What happened
On 14 March 2010, a Hawker 800XP, registration CS-DRP, was prepared for departure from the general aviation apron at London City Airport. During pre-flight preparations, the crew observed that the aircraft's compasses were taking an unusually long time to align. To facilitate the setting of the correct heading, the pilots had left the attitude and heading reference systems (AHRS) in slew mode.
During taxiing, the aircraft was instructed to backtrack along Runway 27, vacating onto the loop taxiway at Hold K and holding short at Hold M. While backtracking, the aerodrome controller offered the crew an immediate takeoff, noting that a landing aircraft was only 4 nautical miles from touchdown. The crew accepted this offer. During this process, the aircraft turned on the runway to face the takeoff direction rather than using the loop taxiway.
Once airborne, the crew received new heading instructions and realized the aircraft was failing to maintain the assigned course. The pilots subsequently adjusted the flight path to correct the deviation. The flight continued without further incident, and no other traffic was impacted by the error.
The investigation
The investigation focused on why the aircraft departed with incorrect heading settings. It was established that the AHRS remained in slew mode during the departure. The investigation also examined the environmental conditions at London City Airport, specifically the presence of magnetic anomalies. It was found that construction and the industrial legacy of the airport's loop taxiway area create magnetic disturbances strong enough to interfere with aircraft heading reference systems. These anomalies primarily pose a risk when pilots lack sufficient time to allow the systems to realign while positioned on the runway.
Findings
- The crew departed the airport without the correct heading established due to the AHRS being left in slew mode.
- The pilot accepted an immediate takeoff offer, which contributed to a rushed departure.
- Magnetic anomalies at the airport, caused by the industrial history and construction of the loop taxiway, can affect the alignment of heading reference systems.
- The risk of such anomalies is most significant when flight crews do not have adequate time to ensure system alignment during runway positioning.