What happened
On two different flights, the flight crews of an aircraft experienced a loss of elevator responsiveness to control inputs. During the first incident, the crew managed the aircraft's pitch using the pitch trim and descended to a lower altitude, at which point elevator control was restored.
During the second occurrence, the crew applied backpressure on the elevator until the control surface "bumped free," allowing for the restoration of normal control. In both instances, the aircraft had departed in rain showers with surface temperatures of 46 degrees (F) during the first flight and 39 degrees (F) during the second.
The investigation
Following the first occurrence, maintenance personnel inspected the vertical stabilizer and discovered ice accretions within the elevator control bay. Additionally, they identified debris that was obstructing the drain holes in that same area. Following the second occurrence, maintenance inspections were performed, but no anomalies were found.