CEN11LA566 · Air Tractor Inc AT-400
Air Tractor Inc AT-400 · Accident: powerplant system/component malfunction/failure while maneuvering
From Private, NE (no airport) to Private, NE (no airport)
Narrative check · The NTSB narrative appears to contradict this record's departure or destination. Values are shown as recorded, not corrected; compare with the narrative.
Event
- NTSB case
- CEN11LA566
- 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 Inc AT-400
- Aircraft type
- Air Tractor AT-400
- 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
- N3659N
- Operator
- Wehrman Jim
- Onboard fatalities
- Unknown
- Route Narrative disagrees
- From Private, NE (no airport)To Private, NE (no airport)
- Aircraft age
- Not recorded
- 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
- Maneuvering
- 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
- Powerplant system/component malfunction/failure
- 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
- Not determined › Not determined
- Personnel issues › Action/decision
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
Probable cause
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN11LA566
- Event ID
- 20110812X65034
- Case number
- CEN11LA566
- 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: local date, investigation status. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2011-08-11.
- API snapshot SHA-256: e8b33d1359c4257d9fd6d1a51f8a43cb2ddba7184d8a7a8473268b7e33e85c36; retrieved 2026-09-15T16:35:53.435Z.