A loss of engine power caused a helicopter to crash into the streets of Cranbrook, B.C., last year, killing four men, the federal Transportation Safety Board said Thursday.

Among the victims was Isaiah Otieno, the son of a Kenyan cabinet minister. The 6'9" student was walking down the street listening to his iPod when the helicopter crashed down on top of him, killing him instantly.

Helicopter pilot Edward Heeb, 57, and BC Hydro employees Dirk Rozenboom, 45, and Robert Lehmann, 37, were also killed.

Sudden loss of power

The board's final report on the crash said the single-engine Bell Jet Ranger, chartered from Bighorn Helicopters Ltd. by BC Hydro to visually monitor transmission lines, was functioning properly until an event caused it to suddenly lose power at 120 feet over the residential neighbourhood.

"This power loss caused a rapid decrease of rotor RPM's and the helicopter descended quickly," the TSB's Bill Yearwood said.

"Before it was too low the pilot was able to maneuver to avoid a house but soon lost control."

What caused the engine to power down remains a mystery, Yearwood said.

Chief investigator Damien Lawson said the last 85 feet of the flight was "essentially a free fall."

"The three men on board could not have survived the impact injuries."

The single engine helicopter was too badly damaged in the post-crash fire to determine why it encountered a power loss, however, a resulting lack of control of the craft is cited as a causal factor.

Lawson said Transport Canada rules should have prevented the chopper from flying at such a low-level over the residential area.

New protocol

BC Hydro, who lost two employees in the accident, changed its helicopter policy after the crash, directing that only twin-engine helicopters be used for most of its operations.

"Initially we stopped flying," spokesperson Susan Danard said. "We just didn't want to put [our employees] in the air."

The power company, who has since stopped low-level flights over developed areas, often charters helicopter flights to monitor transmission lines in remote areas -- something that may change with advancements in new technology.

In Manitoba, power companies are using high-quality video in unmanned flights. Danard says BC Hydro will examine this as an option but rocky terrain may decrease its effectiveness British Columbia.