Accident Overview
On May 27, 2008, at 0903 central daylight time, a Bell 206L-3 helicopter (registration C-GCHG, serial number 51508) operated by Custom Helicopters Ltd. was transporting a lineman to Tower 63 on the Sheridan power line near Cranberry Portage, Manitoba. While hovering near the tower, the helicopter's skid gear became entangled in the uppermost cablespan. The helicopter struck the tower and crashed on the adjacent power line right-of-way. The helicopter was substantially damaged by impact forces and fire; the pilot and passenger both sustained fatal injuries. The accident occurred during daylight hours.
Wreckage and Site Information
The main portion of the fuselage was found 40 feet northeast of the tower and was almost entirely consumed by post-crash fire. The helicopter's skid gear remained caught in the tower cross arm structure. The right skid gear exhibited cable scratches matching the uppermost skyline cables. The skid gear attachment point failed from tensional overload forces in the forward direction. Both upright arms of the hydro tower were damaged, and the westerly cable span was significantly stretched. The main rotor head and blades separated and were found 100 feet east-northeast of the tower. The rotor mast failed due to torsional overload forces consistent with a high-power main rotor strike. The tail boom was torn away and located approximately 60 feet south of the main wreckage area.
Engine examination revealed rubbing on the first-stage compressor rotor casing, collapse of compressor blades on the left side, bending of the left-side inlet guide vane, and rubbing on the last stage of the power turbine rotor tips. No pre-impact mechanical anomalies were found. The helicopter's gross weight was estimated to be within limits. A GPS receiver in the wreckage contained no flight track data for the flight from Tower 142 to the accident site.
Safety Oversight
The operator did not offer or require specialized training for helicopter operations near power lines, nor was it required. No formal procedure existed for line pilots to report hazardous operating conditions. Manitoba Hydro did not have a method of conducting safety audits on contract aviation companies. The most recent Transport Canada audit of the operator took place in November 2003. The operator was not required to have a safety management system.
Findings
The Transportation Safety Board determined that the helicopter was hovering close to the power line tower structure and became entangled in the upper (non-energized) cable span. As a result, the helicopter became uncontrollable, collided with the tower structure, and crashed. The reason for hovering so close to the tower was not determined. The passenger's injuries indicated a fall from the helicopter; the reason was not determined. Weather conditions at the nearest station (Flin Flon, 10 nm north) were wind 020° true at 6 knots, visibility 15 statute miles in light rain, overcast at 1500 feet, which would not have affected the pilot's perception of position. No rain was reported at Tower 142.