de Havilland Canada DHC-4 Caribou crash

	de Havilland Canada DHC-4 Caribou Crash
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The aircraft involved was an experimental, modified version of the Caribou which had undergone conversion to turbine power, and was being tested to check fuel and hydraulic systems on the date of the crash, 27 August 1992. Although the aircraft apparently rotates and climbs normally, photographic evidence indicates that control-surface movement was minimal, suggesting that the gust-locks were engaged. While there was elevator movement upon rotation, the elevators returned to the neutral position and remained there. This is in line with the operation of the gust-lock – if the control surfaces are not in the neutral position when the lock is engaged, movement of the surfaces through neutral will engage it. In addition to preventing control-surface movement, the gust-lock lever is supposed to inhibit the power levers to prevent the pilot from applying take-off power. It was found that the aircraft's take-off distance was 20% longer than expected. Wreckage analysis determined that the rudder lock was fully engaged and the aileron lock had only been disengaged at the moment of impact, supporting the conclusion that the gust-lock system had not been fully disengaged ahead of the flight, and that at least some of the locks had engaged after take-off.