Scraping off ice before take-off? Innovative forecasting system for ice formation on aircraft wings
Like car drivers, pilots also experience problems with ice formation. Not on the windshield but on the wings of their aircraft. The ice needs to be removed before the aircraft can depart. This often forms a bottleneck for departing aircraft in the winter months, leading to delays and high costs.
KDC foundation asked MeteoGroup to develop a model which gives an accurate forecast of the amount and type of ice formation. Initial experiences with the KLM de-icing team are positive.
Foresight is the essence of government
At Schiphol, KLM is responsible for de-icing the aircraft wings of 90% of all aircraft. In general: the more ice, the more capacity the de-icing team needs to have available. The KLM de-icing team currently works mainly on the basis of forecasts of the air temperature and its many years of experience. Can we make these forecasts more accurate? If so, this would improve the planning process for de-icing: it would prevent delays caused by too few team members and save costs by avoiding having an excessive number of team members. Moreover, a reliable de-icing planning process would contribute to stable planning for Schiphol operations.
A forecasting system for ice formation
On behalf of KDC foundation and in conjunction with KLM, MeteoGroup developed a prototype forecasting system for ice formation on aircraft wings. This prototype is designed to give a ten-day forecast of the condition of aircraft wings for each hour.
The test item: a free-standing aircraft wing
Project leader Ingeborg Smeding of MeteoGroup: “For this project we used a free-standing aircraft wing (see figure 1). We installed temperature sensors on it. These sensors provided insight into the precise behaviour of the wing temperature. The test wing was placed at a strategic location: close to where the de-icing team sets to work on aircraft wings, not too close to buildings.
A major factor: wing temperature
Ice formation greatly depends on the weather. Many factors and parameters play a role here. These of course include air temperature and the presence of moisture due to e.g. precipitation, fog or condensation. But the surface temperature is just as important: the wing temperature may be much lower than the air temperature. Project leader Ingeborg Smeding: “During the project we obtained a measurement whereby the wing temperature was 8 degrees lower than the air temperature, a much greater difference than we had anticipated!” This difference in temperature is caused by wings having a much smaller heat capacity and by them cooling down more due to radiation. This phenomenon was already well-known for e.g. asphalt. Yet the effect of this on aircraft wings was a surprise for the aviation sector.
The basis for the forecasting system: a simulation model
During the project MeteoGroup developed a prototype model which simulates ice formation on wings. To this end, MeteoGroup used comparable physical and statistical techniques which it already applies in combating icy conditions on roads and runways. This model forecasts the wing temperature and condition on an hourly basis. Throughout last winter the KLM de-icing team recorded data on the times at which de-icing was conducted. These data were used to check and calibrate the model.
Positive initial response
A prototype of the forecasting system has been made available to KLM via a website. The initial response has been positive. In the following winters, MeteoGroup will continue to conduct measurements and further develop the forecasting system together with KLM. The pilot scheme is currently only operating at Schiphol. Yet other airports and airlines could also benefit from the results. KDC and MeteoGroup are to continue developing the models for this reason. This will include looking at whether adapted measuring equipment would enable measurements to be conducted at different locations throughout an airport.
Last winter MeteoGroup again provided the KLM De-Icing team with a location specific wing temperature and condition forecasts for Schiphol. Winter 2015-2016 was the second mildest winter ever with no significant snowfall in the area of Schiphol. The winter started with a record mild December with hardly any de-icing events. January and February were again mild but less exceptional than December. During January the North of the Netherlands faced serious winter weather with large amounts of freezing rain. As forecasted by MeteoGroup this frontal system with freezing rain did not reach the area of Schiphol, although it was near. In contrast to the previous months, March was colder than normal resulting in an Eastern that was even colder than Christmas. This cold weather resulted in a few tricky “clear–ice” conditions.