Finnish Snowhow

If you want to practice aviation in Finland, there is one thing you need to master – winter operations.

Finnair has always been a trailblazer for winter flying. At the very beginning, this involved operating on sea ice with planes that had been fitted with skis, as this photo from 1928 demonstrates.

It shows Finland’s first ever commercial airline pilot, Gunnar Lihr, demonstrating a coal-burner steam boiler he had devised to Aero’s (later Finnair) founder and first ever director Bruno Lucander, seen on the right. The ingenious device acted as a heater for the Junkers 13’s L-5Z engine, circulating hot water through pipeworks that acted, in a complete role reversal, as a water cooling system during flights.

Since those days, Finnair has distinguished itself as an expert in on-ground icing and as a developer of sensors and de-icing fluids.

Despite immense technological advances, Mother Nature does not make things easy during the winter season. Even today, jet engine compressor vanes must be checked carefully for ice prior to ignition. If ice has formed, it is removed using blowers. Aircraft wings must also be cleared of snow, ice and frost prior to take off. Today, this is done using water and propylene glycol-based detergents. The glycol is used to prevent the water from freezing but many readers may be surprised to discover that the solution is up to 50% water. The first step is to spray hot type I fluid at high pressure. This breaks down the ice mechanically and clears any snow and frost that may also be present. If there is a risk that snow or frost may re-form on the wings, thickened type II or type IV fluid is then applied to the wings, again at high pressure. The fluid is designed to melt any fresh snow and prevent it from adhering to the wing.

The pilot is then responsible for assessing the holdover time, or the time the treatment can be expected to continue to offer protection to the wings, using a series of tables. Relevant factors include the temperature of the wings, the amount of precipitation, wind speed and, naturally, the type of fluid used and amount of glycol it contains. The viscosity must be such that the fluid flows off the wings during the acceleration prior to take off. If the holdover time is exceeded while the aircraft remains on the tarmac, retreatment is required. Fortunately, this is extremely rare.

Performance values are calculated for each takeoff. The gross weight, wind speed, atmospheric temperature, air pressure and, importantly, the friction coefficients recorded on the runway are used to calculate flap positions and speeds, the so-called decision speed V1, rotation speed, the speed at which the aircraft takes off and the minimum safe speed airborne V2. If there is major disruption prior to decision speed, such as engine failure, the aircraft can be brought to a halt on the remaining stretch of runway. If the disruption occurs after decision speed has been reached, the takeoff will be concluded and all obstacles are calculated to be cleared, even with one failed engine.

When operating on icy and slippery runways, particular care is taken to account for the width of the cleared runway in the event of engine failure. The friction coefficients must be such that, in the prevailing wind in an asymmetrical thrust situation, the aircraft can be maintained within the cleared section of the runway. If the coefficients are not sufficient and the cleared area is not wide enough, the aircraft will not be able to take off.
In thick cloud, temperatures may often dip below zero, even in summer. The precipitation in the cloud can form ice on the leading edges of the aircraft wings and engines, which are still cool following time spent at higher altitudes. These edges are kept free from ice thanks to so-called hot engine bleed air. In addition, all external sensors and cockpit windows are electrically heated.

The aircraft’s altitude is calculated using air pressure. As the air thickens in colder conditions, the actual altitude can be lower than that indicated, i.e. the altimeters can “lie”. To account for this, the so-called obstacle clearance must be included in all minimum altitude calculations.

As with takeoff, performance value calculations are repeated for landing. The prevailing runway and weather conditions are used to ensure that the aircraft will come to a halt on the correct runway. In icy conditions, the crosswinds must be sufficiently low to allow directional control even though rudder control is reduced as the aircraft decelerates. The directional control is possible in large part due to the anti-skid system on the breaks, which, as many readers will know, has also been adopted by car manufacturers over the years.

Taxiing the aircraft in icy weather can prove challenging, as is demonstrated on this video.

The most significant risk factor for winter aviation is posed by airports which rarely experience true winter conditions. In recent years a number of key international airports, including Amsterdam, Paris and especially London and Frankfurt, have been caught off-guard by significant snowfall and been forced to close runways following minor snow cover amounting to just 10cm. In the past decade, Helsinki-Vantaa Airport has closed for only a matter of hours due to weather.

A snowfall of 10cm may not sound like much, but for an airport the size of Helsinki-Vantaa, it equates to 7,000 lorry loads of snow. So far this year, we have had a total of 180cm of snow, equivalent to 126,000 loads of the white stuff. The snow is never cleared completely from the area, but is instead transferred from one area to another. In my opinion, both Finnair and Finavia, the service provider, have managed this side of the operations impeccably. Finnair has a good fleet of de-icer vehicles and thanks to Finavia’s 120 strong staff and 50 specialist vehicles, the runways are closed for just 10 minutes out of every full hour, even in heavy snowstorms.

Delays are often calculated in minutes, not in hours. Usually, a dozen or so vehicles are dispatched to clear the runway in a single run. The vehicles are fitted with snowploughs, brushes, blowers and friction meters as well as a range of other equipment. Driving in formation at 60kmph, it does not take them long to clear a runway. The largest vehicles are manufactured by the Finnish Patria-Vammas.

One should not forget, however, that the hardware alone will not guarantee success. To run an airport smoothly through a winter season takes seamless cooperation and careful planning by the airport service provider, air traffic control, airlines, handling companies and all other operators.
The insufficient resources available at the central European airports in recent years have led to the airports and airlines affected suffering financial losses amounting to millions. In my opinion, it is simply not right that airlines and their passengers, who are charged significant navigation and landing fees, should bear the brunt of badly maintained airport facilities. An airport like Helsinki-Vantaa, where safety is considered of paramount importance, is also highly efficient and, as a result, pilot-friendly. I suspect I am not far off in suspecting that the passengers, too, appreciate prompt service.

Already looking forward to the arrival of spring,

Jussi Ekman