曝光台 注意防骗
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windscreen for a constant angle of
approach. The idea is to land with
rear wheels first on a nosewheel
aircraft, and all wheels together on a
taildragger.
Keep your hand on the throttle at all
times, because when you need
power, you will need it now.
Somewhere between 15-30 feet, you
should start the flare, or roundout, by
pulling the control column back,
having closed the throttle first. Keep
pulling back until the aircraft settles
onto the ground (when you should
actually start to flare is difficult to
describe, but my own preference is
when I seem to be going too fast).
When very close to the ground,
further backward movement of the
control column slows you down
rather than keeps your height, and
you would keep it back once a
tailwheel aircraft is on the ground.
You can relax the pressure with a
nosewheel machine, for weight on
the nosewheel to assist steering.
Crosswind landings are more
difficult than crosswind takeoffs,
because the controls are less
responsive (there is no airflow over
them from the powered prop).
There are two methods of
counteracting drift until the final
moments. One is to keep a wing
down into the wind direction (the
sideslip, below). The other, which
requires much practice, and is my
own choice, is to crab in, with the
18 JAR Private Pilot Studies
nose offset into wind, and with
wings level. Then the machine is
straightened with rudder at the point
of touchdown.
For a short field approach, leave the
power on until the landing flare is
completed – in other words, "drive"
it on to the ground. Get the flaps up
straight away. Before going in,
however, bear in mind that the
takeoff run will always be longer –
can you get out again?
Be prepared for quick deceleration
on soft or rough ground, and watch
for the nosewheel – keep the weight
off as long as possible. You might
want to do a low approach first for
inspection purposes, and to chase
the sheep off.
Slipping
To get down more quickly without
increasing the airspeed, you can use
slipping manoeuvre, which exists
when you bank, as if to turn, but
you actually keep straight with
rudder (this is the forward slip). The
sideslip is used when landing in a
crosswind, to keep straight down the
approach, and kick the machine
straight at the last minute.
Stalling
The stall is a condition where the
wings cannot support the aircraft in
the air (that is, lift is still being
produced, but it is not enough).
As mentioned before, the accepted
maximum angle of attack is about
15°. After that, the air flowing round
the aerofoil breaks up badly, making
it unable to create enough lift, as
well as creating large amounts of
drag. The speed at which an aircraft
stalls, however, varies according to
circumstance (remember that an
aircraft with a high stalling speed is
easier to stall).
For one thing, a thick wing will
produce a lower stalling speed than a
thin one, as will one with a larger
wing area against a smaller one. Also,
as air density decreases, the stalling
speed will increase until it reaches
the cruise speed and you won't get
any faster (although the indicated
airspeed remains the same).
Turning has a similar effect, too,
because you are artificially increasing
the wing loading – the steeper the
turn, the greater the increase in
stalling speed.
Because of the above variables, the
quoted stalling speed in the flight
manual is the "clean" speed, which
occurs in a straight and level glide at
maximum weight with no gear and
flaps down.
As an exercise, it's the point at which
the nose drops down when the
elevator is pulled all the way back to
the stops. Since you stall the aircraft
onto the ground every time you land,
practice gained here can only serve
to improve subsequent arrivals on
the runway.
To perform the exercise in straight
and level flight, do the HASELL
check, place the carb air into hot,
and reduce power to zero. Keep the
nose level with the horizon, and be
prepared for the controls to become
mushy and ineffective. Do not use
rudder, except very sparingly to keep
straight, or you might end up in a
spin, and you don't learn to get out
of those until the next lesson.
Allowing it to yaw is just as bad as
using too much rudder, so don't use
Principles of Flight 19
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