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will trip you (there is a natural
tendency to sink as you go forward
anyway). The torque used at this
point will give you a good idea of
what is needed for landing, so be
careful if you are going to a higher
altitude (it reduces at about 2-3% per
1000 feet in a 206).
One technique used in New
Zealand, when you are near all-up
weight and lifting the load into the
hover would be difficult, is to stretch
the longline out behind, attach it to
the helicopter and, keeping it taut,
build up some speed in a parabolalike
manoeuvre before lifting the
load (it's called the slingshot and I’m
told it requires some practice).
However, if a log lifted this way
starts spinning, it will undo the rope,
so another way is to get a 300-foot
line, get into the hover as far back as
possible with a taut line and take off
straight ahead to get some
translational lift. This tends to crack
the blades, though.
Once in flight, remember that the
load is the part that should be kept
straight and level, not the helicopter,
and keep away from anything
underneath that could be damaged
(well, try anyway!). Only with
imminent danger to the aircraft
should a load be jettisoned, usually
from excessive swinging
(commercially, dropping loads is
regarded as a non-macho thing to
do, but it's your backside the
helicopter is strapped to). As a point
of interest, 10 gallons of fuel from
500 feet will go straight to the
basement of a 3-storey house. If you
drop anything obnoxious in water,
expect your company to pay for the
clean-up and testing.
Unless in rough air, beeping the
RPM down helps with the lift and
the fuel burn.
If you get an engine failure in the
mountains with a load attached,
consider not jettisoning it. This may
sound daft, but it may stop you from
falling down a crevice or something
– just try to keep the line taut so you
don’t get a nasty jerk at the end.
Load Behaviour
Every load has its own VNE,
unfortunately usually only found by
experiment, which is why you should
always start off slowly and build up
to a point where it starts to give
trouble, then back off, as low as
possible, so there is less height to get
rid of in a hurry. Most helicopters
will carry loads at quite high speeds,
but the load itself might not be able
to handle it—a sudden input of drag
when something falls off could
become quite a problem. Although
customers don’t like to pay for
unnecessary flying, there’s no rush.
Take it easy. Also, remember your
machine’s VNE with the doors off!
External loads increase the frontal
area of the whole aircraft, which
naturally increases drag, so you will
need more power overall. A load
may be easy to lift, but present
enough drag to cause severe
difficulties, particularly where you
reach power limits too quickly to
maintain forward flight, and the load
overtakes you and pulls you along. A
long-line needs more anticipation, so
you need a high degree of coordination
and patience. It's not the
sort of thing that can be learnt in any
other way than with lots of practice.
186 Operational Flying
Unevenly shaped loads will tend to
spin and, if they're slung without
reference to their centre of gravity,
could tip over. A drogue chute can
stabilise them, but use a windsock
type rather than a pure parachute,
which will bounce around trying to
spill the air out (or punch holes in
it). Naturally, these must be kept well
away from the tail rotor. Logs or cut
timber usually fly poorly unless a tail
is installed, which can be made out
of a bough or piece of plywood, so it
sticks out of the back.
Oscillation or excessive vibration
can come from a number of places,
usually a combination of the stability
characteristics of the load and
forward speed. Heavy or dense
loads, such as bags of cement or
drums of kerosene, will not usually
present problems due to their mass,
but large-volume loads of low
density can oscillate at a certain
critical speed, again usually only
found by trial and error.
You can 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,
　
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