AAIB investigation to ATR 72-212 A, G-COBO
Pitch control difficulty after departing Manchester Airport in icing conditions, diverted to East Midlands Airport, 4 March 2016
Summary:
The aircraft arrived at Manchester Airport from Guernsey and remained on the ground for more than an hour, while it was snowing and the temperature was 0ºC. The flight crew decided no de-icing or anti-icing treatment was needed, as they did not consider the snow was settling on the aircraft, and the aircraft subsequently departed to return to Guernsey.
During the takeoff, the commander exerted less aft pressure on the control column, to rotate the aircraft, than he expected and maximum nose-down pitch trim was then needed to maintain the appropriate climb attitude. The autopilot was engaged four times but on each occasion it disengaged, as designed, and the commander had to apply continuous forward pressure on the control column to retain the desired pitch attitude, as the climb proceeded.
Once at the cruising level, the commander decided he was having to exert excessive forward pressure on the control column and he elected to divert to East Midlands Airport (EMA). While descending, the aircraft flew out of icing conditions and the control difficulties dissipated. The crew assessed that ice contamination had caused the problem and they made a normal landing.
No ice was found on the aircraft during a post-flight inspection but analysis by the manufacturer concluded that, from the start of the flight until the latter stages of the descent, the airflow over the horizontal tailplane and elevator was disrupted by ice contamination.
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