What happened
On 14 March 2008, a Cessna 550 Citation II, registration G-JBIZ, was conducting a positioning flight from Palma de Majorca to Edinburgh. Prior to departure from Palma, the crew noted a 'DOOR NOT LOCKED' warning, which was later attributed to a misaligned striker plate. During the climb, an 'AIR DUCT O’HEAT' warning appeared, and the 'FDR FAIL' caption illuminated after takeoff. The crew also experienced a tripped circuit breaker related to flight recorder equipment cooling.
During the descent into Edinburgh, the crew encountered further issues with the air conditioning system. While under the control of ATC, the pilot noted that the autopilot and yaw damper engagement lights were off, despite attempts to reengage them. The aircraft then exhibited severe control difficulties, including uncommanded left and right rudder sequences and significant pitching. The commander reported the aircraft felt unresponsive and stiff, eventually declaring a 'mayday' due to the perceived loss of control.
To maintain stability, the commander increased speed to 220 kt. The aircraft performed a high-speed approach at approximately 193 kt, landing with the gear up. The aircraft came to a stop near the end of the runway, and the crew initiated an evacuation.
The investigation
The AAIB examined the aircraft and found no evidence of fire or overheat damage. While the crew had reported a strong smell of electrical burning in the rear equipment bay, inspections revealed no obvious damage. The investigation found that the 'FDR FAIL' message was caused by the misaligned door striker plate.
Testing of the autopilot computer revealed that while a loan unit functioned normally, an intermittent defect in the original computer caused uncommanded roll inputs during ground testing. However, investigators found no defects in the rudder or yaw damper systems that could explain the uncommanded rudder movements experienced during the flight.
Findings
- The crew was already under significant stress due to perceived overheat conditions and multiple electrical warnings.
- The crew's failure to use structured decision-making tools, such as the DODAR method, contributed to a high-risk landing approach.
- The lack of visual or aural annunciations regarding the autopilot status contributed to the crew's confusion.
- The increased pitch control forces, likely caused by the aircraft being out of trim, reinforced the crew's belief that they were losing control.
Safety action
- The AAIB noted that EASA had already proposed requirements for pilots to complete initial CRM training before commencing unsupervised line flying.