60-21-01 ALLISON: Amdt. 208 Part 507 Federal Register October 8, 1960. Applies to All Model 501-D13 Series Engines.
Compliance required at next overhaul of engine, power section or torquemeter, whichever occurs first, after the effective date of this AD.
Several cases of rubbing of the torquemeter housing by the torquemeter reference shaft have resulted in complete separation of the housing into two sections. To preclude such failures, a mid-bearing torquemeter assembly, P/N 6823900, identified by a 1/2-inch by 2 1/2-inch blue stripe on the forward bevel of the housing shall be installed. (Allison Commercial Engine Bulletin No. 72-113 covers the same subject.)
This directive effective November 9, 1960.