So how do they stay airborne? There are 3 main types of rising air that glider pilots use:. Air near the ground expands and rises as the surface of the Earth is heated. Certain types of terrain absorb the sun more rapidly than others, like: asphalt parking lots, dark fields, rocky terrain, etc. These spots absorb heat, and heat the air above them, producing thermal air currents. Newly forming cumulus clouds, or birds soaring without flapping their wings, are typically signs of thermal activity.
When a glider pilot is "thermalling," they are finding and riding those thermal columns. And since the thermals can often cover only a small area, thermalling often involves a tight turn to stay inside the pocket of rising air. Along the windward side of the mountain, a band of lift is formed where air is redirected upward by the terrain. Typically, ridge lift extends only a few hundred feet higher than the terrain which produces it. Pilots have been known to go "ridge soaring" for thousands of miles along mountain chains.
However, wave lift is created on the leeward downwind side of the peaks by winds passing over top of the mountain. Wave lift can be identified by lenticular cloud formations - they look like flying saucers. The vertical speed indicator in your cockpit will tell you if you're climbing or descending. If you're flying a glider and suddenly see the vertical speed indicator jump up, you've probably hit a thermal column and should try to stay inside of the rising air for as long as possible.
A string on the windshield indicates to a glider pilot whether or not the glider is flying straight the string is straight or if it is yawing the string is to the right or left. In general, glider pilots try to keep the string straight since the least drag is produced when flying straight through the air. Some gliders carry ballast tanks filled with water. Heavier gliders sink faster than lighter gliders. Glide ratio isn't affected by weight because while a heavier glider may sink faster, it will do so at a higher speed.
The glider comes down faster with more weight, covering the same amount of distance; this is ideal for cross-country flying. A heavier glider, full of ballast, has a reduced climb rate and shorter flight endurance while in a lifting environment. Water ballast can be jettisoned at any time through dump valves to minimize these flight characteristics, and to slow down before landing. Compared to landing in a powered airplane, there are a few key differences when flying a glider.
First, gliders cannot add power if they won't make the touchdown zone. It may seem like a simple concept, but glider pilots are trained to judge their approach so they don't land short, and always wait until they're confident that they have the field made before introducing drag through flaps or spoilers.
The landing itself isn't too different from that in any airplane, you flare until lift reduces, and try to touch down lightly. Since gliders have one wheel, it's a bit of a balancing act to keep the wings off the ground as long as possible.
Gliders are incredible aircraft, and with the right atmospheric conditions, can stay aloft for hours or days at a time. The careful aerodynamic design that goes into building one makes these birds swift and unique.
And if you've never had the chance to fly a glider, we'd recommend you give it a try it. Become a better pilot. Pilots keep an eye out for terrain that absorbs the morning sun more rapidly than surrounding areas. These areas, such as asphalt parking lots, dark plowed fields and rocky terrain, are a great way to find thermal columns.
Pilots also keep a look out for newly forming cumulus clouds, or even large birds soaring without flapping their wings, which can also be signs of thermal activity. Once a thermal is located, pilots will turn back and circle within the column until they reach their desired altitude at which time they will exit and resume their flight. To prevent confusion, gliders all circle in the same direction within thermals.
The first glider in the thermal gets to decide the direction -- all the other gliders that join the thermal must circle in that direction. Ridge lift is created by winds blowing against mountains, hills or other ridges.
As the air reaches the mountain, it is redirected upward and forms a band of lift along the windward side of the slope. Ridge lift typically reaches no higher than a few hundred feet higher than the terrain that creates it.
What ridge lift lacks in height however, it makes up for in length; gliders have been known to fly for a thousand miles along mountain chains using mostly ridge lift and wave lift.
Wave lift is similar to ridge lift in that it is created when wind meets a mountain. Wave lift, however, is created on the leeward side of the peak by winds passing over the mountain instead of up one side.
Wave lift can be identified by the unique cloud formations produced. Wave lift can reach thousands of feet high and gliders can reach altitudes of more than 35, feet. Columns and bands of rising air obviously benefit any glider pilot, but how can you tell if you are flying in one? The answer is the variometer , a device that measures the rate of climb or descent.
The variometer uses static pressure to detect changes in altitude. If the glider is rising, then the static pressure drops because air pressure decreases the higher you go.
If the glider is sinking, then the static pressure rises. The needle on the variometer indicates the rate of change in altitude based on the rate of change of static pressure. When flying through a rising mass of air like a thermal , the needle on the variometer will jump and usually beep to notify the pilot before any change on the altimeter is even noticeable.
The glider is yawing when it is not pointing exactly in the direction it is flying relative to the air around it. Instead the glider is angled sideways and is "slipping" or "skidding" through the air.
The powered aircraft has an engine that generates thrust , while the glider has no thrust. In order for a glider to fly, it must generate lift to oppose its weight. To generate lift, a glider must move through the air. The motion of a glider through the air also generates drag. In a powered aircraft, the thrust from the engine opposes drag, but a glider has no engine to generate thrust. With the drag unopposed , a glider quickly slows down until it can no longer generate enough lift to oppose the weight, and it then falls to earth.
For paper airplanes and balsa gliders, the aircraft is given an initial velocity by throwing the aircraft. Some larger balsa gliders employ a catapult made from rubber bands and a tow line to provide velocity and some initial altitude. Hang-glider pilots often run and jump off the side of a hill or cliff to get going. Some hang-gliders and most sailplanes are towed aloft by a powered aircraft and then cut loose to begin the glide. The powered aircraft that pulls the glider aloft gives the glider a certain amount of potential energy.
The glider can trade the potential energy difference from a higher altitude to a lower altitude to produce kinetic energy, which means velocity.
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