During a wallaby habitat survey of Bluff Mountain the aircraft entered severe turbulence and strong downdrafts. The pilot applied maximum power to avoid impact with the ground and the engine turbine failed. The aircraft entered trees, nosed over and caught fire. The forecast wind speed was 15 to 20 knots and the actual speed was generally close to this. The encounter with the turbulence and downdraft was sudden and unexpected and resulted in the pilot having to use all available engine power in order to regain control. The engine turbine temperature limits were exceeded, leading to the failure of the turbine.