What happened
At approximately 1300 Atlantic Daylight Time, a Bell 407 helicopter, registration C-FTJU, was performing slinging operations roughly 4 nautical miles southwest of Wabush, Newfoundland and Labrador. The aircraft, operated by Universal Helicopters Newfoundland Limited, was transporting a 2,300-pound drill tower using a 90-foot long-line.
As the pilot approached the drill base frame at an altitude of about 220 feet and an airspeed of 36 knots, a loud bang and smoke from the engine exhaust signaled a sudden loss of engine power. This failure caused a rapid decline in main rotor speed and an immediate leftward yaw. The pilot released the drill tower before the aircraft struck the ground approximately nine seconds after the power loss. The pilot sustained minor injuries and was able to exit the substantially damaged aircraft. No fire occurred following the impact.
The investigation
The investigation focused on the mechanical failure of the engine and the flight dynamics following the power loss. Investigators examined the engine components and the pilot'-s response to the emergency. The analysis also considered the aircraft's position within the height-velocity diagram (HVD) and the pilot's use of personal protective equipment.
Findings
- The primary cause of the engine power loss was the failure of the third-stage turbine wheel, which occurred due to the overstress extension of high-cycle fatigue cracks in the blade trailing edges.
- The engine power loss happened at an altitude that did not allow for a safe landing, contributing to the impact.
- The helicopter was operating within the HVD "avoid" range at the time of the failure.
- A delay in lowering the collective lever and failing to immediately correct the left yaw increased the risk of the crash and subsequent damage.
- The pilot was not wearing a flight helmet, which increased the risk of head injuries during the impact.