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though these are not serious (around
5%). The angle of bank to obtain a
given rate of turn increases with
TAS, but you shouldn't need to
make any calculations – the
instrument reads correctly
automatically. If the gyro rotates too
slowly, the device will have less
inertia and be less rigid, so it will tilt
less and indicate a slower rate of turn
than you are actually doing.
The turn and bank indicator (see
pictures above) also has an
inclinometer underneath, but it has a
vertical needle instead of a
horizontal small aircraft. As such it
will only give you the rate of turn.
A Question
1. You've just lost all your electrics,
and you are left with a map and the
E2B compass. Can they be relied on
to get you home?
An Answer
1. You can rely on the map, but the
compass will have been swung with
the electrics on, so all the local
magnetic fields will have changed
with them off. You can therefore
expect large deviation errors.
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 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 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
78 Canadian Private Pilot Studies
all affect density, which ultimately
affects aircraft performance.
The climate of any area is its average
weather. Weather is what happens
when the atmosphere is affected by
heat, pressure, wind and moisture,
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 Seasons
We get seasons because the Earth is
not vertical in space – it is actually
inclined at an angle of 23 ½ ° so that
different areas are pointed towards
the Sun in their turn, and do it for
longer periods, hence Summer.
Pressure Patterns
A column of air above any point has
weight, which is commonly
measured in terms of millibars or
inches of mercury, and called the
atmospheric pressure. This value won’t
change with temperature, but the air
density will, as it is the weight of the
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