ASN Wikibase Occurrence # 295402
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| Date: | Friday 8 August 2003 |
| Time: | 11:53 LT |
| Type: |  Cessna 207A |
| Owner/operator: | Hageland Aviation Inc. |
| Registration: | N6439H |
| MSN: | 20700525 |
| Year of manufacture: | 1979 |
| Total airframe hrs: | 14408 hours |
| Engine model: | CONTINENTAL IO-520F |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Bethel, Alaska -
 United States of America
|
| Phase: | Unknown |
| Nature: | Unknown |
| Departure airport: | Tuluksak Airport, AK (TLT) |
| Atmautluak, AK (4A2) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The commercial certificated pilot was conducting a non-scheduled domestic cargo flight carrying mail, and the airplane was in cruise flight about 1,000 feet agl when the engine lost all power. The pilot performed a forced landing in rough, tundra covered terrain. During the landing, the airplane nosed over. The engine was overhauled 1090.9 hours before the accident. During the overhaul process, the engine case was sent to a vendor to be welded and rebored to match original engine case specifications. A postaccident examination of the engine revealed that the number 1 main bearing was deformed in its bearing saddle, and portions of the number 2 main bearing were flattened, fractured and fragmented, and were found in the engine case. The number 2 bearing saddle was extensively distorted and gouged. The engine crankshaft was fractured at the radius of the number 2 main bearing and the number 3 crankshaft cheek, adjacent to the main bearing surface. The fracture surface had discoloration consistent with high heat, and beach marks consistent with fatigue. The area of the number 2 engine bearing saddle, under the bearing insert, had several areas of cracking and exfoliation of the case material along the edges of the oil supply channel. No evidence of engine case fretting was observed during the examination. The engine case was examined by the manufacturer's metallurgical personnel. The report of examination stated that the case contained no signs of lubrication distress on the journals. The manufacturer's metallurgist stated that a determination of a weld repair at the number 2 main bearing support could not be made with a high degree of certainty, although there were several work order stamps on the crankcase indicating that it had been reworked.
Probable Cause: A complete loss of engine power during cruise flight due to the shifting of a main crankshaft bearing that produced a fatigue failure of the crankshaft. A factor contributing to the accident was unsuitable terrain for a forced landing, which resulted in a nose over .
Accident investigation:
 |
|
Sources:
NTSB ANC03LA091
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 13-Oct-2022 08:04 | ASN Update Bot | Added |
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