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Reflections on a Wandering Life.....
Saturday, January 02, 2021
Science Night - What is a Glider?
What is a glider? Why would you want to fly an airplane that had no engine? First of all, engines are heavy. They add a lot of weight and make the plane harder to fly (although the power provided by the engine compensates for this). Gliders don't need fuel. Of course, because there is no engine, you will have a towing fee. But I think a towing fee would be quite a bit less than fuel. Basically, it's a good way to develop flying skill by flying a vehicle that is very easy to maneuver.
So how did gliders develop into the sophisticated aircraft we see today? To answer that question, we need to go back to the Treaty of Versailles, which the Allied Powerthe s forced on Germany after World War I.
This treaty restricted Germany from developing powered aircraft. But gliders were not prohibited. The Germans took advantage of this loophole to develop very efficient gliders. That's why most of the high performance gliders that you see today are from Germany. They were developing them while everyone else basically saw gliders as a thing of the past. The common thinking was, "Now that we have airplanes with engines, why do we need gliders?"
The effect of this focus the Germans placed on the development of gliders between World War I and World War II is that we now have gliders that are so efficient that, not only do they come down much more slowly that previous heavier and less efficient gliders, but they are so light and so effiecient that they can actually fly even higher than they were when they were released from the two line, by searching for rising air currents. These new, highly efficient gliders that can rise higher by finding air currents are called "sailplanes."
There are two main types of rising air currents. Thermals are rising columns of air that are caused by different rates at which heat from the sun is absorbed by the land. Sailplane pilots can find these by looking for cumulus clouds. The "thermal," or rising air column is actually what produces the cumulus cloud.
The other type of rising air current is caused by wind blowing across the land, which hits a mountain ridge and is forced upward. The video below shows a pilot using this current of air along a mountain ridge to stay aloft for a long period of time. The goal of sailplane pilots is not to see how high they can go. It is to see how long they can stay aloft even though they do not have an engine. Because sometimes a sailplane pilot will get stuck a long distance from the airport and suddenly not be able to find a rising air current, some sailplanes have a small, battery powered engine with a collapsible propeller that pops out and helps the pilot gain some altitude so he has time to find another rising air current.