AD 72-03-06

72-03-06 ALLISON: Amdt. 39-1390. Applies to Models 250-B15A, 250-B15E, 250-B15G, 250-B17, 250-C10B, 250-C10D, 250-C18, 250-C18A, 250-C18B, 250-C18C, 250-C19 and 250-C20 engines. Compliance: Required as indicated, unless already accomplished. To ensure adequate life limit margin for Allison P/Ns 6857912 and 6871872 second stage turbine wheels, accomplish the following: A) Within the next 50 hours' time in service after the effective date of this AD, remove from service all P/Ns 6857912 and 6871872 second stage stabilizer trim and to maintain stabilizer control capability, accomplish the following: (a) For airplanes incorporating stabilizer trim modules having over 1500 hours' time in service. B) Prior to their exceeding 1550 hours' time in service, remove from service all P/Ns 6857912 and 6871872 second stage turbine wheels having 1500 hours or less time in service on the effective date of this AD. Allison Commercial Service Letter No. 250CSL-10, dated December 9, 1971, pertains to this subject. This amendment becomes effective February 8, 1972.