CEN15LA345 · Air Tractor Inc AT 401 UNDESIGNAT
Stones Aerial Applicator Service Air Tractor Inc AT 401 UNDESIGNAT · Accident: aerodynamic stall/spin during takeoff
From Nekoosa, WI to Nekoosa, WI
Event
- NTSB case
- CEN15LA345
- 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 401 UNDESIGNAT
- 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
- N1539U
- Operator
- Stones Aerial Applicator Service
- Onboard fatalities
- Unknown
- Route
- From Nekoosa, WITo Nekoosa, WI
- Aircraft age
- About 23 years (built 1992)
- 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
- Takeoff
- 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
- Aerodynamic stall/spin
- 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 oper/perf/capability
- Environmental issues › Conditions/weather/phenomena
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The commercial pilot loaded the airplane with fuel and a chemical load for the agricultural application flight. During takeoff, the pilot started at the arrival end of the runway, held the brakes, and applied full takeoff power. The pilot reported that the takeoff roll was not noticeably different from any other takeoff he had conducted with a similar load and that the airplane's tail lifted at the usual point on the runway. However, the pilot stated that, as he continued the takeoff roll, the airplane was not "building speed" as it normally did. He attempted to get the airplane airborne but then "he felt that the airplane would not fly," so he dumped some of the chemical load, and the airplane subsequently became airborne. He closed the dump handle because he thought the airplane could clear the corn near the end of the runway; however, the airplane settled back toward the ground. As the pilot attempted to release more of the chemical load, the landing gear and spray booms contacted the corn, and the airplane subsequently impacted terrain, which caused substantial damage.
The airplane manufacturer published a service letter (SL) that contained a procedure allowing the operator to operate the airplane higher than its certificated gross weight for agricultural operations; however, the airplane was calculated to be almost 400 lbs over the maximum gross weight listed in the SL at the time of the attempted takeoff. The SL also stated that, when the airplane is above the certificated gross weight, the operator should use caution when operating the airplane at elevations higher than 1,300 ft; the airport had a calculated density of 2,539 ft. The operation of the airplane in high-density altitude conditions over its maximum gross weight would have degraded the airplane's climb performance and resulted it its inability to remain airborne. The temperature during the accident flight was warmer than earlier in the day. The pilot was not used to flying the airplane in higher temperatures and probably did not account for the high-density altitude at the airport before the flight.
Probable cause
The pilot’s inadequate preflight planning, which resulted in his attempt to take off for the agricultural application flight with the airplane over its maximum gross weight in high-density altitude conditions and led to the airplane’s degraded climb performance and subsequent impact with terrain.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN15LA345
- Event ID
- 20150810X82655
- Case number
- CEN15LA345
- 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: 1e85131f54436dd64d4509bc537370b37d889d05f8c01216a8771f94ba0f4f3b; retrieved 2026-09-16T02:39:09.606Z.