68-22-02 ALLISON: Applies to Model 250-C18, 250-C18A, and 250-C10B engines, to wit Allison Model 250-C18 engines having compressor assemblies installed with serial numbers prior to Serial Number CAC 21073; Model 250-C18A engines having compressor assemblies installed with serial numbers prior to Serial Numbers CAC 20202; and all Model 250-C10B engines. The Allison model engines to which this AD is applicable must be modified in accordance with Allison Commercial Engine Bulletin 250 CEB-51 and 250 CEB-52 dated October 16, 1968, on or before May 1, 1969. Until modified, the engines to which this AD is applicable may be operated provided:
(1) They are not operated with N1 (gas producer) rpm greater than 96.5 percent, except for "takeoff";
(2) Time operated at "takeoff" does not exceed two (2) minutes;
(3) The generator load does not exceed 60 amps when the engine is operating above 70 percent N1 rpm.*
NOTE:
This amendment becomes effective November 1, 1968.
*As a resultof these operating restrictions, the rotorcraft flight manual and certain power plant instrument markings for the Bell 206A, the Fairchild Hiller FH-1100, and the Hughes 369A and 369H helicopters in which these engines are installed may require modifications or the installation of suitable placards. The necessary information for such changes is available from the manufacturers of these helicopters.