How do Gliders Fly?
fly using the same aerodynamic principles as any other aircraft. The gliders wings
create lift as they move through the air. The only thing that differentiates a
glider from a powered aircraft is that, whereas the powered craft uses its motor
to move it through the air, the glider uses that old standby, gravity. In still
air, a glider is always sinking and this is why glider pilots concentrate on finding
rising air commonly known as lift - to counteract the effects
of gravity and stay airborne for as long as possible.
Right now most gliders still depend on weather elements to be successful. However
there have been talks about o2 planning on launching a highly-advanced glider
that can fly even on harsh weather. The said stunt is set to be a publicity stunt
for their next line of mobile phone units billed
to be sturdier and more innovative than other phones in the market. If the rumors
proved to be true, then we might just witness the future of flight-by-gliding
a glider is not as difficult as you may suppose. The controls quite simple to
understand. As you sit in the glider, between your legs is a control column or
This is directly
connected to the flaps on the tail and the wings. At your feet you have two pedals
which are connected to the rudder. Let me explain the use of the stick first.
If you push the stick forward the glider will point down to the ground (as if
going down a rollercoaster). As with anything as you go down hill you pick up
speed. Now if you pull it back the glider will slow down, untill it flies too
slow and the glider falls out of the sky (don't panic its easy to restart them
flying again). If you move the stick from side to side the glider will bank to
the left or right. This will turn the glider, however the glider will tend to
try and fly sideways through the sky which is not very efficient!
solution to this is to bank the glider and use the rudder (controlled by your
feet) together. This is called co-ordinated turn and is one of the first things
you learn when flying a glider.
Most people are amazed that gliders
don't just sink to the ground. One reason is that they are amongst the most efficient
flying machines next to the birds. The efficiency of a glider is expressed by
the ratio of height and distance. For example, a glider with a glide angle of
1:30 when the glider is 1 mile high, means the glider can fly for 30 miles. However
in reality this can be much less becouse of sink (falling air).
a good flying day with plenty of lift (see below for and explanation) you can
easily fly between thermals and travel across the country. I've
set up a game to demonstrate this if you fancy a play. Please be aware the
game is addictive and you may end up playing for hours!!!
On a summer's day, you
can see birds circle upwards without flapping their wings. They are "thermalling".
A thermal is a volume of air that has been heated by the sun more than the surrounding
air - imagine if you were standing on some sunlit concrete, you would feel warm!
As you know, hot air rises and it is by circling within this air that allows birds
- and gliders - to go upwards. Next you may ask "so how do you know where
the thermals are?" Well, sometimes this is educated guess work, based on
how you imagine ground features below you are warming up. However, often cumulus
(cotton-wool type) clouds form at the top of the thermal, marking where the thermals
If you would like
to try this yourself play a game
of flight club!
you may be joined in the thermal by a bird - from a swift to an eagle. You can
never do it as well as they can, but it's great fun trying! Thermals are used
in cross-country flying - you climb in a thermal to gain the height to move forwards
to the next thermal on track (or thereabouts). The largest flight in the UK was
just over 1000 kilometres and took about 12 hours.
Another way of staying up requires
a hill (ridge), and the wind to blow against the face of it. Try to imagine this
scenario - when the wind hits the hill, it gets forced upwards. Again, it is this
upward movement of air that allows gliders to stay airborne. With a long ridge,
it's possible to do large distances without turning, generally flying fast and
low to stay in the best "lift" close to the ridge.
this dune running video
Similar to ridge lift
is a phenomenon called "wave lift". This is a little harder to imagine.
It arises from the wind blowing against a hill again, but this time the air comes
back down (on the far side of the hill) and "bounces" off the ground
and goes back up again creating a very smooth upwards flow of air. Often, this
form of lift is capped by a cigar shaped "lenticular" cloud.
wave may go back down and up again for several cycles, meaning that you don't
actually have to be close to any hills to use it! The furthest flights in gliders
have been done using this lift - the best being 3008 kilometres (1880 miles) which
was done along the Andes, all in one flight and one day. Wave lift is also known
to go very high - the world height record in a glider is just a little short of
the wave flying video (sorry this is quite large)
Now we come to landing.
As you have learnt gliders can stay in the air for a long time and travel great
distances. However some people are a little paranoid about getting back to the
instructor will be a highly experienced glider pilot with hours and hours of flying
time. In his flying career he will have made many, many take offs and landing.
During your flight he will not fly further away from the airfild than he could
glide back without finding any lift. However suppose he was to fly accross country
and find him or herself out of flying distance of an airfield. No problem....
glider piolts are some of the most highly skilled pilots and as part of their
training is the ability to land in fields. The only problem then is to persuade
other members of the club to retrieve you and the glider!
good page on how gliders fly
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