AD 97-12-05 Airworthiness Directives; General Electric Company GE90 Series Turbofan Engines

General Electric Company (GE) GE90 series turbofan engines with Accessory Gearboxes (AGBs) installed, Part Numbers (P/Ns) 1650M71G03 and 1650M71G04. These engines are installed on Boeing 777 aircraft. Note 1: This airworthiness directive (AD) applies to each engine 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 engines 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.

Required as indicated, unless accomplished previously. To prevent a Variable Speed Constant Frequency (VSCF) gearshaft flange ball bearing failure, which could result in an inflight engine shutdown, accomplish the following: (a) Perform a visual check of the engine Debris Monitoring System sensor for debris in accordance with paragraph 2(c) of the [[Page 32027]] Accomplishment Instructions of GE Service Bulletin (SB) No. 79-011, dated April 9, 1997, as follows: (1) For aircraft that have two engines installed incorporating AGBs, P/N 1650M71G03 or 1650M71G04, accomplish the following: (i) Perform an initial visual check on one of the engines installed on the aircraft within 24 clock hours after the effective date of this AD, and thereafter, visually check that engine every other day, at intervals not to exceed 48 clock hours since last visual check. (ii) Perform an initial visual check on the engine not inspected in accordance with paragraph (a)(1)(i) of this AD installed on the same aircraft on the following day, not to exceed 24 clock hours after the visual check of the engine checked in paragraph (a)(1)(i) of this AD; thereafter, visually check this engine every other day at intervals not to exceed 48 clock hours since last visual check. (iii) The visual checks for both engines must be staggered at one day intervals for each engine. (2) For aircraft that have one of the two engines installed incorporating AGBs, P/N 1650M71G03 or 1650M71G04, perform the initial visual check on that engine within 24 clock hours after the effective date of this AD, and thereafter, visually check that engine every other day at intervals not to exceed 48 clock hours since last visual check. (3) If the visual check indicates that debris is present, perform additional maintenance actions in accordance with paragraph 2(c) of the Accomplishment Instructions of GE SB No. 79-011, dated April 9, 1997, prior to further flight. (b) For engines that contain VSCF gearshaft flange ball bearings that may incorporate rivets manufactured from improper material, identified by serial numbers: 900-147, 900-149, 900-151, 900-106, and 900-153, within 7 days after the effective date of this AD, and for engines identified by serial numbers: 900-150, 900-156, 900-157, 900-158, prior to entry into revenue service, accomplish one of the following: (1) Remove from service VSCF gearshaft flange ball bearings and replace with serviceable bearings in accordance with the Accomplishment Instructions of GE SB No. 72-280, Revision 3, dated April 15, 1997; or (2) Remove and replace the 4,500 pound inches VSCF gearshaft assembly with the 3,500 pound inches gearshaft assembly installed in AGB, P/N 1650M71G02, in accordance with the Accomplishment Instructions of GE SB No. 72-283, Revision 4, dated April 17, 1997. Accomplishment of this option constitutes terminating action to the inspection requirements of paragraph (a) of this AD; or (3) Remove and replace the 4,500 pound inches VSCF gearshaft assembly with the 4,500 pound inches gearshaft assembly containing select fit internal radial clearance flange ball bearings, in accordance with the Accomplishment Instructions of GE SB No. 72-286, dated April 14, 1997. (c) An 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, Engine Certification Office. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office. (d) Special 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 aircraft to a location where the requirements of this AD can be accomplished. (e) The actions required by this AD shall be accomplished in accordance with the following GE SBs: ------------------------------------------------------------------------ Document No. Page Revision Date ------------------------------------------------------------------------ 72-283........................ 1, 2 4 April 17, 1997. 3-10 Original March 12, 1997. 11, 12 1 March 20, 1997. 13 Original March 12, 1997. Total Pages: 13. 72-280........................ 1, 2 3 April 15, 1997. 3-12 2 March 19, 1997. Total Pages: 12. 72-286........................ 1-15 Original April 14, 1997. Total Pages: 15. 79-011........................ 1-6 Original April 9, 1997. Total Pages: 6. ------------------------------------------------------------------------ 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 General Electric Technical Services, Attention: Leader For Distribution/Microfilm, 10525 Chester Road, Cincinnati, OH 45215; fax (513) 672-8422, telephone (513) 672-8400 Ext. 114. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (f) This amendment supersedes Telegraphic AD T97-09-51, issued April 22, 1997. (g) This amendment becomes effective on June 27, 1997. Issued in Burlington, Mass., on June 2, 1997. Thomas A. Boudreau, Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service. [FR Doc. 97-14956 Filed 6-11-97; 8:45 am] BILLING CODE 4910-13-U