Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain McDonnell Douglas airplanes, identified above. This proposed AD would require reducing the length of the sump drain collar and replacing the fuel tank sump drain lockring for fuel tanks 1, 2, and 3; and reducing the length of the drain outlet barrel for the auxiliary fuel tank, if applicable. For airplanes with an auxiliary fuel tank, this proposed AD also would require relocating the sump drain outlet to allow draining the sumps without opening the doors of the main landing gear wheel well. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to reduce the potential of ignition sources inside fuel tanks in the event of a lightning strike, which, in combination with flammable fuel vapors, could result in arcing in the fuel tank, fuel tank explosions, and consequent loss of the airplane.