Amateur-built RV4 N423WH accident near Sadler, Texas

Probable cause

The partial loss of engine power for reasons that could not be determined based on the available evidence.

NTSB analysis

The pilot was practicing low approaches at a private grass airstrip and elected to land. He determined he would land too far down the runway and initiated a go-around. The engine initially responded, but the engine power then reduced to idle. He “pumped the throttle” two or three times, and the engine did not respond. He subsequently landed on the runway. The airplane overran the end of the runway and nosed over, which resulted in substantial damage to the rudder, elevator, and left wing.

Postaccident engine runs were conducted with the engine attached to the airframe. The engine started and attempts were made to increase engine rpm. The engine would sputter and lose power momentarily each time the throttle was advanced. During one engine run, the engine stopped when the throttle was advanced. During the final engine run, the engine would not shut down normally using the throttle and mixture control, but it shut down when the ignition was turned off.

The engine, airframe, and throttle body unit were examined, and no preimpact anomalies were noted. Functional testing of the throttle body unit could not be completed due to a lack of access to appropriate test equipment. The reason for the partial loss of engine power could not be determined based on the available evidence.

Text from the NTSB. Open the NTSB docket for CEN21LA078 for the full record.