AD 69-21-01

69-21-01 HUGHES: Amdt. 39-859. Applies to Model 269 and 369H series helicopters with Hughes P/N 269A6027 or 369A5400 tail rotor transmission installed.

Compliance required prior to further flight unless already accomplished.

To prevent loss of tail rotor power due to possible failure of the input pinion shaft (a part of the 369A5425 gear shaft assembly) of certain tail rotor transmissions accomplish the following:

Prior to further flight, determine if the serial number of the transmission gearbox installed is one of those listed in Hughes Service Information Notice, No. N-71, dated September 24, 1969 or later FAA approved revisions (all 269 series), or Hughes Service Information Notice No. HN-1, dated September 24, 1969, or later FAA approved revisions (all Model 369H series). If the gearbox is listed, and if the total time in service of the gearbox is in excess of 90 hours, replace the gearbox before the next flight with a gearbox marked with "M" on the tail rotortransmission identification plate or a serial number not listed in the Hughes Notices. For those gearboxes listed with less than 90 hours total time in service, replace the gearbox before 90 hours total time in service. If the tail rotor gearboxes are in spares inventory and within the listed serial numbers, they must not be installed on any aircraft.

NOTE: The tail rotor transmission identification plate will be stamped with the letter "M" following the serial number to indicate installation of a satisfactory input pinoin shaft.

Hughes Service Information Notice N-71 dated September 24, 1969, or later FAA approved revisions and HN-1 dated September 24, 1969 or later FAA approved revisions cover same subject.

This amendment becomes effective upon publication in the Federal Register for all persons except those to whom it was made effective immediately by telegram dated September 26, 1969.