AD 99-20-09

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires inspections of the lower engine mount to determine if the tangential link upper bolt and nut are oriented properly, and if the tangential link upper bolt nut is torqued within certain limits. Additionally, that amendment requires replacement of the bolt and nut with serviceable parts, if necessary, and requires certain follow-on actions for airplanes on which the upper bolt is missing. This amendment requires accomplishment of a previously optional terminating action or a new alternative terminating action for the repetitive inspections. This amendment is prompted by development of a new terminating action by the manufacturer. The actions specified by this AD are intended to prevent separation of the engine from the airplane due to migration of the tangential link upper bolt.

Final rule

99-20-09 BOEING: Amendment 39-11339. Docket 98-NM-277-AD. Supersedes AD 96-03-01 R1, amendment 39-9538. \n\n\tApplicability: Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747-71A2277, dated November 29, 1995; or Boeing Service Bulletin 747-71A2277, Revision 1, dated May 21, 1998, or Revision 2, dated January 14, 1999; 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 (c)(1) 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 separation of the engine from the airplane, accomplish the following: \n\nRESTATEMENT OF REQUIREMENTS OF AD 96-03-01 R1, AMENDMENT 39-9538: \n\nInspections and Corrective Actions \n\n\t(a)\tWithin 90 days after February 16, 1996 (the effective date of AD 96-03-01 R1, amendment 39-9538), accomplish the requirements of paragraphs (a)(1) and (a)(2) of this AD in accordance with Boeing Alert Service Bulletin 747-71A2277, dated November 29, 1995, or Boeing Service Bulletin 747-71A2277, Revision 1, dated May 21, 1998, or Revision 2, dated January 14, 1999. \n\n\t\t(1)\tPerform a visual inspection to ensure that installation of the tangential link upper bolt nut is on the forward side of the engine mount fitting. \n\n\t\t\t(i)\tIf the tangential link upper bolt nut is installed on the forward side of the engine mount fitting, repeat the visual inspection at intervals not to exceed 18 months. \n\n\t\t\t(ii)\tIf the tangential link upper bolt nut is not installed on the forward side of the engine mount fitting, prior to further flight, remove the nut, bolt, and washers, and reinstall the nut, bolt, and washers in accordance with the service bulletin. Thereafter, repeat the visual inspection at intervals not to exceed 18 months. \n\n\t\t\t(iii)\tIf the tangential link upper bolt is missing from the engine mount fitting, prior to further flight, perform the various follow-on actions in accordance with the service bulletin. (The follow-on actions include visual inspections, magnetic particle inspections, replacement of the lower engine mount fitting with a serviceable part, if necessary; installation of new safety links, bolts, and nuts; and installation of a new tangential link upper bolt.) \n\n\tThereafter, repeat the visual inspection at intervals not to exceed 18 months. \n\n\t\t(2)\tPerform an inspection to verify that the torque value of the tangential link upper bolt (on both sides of the mount) is within the limits specified in the service bulletin. \n\n\t\t\t(i)\tIf the torque value of the tangential link upper bolt nut is within the limits specified in the service bulletin, repeat the inspection (verification) at intervals not to exceed 18 months. \n\n\t\t\t(ii)\tIf the torque value of the tangential link upper bolt nut is outside the limits specified in the service bulletin, prior to further flight, perform a visual inspection of the tangential link upper bolt and washer for any damage or discrepancy, in accordance with the service bulletin. \n\n\t\t\t\t(A)\tIf no damage or discrepancy of the tangential link upper bolt and washers is found, prior to further flight, replace the bolt nut with a new or serviceable part in accordance with the service bulletin. Thereafter, repeat the inspection (verification) specified in paragraph (a)(2) of this AD at intervals not to exceed18 months. \n\n\t\t\t\t(B)\tIf any damage or discrepancy of the tangential link upper bolt and washers is found, prior to further flight, replace the damaged or discrepant part with a new or serviceable part, and replace the bolt nut with a new or serviceable part, in accordance with the service bulletin. Thereafter, repeat the inspection (verification) specified in paragraph (a)(2) of this AD at intervals not to exceed 18 months. \n\nNEW REQUIREMENTS OF THIS AD: \n\nReplacement \n\n\t(b)\tWithin 18 months after the effective date of this AD, accomplish the requirements of either paragraph (b)(1) or (b)(2) of this AD. Accomplishment of either paragraph (b)(1) or (b)(2) of this AD constitutes terminating action for the repetitive inspection requirements of this AD. \n\n\t\t(1)\tReplace the safety links on the aft engine mount with modified safety links in accordance with Boeing Service Bulletin 747-71-2206, dated April 16, 1987; or Boeing Service Bulletin 747-71-2206, Revision 1, dated November 12, 1987, as revised by Boeing Notice of Status Change No. 747-71-2206 NSC 1, dated December 4, 1987, and Boeing Notice of Status Change No. 747-71-2206 NSC 2, dated March 17, 1988. \n\n\t\t(2)\tReplace the tangential link upper bolt on the aft engine mount with a reworked bolt and a new nut retainer, in accordance with Parts 2 and 3 of Boeing Service Bulletin 747-71A2277, Revision 1, dated May 21, 1998, or Revision 2, dated January 14, 1999. \n\nAlternative Methods of Compliance \n\n\t(c)\t(1)\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\t\t(2)\tAlternative methods of compliance, approved previously in accordance with AD 96-03-01 R1, amendment 39-9538, are approved as alternative methods of compliance with this AD. \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\nSpecial Flight Permits \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 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.\n\nIncorporation by Reference \n\n\t(e)\tThe actions shall be done in accordance with Boeing Alert Service Bulletin 747-71A2277, dated November 29, 1995; Boeing Service Bulletin 747-71A2277, Revision 1, dated May 21, 1998; Boeing Service Bulletin 747-71A2277, Revision 2, dated January 14, 1999; Boeing Service Bulletin 747-71-2206, dated April 16, 1987; or Boeing Service Bulletin 747-71-2206, Revision 1, dated November 12, 1987, as revised by Boeing Notice of Status Change No. 747-71-2206 NSC 1, dated December 4, 1987, and Boeing Notice of Status Change No. 747-71-2206 NSC 2, dated March 17, 1988; as applicable. \n\n\t\t(1)\tThe incorporation by reference of Boeing Service Bulletin 747-71A2277, Revision 2, dated January 14, 1999; Boeing Service Bulletin 747-71-2206, dated April 16, 1987; or Boeing Service Bulletin 747-71-2206, Revision 1, dated November 12, 1987, as revised by Boeing Notice of Status Change No. 747-71-2206 NSC 1, dated December 4, 1987, and Boeing Notice of Status Change No. 747-71-2206 NSC 2, dated March 17, 1988; as applicable is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Boeing Service Bulletin 747-71-2206, Revision 1, dated November 12, 1987, contains the following list of effective pages: \n\n\n\nPage Number\n Revision Level\nShown on Page\nDate\nShown on Page\n1-5, 9, 10, 12\n 1\nNovember 12, 1987 \n6-8, 11, 13-18\nOriginal\nApril 16, 1987\n\n\t\t(2)\tThe incorporation by reference ofBoeing Alert Service Bulletin 747-71A2277, dated November 29, 1995, was approved previously by the Director of the Federal Register as of February 16, 1996 (61 FR 10270, March 13, 1996). \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(f)\tThis amendment becomes effective on November 8, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 96-03-01 R1, amendment 39-9538 (61 FR 10270, March 13, 1996), which is applicable to certain Boeing Model 747 series airplanes, was published in the Federal Register on July 16, 1999 (64 FR 38379). The action proposed to continue to require inspections of the lower engine mount to determine if the tangential link upper bolt and nut are oriented properly, and if the tangential link upper bolt nut is torqued within certain limits. Additionally, that action also proposed to continue to require replacement of the bolt and nut with serviceable parts, if necessary, and requires certain follow-on actions for airplanes on which the upper bolt is missing. That action also proposed to require accomplishment of either a previously optional terminating action or a new, alternative terminating action for the repetitive inspections. \n\nComments \n\n\tInterested personshave been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received. \n\n\tThe commenter supports the proposed rule. \n\nConclusion \n\n\tAfter careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed. \n\nCost Impact \n\n\tThere are approximately 421 airplanes of the affected design in the worldwide fleet. The FAA estimates that 185 airplanes of U.S. registry will be affected by this AD. \n\n\tThe inspections that are currently required by AD 96-03-01 R1 take approximately 16 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $177,600, or $960 per airplane, per inspection cycle. \n\n\tThe replacement of the safety link that is required as one option for compliance with this AD action will take approximately 18 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $30,228 per airplane. Based on these figures, the cost impact of this replacement required by this AD on U.S. operators is estimated to be $31,308 per airplane. \n\n\tIn lieu of replacement of the safety link, this AD provides for replacement of the tangential link upper bolt on the aft engine mount with a reworked bolt and a new nut retainer. Such replacement, which is provided as an additional option for compliance with this AD action, will take approximately 20 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $1,888 per airplane. Based on these figures, the cost impact of this replacement required by this AD on U.S. operators is estimated to be $3,088 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." \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 39-9538 (61 FR 10270, March 13, 1996), and by adding a new airworthiness directive (AD), amendment 39-11339, to read as follows: