The accident was caused Causation by atmospheric icing Change on the horizontal stabilizer .

The icing Motion caused Causation the loss Earnings_and_losses of pitch control Control and the aircraft entered Becoming_a_member a steep dive Self_motion .

Also known as atmospheric icing , the ice accumulation caused Causation the deterioration of lift force .

Failure to adhere to the correct procedure for handling an atmospheric icing was also cited Judgment_communication as one of the causes of the crash .

the plane crashed Catastrophe into mount unk near chilliwack , british columbia , canada , on 9 december 1956 after encountering Hostile_encounter severe icing and turbulence over the mountains .

The investigation Scrutiny concluded Coming_to_believe that there were neither technical faults with the aircraft nor pilot error , and that it was not possible to predict the weather conditions which caused Causation the icing Change .

While passing Motion_directional Røros the Heron started Process_start experiencing Know a rapidly accelerating Cause_change_of_strength atmospheric icing which soon was too extensive for the ice protection system to handle .