What happened
On a morning in 2001, an Air Canada Bombardier Regional Jet (ACA381) was on final approach to runway 2t4R at Montréal International Airport (Dorval). Simultaneously, an Airbus Industrie A319 (ACA567) was preparing for departure.
During the initial clearance delivery, the crew of ACA567 incorrectly read back runway 24R instead of the assigned 24L. The controller did not correct this error and subsequently instructed the aircraft to taxi to the 24R holding bay. While the airport controller had cleared the aircraft to taxi to position on runway 24L, the crew—expecting to depart from 24R—taxied onto the active runway. As the controller cleared ACA381 to land, they noticed ACA567 occupying runway 24R. The crew of ACA381 immediately initiated a go-around at approximately 500 feet above the ground to avoid a collision.
The investigation
The investigation examined the staffing and operational procedures in place at the time. The tower was staffed by a supervisor acting as the airport controller and a single controller managing both clearance delivery and ground control. To manage workload, an ad hoc procedure had been established to use runway 24L for departures and 24R for arrivals.
Investigators looked into the handling of flight progress strips and communication protocols. It was found that the clearance delivery controller had overwritten the runway designation on the flight progress strip rather than using the required strikethrough method. Furthermore, the investigation reviewed the lack of coordination regarding changes to established procedures and the failure of the crew to read back the specific runway assignment during their taxi clearance.
Findings
- The clearance delivery controller failed to challenge the incorrect runway readback by the ACA567 crew.
- The controller improperly amended the flight progress strip, which obscured the change in runway assignment.
- The airport controller failed to perform an effective scan of the runway before clearing the arriving aircraft to land.
- The crew of ACA567 did not repeat the runway designation when acknowledging their taxi clearance, preventing the detection of the error.
- There was a lack of communication between the ground controller and the airport controller regarding the deviation from the morning's established departure procedure.
- The presence of another aircraft in a nearby holding bay with a similar paint scheme may have reinforced the controller's incorrect expectation that ACA567 was on the correct runway.