2010-3542. Airworthiness Directives; The Boeing Company Model 747 Airplanes

AGENCY:

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

ACTION:

Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.

SUMMARY:

The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to certain Model 747 airplanes. The original NPRM would have superseded an existing AD that currently requires repetitive inspections of the body station (BS) 2598 bulkhead, and corrective actions if necessary.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. The original NPRM proposed to continue to require those actions using revised service information. For certain airplanes, the original NPRM proposed to require new repetitive inspections, an interim modification, and post-interim modification inspections. For certain airplanes, the original NPRM also proposed to require replacing any previously repaired aft inner chord and reinstalling the terminating modification. The original NPRM resulted from reports of cracked aft inner chords on airplanes after certain requirements of the existing AD were done. This new action revises the original NPRM for airplanes that are converted to the Model 747-400 large cargo freighter (LCF) configuration by reducing the threshold and repeat intervals of certain post-modification inspections. This new action also revises the original NPRM for all airplanes by proposing that certain inspections of the upper aft outer chords and diagonal brace attachment fittings, flanges, and rods continue after the terminating modification. We are proposing this supplemental NPRM 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 supplemental NPRM by March 22, 2010.

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: [phone].
• 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 proposed AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1; fax [phone]; e-mail [e-mail]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221 or 425-227-1152.

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 [phone]) 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 [phone]; fax [phone].

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 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

We proposed to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) with a notice of proposed rulemaking (NPRM) for an AD (the “original NPRM”) to supersede AD 2006-05-06, amendment 39-14503 (71 FR 12125, March 9, 2006). The original NPRM applied to certain Model 747 airplanes. The original NPRM was published in the Federal Register on September 23, 2008 (73 FR 54751). The original NPRM proposed to require repetitive inspections of the body station (BS) 2598 bulkhead, and corrective actions if necessary; and a terminating modification for the repetitive inspections and a post-modification inspection of the modified area. The original NPRM proposed to require those actions using revised service information. For certain airplanes, the original NPRM proposed to require new repetitive inspections, an interim modification, and post-interim modification inspections. For certain airplanes, the original NPRM also proposed to require replacing any previously repaired aft inner chord and reinstalling the terminating modification.

Actions Since Original NPRM was Issued

Since we issued the original NPRM, Boeing informed us that the compliance times of certain post-modification inspections need to be revised for Model 747-400 series airplanes that have been modified to operate in a freighter configuration. These airplanes are referred to as large cargo freighters, or LCF. Boeing states that higher operating stresses for the subject structure on the Model 747-400 LCF airplanes mean that these airplanes need a lower inspection threshold and shorter repeat intervals than those specified in the original NPRM. We agree, and we have revised paragraphs (m), (q), and (r) of the original NPRM to reduce the threshold and repetitive intervals.

In addition, Boeing informed us that for all airplanes certain inspections of the upper aft outer chords and diagonal brace attachment fittings, flanges, and rods need to be continued after the terminating modification is accomplished. Adding the reinforcing modification and replacing the aft inner chord as specified in the NPRM does not alter the upper aft outer chord and diagonal brace attachment fittings, flanges, and rods. Therefore, we have revised paragraph (q) of the original NPRM to specify that certain inspections must continue after the terminating modification.

Comments

We have considered the following comments on the original NPRM.

Request To Revise Costs of Compliance

Northwest Airlines requests that we revise the “Costs of Compliance” section of the original NPRM to include Boeing's current cost of the modification kit. Northwest Airlines states that the current cost is $52,218 rather than the $33,716 quoted in the original NPRM.

We agree that the cost of the modification kit has changed. We have revised the “Costs of Compliance” section of this supplemental NPRM to include the new cost of the kit.

Request To Delay the AD Pending Revised Service Information

All Nippon Airways and Japan Airlines request that we delay issuing the AD until Boeing revises Alert Service Bulletin 747-53A2427 to Revision 5 (we referred to Boeing Alert Service Bulletin 747-53A2427, Revision 4, dated March 6, 2008, in the original NPRM). All Nippon Airways explains that it has discussed several discrepancies in Revision 4 with Boeing, and that Boeing clarified those discrepancies in an information notice (IN). All Nippon Airways states that, since INs are not approved by the FAA, it will be a burden to operators to request alternative methods of compliance (AMOCs) once the proposed rule is mandated. As an alternative, All Nippon Airways proposes that we include the additional information from the IN in the final rule.

In addition, Boeing has informed us that there is a discrepancy in the modification drawing specified in Boeing Alert Service Bulletin 747-53A2427, Revision 4, dated March 6, 2008. The drawing does not include a step to “zero-time” certain existing fastener holes in the affected areas. The zero-timing is intended to remove any undetectable cracks in the affected fastener holes.

We agree that we should refer to the most recent service information possible. We have reviewed Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009. The revised service information includes the information in the IN referred to by the commenter (the IN clarifies fastener codes and repair instructions) and does not require any additional work on airplanes on which the inspections, interim modification, and repair specified in earlier revisions of the service bulletin were done. Therefore, we have revised paragraphs (i), (j), (o), (s), (t), (u), and (v) of this supplemental NPRM to refer to Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009. We have also added new paragraph (w) to the supplemental NPRM to give credit for doing certain actions in accordance with Boeing Alert Service Bulletin 747-53A2427, Revision 4, dated March 6, 2008.

We have also reviewed Boeing Service Bulletin 747-53-2473, Revision 1, dated February 20, 2007; and Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009. We referred to Boeing Service Bulletin 747-53-2473, dated March 24, 2005, as the appropriate source of service information for accomplishing the required actions specified in paragraph (m) of the NPRM.

Boeing Service Bulletin 747-53-2473, Revision 1, dated February 20, 2007, retains and clarifies the same procedures as in Boeing Service Bulletin 747-53-2473, dated March 24, 2005, and adds procedures to replace repaired aft inner chords on certain airplanes on which the actions specified in Boeing Service Bulletin 747-53-2473, dated March 24, 2005, were done.

Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, adds procedures to inspect to determine if certain fasteners were installed, and to do related investigative and corrective actions if necessary, for airplanes on which the support frame modification specified in Boeing Service Bulletin 747-53-2473, dated March 24, 2005; or Revision 1, dated February 20, 2007; was done. The related investigative actions include an open-hole high frequency eddy current (HFEC) inspection of the fastener holes of a certain type of fastener for cracks, and a review of maintenance records to verify that an open-hole HFEC inspection was performed at certain other fastener holes and the holes were zero-timed. For airplanes on which the holes were not zero-timed, the service bulletin specifies an HFEC inspection of the holes for cracks, and corrective actions if necessary. Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, also adds procedures to do post-modification inspections.

We have revised paragraph (m) of this supplemental NPRM to refer to Boeing Service Bulletin 747-53-2473, Revision 1, dated February 20, 2007; and Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009. We have revised paragraph (q) of this supplemental NPRM to refer to Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009.

We have also revised paragraphs (n) and (r) of this supplemental NPRM to refer to Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, for the post-modification inspections.

Explanation of Change to Paragraph (r) of This Supplemental NPRM

Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, also adds procedures for post-modification inspections. In paragraph (r) of the NPRM, we specified doing a post-modification inspection for cracking and repair of any crack, in accordance with a method approved by the FAA. Because Boeing Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, specifies doing support frame post-modification inspections, we have revised paragraph (r) of this supplemental NPRM to refer to that service bulletin. The support frame post-modification inspections consist of the following inspections specified in Parts 1, 2, and 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009.

The “Part 1—Support Frame Inspections” include the following inspections:

• A detailed inspection for cracking of the support frame and access cut-out forward and aft sides at station 2598.
• A surface HFEC inspection for cracking of the lower floor support chord at station 2598.
• A low frequency eddy current (LFEC) inspection for cracking of the support frame outer chord at station 2598.
• A surface and open-hole HFEC inspection for cracking of the support frame outer chord and fitting at station 2598.
• An ultrasonic or surface HFEC inspection for cracking of the support frame outer chord at station 2598.

The “Part 2—Hinge Support Inspection” is an open-hole HFEC inspection for cracking in the back-up fittings, frame support fitting and hinge fitting at station 2598.

The “Part 3—Support Frame Inspections” include the following inspections:

• Detailed inspections for cracking of the frame web around the periphery of the aft inner chord and the entire modified support frame.
• Surface HFEC inspections for cracking in the upper forward inner chord, aft inner chord, upper splice fitting, lower forward inner chord, and frame support fitting, lower splice fitting, hinge frame support fitting.
• An LFEC or open-hole HFEC for cracking in the upper aft inner chord.
• Ultrasonic inspections for cracking in the upper and lower forward inner chord and frame support fitting.
• A surface HFEC inspection for cracking of the frame web.
• An LFEC for cracking in the aft outer chord.

If any cracking is found, the service bulletin specifies the corrective action as contacting Boeing for repair data and doing the repair.

Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, specifies that the initial compliance times for doing support frame post-modification inspections ranges between within 1,500 flight cycles after doing the modification to within 20,000 flight cycles after doing the modification, depending on the inspection and airplane configuration. The service bulletin specifies that the repetitive interval for the support frame post-modification inspections ranges between 1,000 flight cycles and 6,000 flight cycles, depending on the inspection.

Explanation of New Compliance Time for Certain Airplanes in Paragraph (m) of This Supplemental NPRM

For airplanes that are modified as specified in paragraph (m) of the supplemental NPRM and are converted to the Model 747-400 Large Cargo Freighter (LCF) configuration, the repetitive inspection specified in paragraph (k)(2) of this AD must be done thereafter at intervals not to exceed 1,800 flight cycles. We have revised paragraph (m) of this AD accordingly.

Clarification of Compliance Time

We have revised paragraph (q)(2) of this supplemental NPRM to specify that the applicable related investigative and corrective actions must be done before further flight, as specified in Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009.

Explanation of Change Made to Paragraph (x)(3) of This Supplemental NPRM

Boeing Commercial Airplanes has received an Organization Designation Authorization (ODA), which replaces their previous designation as a Delegation Option Authorization (DOA) holder. We have revised paragraph (x)(3) of this AD to delegate the authority to approve an alternative method of compliance for any repair required by this AD to the Boeing Commercial Airplanes ODA.

Explanation of Added/Removed Paragraphs in the Supplemental NPRM

We have added a new paragraph (d) to this supplemental NPRM to provide the Air Transport Association (ATA) of America subject code for this proposed AD. This code is added to make this supplemental NPRM parallel with other new AD actions. We have re-identified subsequent paragraphs accordingly.

Paragraph (n) of the original NPRM indicates that, after the effective date of the AD, Boeing Alert Service Bulletin 747-53A2427, Revision 4, dated March 6, 2008, must be used to accomplish the requirements of paragraphs (h) and (i) of the original NPRM (i.e., paragraphs (i) and (j) of this supplemental NPRM). We have removed paragraph (n) of the original NPRM, and have referred to Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, in paragraphs (i) and (j) of this supplemental NPRM.

Explanation of Additional Change to “Costs of Compliance” Paragraph

We have revised the “Costs of Compliance” section to clarify which costs are retained from AD 2006-05-06 and which costs are new in this supplemental NPRM.

Explanation of Changes Made to the Manufacturer Name

We have revised this supplemental NPRM to identify the legal name of the manufacturer as published in the most recent type certificate data sheet for the affected airplane models.

FAA's Determination and Proposed Requirements of the Supplemental NPRM

We are proposing this supplemental NPRM because we evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design. Certain changes described above expand the scope of the original NPRM. As a result, we have determined that it is necessary to reopen the comment period to provide additional opportunity for the public to comment on this supplemental NPRM.

Costs of Compliance

There are about 998 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this proposed AD. The average labor rate is $80 per work hour.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
Surface HFEC inspections (required by AD 2006-05-06) and open-hole HFEC inspections (new proposed action)	2	None	$160, per inspection cycle	162	$25,920, per inspection cycle.
Detailed inspections (required by AD 2006-05-06)	2	None	$160, per inspection cycle	162	$25,920, per inspection cycle.
Terminating modification (partially required by AD 2006-05-06; additional modification actions in this new proposed action)	126	$52,218	$62,298	162	$10,092,276.
Interim modification (new proposed action)	4	4,000	$4,320	162	$699,840.
Replacement of previously repaired aft inner chords (new proposed action)	2	None	$160	162	$25,920.
Support Frame upper Corner Fastener Inspection (new proposed action)	8	None	$640	162	$103,680.
Post-modification inspection (new proposed action)	4	None	$320	162	$51,840.

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 supplemental NPRM 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
• Incorporation by reference
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-14503 (71 FR 12125, March 9, 2006) and adding the following new airworthiness directive (AD):

The Boeing Company: 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 March 22, 2010.

Affected ADs

(b) This AD supersedes AD 2006-05-06, Amendment 39-14503.

Applicability

(c) This AD applies to The Boeing Company 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 though 1307 inclusive.

Subject

(d) Air Transport Association (ATA) of America Code 53: Fuselage.

Unsafe Condition

(e) 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

(f) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Restatement of Requirements of AD 2006-05-06

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

(g) 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, amendment 39-12318, which was superseded by AD 2006-05-06), 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

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

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

(i) 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; Revision 3, dated September 27, 2001; or Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009; at the latest of the times specified in paragraphs (i)(1) and (i)(2) of this AD, as applicable. Repeat the inspection after that at intervals not to exceed 1,500 flight cycles. After the effective date of this AD, Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, must be used.

(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, amendment 39-12337, which was superseded by AD 2006-05-06).

(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 Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998; or Revision 1, dated October 28, 1999, as applicable.

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

(j) If any cracking is found during the inspections required by paragraph (i) 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; Revision 3, dated September 27, 2001; or Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009. After the effective date of this AD, Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, must be used. Where Boeing Alert Service Bulletin 747-53A2427, Revision 2, dated October 5, 2000; Revision 3, dated September 27, 2001; or Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009; 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 (x) of this AD.

Repetitive Detailed Inspections of BS 2598 Bulkhead

(k) 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, amendment 39-13311, which was superseded by AD 2006-05-06), whichever is later: Do a detailed inspection of the BS 2598 bulkhead for discrepancies (cracking, elongated fastener holes) of the areas specified in paragraphs (k)(1) and (k)(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, except as required by paragraph (m) of this AD. Doing the modification specified in paragraph (m) or (q) of this AD terminates the inspection of the area specified in paragraph (k)(1) of this AD.

(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

(l) If any discrepancy is found during any inspection required by paragraph (k) 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 (x) of this AD.

Terminating Modification With New Compliance Time for Certain Airplanes for the Inspection Specified in Paragraph (k)(2) of This AD

(m) Except as provided by paragraph (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; Revision 1, dated February 20, 2007; or Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009. Repair any cracks before further flight, in accordance with Boeing Service Bulletin 747-53-2473, dated March 24, 2005; Revision 1, dated February 20, 2007; or Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009. Where Boeing Service Bulletin 747-53-2473, dated March 24, 2005; Revision 1, dated February 20, 2007; or Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009 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 (x) of this AD. Accomplishment of the modification terminates the requirements of paragraphs (g), (i), and (k)(1) of this AD. After the effective date of this AD, Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009 must be used for the actions specified in this paragraph. For airplanes that are converted to the Model 747-400 Large Cargo Freighter (LCF) configuration, repeat the inspection specified in paragraph (k)(2) of this AD thereafter at intervals not to exceed 1,800 flight cycles.

Post-Modification Inspection and Repair

(n) Except as provided by paragraphs (q) and (r) of this AD: Within 20,000 flight cycles after doing the modification required by paragraph (m) 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

Terminating Repair for Repetitive Surface HFEC Inspections

(o) As of the effective date of this AD, accomplishing the aft inner chord repair required by paragraph (j) of this AD in accordance with the applicable structural repair manual (SRM) specified in the Accomplishment Instructions of Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, ends the repetitive surface HFEC inspections required by paragraph (i) 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 (m) of this AD has been done in accordance with Boeing Service Bulletin 747-53-2473, dated March 24, 2005: Within 1,500 flight cycles after doing the modification, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later, do a one-time general visual inspection for repairs installed previously on the left and right side aft inner chords. For airplanes with previously installed repairs, before further flight, do rework (i.e., 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 (x) of this AD.

Revised Terminating Modification

(q) Doing the applicable modification required by paragraph (q)(1) or (q)(2) of this AD at the applicable time terminates the requirements of paragraph (m) of this AD and the repetitive inspections required by paragraphs (g), (i), and (k)(1) of this AD. For airplanes that are converted to the Model 747-400 LCF configuration, the inspection specified in paragraph (k)(2) of this AD must be repeated thereafter at intervals not to exceed 1,800 flight cycles.

(1) For airplanes on which the terminating modification required by paragraph (m) 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 the bulkhead, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009; except that where Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, specifies to contact Boeing for modification data, the modification data must be approved in accordance with the procedures specified in paragraph (x) of this AD and the modification must be done within the times specified in this paragraph.

(2) For airplanes on which the terminating modification required by paragraph (m) of this AD has been done in accordance with Boeing Service Bulletin 747-53-2473, dated March 24, 2005; or Revision 1, dated February 20, 2007; as of the effective date of this AD: Within 1,000 flight cycles after the effective date of this AD, or within 1,500 flight cycles after doing the modification, whichever occurs later, do a general visual inspection of the applicable areas specified in paragraphs (q)(2)(i) and (q)(2)(ii) of this AD to determine if certain fasteners are installed, and, before further flight, do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009; except where Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009, specifies to contact Boeing for repair or rework data, the data must be approved in accordance with the procedures specified in paragraph (x) of this AD and the repair or rework must be done before further flight.

(i) For airplanes modified in accordance with Boeing Service Bulletin 747-53-2473, dated March 24, 2005: Inspect the upper forward inner chord, frame support fitting, and splice fitting.

(ii) For airplanes modified in accordance with Boeing Service Bulletin 747-53-2473, Revision 1, dated February 20, 2007: Inspect the frame web and upper shear deck aft side; and the upper forward inner chord, frame support fitting, and splice fitting.

Post-Modification Inspection and Repair

(r) For airplanes on which the terminating modification has been done in accordance with paragraph (m) or (q) of this AD: Perform post-modification inspections of the BS 2598 bulkhead for cracking, in accordance with Parts 1, 2, and 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009. Do the inspections at the applicable times specified in Tables 6 through 9 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009; except where the service bulletin specifies a compliance time after the date of the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD. If any cracking is found during any inspection required by this paragraph, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (x) of this AD. Repeat the inspections thereafter at the applicable times specified in Tables 6 through 9 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2473, Revision 2, dated August 28, 2009. Accomplishing the applicable inspections required by this paragraph terminates the requirements of paragraph (n) of this AD.

Open-Hole HFEC Inspection(s) and Terminating Repair

(s) For airplanes on which the terminating modification required by paragraph (m) 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 Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009. Do the initial inspection at the applicable time specified in Table 1 or 3 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009; except where Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, 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 Accomplishment Instructions of Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009; except where Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, 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 (x) of this AD. Accomplishing the aft inner chord repair in accordance with the applicable structural repair manual (SRM) specified in the Accomplishment Instructions of Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, ends the repetitive surface and open-hole HFEC inspections required by paragraphs (i) and (s)(1), respectively, of this AD for that side of the bulkhead only.

Interim Modification

(t) For Group 1 airplanes, as identified in Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, on which the SRM repair required by paragraph (j) or (s)(2) of this AD has not been done; and on which the terminating modification required by paragraph (m) 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 Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009. Accomplishing the interim modification ends the repetitive surface and open-hole HFEC inspections required by paragraphs (i) and (s)(1), respectively, 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 SRM repair required by paragraph (j) or (s)(2) of this AD has been done; and on which the terminating modification required by paragraph (m) 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 Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, 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 Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009. 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 that 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 (j) or (s)(2) of this AD, the repetitive surface and open-hole HFEC inspections required by paragraphs (i) and (s)(1), respectively, 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 surface or open-hole 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 Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009; except where Boeing Service Bulletin 747-53A2427, Revision 5, dated October 1, 2009, 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 (x) of this AD.

Actions Accomplished According to Previous Issue of Service Bulletin

(w) Inspections, interim modification, and repairs accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-53A2427, Revision 4, dated March 6, 2008, are considered acceptable for compliance with the corresponding action specified paragraphs (i), (j), (s), (t), (u), and (v) of this AD.

Alternative Methods of Compliance (AMOCs)

(x)(1) The Manager, Seattle ACO, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]. Or, e-mail information to [e-mail].

(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 principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(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 Boeing Commercial Airplanes Organization Designation Authorization (ODA) that 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 February 11, 2010.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.