Amateur-built Mark IV accident near Rushville, Nebraska, August 2, 2021

The NTSB's narrative final · quoted from the NTSB record

The pilot reported that after takeoff in the experimental airplane, he noticed that all four cylinder head temperatures (CHT) were higher than they should have been as indicated on the engine monitoring device. He noticed that the CHT never stabilized and never decreased in temperature after the takeoff. The pilot attempted to reduce the high CHT with the throttle and mixture and the CHT kept rising. The pilot decided to return to the departure airport. During the flight back to the airport, the CHT still kept rising, and the engine ceased producing power. The pilot maneuvered the airplane for a forced landing to an open grass field surrounded by rolling prairie and trees. During the forced landing, the nose wheel and the main landing gear collapsed, and the airplane came to rest on the fuselage. Postaccident examination of the landing brake actuator revealed that it likely failed due to compressive overload on the actuator while positioned in the fully extended position. The actuator extension tube was found positioned about midway between the extended and retracted positions The flanges on the nut were fractured in overstress consistent with a compression overload. The brush that is normally attached to the nut above the flange was found in the fully retracted position, indicating that after the nut flanges fractured, the extension tube likely moved to the fully retracted position, pushing the brush along with it. Based on the examination of the landing brake actuator, the landing brake was likely fully extended at the time of the accident. The extended landing brake would have blocked airflow to the engine, causing the engine to overheat and cease producing power. If a cockpit indication system for the landing brake had been installed, the pilot likely could have known the status of the landing brake during the flight and thus retract it. It is likely that the pilot either forgot to retract the landing brake after the previous landing or the pilot may have inadvertently activated it before the loss of engine power. Based on the available evidence it could not be determined exactly when the landing brake was deployed.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.