80-25-01: Tail Rotor Drive Shaft

80-25-01 HUGHES HELICOPTERS: Amendment 39-3980. Applies to Model 369 Series Helicopters certified in all categories. Compliance is required as indicated unless already accomplished. To prevent possible fatigue failure of the Hughes couplings in the tail rotor drive shaft and loss of tail rotor power, accomplish the following: (a) Within 25 hours' time in service from the effective date of this AD, inspect the fore and aft tail rotor drive shaft couplings to determine the serial numbers of the installed couplings. The serial number is on the Bendix part number decal. (b) For those helicopters with the following couplings installed, prior to further flight, remove couplings from service and label couplings "Unairworthy." Hughes Part No. 369H92564, serial numbers 0883U, 0932U, 0933U, 0935U, 0940U, 0950U, 0957U, 0961U, 0971U; and for Hughes Part No. 369A5501, serial numbers 10670U and 10672U. Replace removed coupling with like serviceable part. (c) Installation of any coupling listed in paragraph (b) will render the helicopter unairworthy. (d) Report the serial number of each suspect coupling listed in paragraph (b) found as a result of the inspection of paragraph (a) to the Chief, Engineering and Manufacturing Branch, FAA, Western Region, P.O. Box 92007, World Way Postal Center, Los Angeles, California 90009. Negative reports are not necessary. Reporting approved by Office of Management and Budget, OMB No. 04/R0174. (e) 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. (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. This amendment becomes effective December 4, 1980.