曝光臺 注意防騙 網曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費者

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
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
194 Canadian Professional Pilot Studies
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
aileron, either, because yaw is a
secondary effect of roll. In addition,
aileron drag will only make the
situation worse.
Keep pulling the elevator back, in
attempt to maintain height. About 5-
10 kts before the proper stall, you
might hear the stall warning going (if
you've got one), or feel a little
buffeting in the controls. This is the
Airframes, Engines & Systems 195
aircraft protesting that it can't stay
up in the air, and that it is reaching
the critical angle of attack –
turbulent air is hitting the elevator
and other controls.
At the stall, the nose will pitch
down, usually just after the elevator
reaches its full limit of travel
backwards. The dropping could be
relatively mild, or quite severe,
depending on the design of the
aircraft (sometimes, you don't even
　
中國航空網 m.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：Canadian Professional Pilot Studies1(129)