曝光台 注意防骗
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dampen oscillation by reducing your
airspeed to at least 10% below this
critical one, going slower if necessary
while increasing power. Turning
could provide enough centrifugal
force to stop it as well, which is also
the usual remedy when the load
starts to swing, but this will increase
its effective weight, possibly to more
than your lifting capabilities (a good
reason for not being too tight on
payload), so applying centrifugal
force in these cases could make
things worse.
Load swing is proportional to speed
and length of the sling – the faster
you go, the more it occurs because
of the load’s own lift and drag. As it
takes as long to swing through 15
degrees as it does through 45, like
any pendulum, if you move the
opposite way, as is natural, you just
make the load swing faster. Going
with the swing, that is, load to the
left, helicopter to the left, will stop it
quickest, after coming to a hover.
This has the effect of moving the
fulcrum point from under the
helicopter to over the load, which
removes the directional vector.
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,
pulling the nose further up,
correcting with forward cyclic may
set you nicely up for mast bumping.
The correct thing to do here is to
apply collective, which will also add
an upward force. Using a longer line
will help as well. 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).
Flight Operations 373
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
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 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 work 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 in the cabin, having moved
away vertically first. Behave at all times
as if the load has not been released.
If you can’t hover, just keep max
power in and let the aircraft settle by
itself, without overtorquing – you
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Canadian Professional Pilot Studies2(107)
