NTSB Identification: CEN12LA470
14 CFR Part 91: General Aviation
Accident occurred Sunday, July 22, 2012 in Chicago, IL
Probable Cause Approval Date: 12/19/2012
Aircraft: YAMOKOSKI WILLIAM GLASTAR, registration: N4970Y
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot was on a cross-country flight in an experimental airplane when the engine began to “race.” The pilot tried to reduce power by adjusting the throttle, but the engine and propeller were unresponsive. He then made a forced landing to a soft field, and the airplane nosed over. Examination of the automotive engine revealed that the spline-shaft and adapter gears in the reduction gearbox were worn, which resulted in the gearbox's failure. According to the pilot, the gearbox was not a regularly inspected item for this particular engine/gearbox combination. At the time it failed, the gearbox had accrued 247 total hours since new.

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

Failure of the automotive engine's reduction gearbox while in cruise flight.

Full narrative available

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