Amateur-built THATCHER CX4 N347CX accident near Baker, Florida

Probable cause

The improper engine idle setting, which resulted in a total loss of engine power when the pilot reduced the throttle to idle to initiate a descent.

NTSB analysis

The pilot reported that he had just completed an overhaul of the automotive conversion engine that was installed in the experimental amateur-built airplane. Before the day of the accident, the pilot conducted several engine ground runs. During most of the ground runs, the engine would not run smoothly when at the idle throttle setting; however, on the last ground run, the engine ran smoothly at idle. On the day of the accident, the pilot planned to break in the engine during a flight over the airport. After takeoff, while the airplane was climbing to traffic pattern altitude, the pilot felt something dripping onto his leg and decided to perform a precautionary landing. When he pulled the throttle back to idle to initiate a descent, the engine stopped producing power. Unable to restore power to the engine, he elected to execute a forced landing, during which the left wing impacted a tree. Although the pilot did not run the engine after the accident, his postaccident examination of the engine revealed no anomaly that would have precluded normal operation.

The atmospheric conditions at the time of the accident were conducive to carburetor icing at glide power; however, the airplane’s engine was at a climb power setting before the pilot reduced the throttle to idle to initiate the descent. Therefore, it is not likely that the loss of engine power was the result of carburetor ice. Since the pilot had just completed an overhaul of the engine and the engine would not run smoothly at idle during several engine ground runs, it is likely that the engine idle setting was misadjusted, which resulted in the engine losing power when the throttle was reduced to idle.

Text from the NTSB. Open the NTSB docket for ERA22LA323 for the full record.