AD 60-07-06

60-07-06 MARTIN: Amdt. 118 Part 507 Federal Register March 25, 1960. Applies to All Model 404 Aircraft.

Compliance required as indicated.

Investigation of a recent Model 404 wheels up landing disclosed that the landing gear lock linkage and lock plunger malfunctioned. Inspection of the jury strut revealed that when the lock plunger was pulled back to normal travel limits in operating the "free fall" actuating mechanism to "full travel", the plunger would periodically jam in the retracted position and consequently flare out in the form of a knife edge. Also, cutting action was evident in the forward bushings (in the plunger cylinder) in an area coincident with the two flared edges. To prevent further lock plunger malfunctioning, the following must be accomplished:

(a) Replace lock plunger P/N 404-4088121-3 with new lock plunger P/N 404- 4900121-5 on each main landing gear by July 31, 1960.

(b) At each 320 hours' time in service commencing not later than May15, 1960, visually inspect main and nose gear lock plungers for a spalling or flaring condition. Check the lock plunger for free operation. The plunger should be free from dirt, dust, moisture, ice, etc. If spalling or flaring exists, the lock plunger must be chamfered (rounded out) at the corners of the plunger for the full length of the flat area.

(Martin Service Bulletin No. 404-260 dated October 30, 1952, partially covers this subject.)