AD 97-23-06

97-23-06 SCHWEIZER AIRCRAFT CORPORATION: Amendment 39-10194. Docket No. 96-SW-05-AD. Applicability: Model 269A, A-1, B, and C, and TH-55A helicopters, with main rotor transmission ring gear (ring gear), part number (P/N) 269A5104-5, identified by the letters EGC (Eastern Gear Corporation), ACR (ACR Industries), or the manufacturer code number 23751 (EGC) or 57152 (ACR), installed, 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 (f) 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 failure of the ring gear, loss of drive to the main rotor gearbox, and a subsequent forced landing, accomplish the following: (a) Inspect the ring gear teeth for surface deterioration which includes pitting, excessive wearing, cracking or corrosion in accordance with Schweizer Service Bulletin B-244.2, dated February 19, 1996, as follows: (1) Before further flight, if a clicking or tapping sound or other unusual noise or unusual vibration is detected while operating the helicopter, or if a metal particle is found on the magnetic drain plug during routine maintenance; (2) Beforeinstalling a main rotor transmission which contains an affected ring gear on the helicopter; (3) Within the next 50 hours time-in-service (TIS) after the effective date of this AD, or at the next annual inspection, whichever occurs first. (b) Thereafter, inspect the ring gear teeth at intervals not to exceed 50 hours TIS in accordance with Schweizer Service Bulletin B-244.2, dated February 19, 1996. (c) If surface deterioration which includes pitting, excessive wearing, cracking or corrosion is discovered, before further flight, remove the transmission from service and replace the ring gear with a ring gear, P/N 269A5104-7, serial number (S/N) S2100 or higher number. (d) At the next main rotor transmission overhaul, remove and replace the ring gear, P/N 269A5104-5, identified on the face of the ring gear by the letters EGC, ACR, or the manufacturer code number 23751 (EGC) or 57152 (ACR) and replace it with a ring gear, P/N 269A5104-7, S/N S2100 or higher number. (e) Installation of a ring gear, P/N 269A5104-7, S/N S2100 or higher number constitutes a terminating action for the requirements of this AD and must be annotated on a component log card. A new component log card must be created if a component log card is not in the applicable maintenance records. (f) 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, 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 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. (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, provided no clicking or tapping sound or other unusual noise or unusual vibration was detected on any previous flight. (h) The inspections shall be done in accordance with Schweizer Service Bulletin B-244.2, dated February 19, 1996. 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, NY 14902, ATTN: Publications Dept. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 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 amendment becomes effective on December 10, 1997.