80-26-03 DEHAVILLAND: Amendment 39-3993. Applies to all DeHavilland DHC-4 and DHC-4A aircraft equipped with Pratt & Whitney Aircraft Twin Wasp D-5 and R-2000-7M2 engines incorporating left-hand magneto drive arrangement.
Compliance required within the next 1400 hours in service after the effective date of this AD unless already accomplished.
To preclude failure of the left hand magneto drive mechanism, incorporate the right-hand magneto drive and associated parts as described in Pratt & Whitney Aircraft Service Bulletin No. 1756 dated September 13, 1963, or approved equivalent instructions and parts.
The Twin Wasp D-5 and R-2000-7M2 engines so modified must be redesignated as noted in Section C of the Pratt & Whitney Aircraft Service Bulletin No. 1756, or an approved equivalent instruction.
All equipment instructions and parts must be approved by the Chief, Engineering & Manufacturing Branch, FAA Eastern Region.
(Pratt & Whitney Aircraft Service Bulletin No. 1756 pertains to this subject.)
This amendment is effective December 19, 1980.