CHI01IA246 · Air Tractor AT-401
Air Tractor AT-401 · Incident: propeller failure/malfunction while maneuvering
From Roseland, NE to an unrecorded destination
Event
- NTSB case
- CHI01IA246
- 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
- Incident
- 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
- N4553K
- Operator
- Willmes, Steven J · private individual
- Onboard fatalities
- Unknown
- Route
- From Roseland, NETo not recorded
- 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 · aerial application
- First occurrenceThe 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
- Propeller failure/malfunction
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Propeller system/accessories, blade › Fatigue
- Propeller system/accessories, blade › Separation
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The airplane sustained minor damage when it nosed over during an emergency landing following an in-flight loss of a propeller blade tip. The pilot was uninjured. The pilot stated, "While on a actual spray run the aircraft began to shake and vibrate violently. At that time I shut the power down, climbed about 100 ft to look for a place to land. The area was rolling with pasture land and a corn field in front of me, no roads to land on in the area. ... After a rolling out for a short while in corn the landing gear became stuck in corn and soft sandy soil." A portion of the remaining blade, including the separation, was shipped to the NTSB's Materials Laboratory Division. The laboratory's report stated that "a large portion of the fracture surface was on a 90-degree flat plane with multiple ratchet marks and crack arrest marks on this portion of the fracture surface. These features are typical of a fatigue crack. The fatigue crack originated from multiple origins at the bottom of a gouge on the flat face of the blade about 2.25 inches from the blade's leading edge. The fatigue crack extended through about two-thirds of the blade's cross-section. The remainder of the fracture surface (about one-third of the blade's cross section) was on a 45-degree slanted plane and was typical of an overstress region stemming from the fatigue crack." A section was saw cut from the fracture containing the fatigue origin. The paint was removed from the areas near the crack origin and the surface was re-examined with a scanning electron microscope (SEM). The gouge was measured using the SEM. The report further stated, "The length of the gouge was 0.6 inch (1.5 millimeters), and the depth of the gouge was 0.0055 inch (0.14 millimeters). ... Optical examination of the flat face of the blade near the gouge did not show any evidence of blending or rework in this area." The propeller's last overhaul was completed on January 13, 1998. The propeller accumulated 240 hours of flight since that overhaul.
Probable cause
The propeller blade fatigue leading to its tip separating during an aerial application. Factors were no suitable terrain for an emergency landing, high vegetation, and soft terrain encountered during the emergency landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI01IA246
- Event ID
- 20010803X01596
- Case number
- CHI01IA246
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
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: 6d0641f820d38e20771ddb1632c72c44bec652ad340997660b5344aa5a35a6bd; retrieved 2026-09-22T11:42:53.281Z.