Aero Vodochody L 39 N139AJ accident near Norfolk, Virginia

Probable cause

An uncommanded flap retraction for reasons that could not be determined, as a postaccident examination of the flap system did not reveal evidence of any preaccident anomalies.

NTSB analysis

According to the private pilot of the jet trainer airplane, the airplane was on final approach for landing about 100 ft above ground level and 60 ft from the runway threshold, when there was an "uncommanded" retraction of the flaps. He adjusted the airplane's pitch and advanced the throttle in order to compensate for the flap retraction, increasing the airspeed from 90 knots to 130 knots. The airplane touched down on the runway and the pilot applied the brake pedals, followed by the emergency brake. As the airplane began to veer toward the side of the runway, the pilot released the emergency brake and continued to apply brakes using the brake pedals. The airplane continued off the departure end of the runway, struck trees, and came to rest about 1,050 ft from the end of the 5,350ft-long runway. While impact-related damage prevented a functional test of the airplane's normal and emergency flap extension systems, an examination of the flap system components revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. It is likely that the airplane's increased speed at the time of touchdown resulted in the runway excursion.

Text from the NTSB. Open the NTSB docket for ERA16LA322 for the full record.