What happened
On a night in Newfoundland, two aircraft operating under instrument flight rules were approaching St. John's airport. The first aircraft, a MEDEVAC flight registered as C-FGNL, was initially cleared for an approach to runway 16. However, after reviewing the runway visual range, the pilot requested a change to an approach for runway 11. Simultaneously, Speedair (SPR) 904, registered as C-FIPW, was following approximately 12 miles behind.
As the aircraft progressed, the controller provided radar vectors to C-FGNL for the runway 11 approach. During this period, the distance between the two aircraft decreased significantly. While the required radar separation was 3 nautical miles, the separation dropped to 1.4 nm at the moment C-FIPW landed on runway 16 while C-FGNL was on short final for runway 11.
The investigation
The investigation examined the actions of two air traffic controllers at Gander Centre. The initial controller recognized a potential conflict and instructed C-FIPW to maintain a higher speed, believing the extra distance required for C-FGNL's new approach would maintain separation. However, the controller did not account for the fact that C-FIPW would reduce speed upon intercepting the localizer.
When the relief controller took over the position, the separation was already narrowing. The investigation found that the relief controller observed the developing conflict but did not issue alternative clearances. Both controllers were aware that C-FGNL was operating as a MEDEVAC flight and operated under the assumption that priority handling was necessary, which influenced their decision-making.
Findings
- The relief controller identified the developing loss of separation but failed to take corrective action.
- The controllers' willingness to accept a loss of separation to prioritize a MEDEVAC flight was a primary contributing factor.
- The controller's decision was based on the assumption that priority handling was required for the C-FGNL flight, despite the flight plan's use of the term "MEDEVAC" not necessitating such priority in this instance.