What happened
The agricultural airplane was engaged in cotton spraying operations when the engine began to vibrate significantly. The pilot responded by pulling the aircraft up to gain altitude, but the vibration intensified to a severe degree. Consequently, the pilot reduced power and executed a forced landing in a muddy field. During the landing sequence, the left wing struck tall grass, causing the airplane to cartwheel.
The investigation
Following the incident, the pilot inspected the aircraft and discovered that the propeller had broken off. Examination of the propeller shaft revealed evidence of a pre-existing crack that contributed to the failure.
Findings
The primary mechanical issue was the propeller detachment due to fatigue or stress on the shaft. The ag airplane sustained substantial damage from the cartwheeling motion in the field. The pilot reported no injuries, and the event occurred during the spraying phase of flight.