Flytec-4005

The art of hang gliding

Although the poplular view is that hang gliding was invented in the early 70’s it was in fact invented by John Dickenson of Australia in 1963. However, on 23rd May 1971, the Otto Lilienthal Anniversary Hang Glider meet was held in Southern California. The event attracted enthusiasts from all over the area, about 50 pilots, and really caught the public‘s imagination. It is regarded by many as the starting point of hang gliding as we know it today and as shown here by DeltaGerard.

As an extreme sport, hang gliding has been affected by adverse publicity as, since its inception, it has been considered an unsafe sport. The inherent danger of gliding at the mercy of thermal and wind currents has resulted in numerous fatal accidents and serious injuries over the years – even to experienced pilots.

However, this is misleading in these more modern times. The accident rate from hang glider flying has been dramatically decreased by pilot training. Early hang glider pilots learned their sport through trial and error whereas nowadays, training programs have been developed for today’s pilot, with emphasis on flight within safe limits, as well as the discipline to cease flying when weather conditions are unfavourable, such as excess wind or risk cloud suck.

Which brings me to the essence of this article. How do you learn how to read the winds and thermals?

A glider is continuously descending through nearby air, yet glider pilots can stay airborne for hours by flying in areas of rising air. Once this skill has been mastered, pilots can glide long distances to fly cross country.

There are 4 main types of wind that a hang glider pilot will be looking for: thermals, ridge lift, mountain waves and convergence. Understanding the  presence of wind, the  lift and sink over various types of terrain, is of paramount importance for all pupils.

Wind direction,  wind velocity, terrain shape and obstructions are all obstacles that need to be taken into consideration when making a flight plan.

The most commonly used source of lift are the Thermals. Pilots quickly become aware of land features which can generate thermals and become familiar with visual indications of thermals such as soaring birds, cumulus clouds, cloud streets, dust devils, and haze domes.  Well formed cumulus clouds, with darker bases, suggest active thermals and light winds and in the case of a cloud street pilots learn that they can use a cloud street to fly long straight-line distances by remaining in the row of rising air.

Ridge lift occurs when the wind meets an obstruction such as a mountain, cliff or hill. The air is deflected up the windward face of the mountain, causing lift which gliders can use to gain height by flying along the feature.

The third main type of lift is mountain waves where the pilot uses the lee waves that occur near mountains. The obstruction to the airflow can generate standing waves with alternating areas of lift and sink.

Convergence is, of course, a form of lift which results from the convergence of air masses, such as a sea-breeze front.

It is also important to understand how different wind conditions at the site will affect each and every flight and for this reason it is necessary to lern how to read the windspeed in the air and on the ground. These differing conditions will affect the flight.

Understanding the effects of a crosswind on the ground track will ensure that a pilot will be able to ‘crab’ his glider towards his goal. He must also understand the implications of turning out of the wind and the  relationship between increased bank angle and increased sink rate of the glider.

There’s a lot to learn, but nearly every glider nowadays contains an instrument known as a variometer (a very sensitive vertical speed indicator). That comes back to what we were saying at the beginning of this article – modern technology has made the sport of hang gliding far more safe than it used to be…

A variometer indicates climb rate or sink rate with audio signals (beeps) and/or a visual display. These units are generally electronic, vary in sophistication, and often include an altimeter and an airspeed indicator. The main purpose of a variometer is in helping a pilot find and stay in the ‘core’ of a thermal to maximize height gain, and conversely indicating when he or she is in sinking air and needs to find rising air. Some electronic variometers make the calculations automatically, after allowing for factors such as the glider’s theoretical performance (glide ratio), altitude, hook in weight and wind direction.

File:Gleitschirmvario.jpg

As with all things, it is not enough to reply on an instrument. It is absolutely imperative that you, as the pilot, can ‘read’ the wind incase your variometer is faulty. All equipment must always be checked. Wear and tear happens to the best stuff – it’s not worth taking chances…

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