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ASN Wikibase Occurrence # 176646
Last updated: 23 June 2020
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Type:Silhouette image of generic BE36 model; specific model in this crash may look slightly different
Beechcraft A36 Bonanza
Registration: N3243P
C/n / msn: E-2943
Fatalities:Fatalities: 0 / Occupants: 2
Other fatalities:0
Aircraft damage: Substantial
Location:Bedford, MA -   United States of America
Phase: Landing
Departure airport:Bedford, MA (BED)
Destination airport:
Investigating agency: NTSB
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.

Probable Cause: The mechanic's failure to properly torque the engine-driven fuel pump's return line B-nut fitting.



Revision history:

04-Jun-2015 20:18 Noro Added
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
07-Dec-2017 17:54 ASN Update Bot Updated [Cn, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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