Air show crash still mystery

No one will ever know what caused the fatal crash of a private single-engine vintage plane in front of horrified spectators at an air show in Alberta.

The Transportation Safety Board of Canada says weather was not a factor and a review of the wreckage determined that the engine and flight controls were operating normally on the T-28B Trojan aircraft.

Pilot Bruce Evans of Calgary was performing acrobatic manoeuvres at the Cold Lake Air Show in July 2016 when something went wrong.

The plane hit the ground at high velocity in a near-vertical position.

No air show personnel or spectators were injured.

TSB investigator Fred Burow says the cause of the crash couldn't be determined.

"Being an older aircraft, it doesn't have any monitoring systems on board ... and with the pilot having tragically died, we have no way of knowing what occurred in the cockpit, so we have to go with the evidence that we could find," Burow said Friday.

A TSB report said Evans appeared to have modified the order of his manoeuvres about halfway through his performance, but added that is not unusual for an aerobatic performer.

"The pilot flew from show right to left at about 500 feet above ground level, within the defined airspace for the routine, then entered a roll just before show centre," said the report.

"As the aircraft reached the inverted position, the roll stopped and the nose began to pitch toward the ground ... the aircraft continued toward the ground in an arc until its collision with terrain."

The report said Evans, who was 59, had performed the routine without incident the previous day.

Evans had years of experience. The TSB said he earned a private pilot's licence in 1993, a commercial licence in 1995 and an airline transport licence in 2015. He also had a valid medical certificate.

He had accumulated just over 4,043 flying hours. About 460 of those were on the T-28B Trojan.