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Lecture 7: Flight
 Earth is a the bottom of an ocean of
 Dynamic layers of air interact with
the Earth's surface and the Sun's
energy to produce the phenomenon
of weather.
Earth's atmosphere
 The Earth's atmosphere is a thin layer of
gases that surrounds the Earth.
 It composed of 78% nitrogen, 21% oxygen,
0.9% argon, 0.03% carbon dioxide, and trace
amounts of other gases.
Functions of the Atmosphere
 Source of oxygen and carbon dioxide
 Source of rain.
 Maintains the temperature and climate
that sustain life on earth.
 Protection for the human on the Earth
from the harmful cosmic ray, solar
radiation and ultraviolet (UV) ray.
Atmosphere Layers
Atmosphere Layers
 Atmosphere layers consists of
1. Troposphere (Flying)
2. Stratosphere (Flying)
3. Mesosphere
4. Ionosphere
5. Thermosphere
6. Beyond this layer is free space
 The troposphere is the lowest layer of Earth's
The troposphere starts at Earth's surface and
goes up to a height of 12 km above sea level.
Almost all weather occurs within this layer.
Air is warmest at the bottom of the troposphere
near ground level.
Higher up it gets colder.
Air pressure and the density of the air are also
less at high altitudes.
 The stratosphere is the second layer of
Earth's atmosphere.
 The troposphere occurring between
about 12km to 50km
 Temperatures rise as ozone heats this
layer. Ozone absorbs energy from
incoming ultraviolet radiation from the
 In this layer air are quite stable.
 Commercial jet aircraft fly in the lower
stratosphere to avoid the turbulence
which occur in the troposphere layer.
 Air is thinner at the top of the
stratosphere than it is at sea level.
 Because of this, jet aircraft and
weather balloons reach their
maximum operational altitudes within
the stratosphere.
 The mesosphere is the third layer of Earth's
It starts about 50 km above the ground and
goes all the way up to 80 km high.
Most meteors burn up in the mesosphere.
The top of the mesosphere is the coldest part of
the atmosphere.
It can get down to -90° C (-130° F) there!
As you go higher in the mesosphere, the air
gets colder.
 Ionosphere is the layer of ionized
gasses. It can be a conductor.
 Ionosphere layer can act as reflector
of radio waves.
 This is an image of the space shuttle
as it is orbiting around the Earth. The
space shuttle orbits in the
thermosphere of the Earth.
Why Most Airliners Want to Fly
high the above 20’000ft?
Airliners Want to Fly high the above
20’000ft because…….
 To avoid bad weather
 To save fuel
 To fly faster
 To avoid heavy traffic
 To have clear Visibility
Airliners Want to Fly high the above
20’000ft because…….
 To save fuel
The higher the aircraft altitude the thinner
the air, which means the engine takes in
less air and thus produces less power. As a
result, fuel consumption reduced
 To fly faster
Aircraft can fly faster with less fuel when
flying high compared with flying low.
Airliners Want to Fly high the above
20’000ft because………
 To avoid bad weather
There is hardly any significant weather,
most of the weather that occurs on our
planet happens below 15,000 feet.
 To avoid heavy traffic
The higher the altitude, the less traffic you'll
 To have clear Visibility
The higher the altitude the smoother the air
because you're above the turbulence
associated with thermals. Thus, the visibility
is always better.
Weather & Aviation
Weather & Aviation
 Weather has large influences over our
lives and we have absolutely no
control over.
 Most of the weather that occurs on
our planet happens below 15,000
 Weather is the utmost consideration
of all pilots when planning a flight.
 Temperature affects aircraft
performance and is critical to some
 High temperature reduces air density
and reduces aircraft performance.
 Temperature can be related to cloud
formation, turbulence, and
 Temperature in the cold air can be
critical to icing.
What are the common bad
weathers that could be faced by
Aviation is Weather Sensitive
 Thunderstorms
 Turbulence
 Aircraft Icing
 Clouds/Restricted Visibility
Thunderstorms is a violent storm of
thunder and lightning.
Thunderstorms are usually accompanied
by strong winds, heavy rain and
sometimes snow & hail.
The dangers of flying in or close
to a thunderstorm are:
 Lightning – can cause an aircraft loss of
radio communications & can damage the
aircraft structure.
Hail – can cause the serious damage on
Strong wind – can cause the aircraft crash
during take-off or landing.
Rain - Reduce the visibility and produce the
visual illusion.
Turbulence –can cause an aircraft loss of
How to avoid thunderstorm?
 Don't fly under a thunderstorm even if
you can see through to the other side.
 Turbulence under the storm could be
 Don't land or take off in the face of an
approaching thunderstorm.
 A sudden wind shift or low level
turbulence could cause loss of control.
 Avoid by at least 20 miles any
thunderstorm identified as dangerous
Aircraft Icing
Aircraft Icing
 Icing is the accumulation of ice on the
exposed surfaces of aircraft when
flying through super cooled water
 Pilots and controllers need to be
aware of the icing process.
Icing Formation
 Icing occurs when an aircraft flies
through visible water and the
temperature at the point where the
moisture strikes the aircraft is 0° C or
 Aircraft icing is one of the major
weather hazards to aviation.
Effect of the icing
 Can reduce the aircraft efficiency.
 Can make aircraft loss of control.
 Can affect the aircraft engine
 Cause an aircraft loss of radio
 Can lead to false indications giving
by flight instruments
Effect of the icing
 Ice forming on the wing will reduce the
aircraft efficiency by increasing weight,
reducing lift, decreasing thrust, and
increasing drag.
 Ice forming on the rudder, elevator
aileron, brakes & landing gear could
make aircraft loss of control
 Ice forming on the engine’s inlet
prevents the air intake & could affect the
aircraft engine performance.
 Ice forming on the radio antenna will
cause an aircraft loss of radio
How to avoid icing
 Contact the weather office to obtain a
forecast about expected icing.
 Avoid flight into an area where icing
conditions are known to exist.
 Change altitude to get out of the icing
as rapidly as possible.
How to avoid icing
Always consult a weather office to
obtain a forecast about expected
icing conditions before take-off on
any flight in fall or winter.
Avoid flight into an area where icing
conditions are known to exist.
(Example: wet snow when the
temperature is near 0°C).
Pilot must change altitude to get out
of the icing as rapidly as possible.
Protection from Icing
 Anti-icing: To prevent ice from
 De-icing: To remove ice after it has
 The process of spraying a glycol
solution on the parts of an aircraft to
prevent the formation of ice during
inclement weather conditions
 To prevent ice from forming.
 Electrical systems for keeping critical
areas free of ice.
 De-icing is the process of removing
snow & ice from an aircraft surface.
 Turbulence is one of the most
unpredictable of all the weather
phenomena that are of significance to
 Turbulence is caused by rapid,
irregular motion of the air.
 In severe turbulence, shortly throw an
airplane out of control and can cause
structural damage.
There are many things that cause
turbulence, but four of them are:
1) Thermal activity from the sun
2) Thunderstorms
3) Jetsream wind (high winds that
encircle the globe)
4) Wake turbulence generated behind
large aircraft.
Jetsream wind
Wake turbulence
How to avoid turbulence?
 Keep aircraft distance from
thunderstorm activity whenever
 Get weather reports before and during
 Weather displays will show areas of
turbulence to note or to avoid.
Wind Shear
Wind shear
 Wind shear is a quick change in the
wind speed & direction that can cause
aircraft lose in control.
 If an aircraft experiences a sudden
decrease in wind speed, it can reduce
the lift on its wings to dangerously
low values.
How to avoid wind shear
 Aircraft must be equipped with radar/
sensors that can alert pilots to windshear hazards.
 Many airports now have wind shear
detection equipment near the ends of
runways to warn aircraft if it is too
dangerous to land.