Air Tractor AT 401 N4532F

Summary

On 24 August 2017 at about 15:00 local time, a Air Tractor AT 401 registered N4532F, operated by Fitch's Flying Service, was involved in an accident near Pearsall, Texas, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

24 August 2017 at 15:00

Classification

Accident

Location

Pearsall, Texas, United States

Coordinates

28.8764, -99.0053

Aircraft

Air Tractor AT 401

Registration

N4532F

Category

Airplane

Year built

1990

Engines

1

Operator

Fitch's Flying Service

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Pearsall → Pearsall

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN17LA330

Nobody was injured.

The fatigue crack of an engine cylinder, which resulted in a partial loss of engine power.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.