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where the bottom of the load is.
Specialised Tasks 37
Do not overshoot, as the load will
have its own inertia and will
continue forward of its own volition
(this is what's meant by flying the
load). Backing up to reposition is
always a problem, even with power
in hand, as it's easy to set the load
swinging, and it's better to go around
and try again - there should always
be movement, even if it's vertical.
You should at this point be coming
in nicely on a long approach, aiming
for a point just above the elevation
of the ground plus the length of the
line. Keep moving forward and
down. With power in hand, you
could probably afford to come to a
complete stop, but still aim for a nohover
deposit of the load. Without
much power, you have to aim for
the target directly and place it in one
movement, with a final check at the
last minute, which is something that
only comes with practice.
I have also found it useful, for
positioning, to extend my view
forwards and sideways to prominent
points and line myself up with them,
which is useful when I can't see the
landing point.
In mountains, you have to learn to
ignore the slope, and be aware that
your downwash may well bounce off
it and push the load away from
where it should be, that is,
underneath you, which is why you
might sometimes use very long lines,
when the slope is very steep and you
still find your skids in the trees.
After a job, when landing, curl the
line up on itself, then pull back when
quite close to the ground, ensuring it
is away from your skids.
EM Bird
This is a large gadget used to detect
terrestrial magnetism (anomalies may
indicate the presence of minerals). It
costs around $1.2 m and needs to be
flown very accurately at specific
heights and speeds, for which you
need at least a radalt and GPS,
although some setups use a laser
altimeter, which is accurate to the
foot. It is generally well behaved, but
can be tricky at slow speeds, and the
data gets fuzzy above 80 kts. It is at
the end of a 100-foot line, and needs
to be 100 above the ground anyway,
so you will be at 200 feet, unless
you’re over water or ice, down to 30.
There will be a 10-14 foot height
window to operate in.
There is a PDU (Pilot Display Unit)
on the top of the instrument panel
that gives you information on the
line you're flying or intercepting,
with horizontal track bars indicating
your distance from the centreline in
metres. Although done in VFR, it’s
the sort of job where a little IFR
training comes in handy, as it allows
you to keep your head in the cockpit
a little more and cope with doing
several things at once, such as
thinking several hundred metres
ahead, planning approaches to hills,
power lines and other obstacles. This
will include power and speed
requirements, and fuel.
The operation is dependent on may
things which are critical, such as
maintenance, weather, solar activity,
magnetic storms, etc., so bring a
book. Or three.
38 The Helicopter Pilot’s Handbook
Aerial Application
Aerial application (of pesticides or
fertilizers) means either cropspraying
or top dressing, the latter
being used in forestry (although you
can spray cut blocks with booms
on). Top Dressing is more akin to
load slinging, except you use engine
driven devices like buckets to spread
solutions over forests. Unlike crop
spraying, it can be done in strongish
wind conditions, but, otherwise, it's
characterised by always being in, or
very near, the avoid curve and many
other situations that you're taught to
avoid normally. You can tell with
forests that have been sprayed in the
early stages of their growth as to
whether the pilots were successful or
not—you very often see trees
shorter than others, which is where
they missed. Helicopters are
particularly useful when the leaves
need to be sprayed from underneath,
because of the downwash.
In fact, your downwash (or rotor
wake) can be used to good effect. At
low speed, you can spray a small area
underneath the flight path. At higher
speeds, the wake helps spread the
load behind and to either side (the
term rotor wake means all the air
displaced by the helicopter, as
opposed to just the downwash).
Knowledge of wake management
will therefore help you become a
better spray pilot.
The Rotor Wake
　
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本文鏈接地址：The Helicopter Pilot’s Handbook(25)