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extra time to reach land, and to allow
you to brief and prepare the
passengers better. Maintaining a
constant listening watch helps
somebody know your position, as
does filing a flight plan before going.
Sea Movement
It's a good idea to have a basic
knowledge, as getting the heading
right may well mean the difference
between survival and disaster.
Whereas waves arise from local
winds, swells (which relate to larger
bodies of water), rely on more
distant and substantial disturbances.
They move primarily up and down,
and only give the illusion of
movement, as the sea does not
actually move much horizontally.
This is more dominant than anything
caused by the wind, so it doesn't
depend on wind direction, although
secondary swells may well do. It's
extremely dangerous to land into
wind without regard to sea
conditions; the swell must be taken
into consideration, although it could
assume less importance if the wind is
very strong.
The vast majority of swells are lower
than 12-15 feet, and the swell face is
the side facing you, whereas the
backside is away from you. This
seems to apply regardless of the
direction of swell movement.
The Procedure
You will need to transmit all your
MAYDAY calls and squawks (7700)
while still airborne, as well as turning
on your ELT, or SARBE. If time
permits, warn the passengers to don
their lifejackets (without inflating
them, or the liferafts) and tighten
seat belts, remove any headsets, stow
any loose items (dentures, etc.) and
pair off for mutual support, being
ready to operate any emergency
equipment that may be to hand (they
should have been briefed on this
before departure).
One passenger should be the
"dinghy monitor", that is, be
responsible for the liferaft. If it's
dark, turn on the cabin lights and
ensure everyone braces before
impact (the brace position helps to
reduce the flailing of limbs, etc. as
you hit the water, although its
primary purpose is to stop people
sliding underneath the lap strap;
there are different ones for forward
and aft seats).
Flight Operations 173
If only one swell system exists, the
problem is relatively simple—even if
it's a high, fast one. Unfortunately,
most cases involve two or more
systems running in different
directions, giving the sea a confused
appearance. Always land either on
the top, or on the backside of a swell
in a trough (after the passage of a
crest) as near as possible to any
shipping, meaning you neither get
the water suddenly falling away from
you nor get swamped with water,
and help is near.
Although you should normally land
parallel to the primary swell, if the
wind is strong, consider landing
across if it helps minimise
groundspeed (although in most cases
drift caused by crosswind can be
ignored, being only a secondary
consideration to the forces contacted
on touch-down). Thus, with a big
swell, you should accept more
crosswind to avoid landing directly
into it. The simplest way of
estimating the wind is to examine
the wind streaks on the water which
appear as long white streaks up- and
downwind. Whichever way the foam
appears to be sliding backwards is
the wind direction (in other words,
it's the opposite of what you think),
and the relative speed is determined
from the activity of the streaks
themselves. Shadows and whitecaps
are signs of large seas, and if they're
close together, the sea will be short
and rough. Avoid these areas as far
as possible—you only need about
500' or so to play with.
The behaviour of the aircraft on
making contact with the water will
vary according to the state of the sea;
the more confused and heavy the
swell, the greater the deceleration
forces and risks of breaking up
(helicopters with a high C of G, such
as the Puma, will tip over very easily,
and need a sea anchor to keep them
stable – in fact, the chances of any
helicopter turning upside down are
quite high). Landing is less
hazardous in a helicopter because
you can minimise forward speed. In
fact, if you are intentionally ditching,
you should come to a hover above
the water first, then throw out the kit
and the passengers. Having moved
away from them, settle on the
surface. If you can’t do that, a zero
speed landing should be aimed for,
which means a steep flare a little
　
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