Cessna 172 N347SP accident near Bally, Pennsylvania

Probable cause

The pilot's failure to maintain altitude during low-level aerobatic maneuvers. Contributing to the accident were the pilot's improper decision to attempt the low-level aerobatic maneuvers and his impairment due to psychiatric conditions and the medications he was using to treat them.

NTSB analysis

The commercial pilot was conducting a personal cross-country flight. Several witnesses reported observing different sequences of events. One witness reported seeing the airplane fly in a 90° right bank turn for about 10 seconds as it maneuvered underneath power lines and between two utility towers. After passing under the power lines, the airplane leveled and then impacted the ground. Another witness reported that the airplane was at a lower-than-normal altitude and seemed to be flying "erratically" and "aggressively," and that, at one point, it was "flying on its side." Another witness reported seeing the airplane flying with one wing pointing toward the ground. The witness statements are consistent with low-altitude aerobatic maneuvers. Although some bystanders reported that the engine sputtered and lost power and the pilot reported that a loss of engine power occurred, postaccident examination of the airframe and engine, which included a successful engine test run, revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation.

Toxicological testing of the pilot's specimens revealed that he had high levels of a sedating benzodiazepine, alprazolam, within the toxic range. Additionally, he had a low level of a second sedating benzodiazepine, lorazepam. Both these medications are used to treat significant anxiety disorders, which are associated with performance deficits, particularly in high-workload spatial tasks. It is likely that the pilot's underlying psychiatric disorders and the medications he was using to treat them impaired his judgement, executive functioning, and psychomotor skills and contributed to the accident.

Text from the NTSB. Open the NTSB docket for ERA15LA366 for the full record.