FreeFly Paragliding - How can we fly?

Free-flying is essentially gliding using un-powered, foot-launched aircraft. We fly using an aerofoil, a wing, which allows us to glide smoothly through the air, loosing altitude only gradually. We fly higher by gliding in air that's rising faster than we glide down. Once this skill has been mastered, pilots can stay in the air for hours and glide long distances to fly cross-country (XC).

With my paraglider, for example, I can fly with a 'glide ratio' of about 8:1. This means that if I take-off from a mountain that's 1km high, I can then glide out for 8km before having to land. This is a theoretical calculation based on flying in still air but the air is rarely still! Typically the sky is alive with invisible flows of air that behave like fountains, waterfalls, rivers and waves. It is these energy flows that we exploit to fly, in similar (but deficient) fashion to soaring birds like eagles, hawks, condors and vultures.

Soaring Condor - My Hero! :)

Pre-flight Preparation

A paraglider wing is made of high-performance, non-porous fabric and packs neatly into a rucksack when not in use. Before we launch, we unpack our wing, lay it out in preparation for flight, attach it to our harness and give it a full inspection to insure that everything is in perfect shape. We then organise any extra kit such as flying instruments (outlined below), flying suit, helmet, gloves and in-flight food and drink. Before, during and after set-up we will be monitoring the weather constantly to observe changes in weather patterns such as wind and thermal strength, especially during during lulls and gusts.

Pre-flight Preparation at Killiney, Co. Dublin

Take-off

There are two key stages to launching a paraglider; once secured in the harness and ready to go, we inflate the wing by pulling on the 'riser lines' to enable the air to fill the wing through the cell openings on the leading edge. This suddenly causes the wing to take shape and fly above our heads. Once we're confident that the wing is properly inflated and flying correctly and that the airspace ahead is clear, we take off. To do this, we lean forward and run (usually between two and ten steps) to get the wing up to 'flying speed' and then we lift-off.... Once in the air, we take a deep breath, sit back into our harness and enjoy the flight. We will generally seek out rising air to help us to soar high above the mountain and perhaps towards cloudbase. If there's no 'lift' to be found then we glide calmly towards the planned landing spot and take in the scenery as we fly.

Launching my tandem paraglider - Run, Run, Run!

Paragliding Flight Instruments

The most useful aid for human free-flight (excluding our wing) is called a variometer. As well as telling us our height as we fly this electronic gadget measures whether we are going up or down and exactly how fast we're doing so. Birds are highly sensitive to atmospheric pressure, and can tell when they are in rising or sinking air. Us mere humans can sense the acceleration when we first hit a thermal, but cannot detect the difference between constant rising air and constant sinking air, so we turn to technology to help. Our variometer will beep at a rate and tone to indicate the rate that we're going up or down. Being acutely aware of this enables us to be far more efficient while flying in thermal conditions; flying fast out of sinking air and turning slow tight circles to keep tight in the core of strong thermals - thus staying high and flying further.

Many pilots will also use maps, compasses and GPS to plan routes, plot out goal-points, measure flight distance, avoid restricted airspace and even calculate the ideal speed to fly for maximum glide and efficiency. We will often use VHF radios to communicate with each other and some fly with MP3 players for some in-flight entertainment!

As outlined above we maintain height and fly higher by gliding in air that's rising faster than we're gliding down. Here is a description of the basic sources of lift (Lift is the word we use for rising air that will give us a "lift" upwards) based on how the caused.

My Combined Variometer, Altimeter and GPS unit showing that I'm flying over the ground at 36km/h, at 810m above sea level and 60km distance from where I started the flight - sweet!

Types of Lift

Dynamic Lift is created by air that is forced up and over an obstacle as it moves across the earths' surface. Picture a big mountain along the coastline; when a breeze flows across the sea towards land it will literally bump into the mountain once it reaches the shore. As the wind can't blow through the mountain it must go over it. This mass movement of air over the mountain creates a massive band of rising air in front and above the mountain. We refer to flying in dynamic lift as 'ridge soaring'. If this breeze is constant and not too strong, we could stay up all-day just gliding along through the rising air mass. Dynamic Lift is quite easy to visualise; imagine the mountain to be a big rock on a river bed and picture the breeze as river flowing over it. The water will rise smoothly and steadily up and over the rock as it flows downstream (or downwind) but will go down the far side of the rock in a more violent, turbulent fashion creating swirling eddies that every fish would avoid. That's why we prefer to fly in front of mountains where we can find smooth rising air and avoid the lee (back) side where there is sinking, turbulent air.

Thermic Lift is created when the sun heats the earth, which in turn heats the air directly above it. As the air warms up it becomes relatively lighter (it expands and looses pressure) than the air around and above it. It eventually breaks off from the ground in the form of a rising bubble or column of air. This is a thermal and is the key cross-country free-flying. As free-fliers we seek out these thermals, fly into the middle of them and stay tight in their core as they take us high into the sky. On a good day the thermal will continue to rise until it reaches the point where it has cooled down so much that the moisture it had absorbed low-down now condenses and forms clouds. This is Cloudbase. My words could not do justice to the experience of reaching Cloudbase, kilometers above the Earth's surface, using only the innate, invisible energies of nature. From there we glide out in the direction we're going and try to find another thermal before our gentle glide causes us to seek a landing spot. This is XC (cross-country) flying and is really what it's all about!

Graphic illustration of thermic and dynamic (ridge) lift

Mountain waves: The third main type of lift used by glider pilots is the lee waves that occur near mountains. The obstruction to the airflow can generate standing waves with alternating areas of lift and sink. The top of each wave peak is often marked by lenticular (lens like) cloud formations. This type of lift tends to suit hang gliders and fixed-wing gliders better than paragliders because it tends to involve high winds that could cause smaller craft to fly backwards despite their best intentions!

Convergence: Another form of lift results from the convergence of air masses, as with a sea-breeze front. When two air masses of the same temperature collide and neither is willing to go back down, the only way to go is up. As the name implies, the two winds converge and rise together in an updraft that often leads to cloud formation, and is a good source of lift.

Click here to view some detail about the wings used by paragliders and hang gliders =>

Mountain Wave - lift marked by lenticular clouds