NTSB Identification: IAD04LA018
Accident occurred Wednesday, April 28, 2004 in Bedford, MA
Probable Cause Approval Date: 04/28/2005
Aircraft: Beech A36, registration: N3243P
Injuries: 1 Minor,1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
During the first takeoff after the installation of an overhauled engine, about 400 feet, the engine rpm dropped, then went to zero. The pilot turned back toward the airport and unsuccessfully attempted an engine restart with the boost pump in the "high" position. The airplane subsequently landed perpendicular to a runway, all three landing gear collapsed, and the airplane came to rest between two parked airplanes. During a post-accident examination, the cockpit fuel boost pump lever was found in the "high" position, and there was no evidence of fuel spillage or spray within the engine compartment. In addition, torque paste on the engine-driven fuel pump's return line B-nut fitting was found to be 1/4 turn counter-clockwise (loosened) in relation to the torque paste on the receiving end of a 90-degree elbow fitting. When the B-nut was hand-tightened, the torque paste on both fittings were aligned. When the B-nut was further tightened with a wrench, the paste was misaligned again, but about 1/4 turn further clockwise. Multiple engine runs revealed that when the B-nut was fully tightened with a wrench, and when it was also hand-tightened to the point where the B-nut paste was aligned with the 90-degree fitting paste, the engine ran smoothly. When the B-nut was loosened to a point nearly to where it was initially found, the engine quit. During subsequent testing, while the B-nut was being loosened and the engine started to quit, the boost pump was turned on to the "high" position. The engine then ran, but fuel was sprayed from the fitting. When the B-nut was further backed off, the engine would quit and could not be restarted, even with the boost pump operating. Maintenance facility personnel subsequently conducted similar tests on another airplane with a similar fuel system. When the B-nut was loosened sufficiently to allow fuel leakage, the engine quit. However, during those tests where the engine began to quit and the auxiliary fuel pump switch was placed in the high position, the engine continued to run.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The mechanic's failure to properly torque the engine-driven fuel pump's return line B-nut fitting. Full narrative available
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