How Do Gliders Fly ?
Gliders fly because of the lift generated by the wings as they pass through the air.
In a powered aircraft the engine provides the force to propel the plane through the air. In a glider the force of gravity pulls the plane towards the surface of the earth and just like a paper aerolplane the glider moves forwards as it descends.
A glider is continually descending in the air it is flying through. Typically a glider will descend at 150 feet a minute, it varies from glider to glider. If however the air in which the glider is flying is moving upwards as it is in a thermal then this will affect the apparent descent rate of the glider. If the air ascends at 150 feet a minute then the glider will not descend at all and if the air rises faster than this then the glider will actually climb
How do you control the glider ?
The glider is controlled in exactly the same way that all aircraft are controlled. We have a control column which is connected to small moveable surfaces on the ends of the wings (the airlerons) and the rear of the tailplane (the elevator). Moving the control column changes the angle of these surfaces and deflects the air flowing over them, which in turn moves the wings to roll the glider or changes the attitude of the glider so that it points more up or down.
As long as the glider is moving forward through the air then moving the control surfaces will produce forces that enable the pilot to control the aircraft. Assuming the glider has enough height or can find sources of lift then the pilot can fly anywhere that a powered aircraft can fly and with the same degree of control.
The picture to the left shows the front cockpit of one of our training gliders, the control column is right in the middle with a grey shaft and a black handgrip.
How Does The Glider Get In The Air ?
There are several ways to get gliders airbourne but at Lee on Solent we only use Winching and Aerotow. Winching involves using a very long steel cable one end of which is attached to the glider and the other to a powerful winch positioned at the other end of the airfield. The winch winds the cable in and pulls the glider into the air. The glider climbs very steeply until it is nearly over the winch when the cable is released from the glider and it flies off. The cable is dropped by parachute and wound onto the winch drum ready to be towed out for the next launch. Winching is a very cheap way of launching gliders and despite the limited height obtained is very popular.
Aerotow involves towing the glider on a long rope behind a powered aircraft known as a tug. The takeoff and launch is a lot less dramatic than a winch launch and the tug pilot can tow the glider to pretty much any height and position. This means that on a thermic day the glider can be released actually in a thermal.
How Long Can You Stay Up ?
It depends on what source of lift you are using. Wind generated lift like Wave and Slope lift will be there all the time the wind blows so duration is really a question of how long you can stay awake.
Thermal activity is created by the warming effect of the sun so is limited to daylight hours. Every instructor will have had at least one flight of 5 hours duration in order to get his Silver badge but double this is possible in the right conditions. Pilots are usually travelling cross country when they stay up for such long periods.
One of our club members, managed a 750Km (470 Miles) flight from Lee and was airbborne for over 9 hours. Well done Keith Walton.
The photograph below is the view from 3,000 feet from one of our gliders over Titchfield. One a clear day, you can easily see across to the Isle of White, over towards Brighton and the surrounding areas. Most people are amazed at what you can see when you soaring in a glider.
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