WPR23FA323 · Hensler Howard CASSUTT

The pilot was performing test flights in the accident airplane after he assembled and installed the engine. The pilot (racer) who was scheduled to fly the airplane in an upcoming air race stated that, during the flight before the accident flight, the accident pilot had noticed high engine oil temperature. The racer also stated that the engine oil pressure was low before the accident pilot departed on the accident flight. The racer witnessed that accident, and stated that, after the airplane lifted off about 1/3 down the runway, it entered a climb and then made an abrupt right turn, entered a nose-down attitude, and rapidly descended to the ground. Surveillance video showed the airplane impact the fence and the ground in a slight nose- and left-wing-low attitude. There was no flight track data associated with the accident flight or nonvolatile memory recovered from the airplane. Postaccident examination of the airframe revealed multiple separations in the flight control system; however, there was no evidence of a preimpact mechanical anomaly or malfunction that would have precluded normal operation. The engine examination showed circumferential recessed grooves on multiple crankshaft main journals, longitudinal scoring marks on each of the piston skirts, and severe wear on several of the bearing shell inner surfaces. This engine wear was likely to have caused a malfunction such as a loss of power or engine seizure; however, whether or to what extent an engine performance deficiency contributed to the accident could not be determined. The pilot had reconfigured the airplane from a conventional to a T-tail design. Subsequent flight testing by the pilot’s friend showed that the airplane could enter a “deadband” during turns, in which the elevator would become ineffective. Elevator effectiveness could only be resolved by accelerating. No maintenance or flight records were obtained for the accident airplane, and the pilot’s total and recent experience in the airplane, either before or after the empennage reconfiguration, could not be determined. While the witness’ descriptions of the accident indicate that the airplane may have entered an accelerated stall during the turn, it is also possible that the pilot lost elevator authority while maneuvering at a low altitude and he was unable to recover. Due to the lack of data associated with the accident flight, the circumstances of the loss of control could not be determined. The pilot’s autopsy report identified 75% narrowing of the left anterior descending coronary artery by plaque and no other evidence of significant natural disease; however, there was no forensic evidence that the pilot had a cardiac event in flight, thus it is unlikely that the pilot’s coronary artery disease contributed to the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset