69-18-02 ALLISON: Amdt. 39-831. Applies to Models 250-C10 and 250-C18 Series Engines.
Compliance: Unless already accomplished, within the next 50 hours' time in service after the effective date of this AD, on all engines having 750 or more hours' time in service since new or last overhaul, or at or before 800 hours' time in service on engines that have less than 750 hours' time in service since new or last overhaul at the effective date of this AD, accomplish the following:
To detect excessive wear of the internal splines:
A) Inspect the internal spline on the P/N 6840847 helical power train drive gear using an Allison P/N EX 83339 plug gage. If this gage enters the spline, replace the gear with a new or serviceable part prior to returning the engine to service. Allison Commercial Service Letter No. 250 CSL-35, dated August 15, 1969, pertains to this inspection.
B) When the engine is modified in accordance with Allison Commercial Engine Bulletin No. 250 CEB-61, dated July 25, 1969, the inspections required by Paragraph A of this AD will no longer be required. Gear boxes having Serial Numbers ending in the suffix "B" incorporate Commercial Engine Bulletin No. 250 CEB-61.
This amendment becomes effective September 3, 1969.