Paragliding Principles

How Paraglider Flies

As we know that a paraglider wing when inflated creates an aerofoil shape, and the performance of a wing in terms of flying speeds and glide ratio depends on this shape. The paraglider wing is spread on a flat surface of a mountain perpendicular to the wind and after a through check for tangles in the lines, is connected to the harness by the pilot. A pilot while moving into the wind for takeoff, pulls the ‘A’ risers attached to the leading edge. The wind coming head on enters the cells of the wing.

The air entering inside builds up internal pressure, till it takes more or less aerodynamic shape. The amount of pressure builds up in the wing depends upon the speed of the canopy and the orientation of the cell openings to the direction and strength of the flow. Air enters through the cells move backwards & then to the sides inflating the tips which do not have cell openings. The uniform pressure in the wing is maintained because of crossports or intracellular vents. The reason to keep trailing edge and tips closed is to help the wing in building internal pressure. Without internal pressure the wing cannot take its intended shape.

When the wing is inflated and overhead, or while flying the air meets the leading edge and is separated into two flows. Due to its aerofoil shape (which is less curved at the bottom and more curved on the top) the lower separated air flow moves its course straight and the flow from the top have to travel longer distance. The air molecules separated at the leading edge has to meet at the trailing edge same time. Due to this, the molecules traveling from the top moves faster to cover up the distance. A lower pressure is created on the top and higher pressure at the bottom.

By Bernoulli’s law of physics, accelerated air reduces pressure the air exerts on a surface and we know that anything moves from higher pressure to lower pressure. This difference in pressure on the wing, lift is created. More speed of the wing more the lift. But at the same time other forces such as gravity opposite to lift and drag due to the surface area of the wing, lines & pilot are reducing/ slowing down the speed as well as lift.

The aerodynamic forces acting on a wing results to fly in a down ward sloping direction. We can gain altitude only if the rate of upcoming air is more than the decent rate of wing.

Greater lift & less drag can be achieved for improving performance by modifications in the design of Paraglider. Wings with larger span and smaller chords have better performance but are more susceptible to collapses and require active piloting skills to control. In other words improving the performance level of a wing reduces the safety margin for the pilot. Highly experienced pilots with proper theory and practical knowledge should only try their hands on high performance wings.

Angle of Attack: it is the angle between chord line of a wing & the relative wind (which is exactly opposite to the flight direction). Angle of attack during flying a paraglider is between 3 to 12 degrees. Below 0 degree a negative lift is produced and above 15 degrees or so a stall occurs.
Glide Ratio: it is the ratio calculated by dividing the horizontal distance traveled to the height loss.
Glide ratio: horizontal distance traveled/ Height