NTSB Identification: LAX91LA323.
The docket is stored on NTSB microfiche number 45706.
Accident occurred Saturday, July 20, 1991 in HESPERIA, CA
Probable Cause Approval Date: 07/14/1993
Aircraft: CESSNA C-172P, registration: N54694
Injuries: 2 Uninjured.

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 DECIDED TO DIVERT TO HESPERIA DUE TO WEATHER. DURING THE ENROUTE LET DOWN, THE PILOT DISCOVERED THAT THE THROTTLE CONTROL WAS FROZEN AND COULD NOT BE MOVED WHEN HE ATTEMPTED TO ADD POWER. THE THROTTLE WAS FROZEN AT AN ENGINE POWER LEVEL INSUFFICIENT TO MAINTAIN LEVEL FLIGHT AND THE AIRCRAFT COLLIDED WITH HIGH TENSION POWER LINES WHILE ATTEMPTING TO MANEUVER TO THE RUNWAY. THE AIRCRAFT WAS EXAMINED BY FAA AIRWORTHINESS INSPECTORS WHO CONFIRMED THAT THE THROTTLE WAS FROZEN IN AN INTERMEDIATE SETTING. THE ENGINE WAS OVERHAULED ON JUNE 18, 1991. AT THAT TIME THE CARBURETOR WAS ALSO OVERHAULED, INCLUDING THE INSTALLATION OF NEW THROTTLE BUSHINGS AND A SHAFT. BETWEEN THE ENGINE OVERHAUL AND THE DATE OF THE ACCIDENT, THE AIRCRAFT DISCREPANCY LOG SHEETS MAINTAINED BY SOUTHBAY AVIATION DOCUMENTED SIX PRIOR COMPLAINTS BY RENTER PILOTS THAT THE THROTTLE WAS STICKING ON AN INTERMITTENT BASIS. THE CORRECTIVE ACTION RECORDED ON THE DISCREPANCY SHEETS CONSISTED OF REPLACING THE THROTTLE CABLE.

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

A STUCK ENGINE THROTTLE DUE TO IMPROPER MAINTENANCE PROCEDURES.

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