What happened
On a day involving instrument flight rules (IFR) operations at Winnipeg International Airport, a Piper PA-31 Navajo, registered C-GRNE, was being vectored for a visual approach to runway 36. At the same time, a Mooney M20C, registered C-GKGY, was departing the same runway on an IFR flight plan. To expedite traffic flow, the tower and departure controllers coordinated an early turn for the Mooney to a heading of 250 degrees shortly after takeoff.
Simultaneously, the arrival controller cleared the Navajo to descend from 5000 feet to 3000 feet. Because the aircraft was within the departure controller's airspace, coordination was required; however, the arrival controller bypassed direct verbal coordination with the departure controller, instead receiving approval via a data controller.
As the aircraft progressed, the separation between the two planes dropped to just 0.53 nm laterally and 300 feet vertically, far below the required 3 nm lateral or 1000 feet vertical minimum. The conflict was only identified when the data controller alerted the arrival controller. While the controllers eventually issued traffic information, the Navajo had already crossed the flight path of the Mooney at a dangerously close proximity.
The investigation
The investigation established that the arrival and departure controllers failed to adequately monitor the flight paths of both aircraft. The arrival controller's attention had been diverted by a request from another aircraft for an approach type that did not exist, leading to a breakdown in effective radar scanning.
Furthermore, the arrival controller incorrectly assumed the Mooney was operating under visual flight rules (VFR) and would remain below 2500 feet. This assumption was reinforced by the Mooney's immediate westward turn, which resembled VFR departure patterns. The investigation also noted that the departure controller authorized the Navajo's descent to 3000 feet without providing specific traffic information regarding the Mooney's departure.
Findings
- The primary cause of the loss of separation was the failure of the arrival and departure controllers to adequately monitor the flight paths of the two aircraft on radar.
- The departure controller authorized the Navajo's descent to 3000 feet without notifying the arrival controller of the Mooney's presence.
- The arrival controller assumed the Mooney was a VFR flight and therefore did not believe additional separation measures were necessary.
- The controllers were utilizing non-standard procedures to expedite traffic without implementing additional safety safeguards.
- There was no functioning conflict-alerting tool available to provide an automated warning of the impending collision.