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either get hit by another or hit
something else as you try and keep
up with the tree you are working
with (your downwash won’t be
helping). Its top should be level with
your eyes or the cabin roof, slightly
forward of your right shoulder.
Don’t fixate on the tree top, but
something else that isn’t moving.
Slide the skid in between the
branches until the stem of the tree is
against it, using a little collective just
before contact. Then lower the
collective so the skid rests against
the lower branches to keep it steady
for the clipper, who shouldn’t take
more than a minute to do what’s
required. Before you move away,
check the skid isn’t caught on
anything, then increase collective
and use left cyclic to pull you away
gently. Don’t move directly
sideways, as upwards slanting
branches near the tops of trees could
snag you.
A couple of points to watch – if you
bend a tree beyond the cyclic stops,
when it rebounds you will be out of
limits as you try to correct things.
You will do best to keep level and
use left cyclic with the rebound.
Don’t go straight up or you might
get dynamic rollover. Trees with
bent tops indicate heavy crops and
Specialised Tasks 89
should be avoided, because they will
have too much momentum. If you
have to work round a tree top, hover
away and assume a new position
every time rather than spinning
round it.
Wildlife Capture
Normally done with a pilot and
gunner (who has a net gun), but
there may also be an assistant (called
a mugger) as well. If there isn’t, and
you have to do the job instead, you
should only handle the head of the
animal, so you don’t get injured
unnecessarily. Your briefing should
include getting in and out of the
helicopter whilst in the hover.
A slightly forward C of G is
preferable. Keeping the rotor disc as
flat as possible, and avoiding tight
turns, approach the animal from
behind, slightly away from the skid
and forward of the gunner, almost
definitely with a sideslip. Don’t
fixate on the animal, but keep it in
view with peripheral vision. The
reason for the flat disc is to keep it
out of the line of fire, and high-G
turns will upset the gunner’s aim.
Sometimes the wildlife will be seals,
so you have to wear lifejackets and
stuff, and dodge the waves when
they get a bit big (sometimes you
have to use the waves to get you
back in the air again).
Instrument Flying
This is much the same as for fixed
wing, but there are a couple of
differences worth noting. Firstly,
thrust and lift come from the same
source, that is, the main rotors, so
you can have different attitudes than
expected when climbing, descending,
or in level flight, so you need to
learn particular power settings for
particular stages of flight to do it
correctly. These, of course, are
controlled by the collective and
displayed on the torquemeter. The
AI indicates fuselage and not disc attitude,
so does not always tell you what the
aircraft is actually doing – you could
be nose-up and still descending at 60
kts, so more cross-checking with
other instruments is required than
with a fixed wing aircraft. Put
another way, while it is still
important, the AI loses a little of its
distinction.
Also, the ability to fly at low speed,
say, below 60 kts, means that the
pitot-static instruments become less
reliable. You also get reduced
stability, which is why there is a
minimum IMC control speed (Vmini),
below which you shouldn’t go into
cloud, as well as minimum speeds
with one engine out, should you
have two.
Having said that, the attitude + power
= performance equation is still valid.
90 The Helicopter Pilot’s Handbook
Notes
Operational Stuff
VFR En-Route Minima
A US Army study indicates that it
takes about 5 seconds to perceive a
problem, make a decision and start a
correction. At 80 kts TAS, therefore,
you will move 676 feet and get still
closer as you turn away from an
obstacle, the distance being equal to
the radius of the turn which, in this
case, would be 984 feet, assuming
30° of bank, giving you a total
distance of 1660 feet to cope with,
which is not good if your visibility is
only 1000 feet! So, in bad weather,
you need to slow down, certainly
enough to give you a two-minute
　
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本文鏈接地址：The Helicopter Pilot’s Handbook(60)