AD 2008-10-15

This AD is effective May 20, 2008.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of May 20, 2008.

We must receive comments on this AD by July 21, 2008.

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.

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.

We have received a report of cracking found at fourteen adjacent fastener holes where protruding head fasteners were installed in the upper row of the right stringer 6 (S-6) lap splice, between station (STA) 360 and STA 380. The airplane had accumulated 23,132 total flight cycles. The protruding head fasteners had been installed without external skin doublers 9,757 flight cycles earlier as one of several modification options provided in Boeing Service Bulletin 747-53-2253 (AD 90-06-06, amendment 39-6490 (55 FR 8374, March 7, 1990), requires that one of the modifications specified in the service bulletin be done). Analysis by Boeing indicates that the protruding head fastener modification and the post-modification inspections are not adequate to prevent and detect cracks at the upper row of fasteners in the S-6 lap splices before the cracks reach critical length. The post-modification inspections are given in Boeing Service Bulletin 747-53-2253 and are required by AD 90-23-14, amendment 39-6801 (55 FR 46652, November 6, 1990). Cracking in the fuselage skin, if not corrected, could result in rapid decompression and loss of structural integrity.

We reviewed Boeing Alert Service Bulletin 747-53A2748, dated May 9, 2008. The alert service bulletin describes procedures for an external inspection to determine if acceptable external skin doublers are installed at the left- and right-side S-6 lap splices, between STA 340 and STA 400. For airplanes without the acceptable external skin doublers, the alert service bulletin specifies doing repetitive related investigative actions and corrective actions if necessary. Related investigative actions include external high frequency eddy current (HFEC) and low frequency eddy current (LFEC) inspections of the skin for cracking, as applicable. Corrective actions include repairing cracking and repeating related investigative actions, or modifying the airplane by installing acceptable external skin doublers at both the left- and right-side S-6 lap splices (includes doing an open-hole HFEC inspection of the skin for cracking, and trimming out cracking if necessary). Doing the modification would end the repetitive related investigative actions.

Boeing Alert Service Bulletin 747-53A2748 refers to Boeing Service Bulletin 747-53-2253, Revision 3, dated March 24, 1994; and Boeing Service Bulletin 747-53-2272, Revision 18, dated May 16, 2002; as additional sources of service information for accomplishment of the modification (installation of acceptable external skin doublers).

We are issuing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. This AD requires an external inspection to determine if acceptable external skin doublers are installed at the S-6 lap splices, between STA 340 and STA 400. For airplanes without the acceptable external skin doublers, this AD requires repetitive related investigative actions, as applicable, and corrective actions if necessary. This AD also provides an optional terminating modification for the repetitive related investigative actions.

We consider this AD interim action. We are currently considering requiring the modification (installation of acceptable external skin doublers), which would terminate the repetitive related investigative actions. However, the planned compliance time for the modification would allow enough time to provide notice and opportunity for prior public comment on the merits of the modification.

We have determined that cracking of multiple adjacent fastener holes at the S-6 lap splices adjacent to the flight deck windows could join together and result in large cracks. Considering the number of accumulated flight cycles on the affected Boeing Model 747 airplanes and the consequences of cracking, we have determined that immediate inspections are necessary. Because of our requirement to promote safe flight of civil aircraft and thus, the critical need to assure the structural integrity of the fuselage and the short compliance time involved with this action, this AD must be issued immediately.

Because an unsafe condition exists that requires the immediate adoption of this AD, we find that notice and opportunity for prior public comment hereon are impracticable and that good cause exists for making this amendment effective in less than 30 days.

This AD is a final rule that involves requirements affecting flight safety, and we did not provide you with notice and an opportunity to provide your comments before it becomes effective. However, we invite you to send any written data, views, or arguments about this AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2008-0554; Directorate Identifier 2008-NM-100-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this AD. We will consider all comments received by the closing date and may amend this 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 AD.

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.

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.

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

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

2. The FAA amends § 39.13 by adding the following new AD: