ASN Wikibase Occurrence # 290403
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| Date: | Tuesday 19 August 2014 |
| Time: | 07:40 LT |
| Type: |  Air Tractor AT-401 |
| Owner/operator: | Aurora Cooperative |
| Registration: | N4542W |
| MSN: | 401-0767 |
| Year of manufacture: | 1989 |
| Total airframe hrs: | 7969 hours |
| Engine model: | Pratt & Whitney R-1340-S3H1G |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Wray, Colorado -
 United States of America
|
| Phase: | Initial climb |
| Nature: | Agricultural |
| Departure airport: | Wray, CO (2V5) |
| Wray, CO (2V5) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During initial climb, the pilot felt a subtle vibration from the engine and noticed the manifold pressure dropping rapidly. When he attempted to increase manifold pressure by opening the throttle, the engine began to vibrate violently and lost all power. The pilot made a downwind forced landing, and the airplane nosed over. The engine was later partially disassembled and examined. A small amount of aluminum and steel filings were recovered from oil drained from the rocker arm sump. A cylinder compression check revealed that the Nos. 1 and 3 cylinders were non-functioning and that the No. 4 cylinder exhibited weak compression. The intake valve in the No. 3 cylinder was found to have a ridge worn on its face, and the valve seat was worn excessively. The No. 1 cylinder's exhaust valve was stuck open and was binding in the valve guide. The exhaust valve clearances for the cylinders were then checked and found to be less than the Pratt and Whitney overhaul limits of 0.003" to 0.0055", with a maximum wear limit of 0.010". Most likely, the engine lost power due to the stuck exhaust valve.
Probable Cause: A loss of the No. 1 cylinder's compression due to a stuck exhaust valve caused by a lack of sufficient valve clearance, which resulted in a loss of engine power and a forced landing. Contributing to the loss of engine power were the worn intake and exhaust valves in cylinders No. 3 and 4.
Accident investigation:
 |
|
Sources:
NTSB CEN14LA439
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 06-Oct-2022 14:42 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
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