Accident Overview
A helicopter conducting an agricultural spray flight experienced a sudden loss of drive system connectivity with the engine. According to the operator, the pilot heard a loud noise from the transmission and noted an engine overspeed. The helicopter subsequently yawed and descended approximately 10 feet into the underlying cotton field. Upon contact with the uneven terrain, the helicopter rolled onto its side.
Examination Findings
Post-accident examination of the helicopter's drive system revealed that 12 bolts on the planetary gear flange had fractured. Metallurgical analysis determined that the bolts failed as a result of fatigue cracking. The broken bolts allowed the drive system to separate from the engine, leading to the loss of rotor drive and the subsequent uncontrolled descent.
(Note: No information regarding the helicopter type, registration, operator, date, location, occupants, or injuries was provided in the source.)