AD 49-27-01

49-27-01 CONVAIR: Applies to All BT-13 Series Aircraft.

Compliance required not later than November 1, 1949.

Certain cases of engine failures at takeoff in these aircraft have been traced to fuel starvation as a result of accumulations of water or ice in a short segment of the fuel line, between the fuel selector valve and the emergency pump unit. The segment of fuel line from the valve outlet port to a point approximately 12 inches forward forms a water trap which cannot be drained without disconnecting the line.

To preclude the possibility of engine malfunctioning from ice accumulation in this line, either of the following modifications must be accomplished:

1. Provide a new support bracket for the fuel selector valve which will raise the bottom of the valve, and the lowest point of the fuel line from the valve to the emergency fuel pump unit inlet port, to a height slightly above the level of the emergency pump unit inlet when the aircraft is in the 3-pointposition on level terrain, or

2. Provide a new selector valve, having the outlet port not lower than the inlet ports, and installed in such a manner that there will be a continuous up slope in the fuel lines from the fuel tank outlet to the emergency pump unit inlet when the aircraft is in the 3-point attitude.