59-10-08 PIPER: Applies to Models PA-18, PA-18A, PA-20 and PA-22, Aircraft.
Compliance required not later than July 15, 1959, for Models PA-18, PA-18A, and PA- 22, and not later than November 30, 1959, for the Model PA-20.
Recent occurrences have revealed improper compliance with AD 56-26-02 (Canceled March 24, 1958). Therefore, the tank vents drilled into the gas tank cap must be checked as follows: Insert a 0.030-inch diameter wire into the holes at the bottom of the cap. If the holes are properly drilled the wire can be inserted over 3/4 inch until it hits the inside top of the cap. If the holes are not properly drilled the wire will hit the baffle and only enter approximately 1/4 inch. Also, if the cap has one hole drilled and is marked with an "X" adjacent to the hole, and the cap rattles when shaken, a loose internal rivet is indicated. If either of the latter conditions exist, the following must be accomplished:
Rework the fuel tank caps by drilling two additional 0.067 holes 1/4 inch from the existing center hole. Drill through bottom part of cap and baffle only. Check these newly drilled holes with the 0.030-inch diameter wire as outlined above.
(This airworthiness directive supplements Piper Service Bulletin No. 148A dated May 29, 1957. The drawings included in this bulletin may be referred to as a guide in reworking the fuel tank caps.)