What happened
On 10 December 2010, a Cessna 441 Conquest, registration G-USAR, was conducting a private flight from Zurich, Switzerland, to East Midlands Airport. During the arrival, the aircraft was operating under night conditions with moderate turbulence, light rain, and light icing. The pilot initially intended to perform an ILS approach with the autopilot engaged.
As the aircraft approached the airfield, the aerodrome controller observed the aircraft deviating from the localiser course and performing unusual manoeuvres, including orbiting. The pilot, having inadvertently descended below the assigned altitude, had disengaged the autopilot to correct the height manually. During this transition, the pilot was unable to re-engage the autopilot and subsequently performed a series of erratic heading and altitude changes.
The investigation
The investigation established that the aircraft was transferred from radar to aerodrome control at 7 DME. The controller noted the aircraft was flying erratically and issued instructions to climb and turn. While the pilot followed these instructions, the aircraft continued to exhibit exaggerated movements. The investigation looked into the pilot's transition between automated and manual flight modes and the impact of the aircraft's specific instrumentation on the pilot's situational awareness.
Findings
- The pilot experienced spatial disorientation while attempting to fly the aircraft manually.
- The transition from autopilot to manual flight caused the pilot to become confused by the attitude indicator's 'sky pointer' presentation, an interface with which the pilot was unfamiliar.
- The pilot's decision to continue the approach rather than performing a missed approach contributed to the instability of the flight path.
- The timely intervention by the aerodrome controller allowed the pilot to recover and successfully complete a second ILS approach.