Pilot Debrief

YAMOKOSKI WILLIAM GLASTAR near Chicago, IL — 2012-07-22

Final reportCEN12LA470
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Date
2012-07-22
Location
Chicago, IL, USA
Aircraft
YAMOKOSKI WILLIAM GLASTAR
Registration
N4970Y
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Cruise

Probable cause

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

NTSB narrative

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.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Regular inspection of the gearbox could have identified the wear before failure.

NTSB coding

Evidence available

  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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