Gliders: what are they?


Gliders are aircraft without engines, also known as sailplanes. Most are single-seaters but two-seaters are also used for fun flying with friends and obviously for training. While you are training, you will fly in two-seaters until you are competent enough to fly solo. Two-seat gliders have the same controls and instruments, in both front and back seats, to allow the instructor to demonstrate what is required.
Gliders are built to international standards and are generally stronger than similar sized powered aircraft. In the early days they were usually built from wood, some from metal, but for the past 40 years virtually all of them have been made from glass fibre composites and many now use carbon fibre composites. They are subject to inspection every day they fly and are taken off-line every year for maintenance and inspection. As a result they last for many years, with a few older than 75 years still flying.
Most gliders are designed to be good cross-country aircraft, but some, particularly two seaters, are designed for specific purposes, such as basic training or aerobatics. Most gliders can do a little of everything.
Occasionally, gliders do have engines (although purists argue they are no longer gliders!). These come in two varieties; self-launching or self-sustaining. Self-launchers can launch themselves without any other assistance. Self-sustainers, commonly known as ‘Turbos’, however, are used only to stay airborne if for example if you can't get home on a long cross-country flight.



Soaring: Using air currents to stay airborne.


Staying Up: How does a glider stay airborne? It is always descending through the air it is flying through, in the same way, if it is to keep moving, that a toboggan moves downhill. So to stay aloft, gliders must find air that is rising at least as fast as the glider is descending. There are three main ways in which this can be achieved.



Ridge lift: The club moved here in 1956 and acquired another way of staying aloft. The Cotswold Edge which forms the north-facing hill immediately adjacent to our airfield and the west-facing ridge about a mile to the west. When the wind blows towards those ridges it is forced up and the air ahead of and above the hill provides the rising air required to support gliders. In the early days only the local ridges were used, but as glider performance has improved, given the right wind conditions, we can now soar the ridges south to Bath Racecourse and north to within a few miles of Stratford upon Avon. Even if conditions aren’t right for such long flights, soaring the local ridges is still fun and particularly helpful for pilot training.


Thermals: You may have seen birds circling upwards without flapping. They are "thermalling". A thermal is a volume of air that has been heated by the sun more than the surrounding air, perhaps because the ground under it was drier or darker than that surrounding. As this hot air rises it forms a thermal and by circling within this air, birds or gliders can gain height. Having gained height this can then be used to fly off and hence travel across country. Glider pilots find more thermals to travel great distances by either educated guesswork, based on ground features, or more often by flying to cumulus clouds that form at the top of the thermal. Flights of over 300km are routinely made throughout the summer from this airfield and a few flights of over 750km have been made using thermals.



Wave lift: Harder to explain or imagine than thermal or ridge lift, the phenomenon known in gliding circles simply as "wave", more accurately known as “Orographic Lee Wave”, arises when wind blowing over hills rebounds in the lee of the hills and goes back up again, creating a smooth upward flow of air. This lift is sometimes capped by a cigar-shaped "lenticular" cloud that does not drift with the wind. This wave or oscillation often continues for several cycles downwind, sometimes many cycles downwind, meaning that you don’t necessarily have to be close to hills to use it. The chief attraction of wave lift for glider pilots is the opportunity to go very high – over 20,000ft has been achieved flying from the airfield here at Nympsfield, well above the level where oxygen supply for the pilot is essential.


Training: Learning to glide


Who can learn to glide?: Virtually anyone! No previous flying experience of any sort is required and our membership includes those from the most humble to most sophisticated of professions and from every sort of background. It is necessary to be fit enough to drive and gliders are limited in the size and weight of pilots they can carry. Being exceptionally tall or much over 100kg in weight can be difficult. There are no age limits to taking instruction although the very young are at somewhat of a disadvantage if they cannot reach the controls.

There are no age limits to taking instruction although the very young are at somewhat of a disadvantage if they cannot reach the controls. Ideally they can start to learn when over 13 years of age as once trained can now go solo at 14. Sadly, whilst we give free instruction flying is not free, so some money will be required. However, the most demanding requirement is time. Gliding is time consuming and given the vagaries of our weather fair amounts of patience and persistence are required.

How do we learn to glide? All instruction is given by qualified instructors in club-owned two-seater gliders, one of which is illustrated here as it approaches to land.
Training is progressive; starting with learning what the controls do, then how to use them to control speed and then turn the glider. More and progressively more difficult exercises are introduced and, as progress is made, as well as learning to take off and land, responsibility for decisions is slowly transferred from the instructor to the pupil. It is necessary to learn some theory, but most of what is required can be picked up as you go along, although if you choose to read up as you progress it will speed up your training.
When the instructor decides the time is right, a first solo flight will be made. This is a landmark event, but marks the beginning of a new phase of training as much as an end to the old. Further training in soaring, navigation and how to select and land in fields will be required before a pilot is qualified and this will be fitted around more, longer and higher solo flights.

How long will it take to learn to glide? This is a difficult question to answer. Unfortunately the older we get the slower we learn, so if we start late in life it will inevitably take longer and of course everyone has a different aptitude. We can do little about these matters, however, we can reduce the time and amount of flying required to train by ensuring that we fly regularly. If, as is often the case we are learning in free time at the weekends then it is best to try and fly every weekend that weather permits. It has been suggested that to get to the solo stage a pupil will take 20 flights plus one for every year of their age. This gives the right idea, but is a very, very rough estimate.