NTSB Identification: SEA90FA030.
The docket is stored on NTSB microfiche number 42194.
Accident occurred Friday, December 15, 1989 in AUSTIN, NV
Probable Cause Approval Date: 07/22/1992
Aircraft: CRAWFORD-GORDON THORP T-18, registration: N111GC
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.

DURING A CROSS COUNTRY FLIGHT, THE PILOT MADE AN UNSCHEDULED LANDING AT AN AIRPORT TO CHECK ON A NOISE. SHORTLY AFTER LANDING, THE FLIGHT CONTINUED. RADAR RETURNS INDICATE THAT THE AIRPLANE DEPARTED THE AIRPORT ON A NORTHERLY HEADING AND CLIMBED TO 11,900 FEET THEN BEGAN TO DESCEND, TURNING WESTERLY AWAY FROM RISING TERRAIN. THE AIRPLANE COLLIDED WITH HILLY TERRAIN APRX 14 MILES FROM THE AIRPORT. ONE PROPELLER BLADE HAD SEPARATED AND WAS NOT LOCATED. A METALLURGICAL TEST REVEALED THAT THE BREAK WAS DUE TO HIGH CYCLE BENDING STRESSES INDUCED BY RESONANT VIBRATION. RESEARCH OF THE AIRPLANE'S HISTORY REVEALED THAT ANOTHER ENGINE (DIFFERENT FROM WHICH THE AIRCRAFT WAS ORIGINALLY CERTIFICATED) HAD BEEN INSTALLED ON THE AIRPLANE AND THAT THE PROPELLER (ORIGINAL FROM THE FIRST ENGINE) AT SOME TIME HAD BEEN CUT AND REPITCHED.

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

AN IMPROPER MAJOR ALTERATION PERFORMED BY THE PILOT. AS A RESULT OF THIS MODIFICATION, THE PROPELLER FAILED IN FLIGHT.

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