What happened
On 13 May 2014, a Eurocopter AS 350 BA helicopter, registered C-FHPC, was conducting a mission to inspect vegetation encroachment along a 25-kilovolt power distribution line. The flight, operated by Héli-Boréal inc., included a pilot and an observer. The aircraft was flying near a service road leading to the Hydro-Québec Sainte-Marguerite power dam.
During a right-hand turn within a valley, the pilot identified a 315-kilovolt transmission line crossing the flight path perpendicularly. In an attempt to maneuver away from this obstacle, the pilot increased the radius of the turn; however, a main rotor blade struck the lower wire of the transmission line. This impact caused intense vibrations that compromised the aircraft's controllability. While attempting to land in a small clearing situated beneath the 315-kilovolt lines, the helicopter's skid gear struck trees. The aircraft subsequently rolled to the left and fell roughly 50 feet through the forest canopy, landing on its left side in the snow.
The investigation
The investigation focused on the sequence of events leading to the rotor strike and the subsequent loss of control. Investigators examined the impact with the 315-kilovolt line and the subsequent contact with trees during the emergency landing. The investigation also looked into the delay in emergency signaling, noting that although the 406-megahertz emergency locator transmitter activated upon impact, the Cospas-Sarsat International Satellite System for Search and Rescue did not receive the signal until 25 minutes after the occurrence.
Findings
- The rotor blade strike on a 315-kilovolt power line was the primary event that induced severe vibrations and difficult handling.
- Both occupants sustained serious injuries but were able to evacuate the aircraft.
- The aircraft sustained substantial damage, though no fire occurred following the impact.
- The accident took place during daylight hours.