AD 81-17-04 ACTIVE

81-17-04 HUGHES HELICOPTERS: Amendment 39-4185. Applies to Model 269 helicopters, all models, and TH-55s, certified in all categories, incorporating P/Ns 269A5179 or 269A5179-3 Drive Shaft Coupling Assemblies, and those helicopters incorporating the improved P/N 269A5194 Ring Gear Carrier Assembly.

Compliance required as indicated, unless already accomplished.

To prevent failure of the main transmission, accomplish the following:

(a) For main rotor ring gear driveshaft assemblies, P/N 269A5179 or 269A5179-3:

(1) Within 100 hours' additional time in service from the effective date of this AD, or 600 hours total time in service, whichever occurs later, inspect shaft and coupling assembly lower bearing bore and fasteners for evidence of cracks, fretting, or other stress risers, in accordance with Part IIA and IIB of Hughes Service Notice No. N-179 dated July 17, 1981. If cracks, fretting or stress risers are found, replace with P/N 269A5194 assembly reworked per Hughes Notice No. N142.1, prior to further flight.

(2) Within 100 hours' additional time in service from the effective date of this AD, or 2,000 hours total time in service for 269C aircraft or 2,500 hours total time in service for 269A/A-1/B/TH-55A aircraft, whichever occurs later, remove and replace shaft and coupling assembly with 269A5194 ring gear carrier assembly reworked per Hughes Notice No. N-142.1 dated May 31, 1977.

(b) For main rotor ring gear drive shaft assemblies, P/N 269A5179 not modified per Hughes Notice No. N-114-3 dated September 19, 1977:

Within the next 25 hours' additional time in service after the effective date of this AD, or 400 hours' total time in service, or 300 hours since the last inspection performed per paragraph (a) of AD 77-21-10, whichever occurs later, and at intervals not to exceed 300 hours' time in service thereafter, perform a close visual inspection and penetrant inspection of shaft and coupling fastener area per Part IIB ofHughes Notice No. N-179, for fretting, cracking, or other stress risers. If cracks, fretting or stress risers are found, replace with P/N 269A5194 assembly reworked per Hughes Notice No. N-142.1, prior to further flight.

(c) For main rotor ring gear drive shaft assemblies, P/N 269A5179 previously modified per Hughes Notice No. N-114.3 at or before the accumulation of 1000 hours' additional time in service since modification per Hughes Notice N-114.3, and at intervals not to exceed 500 hours' time in service thereafter, accomplish the visual and penetrant inspections of the fastener areas, as described in paragraph (b), above.

(d) The recurring inspections of paragraphs (b) and (c), above, may be discontinued when P/N 269A5194 assemblies are installed. The service life limit on P/N 269A5194 is 6,000 hours.

(e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate aircraft to a base for the accomplishment of inspections or modificationsrequired by this AD.

(f) Alternative inspections, modifications or other actions which provide an equivalent level of safety may be used when approved by the Chief, Engineering and Manufacturing Branch, FAA Western Region.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Hughes Helicopters, Inc., Centinela and Teale Street, Culver City, California 90230. These documents may also be examined at FAA Western Region Office, 15000 Aviation Boulevard, Hawthorne, California 90261 and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. 20591. A historical file on this AD, which includes the incorporated material in full, is maintained by the FAA at its Headquarters in Washington, D.C. and at FAA WesternRegion Office.

This supersedes Amendment 39-3060 (42 FR 55882), AD 77-21-10.
This amendment becomes effective August 24, 1981.