64-10-05 PRATT & WHITNEY: Amdt. 724 Part 507 Federal Register May 5, 1964. Applies to All Models R-2800-21, -27, -31, -43, -51, -51M4, -59, -63, -71, -75, -75M2 and -79 Series Engines.
Compliance required within 1,400 hours' time in service after the effective date of this AD.
Because of instances of exhaust valve failures, replace the P/N 44764 exhaust valves with P/N's 50724 or 158175 exhaust valves.
This directive effective June 5, 1964.
Revised September 5, 1964.