Accident Overview
On December 7, 2020, at 1528 central standard time, a Vans RV-4 airplane, registration N423WH, sustained substantial damage in an accident near Sadler, Texas. The pilot, the sole occupant, was seriously injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot Account
The pilot reported that he had been practicing low approaches at a private grass airstrip and decided to land. He determined that he would land too far down the runway and initiated a go-around. The engine initially responded, but then power reduced to idle. The pilot “pumped the throttle” two or three times, but the engine did not respond. He subsequently landed on the runway, but the airplane overran the end of the runway and nosed over. The accident resulted in substantial damage to the rudder, elevator, and left wing.
Postaccident Examination
Postaccident engine runs were conducted with the engine attached to the airframe. The engine started on the third attempt and was allowed to idle for about 2.5 minutes, maintaining approximately 1,050 rpm. Several attempts to increase engine rpm resulted in sputtering and momentary loss of power each time the throttle was advanced. During one run, the engine stopped following an attempt to advance the throttle. The engine started again on the fourth attempt, and the sputtering and power loss repeated during each attempt to advance the throttle above idle. The engine was allowed to idle, but attempts to shut it down normally using the throttle and mixture controls were unsuccessful; it shut down only when the ignition was turned off.
The engine was equipped with a Rotech Mk.II 48-4/5 throttle body injector (TBI) unit. Examination revealed that both the throttle and mixture controls were secured properly to the TBI unit. The TBI was removed and examined, and no anomalies that would have precluded normal operations were noted. However, functional testing of the TBI could not be completed due to a lack of access to appropriate test equipment.