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A Short Introduction to the Sport of Gliding
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Modern gliding is all about the joy of flying an engine-less aeroplane in gliding flight,
and successfully using the natural energy in the atmosphere to fly higher, further, faster
or longer.
Flights across country of many hundreds of kilometres are possible in the right soaring
conditions in Great Britain. (Over 1000 km has been achieved in this country!) Today’s
gliders, or sailplanes as they are more properly called, frequently fly distances of
more than 300 kilometres at average speeds of over 80 kilometres per hour. These flights
are usually around pre-planned routes, returning to their own airfield. In the middle of
summer, when the days are longer and the sun is more powerful, the longest flights are
flown; sometimes lasting all day from, perhaps, a launch at before ten o’clock in the
morning to a landing after eight o’clock in the evening. In the spring and autumn,
mountain lee wave conditions allow soaring flights to great heights. Altitudes achieved
are relative to the size of mountains and, since the highest mountains we have are in
Scotland and Wales, the highest climbs are gained there, sometimes to over 30,000 feet.
The world gain of altitude record of 46,266 feet, was achieved in America.
All of this is possible because of the superb performance provided by modern gliders,
which are constructed of space age, composite materials using the latest ergonomic,
safety and aerodynamic design with aeronautical technology. These sailplanes can fly
up to 60 miles from 1 mile (5,280 feet) high, in still air!
Air is, however, rarely still. We are all aware that air moves horizontally along the
ground, the movement we call wind; but the air often has a vertical component, it moves
up and down, or rises and sinks. If a glider pilot uses his skill to fly in rising air
and to avoid sinking air then, although a glider is always descending in the air in which
it is flying, if the air is rising faster than the descent rate of the glider, the
glider will climb relative to the ground. The skill of the glider pilot is, therefore,
to pilot his aircraft accurately and to assess the conditions ahead by reading the sky,
the clouds and the terrain, and then to select the best areas in which to gain a climb.
Sometimes that will be a circling climb in a single thermal, or column of rising air,
and sometimes the pilot will just reduce speed to linger in some rising air before
speeding up again to flash through air that is sinking.
Rising air, which is generally a little known phenomenon of the weather, is therefore very
important to the soaring pilot. It is formed in three ways.
Ridge Lift. The first type of lift used by glider pilots was ridge lift. Ridge lift occurs
when a wind blows up a slope, or ridge. The wind cannot blow through the ridge so it is
forced over it. You may have seen seagulls, scarcely moving their wings, soaring in the wind
as it blows up a steep beach. The vertical component of the wind, if it is more than about
150 feet per minute, will allow a glider to climb, perhaps more than three times the height
of the ridge in strong winds. The Wright brothers, pioneers of powered flight, practised like
seagulls, soaring their prototypes in ridge lift, on the sand dunes at Kittyhawk, before
their epoch-making first powered flight, in 1903.
Thermal Lift. Thermals are masses of warm air, which because they are less dense than surrounding,
cooler air, rise buoyantly. The warm air has been created by contact with a sun-warmed surface
on the ground. A thermal will continue to rise until, due to cooling caused by its expansion
as it rose, with increasing height into reducing air pressure, it is no longer warmer than the
surrounding air. Thermals were first discovered by glider pilots who, whilst flying on a ridge,
noticed that when puffy cumulus clouds came by they found rising air underneath. Of course,
the cumulus cloud had been formed when the thermal, which had contained a certain amount of
invisible water vapour, cooled to a temperature where the vapour condensed to form a cloud.
Nowadays, glider pilots actively seek the rising air they expect to find under puffy, white
clouds. Thermals in clear air rarely go much higher than 6-7,000 feet in Britain, indeed,
a 4,000 foot cloud base could be considered quite good!
Wave Lift. Waves, or vertical oscillations in horizontal airflows, occur whenever the wind
blows. Much of the time they are of little use to glider pilots because the lift associated
with them is weak. Mountain lee waves, however, if the wind is strong enough, often give
lift that can carry gliders to very great heights. Remember the height record of over 46,000
feet!
Waves are caused when a wind blows over an obstruction and, having passed over it, descend on
the other (lee) side. Then, changes in temperature and pressure occur, caused by changes in
height, and the air mass starts to “bounce”, or oscillate. Very much like, in a shallow stream
or brook, the water that continues to ripple downstream of a rock it has passed over. The
altitude that lee waves go to depend on a number of factors, but strong winds and high mountains
are generally required for the best soaring conditions. Equinoctial winds over the mountains in
Scotland and Wales provide mountain lee wave and flights to tens of thousands of feet. The
British record is over 38,000 feet and then the pilot aborted the climb because his oxygen
equipment did not include a pressure suit, which was required in order to go higher. Oxygen
is recommended above 12,000 feet.
Vintage Gliders. Some people enjoy making model aircraft. Many of the older, vintage, gliders
were made of wood and fabric and if viewed through the wrong end of a telescope would look just
like models made on the kitchen table at home. Enthusiasts of Vintage gliding still make and
repair gliders to the original design, but with improved materials and a better knowledge of
construction techniques. Rallies are held internationally which attract old gliders from all
over the world.
Glider Aerobatics. Aerobatics in gliders are an expression of grace and precision in flight,
an aerial ballet that brings pleasure to pilot and spectator alike. A high level of skill is
required for even basic manoeuvres like “looping the loop”; and striving to perform advanced
rolling and inverted manoeuvres require regular practice since they are mentally and
physically taxing. The development of modern unlimited aerobatic gliders, with their high
reserves of structural strength, has made serious aerobatics in gliders possible. Regular
aerobatic competitions are held in the UK for those interested.
Learning to Glide. Gliding is not difficult to learn and most people take 60 - 100 flights
before going solo. If you learned how to drive a car quickly then you will probably learn
to fly quickly. If you were slower to learn then it will take longer. Many young pilots
go solo on their 16th birthday, before they are even old enough to hold a driving licence.
They will have had lots of practice flying with instructors and quite possibly will have
been capable of flying solo long before they are sixteen. Once solo the pilot is not abandoned
to their own devices but is supervised and guided so as to make progress in a safe, structured
way. Sometimes this will mean that they will be prevented from flying solo if the instructor in charge judges conditions to be too difficult for their level of competence. During this early period of their post solo flying they will gradually gain experience in more challenging conditions and will be expected to display higher levels of flying skill and knowledge of rules of the air, weather, navigation and the principles of flight will be acquired.
Most of today’s finest glider pilots started gliding whilst too young to fly solo. The younger
you start, within reason, the faster you learn and will have the highest likelihood of becoming
a pilot able to win competitions. Could you be a member of the British Team squad flying for
your country, or perhaps, a future champion of the world?
The British Gliding Association. The authority controlling all aspects of the sport of
gliding in this country is the British Gliding Association (B.G.A.), whose authority is
devolved from the Civil Aviation Authority (C.A.A.). There are some 100 B.G.A. affiliated
clubs in the UK with a combined membership of about 9000 members. There are about 2,500
solo gliders and about 500 dual training gliders in the U.K. which fly over 100,000 launches
each year.
All Faulkes Flying Foundation instructors are qualified and approved by the B.G.A.
Mike Woollard & Clive Thomas
January 2001
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