Primary finding
Probable cause
The disconnection of the throttle linkage and the resultant power loss. A factor was the lack of suitable terrain for the forced landing.
Investigator assessment
Analysis narrative
As the airplane was descending for landing, the engine lost power. The airplane was substantially damaged during the off-airport forced landing. Post-accident examination disclosed the throttle linkage was disconnected from the throttle shaft arm at the carburetor. The castellated nut and cotter pin were not located. Further inspection of the carburetor arm disclosed a wear pattern of a washer having been placed between the arm and the throttle linkage ball type rod end. A.d. 86-24-07 addresses this problem and, according to the airplane's maintenance records, had been complied; however, a maintenance sign off was not made.
Source record
Factual narrative
On July 31, 1993, at approximately 1100 central daylight time, a Cessna A150M, N8161V, was substantially damaged when it struck power lines and impacted terrain one half mile west of Scholes Field, Gavelston, Texas. The pilot received minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for this personal flight. The pilot obtained a full weather briefing at 0858 from the Conroe, Texas, Flight Service Station (FSS), but elected not to file a flight plan. According to his accident report, he performed an airplane preflight inspection and ascertained that both fuel tanks were filled to capacity. The engine developed "normal power" on takeoff and in cruise but after a 40 minute flight, the engine lost power. The pilot advised Galveston Unicom of the situation and reported his position as approximately two to three miles northwest of the airport. The airplane struck power lines one half mile west of the airport, impacted terrain, and came to rest inverted. Two witnesses to the accident submitted written statements (see exhibits attached). According to the report submitted by the Federal Aviation Administration (FAA) inspector who examined the airplane on August 3, 1993, "The throttle linkage was disconnected from the throttle shaft arm (at) the carburetor...The (castellated nut and cotter pin) could not be located. Inspection of the carburetor arm disclosed a wear pattern of a washer having been placed between the arm and throttle linkage ball type rod end. There was no indication that this wear pattern was recently made, and showed no signs of recent 'working' of the two surfaces." Examination of the airplane's maintenance records indicated compliance with Airworthiness Directive (AD) 86-24-07 which called for the replacement of the existing retention nut with a castellated nut and cotter key; however, a maintenance sign off could not be located in either the aircraft or engine log books. -