Ryanair ice skid blamed on airport blunder
A report into an incident in which a passenger jet skidded off a runway has found that the de-icing of the runway was likely to have had limited effectiveness.
The Ryanair plane from Dublin, with 129 passengers and six crew on board, slid on to a grass verge after reaching the icy end of the runway at Glasgow Prestwick Airport at around 8.45am on December 23 last year.
A report published by the Air Accidents Investigation Branch (AAIB) today said the airport's winter operations team carried out a de-icing run on the runway and linking routes at 4.30am.
The de-icing machine was automatically limited to an application of 20 grams per square metre, the rate appropriate for anti-icing. However, for de-icing, a rate of 30-70 grams per square metre is needed.
De-icing gets rid of ice that has already formed, whereas anti-icing is a preventive measure to stop ice forming.
The report said: "A de-icing run was carried out on the runway but at an application rate only suitable for anti-icing.
"Therefore, it is likely to have been of limited effectiveness."
No one was injured and there was no reported damage to the aircraft.
The report also said the co-pilot did not pass on the exact detail of the "extremely icy" taxiways and apron.
He listened to the Automatic Terminal Information System (Atis) as the plane approached, which gave information about wind speed and braking action in a message which ended with the warning: "Taxiways and aprons are extremely icy. Please use caution."
The co-pilot told his colleagues about the wind and braking action and added: "And it's icy obviously."
The report said: " There was no apparent discussion between the crew about the surface conditions and the potential problems with operating on a slippery surface."
After landing, the plane taxied towards the end of the runway but did not slow down when the brakes were applied.
The commander tried to turn the plane 90 degrees to the left on to the taxiway. However, while the nose slewed 45 degrees to the left, the wheels continued along the runway and the aircraft slid off the paved surface on to the grass at a speed of 24 knots.
It travelled another 20 metres before coming to a stop with its wheels sunk in the grass and the passengers disembarked.
There was no evidence of any technical problem with the braking systems of the aircraft.
The document said the crew of the preceding aircraft did not report any difficulty with braking action on the same runway four minutes earlier.
The AAIB said the airport operator identified a number of areas in its winter operations where its procedures could be improved and made appropriate safety recommendations.