An ill-fated powerline inspection with a helicopter that killed four people in Cranbrook, B.C. was technically against federal regulations, according to the Transportation Safety Board of Canada.

In the TSB's aviation investigation report into the May 13, 2008 crash, investigator Damien Lawson said the low altitude flight to inspect power lines in the city, by BC Hydro and Bighorn Helicopters, would not have been authorized under Transportation Canada regulations had the operator filed for approval.

The height and speed of the single engine helicopter wouldn't have been enough for the pilot to take action in the event of an engine failure.

Yet regulations are so vague most operators have no idea those operations are only permitted in multi-engine helicopters.

"These operations have been going on for 30 years," Lawson told media in Vancouver. "It's proof positive there is a need for consolidation of the regulations to make them perfectly clear."

Pilot Edward Heeb was flying about 120 feet above the ground - with BC Hydro employees Dirk Rozenboom and Robert Lehmann on board - when the engine on his Bell 206B Jet Ranger suddenly lost power.

The chopper missed a residential building but crashed into the street.

All three men were killed along with pedestrian Isaiah Otieno, the son of a Kenyan government minister studying in Canada.

The engine failure was likely caused by a problem with the fuel management system, but the TSB couldn't pinpoint an exact cause.

Matt Kieltyka reports for Vancouver 24 hours.