AD 81-07-10

This amendment adopts a new Airworthiness Directive (AD) which imposes an inspection schedule on the overrunning clutch assembly P/N 369A5350-601 and -603 and a Retirement life on the P/N 369A5364 sprag assembly, which it contains, used in the Hughes Helicopter Model 369 Series Helicopters equipped with any cargo hook. This AD is needed to prevent an overrunning clutch assembly failure which will result in the loss of engine power to the main rotor resulting in a hazardous emergency landing.

Final rule.

Accordingly, pursuant to the authority delegated to me by the Administrator, Section 39.13 of Fart 39 of the Federal Aviation Regulations (14 CFR 39.13) is amended, by adding the following new Airworthiness Directive: Hughes Helicopters: Applies, to all Model 369 Series Helicopters, certified in all categories, that are equipped with any cargo hook. Compliance required as indicated; unless already accomplished. To prevent an overrunning dutch assembly failure which will result in the loss of engine power to the main rotor, accomplish the following: (a) Prior to accumulation of 600 hours total time since new, on overrunning clutch assembly P/N 369A5350-66L or -603, or within 50 hours additional time in service for those overrunning dutch assemblies which have accumulated 600 or more hours, on the effective date of this AD, the overrunning clutch assembly must be disassembled and the sprag assembly P/N 369A5364 inspected in accordance with the instructions specified in Hughes Service Bulletin DN-81 dated March 13,1981, or HN-164 dated March 13, 1981 as applicable. (b) After accomplishment of (a), overrunning dutch assemblies must undergo repetitive inspections at intervals not to exceed 300 hours additional time in service since last such inspection, according to tile procedures of paragraph (a). (c) All sprag assemblies P/N 369A5364 must be removed from service and scrapped after 1800 hours total time in service. (d) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate helicopters to a base for the accomplishment of inspections required by this AD. (e) 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. This amendment becomes effective April 9,1981. (Secs. 313(a), 601, and 603, Federal Aviation Act of 1958, as amended (49 U.S.C. 1354(a), 1421, and 14Z3)i Sec. 6(c) Department of Transportation Act (49 U.S.C. 1855(c)); and 14 CFR 11.89) Note.—The FAA has determined that this regulation is an emergency regulation under the President’s memorandum of January 29, 1981, and an emergency regulation that is not major under Section 8 of Executive Order 12291. It is impractical for the agency to follow the procedures of Order 12291 With respect to this rule, since the rule must be issued immediately to correct an unsafe condition in aircraft» It has been further determined that this document involves an emergency regulation under DOT Regulatory Practices and Procedures (44 FR11034; February 26,1979). If this action is subsequently determined1 to involve a significant regulation, a final regulatory evaluation or analysis, as appropriate, will be prepared and placed in the regulatory docket (otherwise, an evaluation is not required), A copy of it, when filed, may be obtained by contacting the person identified above under the caption “For Further Information Contact.” This rule is a final order of the Administrator under the Federal Aviation Act of 1958, as amended. As such, it is subject to review only by the courts of appeals of the United States of the United States* Court of Appeals for the District of Columbia.

The FAA has determined that the sprag assembly P/N 369A5364, within the overrunning clutch assembly P/N 369A5350-601 or -603, may become worn beyond safe limits when used in sling load operations. Several instances of overrunning clutch assembly fatigue failures have been reported to the FAA. A contributing factor to these overrunning clutch assembly fatigue failures is wear of the clutch sprag alignment cage elements resulting in a lowered torque capability and subsequent sudden failure. Since this condition is likely to exist or develop on other helicopters of the same type design, an airworthiness directive is being issued which requires an inspection schedule and replacement time for the sprag assembly P/N 369A5364, on all series of Hughes Model 369 Helicopters equipped with any cargo hook. Since a situation exists that requires immediate adoption of this regulation, it is found that notice and public procedure hereon are impracticable and good cause exists for making this amendment effective in less than 30 days.