule, we provide the following to clarify events leading up to
this AD. In the late 1990s/early 2000s, the FAA participated with
Boeing in a multi-model investigation on the effects of trailing edge
wing flap skew and flap loss. As a result of this investigation, a
simulation study revealed potential failures that could cause a flap
skew and subsequent flap loss, with potentially catastrophic results.
Conclusion
We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
the AD with the changes described previously. We also determined that
these changes will not significantly increase the economic burden on
any operator or increase the scope of the AD.
Costs of Compliance
There are about 990 airplanes of the affected design in the
worldwide fleet. The following table provides the estimated costs for
U.S. operators to comply with this AD.
Estimated Costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of U.S.-
Work hours Average labor Parts Cost per registered Fleet cost
rate per hour airplane airplanes
--------------------------------------------------------------------------------------------------------------------------------------------------------
310................................................................ $80 $80,023 $104,823 141 $14,780,043
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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.
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), 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.
You can find our regulatory evaluation and the estimated costs of
compliance in the AD Docket.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
0
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 AD:
2008-23-10 Boeing: Amendment 39-15731. Docket No. FAA-2007-0308;
Directorate Identifier 2007-NM-160-AD.
Effective Date
(a) This airworthiness directive (AD) is effective December 22,
2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B
SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-
400F, and 747SR series airplanes, certificated in any category; as
identified in Boeing Service Bulletins 747-27A2398, Revision 1,
dated July 31, 2008; and 747-27A2421, Revision 1, dated July 10,
2008.
Unsafe Condition
(d) This AD results from a joint Boeing and FAA multi-model
study (following in-service trailing edge flap structure and drive
system events) on the hazards posed by skewing and failed flaps.
This study identified the safety concerns regarding the transmission
attachment design and the potential loss of an outboard trailing
edge flap. We are issuing this AD to prevent certain discrepancies
associated with this design (for example, a flap skew or lateral
control asymmetry that can cause collateral damage to adjacent
hydraulic tubing and subsequent loss of a hydraulic system), which
could result in the asymmetric flight control limits being exceeded,
and could adversely affect the airplane's continued safe flight and
landing.
Compliance
(e) You are responsible for having the actions required by this
AD performed within the compliance times specified, unless the
actions have already been done.
Modification
(f) Do the following, as applicable: At the time specified in
paragraph 1.E. of Boeing Service Bulletins 747-27A2398, Revision 1,
dated July 31, 2008; and 747-27A2421, Revision 1, dated July 10,
2008; except as provided by paragraph (g) of this AD, modify the
outboard flap track and transmission attachments by doing all
actions specified in the Accomplishment Instructions of the service
bulletin.
(g) Where Boeing Service Bulletins 747-27A2398, Revision 1,
dated July 31, 2008; and 747-27A2421, Revision 1, dated July 10,
2008; specify compliance times relative to the date on the service
bulletin, this AD requires compliance within the specified
compliance time after the effective date of this AD.
Credit for Actions Done According to Previous Issue of Service
Bulletins
(h) Actions done before the effective date of this AD in
accordance with Boeing Alert Service Bulletins 747-27A2421 and 747-
27A2398, both dated April 19, 2007, are acceptable for compliance
with the requirements of paragraph (f) of this AD.
Terminating Action for Certain Requirements of AD 2001-03-10
(i) Accomplishment of the modification specified in paragraph
(f) of this AD terminates the requirements of paragraphs (a)
[[Page 67726]]
and (b) of AD 2001-03-10, amendment 39-12114.
Parts Installation
(j) After completing the modifications required by paragraph (f)
of this AD, no person may install a part identified in Table 1 of
this AD on the modified airplane.
Table 1--Parts Prohibited From Installation
------------------------------------------------------------------------
Part Part No.
------------------------------------------------------------------------
Hinge brace assembly for Tracks 1 and 8................. 65B15515-1
65B15515-2
65B15515-9
65B15515-10
Hinge brace assembly for Tracks 2 and 7................. 65B15525-1
65B15525-2
65B15525-7
65B15525-8
65B17092-1
65B17092-2
Support housing assembly for Tracks 1 and 8............. 65B81982-( )
Support housing assembly for Tracks 2 and 7............. 65B81950-( )
------------------------------------------------------------------------
Alternative Methods of Compliance (AMOCs)
(k)(1) The Manager, Seattle Aircraft Certification Office (ACO),
FAA, ATTN: Doug Tsuji, Aerospace Engineer, Systems and Equipment
Branch, ANM-130S; telephone (425) 917-6487; fax (425) 917-6590; has
the authority to approve AMOCs for this AD, if requested using the
procedures found in 14 CFR 39.19.
(2) To request a different method of compliance or a different
compliance time for this AD, follow the procedures in 14 CFR 39.19.
Before using any approved AMOC on any airplane to which the AMOC
applies, notify your appropriate principal inspector (PI) in the FAA
Flight Standards District Office (FSDO), or lacking a PI, your local
FSDO.
Material Incorporated by Reference
(l) You must use Boeing Service Bulletin 747-27A2398, Revision
1, dated July 31, 2008; or Boeing Service Bulletin 747-27A2421,
Revision 1, dated July 10, 2008; as applicable; to do the actions
required by this AD, unless the AD specifies otherwise.
(1) The Director of the Federal Register approved the
incorporation by reference of this service information under 5
U.S.C. 552(a) and 1 CFR part 51.
(2) For service information identified in this AD, contact
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington
98124-2207; telephone 206-544-9990; fax 206-766-5682; e-mail
[email protected]; Internet https://www.myboeingfleet.com.
(3) You may review copies of the service information
incorporated by reference at the FAA, Transport Airplane
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or 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 http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
Issued in Renton, Washington, on October 23, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E8-26480 Filed 11-14-08; 8:45 am]
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