Amateur-built BUGATTI-DEMONGE 100P accident near Burns Flat, Oklahoma, August 6, 2016

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

The airline transport pilot departed from a 13,500 ft long runway with a right quartering headwind present on a local test flight in an experimental, amateur-built, twin-engine airplane, which was a replica of a 1930s-era air racer. During the initial climb after takeoff , the airplane entered a right bank followed by a left bank. The left bank increased, and the airplane entered a nose-low descent that continued until it impacted terrain in an inverted attitude. The airplane was equipped with several onboard cameras that captured video footage of the accident flight. The video revealed that the left/forward engine began surging after liftoff and reached its maximum operating speed (red line) twice during the short flight. Although the pilot attempted to control the forward engine rpm with the throttle lever, the throttle inputs had no apparent effect. Based on the design of the propeller drive train, it is a possibility that the forward engine clutch was slipping. The airplane's airspeed decreased below its design stall speed and the angle of attack increased; the airplane then rolled left and subsequently impacted the ground. A postaccident examination of the airplane did not reveal any preimpact flight control anomalies. Examination of the engines did not identify a reason for the surging of the forward engine or slipping of the clutch. The sequence of events as described by witness statements and the onboard video was consistent with a loss of airspeed following an engine anomaly and a subsequent aerodynamic stall. Toxicological testing revealed alcohols were present in samples taken during the autopsy. Given the putrefaction of the samples, it is likely that all detected alcohols were the result of postmortem production. Terrain from the accident site to one quarter mile north of the accident site was suitable for an emergency landing there.

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.