
[Federal Register: September 23, 2008 (Volume 73, Number 185)]
[Proposed Rules]               
[Page 54751-54755]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr23se08-30]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0981; Directorate Identifier 2008-NM-073-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 747 Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede an existing airworthiness 
directive (AD) that applies to certain Boeing Model 747 airplanes. The 
existing AD currently requires repetitive inspections of the body 
station (BS) 2598 bulkhead, and corrective actions if necessary. The 
existing AD also currently requires a terminating modification for the 
repetitive inspections and a post-modification inspection of the 
modified area. This proposed AD would continue requiring those actions 
with revised service information. For certain airplanes, this proposed 
AD would require new repetitive inspections, an interim modification, 
and post-interim modification inspections. For certain airplanes, this 
proposed AD also would require replacing any previously repaired aft 
inner chord and reinstalling the terminating modification. This 
proposed AD results from reports of cracked aft inner chords on 
airplanes after certain requirements of the existing AD were done. We 
are proposing this AD to prevent fatigue cracking of the BS 2598 
bulkhead structure, which could result in inability of the structure to 
carry horizontal stabilizer flight loads, and loss of controllability 
of the airplane.

DATES: We must receive comments on this proposed AD by November 7, 
2008.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://
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: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    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://
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 proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (telephone 800-647-5527) is in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

FOR FURTHER INFORMATION CONTACT: Ivan Li, Aerospace Engineer, Airframe 
Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind 
Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6437; 
fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-0981; 
Directorate Identifier 2008-NM-073-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this

[[Page 54752]]

proposed AD because of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    On February 22, 2006, we issued AD 2006-05-06, amendment 39-14503 
(71 FR 12125, March 9, 2006), for certain Boeing Model 747 airplanes. 
That AD requires repetitive inspections of the body station (BS) 2598 
bulkhead, and corrective action if necessary. That AD also requires 
modification of the bulkhead, including a one-time inspection and 
corrective action if necessary, which terminates certain repetitive 
inspections. In addition, that AD also requires a post-modification 
inspection of the modified area. That AD resulted from reports of 
fatigue cracking on BS 2598 bulkhead. We issued that AD to prevent 
fatigue cracking of the BS 2598 bulkhead structure, which could result 
in inability of the structure to carry horizontal stabilizer flight 
loads, and loss of controllability of the airplane.

Actions Since Existing AD Was Issued

    Since we issued AD 2006-05-06, we have received a report of a 
cracked aft inner chord that was completely severed and a 0.5-inch 
crack in the adjacent frame support on an in-service airplane. These 
cracks have been attributed to fatigue. The airplane had accumulated 
9,988 total flight cycles and 68,081 total flight hours. A surface high 
frequency eddy current (HFEC) inspection had been done on the aft inner 
chord as required by AD 2006-05-06. In addition, we have received 
reports of cracked aft inner chords that had been previously repaired 
and not replaced before the bulkhead was modified in accordance with AD 
2006-05-06. Repaired chords can have an active crack tip that may 
continue to propagate, even if the area has been reinforced.
    Therefore, we have determined that in addition to the repetitive 
surface HFEC inspections required by AD 2006-05-06, repetitive open 
hole surface HFEC inspections are necessary to detect cracks that are 
beneath the surface of the aft inner chords. We also have determined 
that the terminating modification, if installed with a repaired aft 
inner chord in place as required by AD 2006-05-06, does not adequately 
address the identified unsafe condition, and that further rulemaking is 
necessary.

Relevant Service Information

    We have reviewed Revision 4 of Boeing Alert Service Bulletin 747-
53A2427, dated March 6, 2008 (AD 2006-05-06 refers to Boeing Alert 
Service Bulletin 747-53A2427, Revision 2, dated October 5, 2000; or 
Revision 3, dated September 27, 2001; as appropriate sources of service 
information for accomplishing certain requirements). The repetitive 
surface HFEC inspections described in Revision 4 are identical to those 
in earlier revisions of the service bulletin. Revision 4 adds new 
repetitive open hole HFEC inspections to detect cracks in the bulkhead 
splice fitting, frame support fitting, and forward and aft inner chords 
on the left and right side of the BS 2598 bulkhead, and repair if 
necessary. Revision 4 also adds a new interim modification for the aft 
inner chords, which defers the repetitive surface and open hole HFEC 
inspections. The compliance time for accomplishing the initial open 
hole inspection is before 6,000 or 16,000 total flight cycles 
(depending on the airplane configuration), or within 1,500 flight 
cycles after the date on Revision 4 of the service bulletin, whichever 
occurs later. The compliance time for accomplishing repetitive surface 
and open hole HFEC inspections is within 1,500 flight cycles after the 
last surface HFEC inspection of the forward side of the bulkhead or 
within 6,000 flight cycles after installation of the structural repair 
manual repair or interim modification, depending on the airplane 
configuration.
    We also have reviewed Revision 1 of Boeing Service Bulletin 747-53-
2473, dated February 20, 2007 (AD 2006-05-06 refers to Boeing Service 
Bulletin 747-53-2473, dated March 24, 2005; as an appropriate source of 
service information for accomplishing the terminating modification). 
Revision 1 removes the option to re-install an aft inner chord that has 
been repaired before accomplishing the terminating modification. The 
modification and related investigative and corrective actions are 
essentially identical to those specified in Boeing Service Bulletin 
747-53-2473, dated March 24, 2005.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to develop on other airplanes of the 
same type design. For this reason, we are proposing this AD, which 
would supersede AD 2006-05-06 and would retain the requirements of the 
existing AD. This proposed AD would also require accomplishing the 
actions specified in service information described previously, except 
as discussed under ``Differences Between the Proposed AD and Service 
Information.''

Differences Between the Proposed AD and Service Information

    The service information described previously specifies to contact 
the manufacturer for instructions on how to repair certain conditions, 
but this proposed AD would require repairing those conditions in one of 
the following ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.
    For certain airplanes, Boeing Service Bulletin 747-53-2473, 
Revision 1, does not specify a compliance time for replacing the 
previously repaired aft inner chord and reinstalling the terminating 
modification. In developing an appropriate compliance time for these 
proposed actions, we considered the degree of urgency associated with 
the subject unsafe condition, the manufacturer's recommendation for an 
appropriate compliance time, and the average utilization of the 
affected fleet. In light of these factors, we find that a compliance 
time of within 3,000 flight cycles after doing the modification 
required by paragraph (l) of this AD, or within 1,500 flight cycles 
after the effective date of this AD, whichever occurs later, represents 
an appropriate interval of time for affected airplanes to continue to 
operate without compromising safety. This difference has been 
coordinated with Boeing.

Explanation of Change Made to Requirements of AD 2006-05-06 Retained in 
This AD

    We have simplified paragraphs (g), (i), and (k) of this AD by 
referring to the ``Alternative Methods of Compliance (AMOCs)'' 
paragraph of this AD for repair methods.

Costs of Compliance

    There are about 998 airplanes of the affected design in the 
worldwide fleet. The following table provides the

[[Page 54753]]

estimated costs for U.S. operators to comply with this proposed AD.

                                                                     Estimated Costs
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                                                                                                                     Number of
                                                      Average                                                          U.S.-
                Action                  Work hours   labor rate            Parts              Cost per airplane      registered         Fleet cost
                                                      per hour                                                       airplanes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Surface HFEC inspections and open                2          $80  None....................  $160, per inspection             162  $25,920, per inspection
 hole HFEC inspections.                                                                     cycle.                                cycle.
Detailed inspections.................            2           80  None....................  $160, per inspection             162  $25,920, per inspection
                                                                                            cycle.                                cycle.
Interim modification.................            4           80  $4,000..................  $4,320.................          162  $699,840.
Replacement of Previously Repaired               2           80  None....................  $160...................          162  $25,920.
 Aft Inner Chords.
Terminating modification.............          126           80  $33,716.................  $43,796................          162  $7,094,952.
Post-terminating modification                    4           80  None....................  $320...................          162  $51,840.
 inspection.
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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

    We have 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 that the proposed 
regulation:
    1. Is not a ``significant regulatory action'' under Executive Order 
12866;
    2. Is not a ``significant rule'' under the 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket. See the 
ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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 Federal Aviation Administration (FAA) amends Sec.  39.13 by 
removing amendment 39-14503 (71 FR 12125, March 9, 2006) and adding the 
following new airworthiness directive (AD):

Boeing: Docket No. FAA-2008-0981; Directorate Identifier 2008-NM-
073-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by November 
7, 2008.

Affected ADs

    (b) This AD supersedes AD 2006-05-06.

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, 747SR, and 747SP series airplanes, certificated in any 
category, line numbers 1 through 1307 inclusive.

Unsafe Condition

    (d) This AD results from reports of cracked aft inner chords on 
airplanes after certain requirements of the existing AD were done. 
We are issuing this AD to prevent fatigue cracking of the body 
station (BS) 2598 bulkhead structure, which could result in 
inability of the structure to carry horizontal stabilizer flight 
loads, and loss of controllability of the airplane.

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.

Requirements of AD 2006-05-06

Repetitive High Frequency Eddy Current (HFEC) Inspections of the 
Bulkhead Frame Supports

    (f) Before the accumulation of 10,000 total flight cycles, or 
within 1,000 flight cycles after August 16, 2001 (the effective date 
of AD 2001-14-07), whichever occurs later: Do an open-hole HFEC 
inspection to find cracking of the bulkhead frame support under the 
hinge support fittings of the horizontal stabilizer on the left and 
right sides at BS 2598, in accordance with Figure 2 of the 
Accomplishment Instructions of Boeing Service Bulletin 747-53A2449, 
Revision 1, dated May 24, 2001; or Revision 2, dated March 14, 2002. 
Repeat the inspection after that at intervals not to exceed 3,000 
flight cycles. Inspections accomplished before August 16, 2001, per 
Boeing Alert Service Bulletin 747-53A2449, dated June 8, 2000, are 
considered acceptable for compliance with the applicable inspection 
specified in this paragraph.

Repair of Any Cracked Bulkhead Frame Support

    (g) If any cracking is found during any inspection required by 
paragraph (f) of this AD, before further flight, repair using a 
method approved in accordance with the

[[Page 54754]]

procedures specified in paragraph (w) of this AD.

Repetitive Inspections of Inner Chords, Frame Support, and Splice 
Fitting

    (h) Except as provided by paragraph (n) of this AD: Do a surface 
HFEC inspection of the forward and aft inner chords, the frame 
support, and the splice fitting of the forward inner chord of the 
upper corners of the station 2598 bulkhead to find cracking, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-53A2427, Revision 2, dated October 5, 2000; or 
Revision 3, dated September 27, 2001; at the latest of the times 
specified in paragraphs (h)(1) and (h)(2) of this AD, as applicable. 
Repeat the inspection after that at intervals not to exceed 1,500 
flight cycles.
    (1) For airplanes having line numbers 1 through 1241 inclusive:
    (i) Before the accumulation of 6,000 total flight cycles.
    (ii) Within 500 flight cycles after August 28, 2001 (the 
effective date of AD 2001-15-03).
    (iii) For airplanes inspected before August 28, 2001, in 
accordance with Boeing Alert Service Bulletin 747-53A2427, dated 
December 17, 1998 (including inspections of the splice fitting), or 
Revision 1, dated October 28, 1999: Within 1,500 flight cycles after 
accomplishment of the last inspection done in accordance with the 
original service bulletin or Revision 1, as applicable.
    (2) For airplanes having line numbers 1242 through 1307 
inclusive:
    (i) Before the accumulation of 16,000 total flight cycles.
    (ii) Within 500 flight cycles after August 28, 2001.
    (iii) For airplanes inspected before August 28, 2001, in 
accordance with Boeing Alert Service Bulletin 747-53A2427, dated 
December 17, 1998 (including inspections of the splice fitting), or 
Revision 1, dated October 28, 1999: Within 1,500 flight cycles after 
accomplishment of the last inspection done in accordance with the 
original service bulletin or Revision 1, as applicable.

Repair of Any Cracked Inner Chord, Frame Support, or Splice Fitting

    (i) If any cracking is found during the inspections required by 
paragraph (h) of this AD, before further flight, repair in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-53A2427, Revision 2, dated October 5, 2000; or 
Revision 3, dated September 27, 2001; except as provided by 
paragraph (n) of this AD, and except where the alert service 
bulletin specifies that the manufacturer may be contacted for 
disposition of certain repair conditions, before further flight, 
repair using a method approved in accordance with the procedures 
specified in paragraph (w) of this AD.

Repetitive Detailed Inspections of BS 2598 Bulkhead

    (j) Before the accumulation of 10,000 total flight cycles, or 
within 1,000 flight cycles after October 27, 2003 (the effective 
date of AD 2003-19-08), whichever is later: Do a detailed inspection 
of the BS 2598 bulkhead for discrepancies (cracking, elongated 
fastener holes) of the areas specified in paragraphs (j)(1) and 
(j)(2) of this AD, in accordance with the Accomplishment 
Instructions of Boeing Alert Service Bulletin 747-53A2467, dated 
July 26, 2001; or Revision 1, dated April 28, 2005. Repeat the 
inspections after that at intervals not to exceed 3,000 flight 
cycles.
    (1) The lower aft inner chords.
    (2) The upper aft outer chords, and the diagonal brace 
attachment fittings, flanges, and rods.

    Note 1: For the purposes of this AD, a detailed inspection is 
``an intensive examination of a specific item, installation, or 
assembly to detect damage, failure, or irregularity. Available 
lighting is normally supplemented with a direct source of good 
lighting at an intensity deemed appropriate. Inspection aids such as 
mirrors, magnifying lenses, etc. may be necessary. Surface cleaning 
and elaborate procedures may be required.''

Repair of Any Cracked BS 2598 Bulkhead

    (k) If any discrepancy is found during any inspection required 
by paragraph (j) of this AD: Before further flight, repair in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-53A2467, dated July 26, 2001; or Revision 1, 
dated April 28, 2005. If the service bulletin specifies to contact 
Boeing for appropriate action: Before further flight, repair using a 
method approved in accordance with the procedures specified in 
paragraph (w) of this AD.

Terminating Modification

    (l) Except as provided by paragraphs (p) and (q) of this AD: 
Before the accumulation of 20,000 total flight cycles, or within 48 
months after April 13, 2006 (the effective date of AD 2006-05-06), 
whichever occurs later, modify the bulkhead by doing all applicable 
actions including surface and open-hole HFEC inspections for 
cracking of the upper forward inner chords, aft inner chords, upper 
splice fittings, and frame support fittings, as specified in the 
Accomplishment Instructions of Boeing Service Bulletin 747-53-2473, 
dated March 24, 2005. Repair any cracks before further flight in 
accordance with the service bulletin. Where the service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions: Before further flight, repair the cracks 
using a method approved in accordance with the procedures specified 
in paragraph (w) of this AD. Accomplishment of the modification 
terminates the requirements of paragraph (f), (h), and (j)(1) of 
this AD.

Post-Modification Inspection and Repair

    (m) Within 20,000 flight cycles after the modification required 
by paragraph (l) of this AD, inspect the BS 2598 bulkhead for 
cracks, and repair any cracks before further flight, in accordance 
with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO).

New Requirements of This AD

New Revision of Service Bulletin

    (n) As of the effective date of this AD, use only the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
53A2427, Revision 4, dated March 6, 2008, to do the repetitive 
surface HFEC inspections required by paragraph (h) of this AD and 
the repair required by paragraph (i) of this AD.

Terminating Repair for Repetitive Surface HFEC Inspections

    (o) As of the effective date of this AD, accomplishment of the 
aft inner chord repair required by paragraph (i) of this AD in 
accordance with the applicable structural repair manual (SRM) 
specified in the Accomplishment Instructions of Boeing Alert Service 
Bulletin 747-53A2427, Revision 4, dated March 6, 2008, ends the 
repetitive surface HFEC inspections required by paragraph (h) of 
this AD for that side of the bulkhead only.

Replacement of Previously Repaired Aft Inner Chord and Reinstallation 
of Terminating Modification

    (p) For airplanes on which the terminating modification required 
by paragraph (l) of this AD has been done before the effective date 
of this AD, and on which any previously repaired aft inner chord was 
not replaced during that terminating modification: Within 3,000 
flight cycles after doing the modification, or within 1,500 flight 
cycles after the effective date of this AD, whichever occurs later, 
replace any previously repaired aft inner chord with a new aft inner 
chord and reinstall the terminating modification using a method 
approved in accordance with the procedures specified in paragraph 
(w) of this AD. Accomplishment of the replacement and reinstallation 
of the terminating modification terminates the requirements of 
paragraphs (l) and (m) of this AD and repetitive inspections 
required by this AD, except for the inspections specified in 
paragraph (r) of this AD.

Revised Terminating Modification

    (q) For airplanes on which the terminating modification required 
by paragraph (l) of this AD has not been done as of the effective 
date of this AD: Before the accumulation of 20,000 total flight 
cycles, or within 18 months after the effective date of this AD, 
whichever occurs later, modify and do applicable relative 
investigative and corrective actions by doing all the applicable 
actions specified in the Accomplishment Instructions of Boeing 
Service Bulletin 747-53-2473, Revision 1, dated February 20, 2007; 
except where the service bulletin specifies that the manufacturer 
may be contacted for disposition of certain repair conditions, 
before further flight, repair the cracks using a method approved in 
accordance with the procedures specified in paragraph (w) of this 
AD. The applicable related investigative and corrective actions must 
be done before further flight. Accomplishment of the replacement and 
reinstallation of the terminating modification terminates the 
requirements of paragraphs (l) and (m) of this AD and repetitive 
inspections required by

[[Page 54755]]

this AD, except for the inspections specified in paragraph (r) of 
this AD.

Post-Modification Inspection and Repair

    (r) Within 20,000 flight cycles after the modification required 
by paragraph (p) or (q) of this AD, as applicable, inspect the BS 
2598 bulkhead for cracks, and repair any crack before further 
flight, in accordance with a method approved by the Manager, Seattle 
ACO.

Open Hole HFEC Inspection(s) and Terminating Repair

    (s) For airplanes on which the terminating modification required 
by paragraph (l) or (q) of this AD has not been done: Do an initial 
open hole HFEC inspection to detect cracks in the bulkhead splice 
fitting, frame support fitting, and forward and aft inner chords on 
the left and right sides of the BS 2598 bulkhead, in accordance with 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
747-53A2427, Revision 4, dated March 6, 2008. Do the initial 
inspection at the applicable time specified in Table 1 or 3 of 
paragraph 1.E., ``Compliance,'' of the service bulletin; except, 
where the service bulletin specifies a compliance time after the 
date on the service bulletin, this AD requires compliance within the 
specified compliance time after the effective date of this AD.
    (1) If no crack is detected, repeat the open hole HFEC 
inspection thereafter at intervals not to exceed 1,500 flight 
cycles.
    (2) If any crack is detected, before further flight, repair it 
in accordance with the service bulletin; except, where the service 
bulletin specifies to contact Boeing for appropriate action, before 
further flight, repair the crack using a method approved in 
accordance with the procedures specified in paragraph (w) of this 
AD. Accomplishment of the aft inner chord repair in accordance with 
the applicable SRM specified in the Accomplishment Instructions of 
the service bulletin ends the repetitive open hole HFEC inspections 
required by paragraphs (h) and (s)(1) of this AD for that side of 
the bulkhead only.

Interim Modification

    (t) For Group 1 airplanes, as identified in Boeing Alert Service 
Bulletin 747-53A2427, Revision 4, dated March 6, 2008, on which the 
terminating modification required by paragraph (l) or (q) of this AD 
has not been done: Before the accumulation of 12,000 total flight 
cycles, or within 1,500 flight cycles after the effective date of 
this AD, whichever occurs later, install the interim modification 
for the aft inner chords, in accordance with the Accomplishment 
Instructions of the service bulletin. Accomplishment of the interim 
modification ends the repetitive open hole and surface HFEC 
inspections required by paragraphs (h) and (s)(1) of this AD.

Post-Interim Modification/Repair Repetitive Surface and Open Hole HFEC 
Inspections

    (u) For airplanes on which the interim modification required by 
paragraph (t) of this AD has been done or the repair of any cracked 
aft inner chord has been done in accordance with the SRM specified 
in the Accomplishment Instructions of Boeing Alert Service Bulletin 
747-53A2427, Revision 4, dated March 6, 2008, as required by 
paragraph (i) or (s)(2) of this AD; and on which the terminating 
modification required by paragraph (l) or (q) of this AD has not 
been done: At the applicable times specified in Table 1, 2, or 3 of 
paragraph 1.E., ``Compliance,'' of the service bulletin, do a 
surface HFEC inspection to detect cracks on the forward side 
(unmodified area) of the bulkhead and open hole and surface HFEC 
inspections to detect cracks in the modified or repaired area, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-53A2427, Revision 4, dated March 6, 2008. 
Repeat the open hole and surface HFEC inspections thereafter at 
intervals not to exceed 1,500 flight cycles, until the modification 
required by paragraph (q) of this AD is done, as applicable; except, 
for airplanes on which the repair of any cracked aft inner chord has 
been done on only one side of the bulkhead in accordance with the 
applicable SRM as required by paragraph (i) or (s)(2) of this AD, 
the repetitive open hole and surface HFEC inspections required by 
paragraph (h) and (s)(1) of this AD must continue to be done for the 
other side of the bulkhead.

Repair of Any Cracked Inner Chord, Splice Fitting, or Frame Support 
Fitting

    (v) If any crack is detected during any open hole or surface 
HFEC inspection required by paragraph (u) of this AD, before further 
flight, repair any cracked inner chord, splice fitting, or frame 
support fitting, in accordance with the Accomplishment Instructions 
of Boeing Alert Service Bulletin 747-53A2427, Revision 4, dated 
March 6, 2008; except, where the service bulletin specifies to 
contact Boeing for appropriate action, before further flight, repair 
the crack using a method approved in accordance with the procedures 
specified in paragraph (w) of this AD.

Alternative Methods of Compliance (AMOCs)

    (w)(1) The Manager, Seattle ACO, FAA, ATTN: Ivan Li, Aerospace 
Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind 
Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-
6437; 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.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who has been authorized 
by the Manager, Seattle ACO, to make those findings. For a repair 
method to be approved, the repair must meet the certification basis 
of the airplane, and the approval must specifically refer to this 
AD.
    (4) AMOCs approved previously in accordance with AD 2006-05-06 
are approved as AMOCs for the corresponding provisions of this AD.

    Issued in Renton, Washington, on September 11, 2008.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-22215 Filed 9-22-08; 8:45 am]

BILLING CODE 4910-13-P
