Air Tractor INC AT-400 accident near Nelson, Nebraska, August 11, 2011
On August 11, 2011, a Air Tractor INC AT-400, registered N3659N, was substantially damaged in an accident near Nelson, Nebraska (Private airport). It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
Failure of the fuel control unit's spool cap bearing for reasons that could not be determined during extensive postaccident examination, and the pilot’s decision to shut the engine down without sufficient altitude and distance to reach the runway.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 11, 2011
- Place
- Nelson, Nebraska · Private · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Air Tractor INC AT-400 · all AT-400s on the register
- Registration
- N3659N · registry record · serial 400-0294
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
When the pilot was unable to reduce power normally for landing, he used the fuel cut-off lever to shut down the agricultural airplane's turbine engine. However, the pilot stated that he misjudged the airplane’s altitude and distance to the runway when he shut off fuel to the engine, and the airplane landed short of the runway. During postaccident examination, the fuel control unit failed the manufacturer's functional check. The unit was then disassembled, and the spool cap bearing and its associated hardware, including the cap containing the bearing outer race and the post with the bearing inner race, were found damaged. Metallurgical examination of the bearing races found embedded alumina particles. A historical review of the manufacturer's fuel control unit revealed a history of premature spool cap bearing failures in fuel control units installed on other turboprop engines, but not on the accident airplane’s make and model engine. These failures were attributed to high diamond content and other hard particle contamination and could result in fuel flow and power/torque fluctuations. However, no direct link could be established between the accident-related failure and previous failures in other turboprop engines. Although hard alumina particles were found, there was insufficient historical data to support that these particles had attributed to previous bearing failures in this engine. The cause of the spool cap bearing failure could not be determined.
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
- 450340 during 450
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine fuel and control › Fuel control/carburetor › Failure
- cause Not determined › Not determined › (general) › (general) › Unknown/Not determined
- cause Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot
Pilot
- Ratings: single-engine land, none, none, none
- Flight time: 8,000 hours in all; 400 in this make and model; 100 in the last 90 days; 7 in the last 30 days
- Medical certificate: class 2
- Injury: minor injuries
The aircraft
- Airframe total time: 3,900 hours
- Last inspection: type not recorded, December 5, 2010; 197 hours since
- Maximum gross weight: 7,860 lb
- Seats: 1
- Landing gear: fixed
- Engine: Pratt &Whitney Canada PT6-15-AG (turboprop); 0 hours total
The flight
- Departed from: None Private NE at 11:30 pm
- Destination: None Private NE
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 080° at 4 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 64°C, dew point 61°C
- Altimeter: 29.959999 inHg
- Observation at 2:35 pm from HJH, 23 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flig | 1 |
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The docket at the NTSB holds the report as a PDF and the investigation's photographs and documents. This site never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number CEN11LA566.