What happened
On 28 March 2006, a Beech B200 King Air, registration G-PCOP, departed Glasgow Airport for Peterborough. Shortly after takeoff, the pilot observed a failure in the Flight Management System, followed by a progressive loss of all primary flight displays and radio communications. As the aircraft climbed through cloud layers, the pilot became aware of an RAF Tornado aircraft attempting to provide assistance. During this period, the aircraft entered a period of uncontrolled flight within the clouds, which was observed by the RAF crew.
While the pilot eventually managed to stabilize the aircraft and descend to visual meteorological conditions, the flight was marked by significant difficulty in maintaining control. The aircraft subsequently landed at RAF Leuchars. While the crew and passengers escaped without injury, the aircraft sustained significant damage.
The investigation
The AAIB investigation focused on the sudden loss of electrical power and the subsequent structural damage. Although initial ground inspections at Leuchars found no obvious external damage, a later examination at Blackbushe revealed that the outer wing skins and leading edges had been subjected to extreme flight loads, causing wrinkling and bulging. The engines were also removed for inspection.
Testing of the electrical systems, conducted with the assistance of the AASB, failed to replicate a technical malfunction in the generators. However, investigators examined the possibility of inadvertent switch selections. It was noted that if the engine start switches had been left in the 'on' position, the generators would be unable to be reset until the error was corrected, and the heavy current draw would rapidly deplete the battery.
Findings
- The aircraft suffered a simultaneous loss of both DC generators shortly after takeoff.
- The loss of electrical generation led to a rapid depletion of the battery, causing the progressive failure of avionics and radios.
- The pilot's workload was significantly increased by the simultaneous loss of flight information and the need to navigate through cloud layers.
- The aircraft was subjected to high flight loads during the period of uncontrolled flight, resulting in the necessity to replace the outer wing panels.
- The aircraft's warning system did not meet certain airworthiness requirements regarding the visibility of warnings during a double generator failure.