[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
--------------------------------------------------------------------------------------------------------------------------------------------------------

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]
BILLING CODE 4910-13-P