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before diving off the ridge, so you
don’t end up going too fast. Crossslope
drops are OK, provided you
remember where your rotor disk is.
With North American blade
rotation, keep downhill slopes on
your right, so if the bucket doesn't
open or you run out of power, you
can drop the collective, put the nose
down and be able to use the right
pedal to take the strain off the tail
rotor. Always approach at a 45°,
unless you have a bit of height.
In order not to make embarrassing
mistakes, like dropping water in the
wrong place, you need to be aware
that some fires are deliberately set
(see below), to make use of airflow,
as in “backfiring”, and there may
well be someone around with a
driptorch attached to their machine
to do it with.
After the excitement is over, and the
fire comes under control, typical
tasks will be moving men and
materials around, putting out
hotspots, IR scanning, recovering
equipment and generally tidying up.
Aerial Ignition
The waste product from the
activities of slashers, who cut down
trees and undergrowth is, not
surprisingly, called Slash. The
forestry people would normally like
this to rot naturally, but many
farmers disagree and burn it instead.
Because it is both extensive and
inaccessible, helicopters are used to
set the whole lot on fire, but only in
temperatures above freezing, and
below 45 kts, from somewhere
between 150-300 feet. This
technique may also be used when
fighting forest fires:
·  Temporarily knocking down
large smoke columns so Air
Tankers can see where they’re
going, by igniting strips of
forest within about 10-30
metres of, and parallel to, an
active flame front, which starves
it of oxygen. Depending on fuel
types, temperature, dewpoint,
wind velocity, etc. this can last
up to around 20 minutes.
·  Prevention. Forests can be
torched around priority areas,
such as towns or gas plants to
get rid of anything that might
burn later in the fire season.
·  Back burning, when a rapidly
advancing fire is moving
towards a cut line, or natural fire
break, like a creek, although this
could also be done on initial
attack. Parallel strips ignited
between the fire front and the
intended firebreak will
drastically diminish a fire’s
momentum, decreasing its
likelihood to spot across the
firebreak, and keep going, so the
firebreak can be used as a
204 Operational Flying
defensive line. In other words,
the idea is to remove fuel from
the path of a rapidly moving
fire, where the head creates a
powerful convective column
that pulls air in from all sides,
including downwind. When this
flow is steady, a fire is started
ahead of the main fire from a
natural barrier, such as a road or
river, which is sucked in and
creates a wider firebreak
·  Aiding in ground crew mop up,
by burning off unburned areas,
making it safer. Ragged edges
can also be straightened, to
reduce the perimeter and
decrease workload.
·  Reducing the time, effort, and
expense of cutting fire
perimeters for fires with many
fingers, which is very time
consuming.
·  Steering a fire somewhere.
You might carry a drip torch
beneath your machine and get to
become an instant pyromaniac with
a 20-foot flame about 20-25 feet
below the cargo hook, carrying a 55-
gallon fuel drum, associated pipes,
wiring, etc., and a fire extinguisher to
cope with hang fires, or those that
start around the valve outlet when it
closes. Apart from danger to the
helicopter, the mixture could fall off
and start unwanted fires.
The equipment weighs about 550 lbs
when full, and can use straight Jet
Fuel, or have it mixed with a gelling
agent, which makes it cling to foliage
and be more effective (I love the
smell of Petrogel in the morning).
There will be a propane flame for
ignition. As there is a polarityswitching
feature, aircraft rewiring is
unnecessary and, although it
demands a 25-amp circuit breaker,
30 amps is recommended.
Another way is to use polystyrene
balls about an inch across, full of
Potassium Permanganate, injected
with Ethylene Glycol (anti-freeze) in
a special dispenser and ejected from
the aircraft. For maximum safety, the
balls should not ignite inside ten
seconds, but most take about thirty.
　
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