Mooney M20 N3539X accident near Boulder, Colorado

Probable cause

The loss of airplane control for reasons that could not be determined by the postaccident examination, which was limited due to impact damage and postcrash fire.

NTSB analysis

Witnesses reported that, just after takeoff, the airplane rolled left to an inverted position and impacted terrain. One witness reported hearing abnormal engine sounds just before the impact, but other witnesses did not recall hearing anything abnormal. The pilot was departing to the east with a direct crosswind, and the sun was most likely in the pilot's eyes, but it could not be determined what effect this would have on the pilot's control of the airplane. The throttle, mixture, and propeller controls were found in the full power, rich mixture, and high rpm positions, respectively. However, the propeller blade signatures were consistent with the engine operating at a low power setting. A trace amount of water was found in the fuel divider; however, this could have come from post-accident firefighting measures. Due to impact and postcrash fire damage, fuel from the fuel tanks and lines was not available for examination, and the damage also precluded a functional test of the engine and related systems. The investigation could not determine if the engine lost power before the airplane rolled inverted.

Text from the NTSB. Open the NTSB docket for CEN15FA030 for the full record.