ERA20LA077 · Velocity Elite RG

The pilot of the experimental amateur-built airplane stated that the first part of the takeoff roll was normal, but he noticed a sudden lack of acceleration and that the indicated airspeed was not increasing past 60 knots. He aborted the takeoff, reduced engine power to idle, and applied maximum braking. The airplane departed the end of the runway and came to rest on top of a rock embankment, resulting in substantial damage. Examination of the engine revealed no preimpact anomalies that would have precluded normal operation. Examination of the electrically-controlled variable pitch propeller system revealed that the propeller exhibited signs of inadequate maintenance as the gaps between the three propeller blades were not sealed in accordance with manufacturer guidance. Also, corrosion was present on the propeller slip rings (which would have increased electrical resistance), supercams, and spool. Additional examination revealed that the propeller would not change pitch when the switch lever was operated, though electrical continuity was confirmed from the battery to the carbon brushes that were in contact with the slip rings. Examination of the spool that controlled propeller blade pitch angle indicated that the propeller was not in the fine-pitch, high-rpm takeoff position. The planetary gearbox contained very little lubricant and there were areas that were visibly dry. Examination of the electric motor (gear motor), which powered the propeller pitch mechanism, revealed intermittent operation due to worn carbon brushes. Internal examination of the electric motor revealed a broken end on one of the armature coil windings that surrounded one of the three electromagnetic coils in the electric motor, indicating that the motor needed replacement. Review of propeller system maintenance records revealed no entries regarding preventive maintenance of the system in the approximate 2 years before the accident. The propeller manufacturer’s written guidance regarding operation of the propeller revealed that, before takeoff, the engine should be run at wide open throttle and the propeller blade pitch adjusted to the maximum horsepower rpm. Had the pilot performed this check, it would have been apparent that the propeller was not in the correct takeoff setting. Wind conditions at the time of the accident were consistent with a 9-knot tailwind, which would have increased the distance necessary for takeoff and placed the airplane farther down the runway when the pilot aborted takeoff.

Verbatim NTSB analysis and probable cause from the NTSB dataset