The Transportation Safety Board of Canada says non-standard air traffic control language contributed to a near-collision of an AgustaWestland AW139 helicopter and a FedEx Airbus Airbus A300 at Ottawa Macdonald-Cartier International airport in 2014.

The incident happened as the helicopter, operating a medical evacuation flight for a company called 7506406 Canada Inc, began taxiing north on Ottawa’s Taxiway Echo at about 08:46 local time on 5 June of that year, says the TSB's final report, issued 15 July.

As instructed by controllers, the helicopter stopped short of Runway 25, an east-to-west runway that intersects Taxiway Echo.

At about the same time, controllers cleared the FedEx A300, inbound from Montreal, to land on Runway 25.

The pilots of the helicopter were unaware that the FedEx A300 was landing because they were monitoring the ground-control radio frequency.

Around 08:48, the airport controller contacted the AW139 to amend the aircraft’s instrument flight rules (IFR) clearance.

“LF 4 Medevac roger, while we wait…,” said the controller before providing the new clearance. The pilot-not-flying asked the controller to repeat the new clearance.

At the same time, the pilot flying the AW139 began taxiing across Runway 25.

Meanwhile, the FedEx A300 landed on Runway 25 and decelerated to about 10kt, at which time the airliner was about 240ft (73.2m) from the helicopter.

The TSB attributed the near-collision partly to “non-standard phraseology”. The pilot flying could have confused the non-standard phrase “while we wait” with the standard “line up and wait”.

But the report also cites “expectancy” as a factor, noting that the pilot flying the helicopter likely began crossing the runway because he was accustomed to being cleared for takeoff immediately after receiving an amended IFR clearance.

Canada’s TSB says there were 4,135 runway incursions, including those between aircraft and vehicles, between 2004 and 2013 in Canada.

“These instances are rare, but their consequences can be catastrophic,” says the report.

Source: Cirium Dashboard