Incident Overview
A pilot on a nonscheduled cargo flight was dispatched to an airport other than his usual destination because the alternate airport had a precision instrument approach, while his usual airport did not. The pilot chose to fly to his usual airport and attempted a non-precision instrument approach. The airport had both a VOR and an NDB approach; the NDB approach was noted as being out of service, although a radio signal was still emanating from the navigation aid.
Approach and Collision
The pilot was cleared for the VOR approach. However, instrumentation inside the cockpit was found set for the NDB approach, and radar track data disclosed that the flight path was consistent with the NDB approach path rather than the VOR's. The reported weather at the airport was 1.25 miles visibility with a 200-foot overcast in mist. The airport's minimum NDB approach altitude is 652 feet above touchdown height. The airplane did not reach the runway and collided with a pole and a building.
Aircraft Examination
Inspection of the airplane disclosed no evidence of any preimpact mechanical malfunctions.
Probable Cause
The probable cause of the accident was the pilot's descent below minimum descent altitude while on a non-precision approach. A contributing factor was a low ceiling.