Amateur-built EAGLE N106BD accident near Rexburg, Idaho

Probable cause

A loss of engine oil pressure, which led to the subsequent uncommanded loss of thrust and decrease in the propeller rpm during a low-level aerobatic maneuver.

NTSB analysis

The airline transport pilot, who was also the owner/ builder of the experimental aerobatic airplane, was practicing aerobatic maneuvers for an upcoming airshow. An amateur video captured a portion of the flight and accident sequence. The video shows the airplane conducting several continuous right rolls at an approximate constant altitude and pitch attitude. During the accident sequence, the airplane continued to roll, but it began to descend while maintaining a relatively level pitch attitude. When the airplane was about 100 ft above the ground, it stopped rolling and then continued to descend in a significant right-wing-down attitude. Examinations of the wreckage did not reveal any preimpact mechanical deficiencies or failures that would have precluded continued flight; however, no detailed examinations of the wreckage or any components were conducted.

The pilot reported that, while conducting the maneuver just before the accident, he "heard and felt" an uncommanded decrease in rpm, which he believed was caused by the decrease in engine oil pressure that occurs during aerobatics, and a subsequent uncommanded change in propeller blade pitch. Based on the available evidence, it is likely that, during the aerobatic maneuver, the airplane lost oil pressure, which resulted in a decrease in thrust and change in propeller blade pitch, and that the airplane had insufficient power and altitude for the pilot to recover from the maneuver. The pilot reported that he had installed an accumulator to prevent the decrease in engine oil pressure; it could not be determined why the accumulator did not function during the accident flight.

Text from the NTSB. Open the NTSB docket for WPR12LA265 for the full record.