Canadian Safety Board Finds Compressor Failure Caused Helicopter Crash
During the marker ball installation on lines above the North Saskatchewan River, the single-engine helicopter was hovering 325 feet above the ground when it experienced an engine failure and hit the ground. Both the pilot and the platform worker were killed.
Engine failure at low altitude led to the fatal October 2015 crash of an Oceanview Helicopters Ltd. helicopter near Paynton, Saskatchewan, as its crew were installing marker balls on SaskPower hydro lines, the Transportation Safety Board of Canada (TSB) concluded Feb. 2.
TSB's investigation report A15C0146 outlines findings in the case. The Hughes 369D helicopter operated by Oceanview Helicopters was conducting aerial work on Oct. 22, 2015, with a pilot and an external platform worker on board. During the marker ball installation, the single-engine helicopter was hovering 325 feet above the ground when it experienced an engine failure and hit the ground. Both the pilot and the platform worker were killed, and the helicopter was destroyed by fire after the impact. The accident occurred on an island in the North Saskatchewan River.
Investigators determined it is likely that the failure of an internal engine component resulted in the loss of engine power while the helicopter was in a hover, and there was insufficient altitude to conduct an autorotation landing. The report also found the risk of injury or death increases if a single-engine helicopter is operated at altitudes and airspeeds from which a successful autorotation landing may be difficult to perform.
Oceanview Helicopters Ltd., which was contracted by Forbes Bros. Ltd. to carry out the aerial work and install marker balls on power lines strung over the North Saskatchewan River, voluntarily suspended external platform worker operations after the accident and has not resumed them, the report says. It says Forbes Bros. Ltd. reported it has reviewed its helicopter operation standards, adopted the Helicopter Association of Canada Pre-Flight Risk Assessment best practice as a requirement for all Forbes Bros. Ltd. helicopter vendors, and engaged third-party aviation safety experts to assist in evaluating its helicopter practices.
The board's findings are:
1. It is likely a stage 2 compressor blade was subject to fatigue and eventual overload failure, resulting in a loss of engine power.
2. The engine failure occurred while the helicopter was in a hover. There was insufficient altitude to conduct a successful autorotation, and the helicopter collided with the terrain.
3. If a single-engine helicopter is operated within the confines of the cross-hatched region of the Height Velocity Diagram, the likelihood of a successful autorotation after an engine failure is significantly reduced, increasing the risk of injury or death.
4. If operators do not follow manufacturer-recommended procedures when operating in an erosive/corrosive environment, there is an increased risk of an undetected and premature failure of the compressor.
The board concluded the compressor failed before its prescribed overhaul period had elapsed.