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transit, and to stop for non-traffic
purposes (refuel, emergency) without
prior permission from the State
concerned. However, you may have
to follow prescribed routes for safety
or security reasons.
Before entering the sovereign
airspace of a foreign State with the
intention of landing there, the
aircraft must be airworthy, with all
relevant documents, including the C
of A on board.
Crew licences must be issued by the
State of registration. They are
recognised by other States as long as
they exceed ICAO requirements
(this also applies to Certificates of
Airworthiness).
The Certificate of Registration must
be carried at all times.
Weather
Around the Earth is a collection of
gases, called the atmosphere. 21% of it,
luckily for us, is oxygen, but 78% is
nitrogen, with 1% of odds and ends,
like argon, that need not concern us
here, plus bits of dust and the odd
pollutant. What is important,
however, is varying amounts of
water vapour which will produce
clouds. Because it weighs fiveeighths
of an equivalent amount of
dry air, it will also reduce your
engine's punch, but that’s the subject
of another chapter. The nitrogen, as
an inert gas, is there to keep the
amount of oxygen down, since it is
actually quite corrosive.
The atmosphere is split into four
concentric gaseous areas. Starting
from the bottom, these are the
troposphere, stratosphere, mesosphere and
thermosphere, although the last two are
not important right now. The first
two are, however, and the boundary
between them is called the tropopause,
a freezing layer of dry air. Its
relevance here is its involvement in
producing jetstreams, or tunnels of
high winds that give attendants less
time for a smoke on flights going
East across the Atlantic. Its height
over the Equator is around 60,000
feet, more than it is at the Poles
(35,000), because the air is warmer
there and has expanded, taking the
tropopause with it.
So, underneath the tropopause is the
troposphere, and above it is the
stratosphere, where the temperature
remains relatively constant with
height – it decreases with height in the
troposphere, which is where weather
happens (temperature stops
decreasing at the tropopause). The
troposphere contains more than
80% of the mass of the atmosphere.
Although the air gets thinner the
higher you get, the proportions of
the gases making it up stay the same,
because of the constant mixing. If
the air wasn't continually being
stirred up, the heavier gases would
sink to the lower levels.
The climate of any area is its average
weather. Weather is what happens
when the atmosphere is affected by
heat, pressure, wind and moisture,
114 Canadian Professional Pilot Studies
but heat has arguably the most
effect, since changes in weather
occur when temperature changes.
Heat arises from the Sun's rays
passing through the atmosphere and
being converted to longer wave
radiation when they hit the ground.
The darker the area that is hit, the
more absorption takes place, and the
more heat is generated. Thus, any
heat in the Earth comes from the
Earth itself, and only indirectly from
the Sun. In other words, moisture in
the atmosphere acts like the glass in
a greenhouse, that lets short wave
radiation in, and long waves out.
The Gas Laws
The atmosphere will be wetter or
drier, warmer or colder, or denser or
lighter in different areas. The key
words here are therefore humidity,
temperature, pressure, density and
radiation, as it behaves like any other
gas, and obeys all the physical laws,
such as expanding when heated, etc.
Temperature, pressure and humidity
all affect density, which ultimately
affects aircraft performance.
Charles' Law states that temperature
is directly related to volume. Boyle
discovered that pressure is inversely
related to it, and Dalton says that the
total pressure of a mixture of gases is
the same as the sum of the partial
pressures of the gases it is made of,
which is relevant when it comes to
dealing with oxygen (see Human
Factors). In other words, each gas's
pressure contributes a part of the
total pressure according to its
constituent proportion.
Thus, there are three variables when
it comes to gases – pressure, density
and temperature, which are all
intimately related. For example, if a
gas were restrained in a rigid
　
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