Griffon CH146475
17 September 2003
Goose Bay, Labrador
On 17 September 2003 the crew of Griffon 146475 was conducting Stokes litter hoist training within the boundaries of 5 Wing Goose Bay. This training involves transferring a litter from the ground to the aircraft while the aircraft is in a 50-foot hover. During Stokes litter hoisting, the SAR tech uses a rope to guide the litter from the ground. The flight engineer operates the hoist until the final recovery of the litter into the aircraft. At this point, control of the hoist is transferred to the non-flying pilot. This allows the flight engineer to manage the litter with both hands while the non-flying pilot operates the hoist.
In this accident, control of the hoist had just been transferred from the flight engineer to the non-flying pilot when the aircraft began to sink and yaw to the right. The flying pilot initiated actions for a suspected tail rotor failure that included rolling both throttles to idle and entering auto-rotation. The aircraft landed in a flat attitude and suffered “B” category damage. All of the crewmembers on board the aircraft suffered injuries due to ground impact forces (1 major and 3 minor injuries).
The investigation revealed that there were three main contributing factors to this accident. The first factor was that the non-flying pilot caused a power reduction by toggling the ‘beep' switch instead of the intended hoist over-ride switch. The second factor was that the flying pilot misinterpreted a ‘beep' down as a tail rotor failure, and finally, the last factor was an ineffective auto-rotation.
Recommendations include a re-design of the ‘beep' and hoist over-ride switches to reduce the possibility of mis-identification of the switches and inadvertent beep switch activation. It is also recommended that simulator training be enhanced to include more, and varied, engine malfunctions from the hover. And finally, it is recommended that the realism and visuals of the CH-146 simulator be upgraded in the zero to fifty-foot range to increase the realism in the landing phase during emergency training in the simulator.
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