曝光台 注意防骗
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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
188 Operational Flying
resonance of the blades matches that
of a vibrating rope. The collective
movements to correct this get out of
phase, due to the response lag, and
the answer is simply to stop moving
the collective or go into
autorotation, as the machine will
self-destruct about the fifth bounce.
A little extra friction will help.
If a load starts spinning in flight, and
continues in the hover (or your
downwash sets it going), gently put it
on the ground and pick it up again.
If you have to hold a load while it is
being secured to something else, take
care to ensure that ground crews
don’t get themselves into positions
that could be dangerous if you have
to release it - be conservative with
allowable side winds.
It's a good idea, particularly with a
long line (see below) to unhook if
you shutdown, as it is very easy to
take off and forget it is there.
Vertical Reference (Longlining)
Longlining is slinging with a line
over 75 feet long. To do this
successfully, you have to maybe look
downwards out of the door or a
bubble window, and not through the
front with a mirror, which is the
more traditional method, hence its
alternative name of Vertical Reference
(having said that, in some machines,
notably the Astar, it's quite difficult
to look out of the door, and the
weather often means you need the
doors on, so using mirrors is
sometimes the only way). The long
line has a hook at the end, which is
inside a metal brush cage, to both
protect it and provide weight when
you are flying around with only the
line attached. As the extended hook
needs an electrical supply, there will
be an extra cable to control it, taped
to the longline or incorporated
directly into it. It will have a couple
of spare feet at either end, which
should be kept well away from the
manual release. You may also find a
couple of changes to the airframe, in
the shape of bubble windows, or
instruments being repeated to the
side (don’t kick them on your way
in) so you can see them, although
you soon get used to the sound of
machinery getting near to the
overtorque stage (don’t ask!).
A metal line is made of two strands
of wire rope, wound around each
other, to help prevent spinning.
Kevlar (i.e. Spectra) ones are
extremely light by comparison, but
just as strong, although they can
stretch. The only real pain with them
is ground handling, because they
have a tendency to get tangled up
into knots if they don't have a
protective covering (one suggestion
is to get a large bucket, place the
hook in and loop the line around the
inside). However, they can also pick
up twigs, etc., and grease from drills
is apparently not good for them -
they can also snag on trees, as I
found out once. Being light, they can
be hard to punch off in those
circumstances, and tricky to position
for the crews in a wind when empty.
You need to be particularly careful
not to kink any line, which means
not driving over it, landing on it,
dragging it along the ground, or
dropping it from great heights.
Long-lining (or vertical reference)
proficiency to some customers
involves putting a small load at the
end of a 100 ft line onto a 4 x 8 ft
sheet of plywood three times from
Special Use Of Aircraft 189
different approach angles, or even
putting a load into a barrel.
The human eye is actually a very
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