Pilots of an Embraer regional aircraft landing on an icy runway at Halifax warned that it was like a "skating rink" before the following flight, a Boeing 767-300ER, spun on the same runway as it rolled out.
Transportation Safety Board of Canada says the Embraer had landed on runway 23 some 7-8min before the Air Canada 767, and informed Halifax tower controllers that braking action was "very poor".
Its crew then told ground controllers, on a separate frequency, that the runway was "very, very icy – it's basically a skating rink".
The tower controller advised a Bombardier turboprop crew, on approach to runway 32, that the Embraer pilots had reported "poor" braking action on runway 23, and told the Halifax terminal controller about the Embraer crew's remarks.
This terminal controller then informed the 767 pilots that the Embraer crews had described the runway as "very slippery – he barely got stopped towards the end of it".
The inquiry into the incident, on 4 March this year, points out that the phrase "very poor" – consistent with braking condition terminology – was "not relayed" to the crew.
Although air navigation service Nav Canada permits use of plain language, the inquiry states: "Use of standard phraseology between pilots and air traffic controllers may help reduce the likelihood of misunderstanding the degree to which a runway may be contaminated."
The 767 crew had originally planned to land on runway 32 but opted for runway 23 owing to its greater length and its precision-approach system with lower minimums.
But the wind situation meant that the aircraft would face a crosswind from the right of 17kt, gusting to 26kt, and a tailwind of 10kt gusting to 15kt.
After receiving the terminal controller's remarks, relayed from the Embraer pilots, the 767 crew prepared for an "aggressive" deceleration early in the landing roll, through reverse-thrust and autobraking, says the inquiry, to reduce exposure to the slippery far end of the runway.
The 767 landed within the first third of the runway at around 140kt but braking action was observed to become nil as the aircraft slowed, and the jet began to slide as it reached 15kt.
Asymmetric reverse-thrust to correct the "weathervaning" – the tendency to yaw owing to crosswind pressure on the vertical fin – could not prevent the aircraft being pushed sideways, and its nose-wheel rolled into the snow off the right edge of the runway.
"This caused the forward motion of the aircraft to be translated into a slow sideways drift and clockwise rotation on the icy runway," says the inquiry, and the aircraft spun 180° before coming to rest.
Halifax airport has since upgraded its weather information system, which doubles the number of sensors – previously three in the centreline of each runway – and automatically refreshes on the airfield maintenance supervisor's portable electronic device.
Air Canada is also modernising its runway condition reporting system to include options for automatic condition updates.
