DATA MANAGEMENT
Safer landings on runways with Big A
nyone who has driven on snow or ice can imagine the problem pilots face when landing on a runway in winter. A passenger car weighs less than 2 tonnes and when the temperature is around or
below freezing, is hopefully rarely driven faster than 80-90 km/h! A pilot’s problem is on another scale: a full passenger plane can weigh over 60 tonnes, and the landing speeds can be as high as 270 km/h. “Under such conditions, it is an advantage if the
pilot knows how slippery the runway is long before touchdown. With this information, the pilot can calculate the best distribution of braking power between the three available systems - disc brakes in the landing gear, thrust reversers on the engines, and air brakes that can increase drag during landing,” says Professor Arne Huseby at the Department of Mathematics at the University of Oslo. Now, 16 Norwegian airports have installed
information systems that allow the pilots to distribute the braking power in the safest way possible. Data are used to tell them how slippery the runway is – ahead of landing. Huseby has been key in developing the Integrated
Runway Information System (IRIS), used by the 16 airports. All of them have their own weather stations combined with temperature gauges in the runways, and the system collects a wealth of data about every condition that can affect the aeroplane’s braking distance. The data are used to analyse and describe the conditions at each airport on a five-step scale from “Poor” to “Good”.
ONE MINUTE INTERVALS When IRIS is operating, comprehensive weather and runway data are gathered and sent to a central computer server. At one minute intervals, the server analyses the data and sends a notification to the ground crew at any of the 16 airports if the calculations show that landing conditions are difficult. The ground crew can then pass the information on to the pilots. “The alerts from the server are not sent directly to
the pilots, because this is primarily designed as a support system for the ground crews. The reason is, among other things, that communication from airports to pilots is subject to a very strict international regulatory framework,” Huseby says. Senior advisor Stig Jone Nevland at the Airline
30 /// Environmental Engineering /// March 2018
❱❱ Professor Arne Huseby: “It was much more difficult to develop this system than everyone thought from the beginning”
Airline pilots have a difficult task when landing aeroplanes on icy runways but a new development from the frozen North will reduce the risk of accidents. Andy Pye reports from Norway
Operations Division of Avinor, the Norwegian airport operator, says: “Avinor wants to be global leader with regard to winter operations of airports, and the IRIS system has made a significant contribution to this. In addition, we have invested a lot in training for such conditions. “The airlines operating in Norway are very happy
about the system, and the pilots say IRIS is a valuable support that gives them more accurate information about runway conditions. SAS and Norwegian have given us access to sensitive flight data. Thus, no-one else in the world has better data than Avinor about what we call friction-restricted landings – landings on slippery runways.”
BETTER INFORMATION The initiative for the project originally came from Avinor in around 2000, because they identified a need to provide better information to pilots when landing during winter conditions in Norway. “At that time, when conditions could be difficult,
ground crews had to close the runway and send out a car with a mounted friction meter. After this inspection, they used to handwrite a SnowTam report (SNOw Warning To Airmen), so the whole process was quite cumbersome. In addition, the friction measurements were quite unreliable,” Huseby remembers. Avinor began digitising and automating the report
format, but it also wanted to prepare reports without having to close the runway to perform friction measurements. Could it be possible to measure a number of factors such as ground temperature, air temperature, humidity, rain- or snow-fall and wind speed, and calculate the friction from this? “It was a charming idea, but it was too simple,”
recounts Huseby. “A preliminary study indicated that it should be possible to establish a statistical relationship between weather parameters and runway conditions. But we gradually realised that the relationships between weather data, flight data and braking intensity were very complicated. One of the problems was that the relationships between a variety of the relevant conditions, such as friction and temperature, are not linear,” says Huseby. At this time, Avinor meteorologist Marit Rabbe
also became involved in IRIS. Based on her insight, the IRIS group developed a number of scenarios. Huseby later rewrote these into a mathematical
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