What happened
On a morning in Manitoba, a Bell 206L-3 helicopter, registered C-GCHG, was performing utility support duties for Manitoba Hydro. The aircraft was engaged in transporting maintenance personnel to various towers along the Sheridan power line. After dropping off personnel at a previous location, the helicopter approached Tower 6 and attempted to hover near the structure to deliver a lineman.
During this hover, the helicopter's skid gear became caught in the uppermost cablespan of the tower. This entanglement caused the aircraft to strike the tower structure, triggering an electrical short that tripped a circuit breaker. The impact and subsequent entanglement caused the helicopter to become uncontrollable, leading to a crash on the adjacent power line right-of-way. The aircraft sustained significant damage from the impact and a following fire. The pilot and the passenger both sustained fatal injuries.
The investigation
Investigators examined the wreckage and the tower structure, noting that the skid gear attachment point had failed due to extreme tension. The main rotor head and blades were found separated from the fuselage, with the rotor mast showing signs of failure consistent with a high-power strike. The engine components also showed evidence of damage sustained while the drive-train was operating under power.
Technical reviews of the aircraft's maintenance records showed that C-GCHG had been maintained according to regulations and that the weight and balance were within limits. The weather at the time of the accident was clear enough for visual flight rules, with visibility of 15 miles and an overcast ceiling of 1,500 feet.
Findings
- The primary cause of the accident was the entanglement of the helicopter's skid gear in the upper cable span while the aircraft was hovering near the tower.
- The operator lacked specialized training programs to help pilots identify and mitigate the specific hazards associated with flying near power lines.
- There was no formal system in place for pilots to report hazardous operating conditions to management.
- The utility company, Manitoba Hydro, did not have an audit process to evaluate the safety standards of its contracted aviation services, which could have identified the need for specialized training.
Safety action
Following the investigation, Manitoba Hydro submitted findings to its internal audit department for review and committed to implementing a "Safe Work Procedure Standard" for personnel and pilots involved in power line inspections.