曝光台 注意防骗
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impact energy. A short delay on the
approach could mean the clearance
of a group of birds, as they do move
in waves. Groups of birds will
usually break away downwards from
anything hazardous, so try to fly
upwards if possible. You could also
use landing lights to make yourself
more visible, especially where two
are flashing alternately. Avoid freshly
ploughed or harvested fields, and
beware of updraughts in mountains
areas, where birds will be trying to
get some free lift. Birds are most
active at dawn and dusk.
The force from a bird impact
increases with the square of the
speed—at 110 kts, the impact from a
1 lb bird can exceed 1200 lbs
sq/inch (the force is actually
determined by the square of your
speed multiplied by the mass of the
bird). The problem is that, below a
certain weight, the windshield will
only be designed to keep out rain
and insects. However, a hot
windshield is more pliable and less
likely shatter if it gets hit—some
aircraft need these on for take-off
and landing, but if there is nothing in
the flight manual, use 15 minutes.
Overheating is as bad as
underheating, so be wary if your
aircraft has been left in the sun a
long time. If you get a birdstrike,
stop and inspect the damage
immediately. If you can't, make sure
you have controllability before trying
to land again—fly the aircraft first.
Flight Operations 363
There are a lot of bird migration
maps in the RAC section of the AIP
(1-29).
Winter Operations
Although colder air means there's
less danger of exceeding temperature
limits, there are hazards, too,
including freezing precipitation, low
ceilings and cold temperatures.
Rapid changes in these are typical,
and it’s possible to get weathered in
for days at a time, so don’t forget
your chocolate bars.
The Weather
In the Frozen North, the best
conditions are in late winter or early
spring, with a major problem being
darkness. Once the snow is down,
the air is quite dry and it can stay
clear and cold for long periods, so
you can ignore fog and the rest until
it gets a bit warmer.
Above the 60th parallel, don’t expect
the weather to behave rationally at
all. For example, further South, the
East wind is responsible for bad
flying conditions, but up there the
West wind is the one to look out for,
as well as large swings between low
and high pressure which will often
bear no relation to what the weather
is doing (so don’t rely on cloud
shadows over the ground as an
indicator of surface wind speed).
Aside from barometric changes, look
out for wind shifts, which will bring
changes in wind speed and amounts
of blowing snow and less visibility –
even a difference of 100 feet in
elevation can mean the difference
between snow or not. Temperature
changes often mean bad weather is
approaching from the North – if it
drops, expect ice crystal fog, which is
the low level equivalent of contrails
made at high altitude, and created by
air disturbance, which could actually
be from the aircraft itself. Rising
temperatures will produce melting
and poor visibility. The chill factor
from rotors can reduce the ambient
temperature by several degrees.
When it gets to below -20 or so,
contact gloves will prevent your skin
freezing when it comes in contact
with cold metal, which is a more
efficient conductor of heat than air
is. You may also need sunglasses.
Always dress properly—in a forced
landing it could be that the clothes
you wear will be the only protection
you have. Also, being cold when you
are actually flying is a Flight Safety
hazard – metal foot pedals will
conduct heat away from your boots
very quickly. Extra time for planning
should always be allowed and the
pre-flight inspection should include
you—being improperly dressed and
making a series of short exposures
will fatigue you more quickly,
especially when the clothes you are
wearing are bulky and awkward to
move in. Maintain blood sugar levels
as more calories are consumed in the
cold (you need 3000 calories a day in
Norway). If the air is very dry (like in
the Arctic), you will lose fluids more
quickly through the usual ways, but
especially breathing. Losing 10%
causes cause delirium, and a 20%
loss is fatal. You could try and eat
snow, but the conversion to water
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Canadian Professional Pilot Studies2(100)
