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Tailwind landing factor in Boeing 737-800 runway excursion, Canada
22 May 2021

In its newly released investigation report the Transportation Safety Board of Canada (TSB) found that changing runways without recalculating the landing distance required based on the changes in wind and runway surface conditions, led to a runway overrun in Halifax, Canada, in 2020.

On 5 January 2020, a WestJet Boeing 737-800 aircraft was conducting flight WJA248 from Toronto/Lester B. Pearson International Airport, Ontario, to Halifax/Stanfield International Airport, Nova Scotia, with 172 passengers and six crew members on board. The flight crew had originally planned to conduct an approach for runway 05. However, due to a lowering ceiling and reduced visibility, the crew requested to change to the runway 14 instrument landing system approach, which allows for landing with lower minimum ceiling and visibility requirements than the approach to runway 05. The aircraft then touched down with a tailwind component on the wet, snow-covered runway. The aircraft could not be stopped and it overran the end of runway 14, coming to rest in snow with the nose wheel approximately 91m beyond the runway end. There were no injuries and no damage to the aircraft.

The investigation found that, while preparing for the runway change, the flight crew mentally assessed that the head wind for Runway 05 would become a crosswind for runway 14. As a result, they did not recalculate the effects of the wind for the approach to runway 14, but rather considered that the landing distance and the target approach speed calculated for Runway 05 were still appropriate. However, the reported wind speed and direction changed as the flight progressed, resulting in a tailwind component that exceeded the operator’s limitation, a lower required approach speed, and a landing distance that exceeded the runway length available. None of this was recognized by the flight crew and, as a result, they continued the approach to runway 14. The unchanged target approach speed combined with the tailwind component resulted in the aircraft touching down at a faster groundspeed, thus requiring a longer stopping distance. The wet snow contamination on the runway reduced braking effectiveness, which also contributed to an increase in landing distance.

Following the occurrence, WestJet highlighted to its pilot group the importance of using the actual runway intended for landing when making pre-landing performance calculations. The company also revised its emergency response checklist to include the requirement to pull the cockpit voice recorder and flight data recorder circuit breakers after an incident, and is now monitoring for landings that exceed the maximum tailwind component in its flight data monitoring program.

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