The Transportation Safety Board says investigators have been unable to determine why a helicopter crashed in Campbell River, B.C., in October last year.
One pilot was killed when the ASAP Avionics Services Robinson R44 Astro hit the ground in dense bush near the city's airport.
The helicopter took off from the airport with two pilots on board, according to the TSB report.
The purpose of the flight was to allow one of the pilots to demonstrate his ability to conduct slow flight manoeuvres for potential future employment.
After conducting flight exercises several kilometres away, the aircraft headed back to the airport to conduct hover exercises.
Call for mandatory cockpit data
On the final approach, control of the helicopter was transferred from one pilot to the other, the report said.
The helicopter began to spin at a slow speed while close to the ground and travelled in a northwesterly direction.
After it gained some altitude, it then struck a tree about a kilometre away from the runway and crashed.
One pilot was killed and the other was seriously injured.
The TSB found both pilots were qualified, the helicopter had been maintained according to regulations, and weather was not a factor.
Investigators could not determine why the pilots lost control and the helicopter collided with terrain, the report said.
The agency is renewing calls for cockpit or data recording devices to be mandatory for commercial and private operators — something that is not currently required.