The pilot and pilot-rated passenger were performing aerobatic maneuvers in the experimental amateur-built Acro Sport II near Middletown, Ohio.
A witness reported she heard the airplane approaching and then saw it at a lower altitude than she normally saw aircraft in the area. The airplane then started to pitch nose up into a loop. As it reached the top of the looping maneuver, the sound of the engine stopped, and the plane immediately started descending.
The airplane then entered a spiral/spin, and the witness lost sight of the airplane behind some trees. She then heard the sound of an engine, consistent with the pilot adding engine power, followed immediately by the sound of impact. The airplane was engulfed in flames upon her arrival. Both people aboard the plane died in the crash.
The witness demonstrated what she had seen with a model airplane, and the demonstration was consistent with an attempted loop with a spin out of the top of the maneuver.
Marks at the accident site revealed that the airplane was producing power at the time of impact.
An examination of the engine and flight controls did not reveal any preimpact anomalies that would have precluded operation. A weight and balance calculation showed that the airplane was within its published limits.
The airplane likely experienced an aerodynamic stall at the top of the looping maneuver and then entered a spin from which the flying pilot was not able to recover. The investigation could not determine which occupant was manipulating the controls during the flight.
The NTSB determined the probable cause as the failure of the flying pilot to maintain airplane control after an aerodynamic stall/spin occurred during the aerobatic maneuver following a reported intermittent loss of engine power for reasons that could not be determined during post-accident examinations.
NTSB Identification: CEN14LA507
This September 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.