NTSB Identification: CHI01LA135.
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Accident occurred Saturday, May 12, 2001 in Warsaw, IL
Probable Cause Approval Date: 08/21/2001
Aircraft: Air Tractor AT-401, registration: N1008Q
Injuries: 1 Uninjured.

NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The airplane sustained substantial damage when the airplane nosed over during a forced landing following an in-flight loss of engine power. The pilot reported no injuries. The pilot stated, "At approximately 10:30 AM spraying operation was nearing completion when in a pull out of the field being sprayed the engine made a bang, started running very rough and backfiring. Within a couple seconds the engine had lost all power and died. The pilot landed in a field that happened to be very soft and sandy. The aircraft rolled approximately 100 ft on its wheels before nosing over on its back. After further investigation it was determined a rocker shaft housing had broken on the #4 cylinder. As a result the exhaust valve was not opening. As the intake valve opened, it created backfiring into the induction system causing the engine to fail."

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the rocker assembly failure during low level maneuvering. Factors were the soft and sandy terrain and the unsuitable terrain the pilot encountered during the forced landing.

Full narrative available

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