Glider Pilots Should Learn From Falcons

12 December 2010
Posted by Chris Smith.

Gliding in all its forms has become a relatively popular pastime, and if you want to glide for anything more than a few minutes you have to take advantage of thermals, which are areas of warm air rising amongst the colder surrounding air. If you can keep your glider inside this column you will be lifted up without having to do any work.Dg800 Glider

The problem is of course that air is transparent so you can not see the thermals, and you are restricted to just feeling their effects. Therefore various rules have been worked out so that the glider stays in the thermal, essentially leaving you spiralling around, making the spiral larger if your rate of climb improves, so your wings are flatter, and making it tighter if it gets worse.

This system works well if you have a clean thermal, but if there is a lot of turbulence, you get temporary updrafts which is easy to confuse with a real thermal.

Zsuzsa Ákos and colleagues at Eötvös University in Budapest have been studying the flight of perguine falcons with attached GPS receivers. They have noticed that rather than always spiralling in one direction they occasionally swap direction, this sounds stupid as this will cause them to leave the thermal they are in, but in very turbulent air this means that they can test a larger volume of air for other better thermals, and if they find one they will stay in it, and in computer simulations it turns out to be better than the more conventional strategy.

This is of interest to glider pilots, but also to manufacturers of unmanned air vehicles which could save lots of energy by soaring, and nice simple rules like these allow them to soar without using up lots of energy calculating what to do next.

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