What happened
On January 22, 2020, at approximately 18:00 UTC, a Hawker 400XP, registration SP-TTA, was performing a commercial flight (CAT) from Chambery (LFLB) to Leeds/Bradford (EGNM) with four passengers on board. The flight was conducted under IFR in VMC conditions. During the flight, the destination airport was changed to Newcastle International (EGNT).
The takeoff, climb, and cruise phases proceeded normally without any issues regarding engine control. However, just before the descent began, the crew attempted to adjust the flight speed and discovered that the left engine control lever was stuck. The lever would not move in the desired direction and remained fixed at 95% power.
The crew immediately notified Air Traffic Control (ATC), declared a PAN PAN, and requested an earlier descent to allow for a shallower descent gradient, ensuring the aircraft did not exceed speed limitations. After approximately 10 minutes of flight at FL150, the crew found that the engine control lever had returned to its full range of motion. They subsequently canceled the PAN PAN and continued to the destination, landing safely and without further incident.
The investigation
The PKBWL examined the sequence of events and the environmental conditions present during the flight. The investigation noted that heavy rain occurred during the takeoff from LFLB. The investigators considered that moisture may have reached the engine control lever linkages. At the cruise altitude of FL400, where the external temperature was -63°C, this moisture likely caused the linkages to freeze or ice over.
Findings
- The primary cause of the event was the probable freezing or icing of the left engine control lever linkage caused by atmospheric conditions during takeoff, climb, and cruise.
- The crew's actions were evaluated as correct and professional.
- The release of the lever was attributed to the increase in ambient temperature during the descent, which allowed the ice to melt.