Accident Mooney M20F N6442Q,
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ASN Wikibase Occurrence # 296278
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Date:Sunday 12 January 2003
Time:15:47 LT
Type:Silhouette image of generic M20P model; specific model in this crash may look slightly different    
Mooney M20F
Registration: N6442Q
MSN: 670521
Total airframe hrs:4586 hours
Engine model:Lycoming IO-360-A1A
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Location:Tacoma, Washington -   United States of America
Phase: Unknown
Departure airport:Puyallup, WA (1S0)
Destination airport:Olympia Airport, WA (OLM/KOLM)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
The pilot reported that while en route, the engine backfired, followed by a total loss of power. The pilot initiated a forced landing, attempting to land at a nearby airport. The aircraft was unable to reach the runway and collided with trees and brush about 200 yards short of the runway. During a post-accident engine examination, the crankshaft was found fractured through the forward side of the number four journal. Metallurgical examination of the fracture surface revealed that the crankshaft failure was the result of fatigue initiating at a subsurface inclusion. Scanning electron microscopic examinations established that the fatigue initiated at a single subsurface site located 0.023 inch below the journal surface. Closer inspection found an approximate 0.002 to 0.003 inch diameter pit at the origin location. The pit was mostly empty but contained remnants of material that was identified by energy dispersive x-ray spectroscopic as mostly aluminum and calcium. The age of the crankshaft could not be determined but appeared to be an older crankshaft that was manufactured prior to the manufacturers transition to vacuum arc remelted steels which have higher fatigue strengths and which almost eliminates the presence of inclusions.

Probable Cause: A loss of engine power during cruise flight due to fatigue failure of the crankshaft as a result of an inadequate quality of material during the manufacturing process. Trees were a factor.

Accident investigation:
Investigating agency: NTSB
Report number: SEA03FA025
Status: Investigation completed
Duration: 1 year and 2 months
Download report: Final report



Revision history:

13-Oct-2022 18:40 ASN Update Bot Added

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