AAIB investigation to ATR 72-212 A, 500 Version, G-COBO
Loss of control, 5 nm north of reporting point ORTAC, 21 December 2016.
Summary:
The aircraft was on a scheduled flight from Guernsey to Manchester. While climbing to a cruising level of FL170 the aircraft began to accrue airframe icing. The crew were presented with a DEGRADED PERF and an INCREASE SPEED caution. The appropriate checklists were not fully actioned and the correct climb speed was not maintained because the crew focused on climbing the aircraft clear of the cloud and icing conditions. The aircraft experienced an in-flight upset whilst levelling at FL130 (as requested by the pilots) and commencing a turn instructed by ATC. The aircraft was subsequently recovered to controlled flight, after which the crew elected to return to Guernsey. There were no injuries.
The loss of control resulted from airframe icing accrued during the climb and incomplete use of the appropriate checklists, leading to selection of an unsuitable speed followed by the use of the LNAV mode of the flight director to initiate a turn.
The operator and manufacturer took several safety actions, including an amendment to the aircraft’s checklist and operating manuals.
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