What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Climbing out of FL350 in known icing (-23C, 1000 feet per minute, autopilot engaged, wing/engine anti-ice on), the aircraft suddenly pitched nose down. Upon detecting the pitch change the autopilot was disengaged. The controls were difficult to move along the vertical axis and each control input required excessive force to pitch the aircraft in a climb or descent. The aircraft seemed unstable and the nose would continue to pitch down or up excessively with gentle control inputs. After descending to below the freezing level (FL18), there was a sudden loosening of the rigidity in the controls and normal inputs and
Force could be used to adjust the pitch of the aircraft. Landing was uneventful.
As the FAA filed it
CLIMBING OUT OF FL350 IN KNOWN ICING (-23C, 1000 FEET PER MINUTE, AUTOPILOT ENGAGED, WING/ENGINE ANTI-ICE ON), THE AIRCRAFT SUDDENLY PITCHED NOSE DOWN. UPON DETECTING THE PITCH CHANGE THE AUTOPILOT WAS DISENGAGED. THE CONTROLS WERE DIFFICULT TO MOVE ALONG THE VERTICAL AXIS AND EACH CONTROL INPUT REQUIRED EXCESSIVE FORCE TO PITCH THE AIRCRAFT IN A CLIMB OR DESCENT. THE AIRCRAFT SEEMED UNSTABLE AND THE NOSE WOULD CONTINUE TO PITCH DOWN OR UP EXCESSIVELY WITH GENTLE CONTROL INPUTS. AFTER DESCENDING TO BELOW THE FREEZING LEVEL (FL18), THERE WAS A SUDDEN LOOSENING OF THE RIGIDITY IN THE CONTROLS AND NORMAL INPUTS AND
FORCE COULD BE USED TO ADJUST THE PITCH OF THE AIRCRAFT. LANDING WAS UNEVENTFUL.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.