NTSB Identification: NYC92FA055.
The docket is stored on NTSB microfiche number 47687.
Accident occurred Thursday, February 06, 1992 in RICHMOND HTS., OH
Probable Cause Approval Date: 06/21/1993
Aircraft: AERO COMMANDER 500S, registration: N725AC
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

THE PILOT HAD THE WASTE GATES ON THE TURBOCHARGES ADJUSTED AND WANTED TO TEST FLY THE AIRPLANE AFTER THE WORK WAS COMPLETED. THE AIRPLANE DEPARTED AND HAD REACHED AN ALTITUDE OF ABOUT 1000 FEET WHEN WITNESSES HEARD AN ENGINE SPUTTER. THE AIRPLANE WAS SEEN MAKING A LEFT TURN AND ENTER A NOSE LOW, LEFT SPIN BEFORE IMPACTING THE TERRAIN. A TEAR DOWN OF THE LEFT ENGINE REVEALED THAT THE EXHAUST VALVES IN CYLINDERS #3 AND #5 WERE BURNT THROUGH AT THE VALVE HEAD. THE #5 EXHAUST VALVE HAD A DEEP PREEXISTING DEEP MARK ON THE VALVE STEM. THE FAILURES OF BOTH VALVES WERE SUFFICENT ENOUGH TO CAUSE A POWER FAILURE IN THE LEFT ENGINE.

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

THE PILOT'S IMPROPER EMERGENCY PROCEDURES AND FAILURE TO MAINTAIN CONTROL OF THE AIRPLANE, WHICH RESULTED IN AN INADVERTENT SPIN AT TOO LOW AN ALTITUDE TO ALLOW RECOVERY. FACTORS IN THIS ACCIDENT WERE; A POWER LOSS IN THE LEFT ENGINE AS RESULT OF THE EXHAUST VALVE FAILURES IN CYLINDERS #3 AND #5.

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