Arion Aircraft Llc LIGHTNING LS-1 N341AL accident near Van Nuys, California

Probable cause

The pilot's loss of airplane control due to an exceedance of the airplane's critical angle of attack, which resulted in an accelerated stall and subsequent impact with a building. Contributing to the accident was the pilot's unreported physiological impairment from traumatic brain injury, which impaired his ability to safety operate the airplane.

NTSB analysis

The pilot of the light sport airplane contacted the tower controller at his destination airport, where he planned to complete several touch-and-go maneuvers. The airplane touched down hard on the runway, and during the subsequent takeoff, the pilot reported to the controller that he heard a "banging" sound. The controller observed the left main landing gear "dangling" from the airplane. The pilot advised the controller that he planned to return to the airport for landing; however, as the airplane reached the airport boundary, it began a left turn that gradually progressed into a 70° bank angle. The airplane's bank angle increased further before the airplane entered a nose-down attitude and impacted a building, consistent with an aerodynamic stall.

A normal standard-rate turn would have allowed the pilot to rejoin the downwind leg of the traffic pattern and provided additional time to configure the airplane for a normal landing. However, the aggressive bank angle increased the airplane's stall speed and likely contributed to the pilot's exceedance of the airplane's critical angle of attack.

Examinations of the airframe and engine did not reveal any mechanical malfunctions or anomalies that would have precluded normal operation, although the engine ran about 200 rpm below its maximum power output during the engine run. Although the source of this power loss could not be confirmed, it may have been the result of a reduction in fuel flow from a torn carburetor diaphragm and bent float. Data obtained from the airplane's engine monitor revealed that the engine achieved rated power throughout the accident flight, which suggested that the damage observed to the carburetor was the result of impact. A witness reported hearing the engine sputtering seconds before the airplane impacted the ground, and recorded engine data showed a corresponding decrease to idle power. It could not be determined why the pilot may have retarded the throttle to idle power.

The pilot allowed his Federal Aviation Administration (FAA) medical certificate to expire about 2 years before the accident, a few months after he sustained traumatic injuries, including a traumatic brain injury, in a car accident. Although his personal medical records did not show any permanent neurocognitive or physiological defects, formal testing was not documented. However, acquaintances and flight instructors who flew with the pilot stated that his ability to control the airplane and his decision-making capacity were affected by his injuries. The pilot continued to fly and was involved in three incidents that resulted in damage to the accident airplane; evidence suggested the pilot's physiological condition remained unchanged until the day of the accident. Thus, it is likely that the pilot's injuries impaired his ability to safely operate the airplane and directly contributed to the accident. Furthermore, the pilot ignored recommendations from other pilots to stop flying and continued to operate the airplane with a known physiological impairment.

Text from the NTSB. Open the NTSB docket for WPR16FA157 for the full record.