Cessna 172RG N9627B accident near Moorpark, California

Probable cause

A partial loss of engine power due to the disconnection of the throttle control cable from the throttle arm due to the operator's improper maintenance. Contributing to the accident was unsuitable terrain for a forced landing.

NTSB analysis

While performing air work during the instructional flight, the student attempted to increase engine power above idle, but upon pushing the throttle control knob forward, the engine's power did not increase. The certified flight instructor (CFI) verified that there was no change in engine power with movement of the throttle control, and he believed that the control had likely become disconnected from the carburetor. The CFI performed a forced landing on the nearby rough terrain. During landing, the airplane impacted a berm and nosed over. An examination of the airplane revealed the throttle control cable was in fact disconnected from its respective carburetor attachment fitting and undamaged. Also, the threaded portion of the cable's attachment end was found without damage. The jam nuts, which normally secure the throttle cable to the carburetor attachment fitting, were found tight against each other, but backed off from their designated location, and were not positioned close enough to the rod end to secure the cable to the carburetor throttle arm. The operator's mechanics were responsible for, and had performed, recent maintenance and inspections of the flight school's airplane. The accident airplane's last 100-hour inspection had been performed on July 3, 2008, 6 days prior to the accident. The security and condition of the engine control connections to the carburetor are part of this inspection.

Text from the NTSB. Open the NTSB docket for LAX08LA221 for the full record.