Air Tractor INC AT 401 accident near Pearsall, Texas, August 24, 2017
On August 24, 2017 at about 3:00 pm local time, a 1990 Air Tractor INC AT 401, registered N4532F, was substantially damaged in an accident during maneuvering (low-alt flying) near Pearsall, Texas. 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).
The NTSB's probable cause their words, unchanged
The fatigue crack of an engine cylinder, which resulted in a partial loss of engine power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 24, 2017 · about 3:00 pm local time
- Place
- Pearsall, Texas · 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 401 UNDESIGNAT, built 1990 · all AT 401s on the register
- Registration
- N4532F · registry record · serial 401-0769
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot was conducting a local, agricultural application flight when the engine experienced a partial loss of power during a spray pass. The pilot's corrective actions did not restore normal engine operation, and he conducted a forced landing to a nearby field. The airplane descended into tall vegetation and landed in soft, sandy soil and then decelerated rapidly and nosed over. Postaccident engine examination revealed a circumferential fracture of the No. 9 cylinder. Further examination determined that the cylinder fractured from a fatigue crack that had initiated at multiple locations at a valley between two cooling fins on the outside surface. The fatigue crack progressed inward and circumferentially around the cylinder before finally cracking in overstress. No discrepancies, such as corrosion pits, wear marks, or machining marks, were found at the crack initiation sites. The cylinder met the airplane manufacturer's material and hardness specifications. The fracture would have allowed combustion gasses to escape during engine operation and led to a corresponding loss of cylinder compression, which would have led to erratic engine operation and a partial loss of power. According to engine logbook documentation, no cylinder cracks were found during an airworthiness directive inspection completed about 64 flight hours before the accident.
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 (partial) during maneuvering (low-alt flying) defining event
- Attempted remediation/recovery during maneuvering (low-alt flying)
- Off-field or emergency landing during landing
- Nose over/nose down during landing
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng cyl section › Fatigue/wear/corrosion
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land
- Flight time: 609 hours in all; 290 in this make and model; 220 in the last 90 days; 108 in the last 30 days; 545 as pilot in command; 0 on instruments
- Last flight review: March 10, 2017
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: ctr
- Injury: no injuries
The aircraft
- Airframe total time: 6,228.1 hours
- Last inspection: annual inspection, March 1, 2017; 264 hours since
- Maximum gross weight: 7,860 lb
- Seats: 1
- Landing gear: fixed
- Engine: Pratt & Whitney R-1340AN-1 (piston); 8,899 hours total
The flight
- Departed from: T30 Pearsall TX at 2:00 pm
- Destination: T30 Pearsall TX
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 120° at 5 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 12,000 ft
- Temperature: 82°F (28°C), dew point 72°F (22°C)
- Altimeter: 29.92 inHg
- Observation at 2:53 pm from COT, 20 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
5 documents, released by the NTSB on January 3, 2020. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 2 | Materials Laboratory Factual Report | PDF, 18 pages | View Download |
| 3 | Engine Logbook (Excerpts) | PDF, 9 pages | View Download |
| 4 | Airworthiness Directive No. 99-11-02 | PDF, 6 pages | View Download |
| 5 | Service Bulletin No. 1787 | PDF, 4 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
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.