AD 98-18-23

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive high frequency eddy current (HFEC) inspections to detect cracking on all surfaces of the upper recesses in certain latch support fittings of the cargo doorway, and replacement of cracked fittings with new fittings. The existing AD also provides for optional terminating action for the repetitive inspections. This amendment requires accomplishment of the previously optional terminating action. This amendment is prompted by reports indicating that the repetitive inspections required by the existing AD may not detect cracked fittings in a timely manner. The actions specified by this AD are intended to prevent the cargo door from opening while the airplane is in flight, which could result in rapid decompression of the airplane.

Final rule

98-18-23 BOEING: Amendment 39-10739. Docket 97-NM-47-AD. Supersedes AD 93-02-16, Amendment 39-8500. \n\n\tApplicability: Model 747 series airplanes, line numbers 1 through 200 inclusive; having 7079-T6 aluminum latch support fittings; 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 request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent the cargo door from opening while the airplane is in flight, which could result in rapid decompression of the airplane, accomplish the following: \n\nRESTATEMENT OF THE REQUIREMENTS OF AD 93-02-16: \n\t(a)\tWithin 60 days after March 11, 1993 (the effective date of AD 93-02-16, amendment 39-8500), perform a high frequency eddy current (HFEC) inspection to detect cracking on all surfaces of the upper recess in each 7079-T6 aluminum latch support fitting of the cargo doorway, in accordance with Boeing Service Bulletin 747-53A2377, Revision 1, dated January 28, 1993, or Revision 2, dated October 6, 1994. After the effective date of this AD, only Revision 2 of the service bulletin shall be used. \n\n\tNOTE 2: Boeing Service Bulletin 747-53A2377, Revision 2, dated October 6, 1994, references Boeing Service Bulletin 747-53-2200, Revision 1, dated November 16, 1979, as an additional source of service information for the replacement of these fittings. \n\n\t\t(1)\tIf any cracking is found on any fitting, prior to further flight, replace the cracked fitting with a new 7075-T73 aluminum latch support fitting in accordance with Boeing Service Bulletin 747-53A2377, Revision 1, dated January 28, 1993, or Revision 2, dated October 6, 1994. After the effective date of this AD, only Revision 2 of the service bulletin shall be used. \n\n\t\t(2)\tIf no cracking is found on any fitting, repeat the HFEC inspection thereafter at intervals not to exceed 18 months until the requirements of paragraph (b) of this AD are accomplished. \n\nNEW REQUIREMENTS OF THIS AD: \n\n\t(b)\tWithin 18 months after the effective date of this AD, replace all 7079-T6 aluminum latch support fittings with new 7075-T73 fittings, in accordance with Boeing Alert Service Bulletin 747-53A2377, dated December 10, 1992, Boeing Service Bulletin 747-53A2377, Revision 1, dated January 28, 1993, or Boeing Service Bulletin 747-53A2377, Revision 2, dated October 6, 1994. Replacement of all latch support fittings constitutes terminating action for the inspection requirements of this AD. \n\n\t(c)\tAs of the effective date of this AD, no operator shall install any 7079-T6 aluminum latch support fitting of the cargo door on any airplane. \n\n\t(d)\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 3: 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(e)\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(f)\tThe actions shall be done in accordance with Boeing Alert Service Bulletin 747-53A2377, dated December 10, 1992; Boeing Service Bulletin 747-53A2377, Revision 1, dated January 28, 1993; or Boeing Service Bulletin 747-53A2377, Revision 2, dated October 6, 1994. \n\n\t\t(1)\tThe incorporation by reference of Boeing Alert Service Bulletin 747-53A2377, dated December 10, 1992, and Boeing Service Bulletin 747-53A2377, Revision 2, dated October 6, 1994, is approved by the Director of the Federal Register, in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. \n\n\t\t(2)\tThe incorporation by reference of Boeing Service Bulletin 747-53A2377, Revision 1, dated January 28, 1993, was approved previously by the Director of the Federal Register as of March 11, 1993 (58 FR 11190, February 24, 1993). \n\n\t\t(3)\tCopies 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(g)\tThis amendment becomes effective on October 20, 1998.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 93-02-16, amendment 39-8500 (58 FR 11190, February 24, 1993), which is applicable to certain Boeing Model 747 series airplanes, was published in the Federal Register on December 11, 1997 (62 FR 65233). The action proposed to continue to require repetitive high frequency eddy current inspections to detect cracking on all surfaces of the upper recesses in certain latch support fittings of the cargo doorway, and replacement of cracked fittings with new fittings. The action also proposed to require accomplishment of the previously optional terminating action. \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\nSupport for the Rule \n\n\tSeveral commenters support the proposed rule. Request to Revise Cost Estimate \n\n\tOne commenter requests that the cost estimate for the proposed rule be increased to $4,500 per installation to reflect replacement of two truss fittings associated with each latch support fitting. The commenter notes that certain truss fittings ((the subject of AD 79-17-02 R2, amendment 39-3867 (45 FR 52357, August 7, 1980)) and certain latch support fittings (the subject of this AD) are made of the same 7079-T6 material. The commenter reports that it intends to replace the truss fittings at the same time it replaces the latch support fittings. \n\n\tThe FAA does not concur that the estimated cost of replacement of the latch support fittings should be increased to $4,500 per installation. This AD does not require replacement of any truss fittings that are attached to the latch support fittings. Although AD 79-17-02 R2 requires that the truss fittings be inspected, it does not require replacement because of the fail-safe design that incorporates two truss fittings for each latch support fitting. While the FAA acknowledges that it would be prudent for operators to replace those truss fittings at the same time the latch support fittings are replaced, this AD does not require replacement of any truss fittings. No change to the cost estimate of the final rule is necessary. \n\nRequest to Reduce Compliance Times \n\n\tOne commenter (the Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom) requests that the compliance time for the proposed actions be reduced. Specifically, the CAA suggests that the inspections be performed at 3-month intervals and the latch support fittings replaced within 12 months. In support of its recommendation, the commenter refers to a report of an 8-inch crack found in a latch support fitting on a Boeing Model 747 series airplane. The fitting had been inspected twice in a 6-month period; no crack had been found during the first inspection. The commenter suggests that, based on the reported incident, such reduced compliance timeswould be more realistic. \n\n\tThe FAA does not concur with the request to reduce the compliance times. The FAA finds that the proposed 18-month replacement threshold will provide an acceptable level of safety because of the fail-safe capability resulting from multiple latch support fittings. In addition, the 18-month compliance time will allow for the fittings to be replaced during scheduled maintenance at regular maintenance bases, thereby minimizing the impact on affected operators. The FAA recognizes the CAA's jurisdiction and authority to require accomplishment within its suggested inspection interval and replacement threshold on affected airplanes within the United Kingdom. \n\nComment Concerning Availability of Materials \n\n\tOne commenter states that the 18-month replacement threshold required by this AD should not present a scheduling problem provided that materials are available from the manufacturer. \n\n\tAt this time, the FAA is not aware of any scheduling difficulties that may delay operators' acquisition of the required materials for timely compliance with this AD. \n\nChange to the Rule \n\n\tOperators should note that new paragraph (b) of the final rule has been revised to include an additional source of service information for accomplishment of the replacement. This change allows operators to replace the support fittings in accordance with Boeing Service Bulletin 747-53A2377, Revision 1, dated January 28, 1993, in addition to the other cited versions of alert service bulletin. \n\nConclusion \n\n\tAfter 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 change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 200 Boeing Model 747 series airplanes of the affected design in theworldwide fleet. The FAA estimates that 115 airplanes of U.S. registry will be affected by this AD. \n\n\tThe inspections that currently are required by AD 93-02-16, and retained in this AD, takes approximately 31 work hours per airplane, per inspection cycle, to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required inspections on U.S. operators is estimated to be $213,900, or $1,860 per airplane, per inspection cycle. \n\n\tThe new action (replacement of the latch support fittings) that is required by this AD will take approximately 1,019 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $20,917 per airplane ($12,888 for all aft door fittings; $8,029 for all forward door fittings). Based on these figures, the cost impact of the new replacement requirements of this AD on U.S. operators is estimated to be $9,436,555, or $82,057 per airplane. \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\nRegulatory Impact \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\n\tAir 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. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\t2. Section 39.13 is amended by removing amendment 39-8500 (58 FR 11190, February 24, 1993), and by adding a new airworthiness directive (AD), amendment 39-10739, to read as follows: