AAIB investigation to Quik GT450, G-DTAR
Heavy landing and go-around due to wake turbulence, Perth Airfield, 15 September 2018.
Summary:
The instructor was conducting training, flying circuits using Runway 27 at Perth Airport. During a downwind leg, a helicopter departed the airport from a pad south of the runway. The wind was estimated to be from 240° at less than 5 kt. The instructor discussed the wake turbulence risk but assessed that it would have dissipated before they reached the runway. When they encountered turbulence a few feet above the runway, the instructor applied full power, but the aircraft made heavy contact with the runway before continuing the go-around. In the circuit, he released the throttle which had become stuck at cruise power, before carrying out a successful glide landing.
CAA Safety Sense leaflet 15c “Wake Vortex” and NATS Aeronautical Information Circular P 001/2015, “Wake turbulence” provide pertinent information. Helicopters generate vortices radially in the hover. In forward flight, helicopters generate trailing vortices either side of the disk, much like wingtip vortices of a heavier aircraft. These descend and if they reach the ground will split and move sideways at approximately 5 kt in still air. When generated close to the ground, vortices can persist for about 80 seconds. In this case, the prevailing light winds would have been favourable for sustaining a vortex and drifting it towards the runway.
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