Piper PA 28-140 N7PM accident near Wickenburg, Arizona

Probable cause

A partial loss of engine power due to a separation of the mixture control cable clamp, which was either not installed or secured correctly during maintenance.

NTSB analysis

The flight instructor and private pilot were approaching the airport for landing. According to the flight instructor, when the pilot applied engine power to arrest the airplane's descent, the engine did not respond. Because the airplane was not within gliding distance of the runway, the pilots performed an emergency landing on desert terrain, sustaining substantial damage to both wings, the fuselage, and empennage.

Examination of the engine revealed that the carburetor mixture control cable clamp, which should have been located between the firewall and the carburetor mixture control arm, was missing. Without the clamp, the mixture control cable could flex, which resulted in no corresponding movement of the arm when the mixture control lever was adjusted in the cockpit. A test of the engine with a makeshift clamp revealed no anomalies.

It is likely that, because the airplane had flown about 1 hour before the accident, the mixture control cable clamp separated during the flight, and the mixture control arm became stuck in a reduced-fuel position, resulting in a partial loss of engine power. The engine had been reinstalled on the airplane about 1 hour tachometer time before the accident. It is likely that the clamp was improperly installed or secured at that time.

Text from the NTSB. Open the NTSB docket for WPR16LA033 for the full record.