AD 51-02-01

51-02-01 DOUGLAS: Applies to All Model DC3 Series Aircraft With Ramp Type Main Entrance Doors Hinged at the Bottom.

Compliance required as indicated below.

(1) At next No. 1 inspection or equivalent and at regular intervals not to exceed approximately 100 hours, inspect the main entrance door hinges and locking and warning mechanisms for alignment and/or adjustment until the rework of item (2) is accomplished.

(2) Compliance required by July 1, 1951.

A. Install an inspection window for at least the uppermost main entrance door locking bayonet. The installation to be in a manner to permit visual observation of the bayonets in the locked position so that it can be determined by visual means that the door is properly closed and locked. The bayonets and adjacent structure should also be appropriately marked with a paint stripe to indicate when the bayonets are in the locked position.

B. Provide means to prevent disengagement of bayonets by creeping due to vibration or other loads in flight. A notched bayonet installation similar to that covered in Metropolitan Airparts Service Bulletin No. MAP-1A for their airstairs Model A; or similar to the notched bayonet installation used on the Douglas DC-6 and Super DC3 main entrance doors; or a spring loaded positive over center latching mechanism will be considered to meet this objective.

(3) Compliance required by January 1, 1953.

To reduce the possibility of inadvertent opening of the door in flight install stops to positively limit the lock mechanism travel in accordance with Metropolitan Airparts Service Bulletins No. MAP-4A, MAP-5A, or MAP-6A (for Model A, C, or D Airstair Doors, respectively) or equivalent.