Clear for take-off

Aircraft crashes on runways and multiple car pile-ups caused by poor visibility could be significantly reduced using a fog-dissipation filter being developed in Russia.

Researchers at the Central Aerological Observatory in Moscow are developing the special thermodynamic filter, which can disperse fog at a distance of up to 150m.

Fog is a particular problem at airports when aircraft are taxiing to and from the runway, said Albert Chernikov, director of the observatory.

In October 2001, 118 people were killed at Milan’s Linate airport, in Italy’s worst ever aviation disaster, when a Scandinavian Airlines System aircraft ploughed into a business jet that had wrongly crossed the runway in thick fog.

‘Airports need to be clear from fog, particularly while the aircraft is taxiing, to allow the planes to get safely from the runway to the terminal,’ said Chernikov.

The thermodynamic system creates a warm jet of air, around 5-10º higher than that of the surrounding environment, in which the fog droplets evaporate. The team has tested the system inside a fog chamber, and claims one large device, 15-20m in diameter, could disperse fog on a runway for 150-200m.

The team is also developing a smaller electrostatic filter, to prevent multiple car pile-ups, capable of dispersing fog for up to 10m on either side of the road. Vehicle makers are already developing in-car radar systems that will give drivers advance warning about collisions ahead, but the filter would allow roads to be cleared of fog before accidents are allowed to happen.

The fog filter is based on two electrodes. Fog particles caught in the electrostatic field between them acquire an electrical charge, and as a result are attracted towards one of the electrodes. The particles stick to the electrode and lose their charge, turning the fog into water. The device takes just seven minutes to disperse fog. Existing fog dissipation methods can only disperse freezing fog. Warm fog is more difficult to remove, as it is thermodynamically stable, meaning it requires a great deal of energy to disperse.

The researchers have been working with the Italian Highway Authority, and have tested the filter on a 4km stretch of the Venice-Trieste highway. During this testing the team discovered the most effective way of using the filters is to place them along the central reservation, separated by screens.

A number of filters would need to be installed to clear an entire stretch of road or runway, said Chernikov. The researchers created fog and then tested the filter in various weather conditions, including a sunny day with gradual temperature increase, and on cold evenings.