AD 94-12-06

94-12-06 SCHWEIZER AIRCRAFT CORPORATION AND HUGHES HELICOPTERS, INC.: Amendment 39-8934. Docket Number 92-ASW-50. Supersedes AD 80-02-14, Amendment 39-3668.

Applicability: Model 269A, 269A-1, 269B, 269C, and TH-55A helicopters, with lower belt drive pulley bearings, part number (P/N) 269A5050-57 or 269A5050-80, installed, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the lower belt drive pulley bearings (pulley bearings), loss of power to the rotor systems, and subsequent loss of control of the helicopter, accomplish the following:

(a) Within the next 50 hours' time-in-service (TIS) after the effective date of this AD, replace all pulley bearings, P/N 269A5050-57 or 269A5050-80, that have accumulated 1,750 or more hours' TIS on the effective date of this AD. For pulley bearings that have accumulated less than 1,750 hours' TIS on the effective date of this AD, replace these pulley bearings on or prior to attaining 1,800 hours' total TIS. If replaced with pulley bearings, P/N 269A5050-57 or 269A5050- 80, the repetitive inspection requirements of paragraph (d) of this AD are applicable.

NOTE: The following paragraphs of the AD, relative to bearing retention system inspection, cover two systems of retention. At delivery, all Model 269A, 269A-1, 269B, TH-55A, and certain 269C helicopters, serial numbers 1 through 589, were equipped with sheet metal lower bearing straps, P/N 269A5463. Model 269C helicopters, serial numbers 590 and subsequent, were equipped with machined lower bearing caps that are part of a 269A5573-11 "H" frame assembly. Paragraph (b) concerns the sheet metal straps and paragraph (c) concerns the machined caps.

(b) Within the next 50 hours' TIS after the effective date of this AD, on helicopters equipped with sheet metal lower bearing straps, P/N 269A5463--

(1) Inspect the pulley bearings in accordance with paragraphs a. through f. ofPart I of Schweizer Aircraft Corporation or Hughes Helicopters, Inc. Service Information Notice (SIN) N-146.2, dated December 7, 1979, and,

(2) Shim bearing straps in accordance with paragraph h.(2) of Part I of SIN N-146.2, dated December 7, 1979.

(c) Within the next 50 hours' TIS after the effective date of this AD, on helicopters equipped with machined lower pulley bearing caps (caps) that are part of a 269A5573-11 "H" frame assembly, inspect caps and frame assembly lower bearing bore for out-of-roundness in accordance with paragraphs l. through p., Part I of SIN N-164, dated December 7, 1979.

(1) If out-of-roundness exceeds 0.001 inch Total Indicator Reading (T.I.R.), reverse the caps and repeat the inspections of paragraph (c) of this AD for both caps.

(2) If out-of-roundness exceeds 0.001 inch T.I.R. after reversing and reinspecting the caps, replace both caps with two lower bearing straps, P/N 269A5463, in accordance with paragraph r. of Part I of SIN N-164, dated December 7, 1979.

(d) Within 300 hours' TIS after accomplishing paragraphs (b) or (c) of this AD, and thereafter at intervals not to exceed 300 hours' TIS from the last inspection, inspect the pulley bearings in accordance with paragraph a. through e. of Part III of SIN N-164, dated December 7, 1979.

(e) Before returning any helicopter equipped with a replacement "H" frame assembly to service, accomplish the inspections of paragraphs (b) or (c) of this AD as appropriate.

(f) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, New York Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, New York Aircraft Certification Office.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York Aircraft Certification Office.

(g) 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 helicopter to a location where the requirements of this AD can be accomplished.

(h) The inspections and replacements shall be done in accordance with Schweizer Aircraft Corporation or Hughes Helicopters, Inc. SIN N-164 and SIN 146.2, both dated December 7, 1979. 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 Schweizer Aircraft Corporation, P.O. Box 147, Elmira, New York 14902. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(i) This amendmentbecomes effective on September 19, 1994.