What happened
On 23 February 2005, a Jetstream 4100, registration G-MAJM, was performing a scheduled passenger flight from Aberdeen to Newcastle. While climbing through 9,000 feet, the aircraft experienced a sudden and sharp pitch change immediately after the autopilot was engaged. Upon disengaging the autopilot, the crew discovered that pitch control was severely restricted, with significantly limited nose-up capability. The first officer attempted to manage the aircraft manually but found the control column movement highly constrained; the captain subsequently took control and found slightly better responsiveness.
The crew declared a PAN and initiated a return to Aberdeen. They opted for a long, shallow approach to manage the flight path. As the aircraft descended, the level of control improved, and full authority was eventually restored before the aircraft touched down safely. There were no injuries and no fatalities among the three crew members and seven passengers on board.
The investigation
Investigators examined the aircraft's condition following the incident. While the aircraft had been parked outside during a period of snowfall, visible ice had been removed prior to departure. However, no de-icing fluid had been applied, and the upper surfaces of the horizontal tail were not specifically inspected or treated. During the pre-flight check, the pilot noted that the top of the tailplane was not visible from the ground, though flight controls initially appeared to move freely.
Post-flight inspections revealed that ice was shedding from the gap between the elevator leading edge and the fixed tailplane. Further examination in a hangar confirmed that this gap had become filled with ice. The investigation found no mechanical faults with the elevator hinge bearings or the elevator actuating system.
Findings
- The primary cause of the control restriction was ice accumulation within the gap between the elevator leading edge and the fixed tailplane.
- The accumulation was likely initiated by residual ice on the tailplane surfaces that was not visible during the pre-flight inspection and was not removed by de-icing fluid.
- Further ice buildup occurred as the aircraft transitioned into cloud layers during the climb.
- The crew did not utilize the manual disconnect handle for the independent elevator control systems, as the captain was able to maintain sufficient control using the elevator trim.