曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
going that way before correcting it,
then you will be almost pushing it
into place. Put simply, don’t pull the
load the way you don’t want it to go.
You can do the same with a fore and
aft swing, but watch out! Very often,
a load can suddenly produce more
drag, if something breaks off, for
instance, which puts the nose down,
which you correct with aft cyclic that
simply puts the tail rotor nearer the
line. If the load starts forward again
(as it will), and pulls the nose further
up for you, correcting with forward
cyclic may set you nicely up for mast
bumping, or at the very least leave
you hanging with the stick right
back. The correct thing to do here is
to apply collective, which will also
add an upward force (assuming the
clouds aren’t too low). Using a
longer line will help. Tail rotor
pedals can also be used – when the
ball is out to one side, use the
opposite pedal when it starts to
come back (not before). It is always
a good practice not to rush the
takeoff and to lift without a swing in
the first place.
Scaffolding and planking can swing
violently with only a few knots
change in airspeed, and aerofoil
shapes could even generate their
own flying characteristics. Bulky
loads with a tendency to float, such
as empty containers, will benefit
from leaving doors or panels open,
which will reduce drag and keep the
load facing in one direction.
Setting Down
Approach into wind as much as
possible, coming into the hover high
enough not to drag the load, so you
might be slightly steeper than
normal. You’re best to undershoot
rather than overshoot, as it’s easier
to creep up to a target than go round
again if you miss it. To preclude an
airflow change making the load
unstable, slow down before
descending. If the load hits the
ground, stop moving forward.
Because of inertia, all manoeuvres
should be anticipated well in advance
and made smoothly (not suddenly)
with reference to the speed of the load over
the ground. In a confined area, the
load will tend to pull you down as
the wind effect is lost, so a couple of
knots in hand under these
circumstances may be desirable.
Keep a constant scan going, because
you need all the information you can
get, especially when it comes to
depth perception. If everything goes
pear-shaped, it’s because your scan
has stopped, as it might if you get
fixated suddenly tense up on the
Specialised Tasks 31
controls. Relax and start looking
around again, it will soon get better.
Once in the hover, you again come
under the guidance of a marshaller,
who signals descent until the load
touches the ground and the cables
become slack (if you haven’t got a
marshaller, you can judge your
height from whether the ground
crew are looking up or down).
Release the cables after moving to
one side so they do not foul the load
or hit someone on the head. Don’t
drop cables from anything more
than normal hover height, and
especially not under too much
tension, or you’ll get somebody in
the eye (also, whatever is in the hook
shoots downward at a fast rate, and
the hook itself will be opened
violently and may be damaged). A
manual release is provided if the
electrical one doesn't operate, and,
once it has done so, you should see a
"load released" signal from the
marshaller, whereupon you hover by
the side of the load while the
replacement sling is placed inside the
cabin, having moved away vertically first.
Behave at all times as if the load has
not been released.
If you can’t hover, keep max power
in and let the aircraft settle, without
overtorquing – you will only be
pulled down as far as it takes for the
load to reach the ground, so just try
and give it a gentle arrival. If you are
delivering the load by yourself, land
behind it, as far back as possible so
you don’t get the sling under the
skid, and to provide a little tension
for the hook mechanism to work.
There is a phenomenon called
Collective Bounce that occurs when a
sudden vertical force is placed on the
helicopter, making you think the
load has reached the ground.
Although really relevant to larger
machines, it can occur on smaller
ones as well, and arises when the
resonance of the blades matches that
of a vibrating rope. The collective
movements to correct this get out of
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
The Helicopter Pilot’s Handbook(20)
