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What are the aerodynamics of a glider?
Like most airplanes, gliders use ailerons, a rudder, and an elevator to fly. Flaps are fitted on gliders to control descent rates by producing drag and increasing lift. Many modern gliders also use airbrakes or spoilers which, when used, drastically disrupt airflow over the wing, increasing drag and reducing lift.
How does air move over a wing?
A wing is shaped and tilted so the air moving over it moves faster than the air moving under it. As air speeds up, its pressure goes down. So the faster-moving air above exerts less pressure on the wing than the slower-moving air below. The result is an upward push on the wing—lift!
How does a hang glider descend in the air?
Meanwhile, the downward and forward motion of the wing compresses the air flowing under the wing. The aerofoil is then drawn up into the area of low pressure, producing lift. If the air is still, it will slowly descend. A hang-glider descends at the rate of about 1 metre per second (a slow walking pace of about 3.6 km/h).
What happens to static pressure on a glider?
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.
How is the performance of a glider measured?
Angling the glider downward, trading altitude for speed, allows the glider to fly fast enough to generate the lift needed to support its weight. The way you measure the performance of a glider is by its glide ratio.
What makes a hang glider drop like a stone?
The aerofoil shape of the wing stops the hang-glider from dropping like a stone. It produces lift. The aerofoil forces the air flowing over the top of the wing to travel faster, thereby ‘stretching’ it to produce a low-pressure area. Meanwhile, the downward and forward motion of the wing compresses the air flowing under the wing.