CEN14LA439 · Air Tractor AT-401
Air Tractor AT-401 · Accident: loss of engine power (total) during initial climb
From 2V5 · Wray, CO to 2V5 · Wray, CO
Event
- NTSB case
- CEN14LA439
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Air Tractor AT-401
- Aircraft type
- Air Tractor AT-401
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N4542W
- Operator
- Aurora Cooperative
- Onboard fatalities
- Unknown
- Route
- From 2V5 · Wray, COTo 2V5 · Wray, CO
- Aircraft age
- About 25 years (built 1989)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 137: Agricultural
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Initial climb
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of engine power (total)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft power plant
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN14LA439
- Event ID
- 20140819X34156
- Case number
- CEN14LA439
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 5ddf0009a1892d17c87466ebd57a69e8ae34208a2a09bfe8de4ca8c77e9a0ee6; retrieved 2026-09-16T01:39:20.723Z.