Here’s Why This Air Canada Plane Slid Off the Runway at Pearson

An independent investigation report probing the cause of an Air Canada plane spinning off the runway at Toronto’s Lester B. Pearson International Airport in Mississauga has been released.

There were 119 passengers and six crew members on board.

The Transportation Safety Board of Canada (TSB) has released findings into the Feb. 25, 2017 runway excursion of Air Canada flight 623, or AC623, at Pearson.

Poor visibility and limited visual cues led to the incident — weather conditions and lack of runway centreline lighting reduced the indicators available to recognize the aircraft’s drift in time to correct the trajectory or to execute a safe go-around, the investigation determined.

The Airbus A320 was completing an evening flight to Toronto from Halifax’s Stanfield International Airport in Nova Scotia.

The plane began to deviate to the right of the runway centreline just before touchdown.

“It deviated further to the right after touchdown and entered the grassy area to the west of the runway before traveling 2,390 feet through the grass parallel to the runway before returning to the pavement,” reads a TSB news release.

During the excursion, the aircraft struck five runway edge lights, causing minor damage to the left outboard wheel and the left engine cowling.

No injuries were reported.

The investigation found that during the final approach phase, “while the aircraft was less than 30 feet above ground and on the runway centreline, a right roll command input caused the aircraft to enter a shallow right bank and start drifting to the right.”

The crew had “limited visual cues to accurately judge” the aircraft’s lateral position because of rain, reduced windshield wiper capability and lack of runway centreline lighting.

The severity of the drift wasn’t recognized “until the aircraft was less than 10 feet above ground and rapidly approaching the runway edge, which left limited time to correct the aircraft’s trajectory before contacting the surface. Given the risks involved in executing a go-around from a low level in response to significant drift, the pilot continued the landing sequence while attempting to minimize the extent of the excursion.”

Air Canada has since instituted a program for inspections of windshield wiper tension, developed a drift training scenario for the simulator, and issued further flight crew guidance on lateral drifts and lateral runway excursions, according to the TSB.

The board is an independent agency that investigates marine, pipeline, railway and aviation transportation occurrences for the advancement of transportation safety.

The TSB doesn’t assign fault or determine civil or criminal liability.