NTSB Identification: DEN89LA082.
The docket is stored on NTSB microfiche number 38756.
Accident occurred Monday, March 06, 1989 in CUSTER, SD
Probable Cause Approval Date: 05/22/1990
Aircraft: STINSON 108-2, registration: N150C
Injuries: 1 Serious.

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 PRIVATE PLT WAS PERFORMING A FLIGHT FOLLOWING HIS INSTALLATION OF TWO MAGNETOS. A WITNESS AND THE PLT REPORTED THAT ON CLIMB OUT THE ENGINE QUIT. THE PLT SAID HE HEARD SOMETHING BREAK IN THE ENGINE. THE PLT ATTEMPTED TO LAND ON A GRAVEL DRIVEWAY SOUTH OF THE RUNWAY. AT IMPACT, THE MAIN LANDING GEAR COLLAPSED. THE PLANE CAME TO REST AFTER SLIDING 150 FT. A POST ACCIDENT INSPECTION REVEALED THAT BOTH MAGNETOS HAD BEEN INSTALLED WITHOUT COTTER PINS ON THE DRIVE GEAR RETAINING NUTS. THIS RESULTED IN THE NUTS BACKING OFF, DISCONNECTING THE MAGNETOS, AND ONE OF THE GEARS FALLING INTO THE ENGINE, RESULTING IN THE REPORTED STOPPAGE.

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

THE IMPROPER MAINTENANCE BY THE PILOT IN COMMAND/OWNER IN THAT THE MAGNETO DRIVE GEAR RETAINING NUTS WERE NOT SAFETIED WHICH RESULTED IN THEM BACKING OFF, DISCONNECTING THE MAGNETOES AND ONE OF THE GEARS FALLING INTO THE ENGINE.

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