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above the snow, so the downwash is
always behind you, using the aircraft
shadow, a smoke grenade or the
landing light to provide texture to
the surface. Even a fuel drum makes
a good visual reference. Another
good trick is to use a dark-painted
stake with a flag on it – the flag
makes the stake behave like a dart,
so the point goes into the snow, and
acts as a wind indicator afterwards.
Do not hover, don’t go beyond the
marker, and try to land just as the
snow cloud develops.
When you commit yourself,
however, you will need to check the
firmness of the surface, which is not
usually a problem at a camp or
something, as the ground crew will
have done this for you. The danger
lies when you're going to an
unchecked site for the first time.
Touch down lightly without delay,
treating it as a sloping ground
landing, as the vibration of the
helicopter itself can cause ice to
crack. Any form of load spreading is
a good idea if you can take
advantage of it, like landing on a log
pad, although your landing gear will
largely determine what you can use.
As an example, a fully loaded
JetRanger on floats weighs 133 lbs
per sq foot, whilst one on skids and
bear paws is nearer 400. Whatever
you choose, it needs to be twice as
thick if you intend staying overnight.
Another method, possibly better for
beginners, is to come to a high hover
(with escapes) to allow the
downwash to clear the snow, then
lower the machine slowly and
smoothly, so you need to be wary if
you’re heavy. Still another is a really
shallow approach on the edge of
translational lift, to slowly move
forward onto the site with your skids
on the ground.
Once landed, bounce the skids a
little to see if there's a crust,
although you should be careful with
the Astar as too much downward
force on the blades could cause the
head to crack, aside from pushing
the belly panel up into the controls
(watch out for the swinging hook,
too, which could cause loss of fuel).
The belly landing light is a great
snow scoop which could affect the
controls as well.
Keep your RPM to flying levels until
you're sure you're on firm ground.
82 The Helicopter Pilot’s Handbook
Always keep the helicopter light on
the skids until passengers are clear,
regardless of the surface. Don’t let
anyone out till you’re happy.
The colour of ice can be a good clue
as to its suitability. White or blue is
the thickest, and therefore safest,
whereas black ice may have running
water underneath and will be quite
thin (for this reason, avoid inflows
or outflows of streams or rivers).
Granular, dirty looking ice is melting.
Large puddles or sheets of water are
also a dead giveaway. However, ice is
never really safe – it doesn’t matter
how many heavy water trucks the
customer may have parked there that
week, helicopters vibrate a lot more
than trucks do or, more particularly,
in a different way, and the hole
punched through for the hosepipe
has already weakened the structure.
Also, however thick they tell you the
ice is, you have no way of knowing
whether it is actually supported by
water underneath (the level may
have dropped), or whether any
running water has eroded the under
surface. Neither do you know
whether any snow on top has
shielded the ice from the cold, or
whether the Sun’s rays have reacted
with bare ice to act as a lens and
create temperatures dangerously
close to a thaw, during which ice
several feet thick can often become
composed of long vertical needles,
known as candle ice. Always try and
land somewhere else first.
Shut down carefully on an icy
surface, anticipating ground spin
(especially in a Gazelle). After final
shutdown, fill any fuel tanks to
prevent condensation, always being
aware of your next payload. Remove
batteries if temperatures are forecast
to be below -10oC. Try to park the
machine facing the sunrise, so the
Sun’s warmth can help with de-icing
the windscreen.
Also see that the battery is fully
charged before departing from base,
and consider taking a spare, together
with an external start cable— if the
ship’s battery runs down completely,
the plates will become sulphated and
won’t actually hold a charge so, even
if you start from an external source,
you won’t be able to start again
　
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本文鏈接地址：The Helicopter Pilot’s Handbook(55)