ASN Wikibase Occurrence # 296278
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| Date: | Sunday 12 January 2003 |
| Time: | 15:47 LT |
| Type: |  Mooney M20F |
| Owner/operator: | Private |
| Registration: | N6442Q |
| MSN: | 670521 |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Tacoma, Washington -
 United States of America
|
| Phase: | Unknown |
| Nature: | Private |
| Departure airport: | Puyallup, WA (1S0) |
| 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:
 |
|
Sources:
NTSB SEA03FA025
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 13-Oct-2022 18:40 | ASN Update Bot | Added |
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