GREAT PLANES FLING Buku Petunjuk - Halaman 13

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circling (especially in a contest where every second counts). Fly

straight ahead until you feel like you are in the strongest lift, fly

a couple of seconds farther (so your circle will be centered in

the strongest lift) and then start circling in a fairly tight but

smooth turn. When the sailplane is low the turns have to be

tighter to stay in the strongest lift. As the plane gains altitude, the

turns can be larger and flatter. The flatter the turn, the more

efficient the plane is flying, but don't be afraid to really "crank" it

into a steep bank when you are low. If you see the plane falling

off on one side of the turn, move your circle over into the stronger

lift. Thermals move along with the wind so as you circle you will

be swept along with it. Be careful when thermaling, that you don't

get so far downwind you can't make it back to the field to land.

If the sailplane is flying along straight and all of a sudden

turns, let the plane continue to bank (you may have to give

it some rudder to keep it banking) until it has turned 270°

(3/4 of a full circle). Straighten out the bank and fly into

whatever turned the plane. If you encounter lift, and you

won't every time, start circling just as you did when flying

directly into a thermal.

Thermals are generated all day long, but the strongest

thermals are produced when the sun is directly overhead.

10:00 am – 2:00 pm seems to be the best time to get those

"killer" thermals. Some of these thermals can be very large

and you may find it hard to get out of them. If you find

yourself getting too high, don't dive the plane to get out of

the lift. Sailplanes are very efficient aircraft and they will

build up a lot of speed and could "blow up" in the rough air

of a thermal. The easiest way to lose altitude is to apply full

rudder and full up elevator. This will put the plane into a tight

spin that will not over stress the airframe but it will enable it

to lose altitude very quickly. This is especially helpful if the

sailplane gets sucked into a cloud or it gets too high to see.

The twirling action will give the sun a better chance of

flashing off of the wing and catching your attention. When

you are high enough and want to leave the thermal, add a

little down trim to pick up some speed and fly 90 degrees to

the direction of the wind. If you are not real high and want to

find another thermal, you may want to look upwind of the

last thermal. The same source that generated this thermal is

probably producing another. Just watch out for "sink" which

is often found behind and between thermals.

As you might expect, with all this air rising, there is also air

sinking. This air is the sailplane pilot's nightmare that can

really make soaring challenging. "Sink" is usually not as

strong as the thermals in the same area, but it can be very

strong. Down drafts of many hundreds of feet per minute are

common on a good soaring day. These down drafts can

make a sailplane look like it is falling out of the air. Because

of this, it is important that you do not let the sailplane get too

far downwind.

When encountering sink, immediately turn and fly 90

degrees to the direction of the wind (towards you if

possible). Apply a little "down elevator" and pick up some

speed to get out of the sink as fast as possible. Every

second you stay in the sink is precious altitude lost.

Slope Soaring

Slope soaring is a type of flying that is very popular in hilly

regions and along the coasts. This type of soaring is

possible when the wind is blowing directly up a hill or cliff. As

the wind hits the slope it is forced up, producing lift which

can be utilized by real sailplanes, hang gliders, birds and

even model sailplanes. To be able to slope soar, you need a

slope with a smooth piece of land (or water) out in front of it

and a breeze blowing pretty close to straight up the slope.

The higher and steeper the hill or cliff the better. Also the

larger and smoother the land out in front the better. The air

flowing along hits the hill, is forced up and can generate a

very large area of lift. Behind the hill is a large area of

turbulent air that can be very dangerous to try to fly in. The

faster the wind is blowing, the stronger the lift and

turbulence will be. To fly off a slope, stand near the edge and

throw the sailplane (nose down) into the wind. As the

sailplane flies out into the "band" of lift it will begin to gain

altitude. Turn and fly parallel to the slope and make all of

your turns into the wind (especially when you are close to

the slope). You will be surprised at the altitude you can gain

just from slope lift. Thermals will often be "popped loose" by

these slopes. If you catch a thermal and follow it downwind,

be very careful to stay high enough to make it back to the

slope without flying through the turbulent air behind the

slope. If you don't have enough altitude you may want to

land a good distance behind the slope if possible to avoid

this turbulent air.

Slope Landings

Landings can be very tricky on some slopes. On gentle slopes

you can often fly very close to the top of the slope and "slide"

into the top of the slope without encountering any turbulent air.

On steeper slopes you may have to be a little more aggressive

to get the plane out of the lift. In any case it is a good idea to plan

your landing before launching your plane.

Have a ball! Remember to always stay in control and fly

in a safe manner.

GOOD LUCK AND GREAT FLYING!

Make a copy of this identification tag and put it on or

inside your model.