Cobalt Aircraft Industries Inc Co50 VALKYRIE N523CA accident near Atwater, California

Probable cause

A loss of aileron effectiveness due to the airplane's design configuration, which resulted in the pilot's inability to control the roll axis and led to a hard landing.

NTSB analysis

The pilot reported that the purpose of the flight was to evaluate handling qualities of the experimental airplane at various configurations specified in the test card. After rotation, with the airplane about 50 ft above ground level (agl), the pilot experienced a loss of aileron control. As the airspeed increased, he began to attain some controllability and climbed to about 1,400 ft agl. After about 20 minutes of manipulating the flight controls and practicing climbing and descending using the trim, he stabilized the airplane around 90 kts. He thought that he would be able to land the airplane at an increased airspeed using steady thrust control and the rudder for directional control. During landing, with the airplane about 10 ft above the runway surface, the airplane experienced a loss of lift and landed hard, which resulted in damage to the right wing spar. For the test flight, the airplane manufacturer had changed the winglet position, which contributed to a loss of aileron effectiveness.

Text from the NTSB. Open the NTSB docket for WPR17LA201 for the full record.