Departure and Initial Climb
At about 1935 mountain daylight time (MDT), a Canada 3000 Airbus A320, designated CMM368, departed runway 28 at Calgary International Airport, bound for Toronto. Shortly after, a Turbo-Commander 690, designated N48BA, departed runway 34 for Kalispell, Montana. CMM368 was cleared to climb to FL 250, while N48BA was cleared to FL 210. Both aircraft received vectors from Calgary Departure, with CMM368 turning left to a heading of 090°M and N48BA turning right to 150°M.
Traffic Advisory and Resolution Advisory
As CMM368 climbed through approximately 12,000 feet at 300 KIAS, its Traffic Collision Avoidance System (TCAS) issued a Traffic Advisory (TA), showing the target at the eleven o'clock position, 3 to 4 miles away, 700 feet below and climbing. Immediately, a Resolution Advisory (RA) commanded "DESCEND CROSSING DESCEND." The captain initiated a descent. The pilot of N48BA sighted CMM368, turned right, and increased climb rate. A second RA then instructed CMM368 to "INCREASE DESCENT."
Loss of Separation
The aircraft came within 500 feet horizontally and 500 feet vertically, where either 3 nautical miles horizontal or 1,000 feet vertical separation was required. The last air traffic control (ATC) communication with either aircraft occurred at 1939:50 MDT.
Runway Assignment and Procedures
Noise abatement procedures published in the Canada Air Pilot dictated that aircraft with northern or eastern designations use runway 34. CMM368, eastbound, requested and was cleared for runway 28. N48BA, taxiing from the south end, was cleared for runway 34 to reduce taxi time. The two-runway system (co-active runways) was in use, with north and eastbound traffic normally released from runway 34 and south and westbound from runway 28. The controller's willingness to shorten taxi distances resulted in a deviation from standard flow.
ATC Coordination and Monitoring
The Departure Controller coordinated with the Arrival Controller and cleared both aircraft to their flight planned altitudes. At the time N48BA contacted Departure, CMM368 was at 8,500 feet at 190 knots. The controller expected CMM368 to maintain a climb rate of about 2,500 feet per minute based on experience, but the A320's climb rate decreased to about 800 feet per minute as it accelerated to 320 KIAS after passing 10,000 feet. The controller did not detect this change, as he did not sufficiently monitor the progress of the flight due to other responsibilities and inadequate radar scanning.
Controllers' Tools and Procedures
Available tools included predicted track lines and range bearing lines, but they were not used. The controller had turned his attention to other aircraft after assessing vertical and lateral spacing as adequate. He only looked back when CMM368 reported a TCAS descent.
Traffic Conditions and Weather
Traffic conditions at Calgary were reported as moderate with moderate complexity. Staffing met unit standards. The weather was visual meteorological conditions (VMC) with high thin scattered cloud.
Adherence to Standard Procedures
The NAV CANADA ATC Manual of Operations specifies vertical separation standards. When N48BA contacted Departure, CMM368 was passing 8,500 feet; therefore, the appropriate altitude clearance for N48BA should have been 8,000 feet. Deviation from standard procedures increased workload and risk. The pressure to move traffic quickly without undue delay was the overriding factor in allowing non-standard runway departures.