AD 96-26-52 R1

This amendment revises an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections of the access doors to the midspar/spring beam fuse pins on all engine pylons to detect cracks on the external surface; repetitive inspections of each midspar/spring beam fuse pin to detect if it protrudes beyond its mating nut by a specified distance; and repair of any discrepancy found. The actions specified by that AD are intended to prevent migration of this fuse pin, which, if not detected and corrected in a timely manner, could result in failure of the engine pylon and consequent separation of the engine from the wing. This amendment increases the intervals between inspections of the access doors and each midspar/spring beam fuse pin, and consequently decreases the frequency of inspections. This amendment is prompted by new data provided by the manufacturer indicating that the reported migration of the fuse pin was apparently the result of an incorrectly installed nut.

Final rule

96-26-52 R1 BOEING: Amendment 39-10027. Docket 97-NM-12-AD. Revises AD 96-26-52, Amendment 39-9868. \n\n\tApplicability: Model 747 series airplanes having line numbers 1 through 1046 inclusive; certificated in any category; that meet all of the following criteria: \n\n\t equipped with Pratt & Whitney Model PW4000 series engines, or General Electric Model CF6-80C2 series engines, or Rolls Royce Model RB211 series engines; \n\t on which fuse pins having part numbers 310U2301-101, -116, -117, or -120 ("third generation" fuse pins) are installed at the midspar/spring beam fittings of the engine pylon; and \n\t on which the modification of the nacelle strut and wing structure in accordance with Boeing Alert Service Bulletin 747-54A2156 or Boeing Alert Service Bulletin 747-54A2157, as applicable, has not been accomplished. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (c) 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 failure of the engine pylon and consequent separation of the engine from the wing, due to migration of the fuse pins installed at the midspar/spring beam fittings of the pylon, accomplish the following: \n\n\t(a)\tWithin 15 days after January 8, 1997 (the effective date of AD 96-26-52, amendment 39-9868), accomplish the requirements of paragraphs (a)(1) and (a)(2) of this AD. \n\n\t\t(1)\tPerform a detailed visual inspection of the access doors to each midspar/spring beam fuse pin on each engine pylon to detect cracks on the external surface of the doors. \n\n\t\t\t(i)\tIf no cracking is detected during the inspection, repeat that inspection at intervals not to exceed 1,000 landings or 5,000 hours time-in-service, whichever occurs later, but not to exceed 18 months. \n\n\t\t\t(ii)\tIf any cracking is detected during the inspection, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Thereafter, repeat the inspection at intervals not to exceed 1,000 landings or 5,000 hours time-in-service, whichever occurs later, but not to exceed 18 months. \n\n\t\t(2)\tGain access through the aft fairing doors of each engine pylon to each midspar/spring beam fuse pin and its mating, self-locking nut, and perform a detailed visual inspection of each fuse pin to verify that at least one thread of the fuse pin protrudes beyond its mating, self-locking nut. \n\n\t\t\t(i)\tIf no discrepancy is detected during the inspection, repeat that inspection at intervals not to exceed 1,000 landings or 5,000 hours time-in-service, whichever occurs later, but not to exceed 18 months. \n\n\t\t\t(ii)\tIf the inspection reveals that at least one thread does not protrude beyond its mating, self-locking nut, prior to further flight, repair in accordance with a method approved by the Manager, Seattle ACO. Thereafter, repeat the inspection at intervals not to exceed 1,000 landings or 5,000 hours time-in-service, whichever occurs later, but not to exceed 18 months. \n\n\t(b)\tAccomplishment of the modification of the nacelle strut and wing structure in accordance with Boeing Alert Service Bulletin 747-54A2156, Revision 2, dated December 21, 1995, or earlier revisions (for airplanes equipped with General Electric Model CF6-80C2 series engines, or Pratt & Whitney PW4000 series engines); or Boeing Alert Service Bulletin 747-54A2157, Revision 2, dated November 14, 1996, or earlier revisions (for airplanes with Rolls Royce Model RB211 series engines); as applicable; constitutes terminating action for the repetitive detailed visual inspections required by paragraphs (a)(1) and (a)(2) of this AD. \n\n\t(c)\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 ACO. 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\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(d)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(e)\tThis amendment becomes effective on June 18, 1997.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by revising AD 96-26-52, amendment 39-9868 (62 FR 302, January 3, 1997), which is applicable to certain Boeing Model 747 series airplanes, was published in the Federal Register on February 12, 1997 (62 FR 6499). That action proposed to continue to require repetitive inspections of the access doors to the midspar/spring beam fuse pins on all engine pylons to detect cracks on the external surface, repetitive inspections of each midspar/spring beam fuse pin to detect if it protrudes beyond its mating nut by a specified distance, and repair of any discrepancy found. That action also proposed to increase the intervals between inspections of the access doors and each midspar/spring beam fuse pin, and consequently decrease the frequency of inspections. \n\nComments on the Proposal \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the two comments received. \n\n\tOne commenter supports the proposal. \n\n\tOne commenter requests that the proposed frequency of repetitive inspections of the access doors to each midspar/spring beam fuse pin and each fuse pin be altered to 5,000 hours time-in- service, or 15 months, whichever occurs first; this interval is equivalent to the maintenance interval specified in the operator's Maintenance Review Board (MRB) report. The commenter considers that adoption of the FAA's proposed interval of 1,000 landings or 18 months, whichever occurs first, would require certain operators to schedule special times for the accomplishment of this inspection. \n\n\tThe FAA concurs that the compliance times can be revised somewhat. The FAA's intent was that inspections be conducted during a regularly scheduled maintenance visit for the majority of the affected fleet, when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. Based on the information supplied by the commenter, the FAA recognizes that 5,000 hours time-in-service corresponds closely to the interval specified in the operators' MRB report. In light of this, the FAA has revised paragraphs (a)(1)(i), (a)(2)(i), and (a)(2)(ii) of the final rule to reflect a compliance time of "intervals not to exceed 1,000 landings or 5,000 hours time-in-service, whichever occurs later, but not to exceed 18 months." The FAA does not consider that this revision of the compliance time will adversely affect safety. \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 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\nCost Impact \n\n\tThere are approximately 459 Boeing Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 44 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 4 work hours per airplane to accomplish each cycle of required inspections, at an average rate of $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $10,560 per inspection cycle, or $240 per airplane, per inspection cycle. (By increasing the intervals between inspections, this AD will result in inspections being conducted less frequently than is now required.) \n\n\tThe cost impact figure discussed above is 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 relationshipbetween 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 39Air transportation, Aircraft, Aviation safety, 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\n PART 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 39-9868 (62 FR 302, January 3, 1997), and by adding a new airworthiness directive (AD), amendment 39-10027, to read as follows: