AD 95-02-07 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires installation of a seal on the wing front spar at each engine strut. This amendment is prompted by a report of a fire that occurred due to fuel leakage from the fuel line coupling in the engine strut area along the wing front spar while the airplane was on the ground after engine shutdown. The actions specified by this AD are intended to ensure that fuel is contained within the strut drainage area and channeled away from ignition sources.

Final rule

95-02-07 BOEING: Amendment 39-9126. Docket 94-NM-52-AD. \n\n\tApplicability: Model 747 series airplanes, equipped with General Electric CF6-45 or CF6-50 engines, or Pratt & Whitney JT9D series engines; as listed in Boeing Service Bulletin 747-28-2160, Revision 1, dated December 16, 1993; certificated in any category. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (b) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo ensure that fuel is contained within the strut drainage area and channeled away from ignition sources, accomplish the following: \n\n\t(a)\tWithin 18 months after the effective date of this AD, install a seal on the wing front spar at each engine strut in accordance with Boeing Service Bulletin 747-28-2160 dated July 23, 1992, or Revision 1, dated December 16, 1993. \n\n\t(b)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\n\t(c)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(d)\tThe installation shall be done in accordance with Boeing Service Bulletin 747-28-2160, dated July 23, 1992, or Boeing Service Bulletin 747-28-2160, Revision 1, dated December 16, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(e)\tThis amendment becomes effective on March 16, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes was published in the Federal Register on June 9, 1994 (59 FR 29744). That action proposed to require installation of a seal on the wing front spar at each engine strut. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposed rule. \n\n\tSeveral commenters state that the one reported incident was an "isolated incident" and is not characteristic of industry findings. One commenter also states that the incident was not a safety- of-flight issue since the reported fire occurred while the airplane was on the ground. Because of this, these commenters request that the FAA withdraw the proposed rule. The FAA does not concur. Asexplained in detail in the preamble to the proposed rule, airflow when the airplane is in flight or airflow from the engine running when the airplane is on the ground does prevent fuel from leaking onto hot engine surface. However, a potential unsafe condition still exists because fire can occur after engine shutdown as a result of the fuel dripping onto the hot engine surface. The reported fire demonstrates that the design of the flammable fluid drainage system does not adequately separate the fuel leak from the hot surface of the engine following engine shutdown. The FAA has determined that the actions required by this AD are warranted in order to address that unsafe condition. \n\n\tSeveral commenters contend that the proposed installation of a seal on the wing front spar at each engine will not prevent a fuel leak from occurring. One commenter states that individual modifications, such as the proposed modification, should only be required as part of a more comprehensive program of modifications that will address all known fuel system leakage problems. (The commenter did not, however, provide any specific details of a program.) Another commenter states that periodic replacement of the O-rings in the fitting would prevent the leakage of fuel; therefore, the proposed installation is not necessary. Because of these items, these commenters request that the rule not be issued. The FAA does not concur. Each incident report and each modification presented to correct causes of fuel leakage incidents is evaluated by the FAA. Both the effectiveness of the modification and the economic impact to accomplish corrective action required by an AD are considered. The FAA has determined that the installation required by this AD will improve the drainage system and prevent future fires that could be caused by fuel leakage from the fuel line (Wiggins) coupling in the engine strut area. Scheduled replacement of the O-rings may reduce the potential for fuel leaks caused by worn or aged O-rings, but it will not eliminate all causes of fuel leakage in the area of the modification. \n\n\tOne commenter states that the seal described in the proposed rule will be replaced during an anticipated "Boeing Model 747 strut modification program," and that installing the seal before modifying the strut area would provide a short-lived increase in safety. This commenter, therefore, considers the proposed installation to be unwarranted. The FAA does not concur. The planned strut modification program does not include a requirement for incorporation of the installation required by this AD, nor has a compliance time for the strut modifications been established; it is likely that the compliance time may be a period of three to five years. Although the planned strut modifications may require the removal and reinstallation of the seal installation required by this AD, the risk of a fire occurring before the planned strut modification program is implemented outweighs the convenience of waiting to install the seal until the strut modification is accomplished. The installation required by this AD can be incorporated during normal scheduled maintenance periods, thereby reducing the costs associated with this installation since access to this area will be necessitated in order to accomplish other scheduled maintenance actions. \n\n\tSeveral commenters request that the FAA extend the proposed compliance time for the installation. Some of the commenters request the compliance time be extended from the proposed 12 months to as much as 48 months. This would permit ample time to accomplish the installation during scheduled maintenance periods. One of these commenters requests that the compliance time be extended to coincide with the planned strut modification program to reduce the additional cost to the operators. The FAA concurs that the compliance time may be extended somewhat. In developing an appropriate compliance time for this AD action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but the practical aspect of incorporating the required installation into affected operators' scheduled maintenance visits, when the airplanes would be located at a base where facilities and trained personnel would be readily available, if necessary. The FAA has reviewed data submitted by the manufacturer as to recommended installation time, and concurs with the commenters' requests for an extension. The FAA has determined that extending the compliance time from 12 months to 18 months will not compromise safety. Paragraph (a) of the final rule has been revised accordingly. \n\n\tAs a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been added to this final rule to clarify this requirement. \n\n\tAdditionally, the FAA has recently reviewed the figures it has used over the past several years in calculating the economic impact of AD activity. In order to account for various inflationary costs in the airline industry, the FAA has determined that it is necessary to increase the labor rate used in these calculations from $55 per work hour to $60 per work hour. The economic impact information, below has been revised to reflect this increase in the specified hourly labor rate.After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.\n\n\tThere are approximately 610 Boeing Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 183 airplanes of U.S. registry will be affected by this AD, that it will take approximately 14 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $57 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $164,151, or $897 per airplane. \n\n\tThe total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any ofthe requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tThe regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.\n \n\tFor the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\n\nAdoption of the Amendment \n\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1.\tThe authority citation for part 39 continues to read as follows: \n\tAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended)\n \n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive:

The service information referenced in this AD may be obtained from Boeing\nCommercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

G. Michael Collins, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2689; fax (206) 227-1181.