What happened
On an instrument flight rules arrival from the south, a de Havpland Dash 8 (registration QXE260) was being vectored toward Vancouver International Airport. While following the Acord 9 arrival procedure, the aircraft was instructed by air traffic control to fly a heading of 340° and maintain 5000 feet. This specific vector directed the aircraft toward terrain to the north where the minimum vectoring altitude (MVA) is 7000 feet.
During the approach, the air traffic controllers became preoccupied with coordinating other aircraft. This distraction caused them to lose track of the aircraft's position. A coordinator eventually alerted the controllers to the aircraft's proximity to the terrain. The controller then issued a rapid series of instructions, including a sharp left turn and a climb to 7000 feet. Despite the altitude deviation, the aircraft managed to climb to the required level before exiting the MVA area and landed safely on Runway 08L.
The investigation
The investigation established that the controller's instructions placed the aircraft on a path toward higher terrain at an altitude below the required minimums. At the time of the event, the arrival sector was being managed by a trainee and an on-the-job instructor (OJI). The controllers were distracted by the coordination of two other aircraft and failed to use memory aids, such as flight progress strip markers, to track the aircraft's status.
Technical reviews revealed that the radar data-processing system in use did not feature a minimum safe-altitude warning (MSAW) system to alert controllers of altitude deviations. Additionally, the Acord 9 arrival chart did not explicitly warn pilots of the possibility of being vectored north toward high terrain, nor did it provide information regarding the navigational limitations in that area. While the aircraft was equipped with a ground proximity warning system (GPWS), it did not activate because the aircraft was not yet in a flight path that triggered a terrain warning.
Findings
- The air traffic controller issued a heading that necessitated immediate corrective action to maintain terrain separation.
- The controllers lost situational awareness of the aircraft's position due to distractions from other traffic duties.
- No manual or automated safeguards, such as memory aids or an MSAW system, were utilized or available to prevent the altitude deviation.
- The arrival charts lacked sufficient information regarding the risks of northern vectors, which hindered the flight crew's ability to maintain independent situational awareness.