Air Tractor AT-401 accident near Wray, Colorado, August 19, 2014
On August 19, 2014 at about 1:40 pm local time, a 1989 Air Tractor AT-401, registered N4542W, was substantially damaged in an accident during initial climb near Wray, Colorado. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 19, 2014 · about 1:40 pm local time
- Place
- Wray, Colorado · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Air Tractor AT-401, built 1989
- Registration
- N4542W · no longer on the register · serial 401-0767
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (total) during initial climb defining event
- Off-field or emergency landing during emergency descent
- Nose over/nose down during landing (landing roll)
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip engine power section › Malfunction
- factor Aircraft › Aircraft power plant › Engine (reciprocating) › Recip engine power section › Damaged/degraded
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land
- Flight time: 750 hours in all; 400 in this make and model; 250 in the last 90 days; 170 in the last 30 days; 625 as pilot in command
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: sngl
- Injury: minor injuries
The aircraft
- Airframe total time: 7,969 hours
- Last inspection: 100-hour inspection, August 8, 2014; 30 hours since
- Maximum gross weight: 7,880 lb
- Seats: 1
- Landing gear: fixed
- Engine: Pratt & Whitney R-1340-S3H1G (piston); 6,955 hours total
The flight
- Departed from: 2V5 Wray CO at 1:00 pm
- Destination: 2V5 Wray CO
- Flight plan: none
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 61°F (16°C), dew point 55°F (13°C)
- Altimeter: 29.95 inHg
- Observation at 1:15 pm from 2V5
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.