well, it sounds like a concussion.
A family member of Yingling’s said the motor on the plane wasn’t running right and Yingling was riding with Hanna to kind of check it out. Yingling reportedly said he didn’t remember anything other than getting in the airplane. Hanna owns the plane, according to the source, who preferred to remain anonymous, and Yingling thought Hanna was OK after the crash. Yingling is a mechanic and pilot, the source said, and he noted that Hanna is too. The source said that Yingling was told that he got out of the plane on his own and walked to the ambulance.
https://aviation-safety.net/wikibase/348780
