AD 79-18-13

79-18-13 DETROIT DIESEL ALLISON: Amendment 39-3548. Applies to all Model 250-C28B and 250-C28C Series engines equipped with third stage turbine wheel P/Ns 6898553 or 6898773 installed in, but not limited to Bell 206L-1 rotorcraft certificated in all categories. Compliance required as indicated unless previously accomplished. A. For turbine wheels with less than 300 hours total time in service, compliance is required before reaching 325 hours total time in service. B. For turbine wheels with more than 300 hours total time in service, compliance is required within 25 hours time in service. To preclude engine power loss due to possible turbine blade failure, remove above listed third stage turbine wheels from service. This amendment becomes effective September 6, 1979, as to all persons except those to whom it was made immediately effective by the airmail letter dated July 19, 1979, which contained this amendment.