What happened
On 26 April 2012, a Piaggio P.1im80 Avanti II, registration PH-DLN, departed London City Airport and entered a conflict course with an Avro 146-RJ85, registration EI-RJW, which was on final approach to Runway 27. While the Piaggio P.180 Avanti II was climbing, it deviated from its approved departure route, turning onto a south-easterly track that intersected the approach path of the Avro 146-RJ85.
An air traffic controller identified the deviation and issued instructions to the crew of PH-DLN to turn left. When the aircraft failed to respond immediately, the controller issued an "AVOIDING ACTION" instruction, specifying the presence of conflicting traffic. At the moment of closest approach, radar showed a lateral separation of 2.7 nm and a vertical separation of 700 ft. No TCAS warnings were triggered for either aircraft.
The investigation
The investigation established that the crew of PH-DLN had experienced incorrect heading indications on their cockpit displays. Prior to takeoff, the crew had selected the Directional Gyro (DG) mode on their Horizontal Situation Indicator (HSI) and adjusted the heading to match the runway QDM. After takeoff, they transitioned to slaved mode, but the heading information remained inaccurate.
It was discovered that the crew was preoccupied with managing the aircraft in turbulent conditions, which prevented them from noticing the navigational error until after they had complied with the controller's turn instruction. Following the ATC intervention, the crew reset their instrumentation, which corrected the discrepancy.
Findings
- The primary cause of the deviation was an operational error involving the incorrect setting of the heading reference system.
- The crew's attention was diverted by the necessity of flying the aircraft through turbulence.
- The crew had manually adjusted the HSI to match the runway QDM while in DG mode at the holding point, which led to the erroneous heading information remaining active.
- The crew did not recognize the error until the aircraft was instructed to turn by air traffic control.