Cessna 172N N75775 accident near Longmont, Colorado

Probable cause

The disconnected throttle control that resulted in a loss of engine power due to improper maintenance.

NTSB analysis

The student pilot stated that he was on final approach when he noticed that the engine was not responding to his throttle control changes. The engine speed was about 2,000 rpm when he attempted a go-around; however, the engine power did not increase as he applied full throttle, and the airplane would not climb due to the low power setting. The student noted that the engine subsequently lost power completely and he executed a forced landing to a field. During the landing, the airplane struck a fence and nosed over. The airframe sustained substantial damage to the right wing, vertical stabilizer, and rudder.

A post-accident examination determined that the throttle cable was disconnected from the carburetor. Both the throttle cable and the carburetor control arm moved freely and there was no evidence of damage to either component. The connecting hardware – bolt and nut – were not observed at the time of the examination.

Airplane maintenance records revealed that a 100-hour inspection was completed three weeks before the accident, and the engine carburetor was replaced at that time. The airplane had accumulated about 9.9 hours flight time since that maintenance work. The mechanic stated that an apprentice had replaced the carburetor and the mechanic had gotten busy with other tasks and did not fully inspect the apprentice’s work.

Text from the NTSB. Open the NTSB docket for CEN25LA168 for the full record.