95-21-02: Main Rotor Drive Shaft

95-21-02 SCHWEIZER AIRCRAFT CORPORATION and HUGHES HELICOPTERS, INC: Amendment 39-9387. Docket No. 94-SW-02-AD. Supersedes AD 93-14-06, Amendment 39-8630. Applicability: Model 269A, 269A-1, 269B, 269C, and TH-55A helicopters, with main rotor (M/R) drive shaft part number (P/N) 269A5305-3 or 269A5305-11 installed, except those M/R drive shafts having a serial number with a prefix of "SZ" or "ZS", certificated in any category. NOTE 1: This AD applies to each helicopter 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 helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (d) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD. Compliance: Required as indicated, unless accomplished previously. To prevent structural failure of the M/R drive shaft, separation of the M/R from the helicopter, and subsequent loss of control of the helicopter, accomplish the following: (a) Inspect the M/R drive shaft for cracks, distortion, corrosion, or other surface damage, using either the radiographic inspection procedure or the other non-destructive inspection procedure in accordance with Part I of Schweizer Service Bulletin B-255.1 (SB), dated February 1, 1993. Conduct this inspection at the time intervals and under the conditions stated in the following: (1) Inspect M/R drive shafts with serial numbers (S/N) S0001 through S1111, and any drive shaft without an "S" prefix on the S/N, having less than 1,100 hours time-in-service (TIS) on the effective date of this AD-- (i) At the next removal of the drive shaft; (ii) Within the next 600 hours TIS; (iii) Prior to attaining 1,200 hours total TIS; or (iv) Within 1 year after the effective date of this AD, whichever occurs first. (2) Inspect M/R drive shafts with S/N S0001 through S1111, and any drive shaft without an "S" prefix on the S/N with 1,100 hours or more TIS on the effective date of this AD-- (i) Within the next 100 hours TIS; or (ii) At the next removal of the drive shaft; or (iii) Within 1 year after the effective date of this AD, whichever occurs first. (3) Inspect M/R drive shafts with S/N S1112 and higher, regardless of the number of the total hours TIS on the effective date of this AD-- (i) Within the next 25 hours TIS; (ii) At the next removal of the drive shaft; or (iii) Within 1 year after the effective date of this AD, whichever occurs first. (4) Inspect the M/R drive shaft before further flight if M/R vibrations occur that cannot be corrected with track and balance procedures, or if M/R track and balance procedures are required more than once within a 25-hour TIS interval. (b) Inspect any replacement M/R drive shaft, except those that have a serial number with a prefix of "SZ" or "ZS", prior to installation in accordance with the procedures in Part I of the SB, dated February 1, 1993. (c) Replace any unairworthy M/R drive shaft with an airworthy M/R drive shaft before further flight. (d) 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, whomay concur or comment and then send it to the Manager, New York Aircraft Certification Office. NOTE 2: 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. (e) 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) only for those helicopters that do not exhibit M/R vibrations due to uncorrected out-of-track or out-of-balance conditions specified in paragraph (a)(4) of this AD. The special flight permit allows flight of the helicopter to a location where the requirements of this AD can be accomplished. (f) The inspections and replacement, if necessary, shall be done in accordance with Schweizer Service Bulletin B-255.1 (SB), dated February 1, 1993. This incorporation by reference was previously approved by the Director of the Federal Register in accordance with 5U.S.C. 552(a) and 1 CFR part 51 as of October 29, 1993 (58FR53120, October 14, 1993). 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 76137; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC. (g) This amendment becomes effective on November 17, 1995.