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AVIATION HISTORY
Lecture 6: Flight
Environments
Earth's atmosphere
 The Earth's atmosphere is a thin layer of gases
that surrounds the Earth.
Importance of Atmosphere??
•Source of oxygen and carbon dioxide.
•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
The Earth’s atmosphere is divided into 5 layerstroposphere is where all weather changes take place, the
stratosphere is where aircraft fly and has ozone layer,
then the mesosphere, ionosphere and finally the
thermosphere, which is the topmost layer
IONOSPHERE
Troposphere
 The troposphere is the lowest layer of
Earth's atmosphere.
 The troposphere starts at Earth's surface
and goes up to a height of 11 km above
sea level.
 Between 0-36’000 feet.
 Almost all weather occurs within this
layer (below 15’000 feet).
 Air pressure and the density of the air
are also less at high altitudes.
Stratosphere
 The stratosphere is the second layer of
Earth's atmosphere.
 The stratosphere occurring between
about 11 km to 50km or (36’000 feet160’000 feet)
 Ozone is primarily found in this layer
(Ozone layer). It is important to protect
living earth from the harmful effects of
the sun's ultraviolet (UV) radiation.
 Without the ozone layer life could not
exist on the Earth's surface.
Mesosphere
 The mesosphere is the third layer of
Earth's atmosphere.
 It starts about 50 km above the ground
and goes all the way up to 80 km high.
Ionosphere
 Ionosphere is the layer of ionized gasses.
It can be a conductor.
 Ionosphere layer can act as reflector of
radio waves.
Thermosphere
 The last atmospheric layer has an
altitude greater than 80 kilometers and
is called the thermosphere.
The space shuttle orbits in the thermosphere of
the Earth.
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
feet.
 Weather is the utmost consideration
of all pilots when planning a flight.
Aviation is Weather Sensitive
 Thunderstorms
 Turbulence
 Aircraft Icing
 Wind Shear
Thunderstorms
Thunderstorms
Thunderstorms is a violent storm of
thunder and lightning.
Thunderstorms are usually accompanied
by hailstone , strong winds, and
heavy rain.
Hazards Of Flying In
Thunderstorms
1. Lightning
 Lightning is the natural high-voltage
electrical discharge between a cloud and
the ground.
 Lightning affect the aircraft by build up
the static electricity in the airframe.
 Thus, could lead to the loss of radio
communications , damage the aircraft’s
structure, making instrument reading
impossible and affect the crew's vision
Hazards Of Flying In
Thunderstorms
2. Hailstone
 Hailstone is a small pellet of ice which falls
from clouds.
 Can cause serious damage to an airplane.
3. Strong wind
 Can cause the aircraft crash during take-off
or landing.
4. Heavy Rain
 Can reduce the visibility, produce the visual
illusion, affect the braking action needed for
landing.
Turbulence
Turbulence
 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.
Wake turbulence generated
behind large aircraft.
Jetstream wind
(high winds that encircle the globe)
How to avoid turbulence?
 Get weather reports before and during
flights
 Weather displays will show areas of
turbulence to note or to avoid.
How to avoid thunderstorm?
 Don't fly under a thunderstorm even if
you can see through to the other side.
 Avoid by at least 20 miles any
thunderstorm identified as dangerous
 Don't land or take off in the face of an
approaching thunderstorm.
Aircraft Icing
Aircraft Icing
 Icing is the accumulation of ice on the
exposed surfaces of aircraft.
 Icing occur above the freezing level
where the water droplets are super
cooled.
 Pilots and controllers need to be
aware of the icing process.
Effect of the icing
1. Can reduce the aircraft efficiency.
 Aircraft’s efficiency reduce because lift
decrease, thrust decrease while weight and
drag increases.
Effect of the icing
2. Can make aircraft loss of control
 Ice forming on the rudder, elevator aileron,
brakes & landing gear could make aircraft loss
of control
3. Can affect the aircraft engine performance.
 Ice forming on the engine’s inlet prevents the
air intake & could affect the aircraft engine
performance.
4. Cause an aircraft loss of radio communications.
 Ice forming on the radio antenna will cause an
aircraft loss of radio communications.
5. Can lead to false indications giving by flight
instruments. (Ice forming on Pitot-Static
System)
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.
(Example: wet snow when the
temperature is near 0°C).
 Change altitude to get out of the icing
as rapidly as possible.
Protection from Icing
 Anti-icing: To prevent ice from
forming.
 De-icing: To remove ice after it has
formed
Anti-icing
 The process of spraying a glycol
solution on the parts of an aircraft to
prevent the formation of ice during
inclement weather conditions
Anti-icing
 Electrical systems for keeping critical
areas free of ice.
De-icing
 De-icing is the process of removing
snow & ice from an aircraft surface.
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.
Why do Airplanes Fly at High
Altitudes?
Flying High
 Depending upon the length of the flight
and the type of aircraft, cruising
altitudes typically vary between
approximately 25,000 feet and 40,000
feet (FL 250-400).
 This altitude allows the aircraft To:
 Avoid bad weather
 Increase engine efficiency and save fuel
 Avoid obstacles/mountains
 Have clear Visibility
 Avoid collision with another aircraft
Flying High
1. To avoid bad weather
 Most of the weather that occurs on our planet
happens below 15,000 feet.
 There are generally fewer clouds and less
turbulence at high altitudes.
 Beside that, the air is thinner at high altitude.
So, there is also less ice accumulation at high
altitudes.
 Thus, flying high is safer region from bad
weather.
Flying High
2. To increase engine efficiency and save
fuel
 The higher the aircraft altitude the thinner
the air.
 As the air becomes thinner, it creates less
resistance to objects flying through it.
 Therefore, less thrust is needed to move
the aircraft forward at a given speed.
 As a result, airplanes can fly more
efficiently at higher altitudes with less fuel.
Flying High
3. To avoid obstacles/mountains
 Himalayan mountain includes over 100
mountains exceeding 7,200 m (23,622
ft).
 Aircraft flying high in order to avoid the
collision with the high mountain.
Flying High
4. To have clear Visibility
 The higher the altitude the smoother the air,
thus the visibility is always better.
 Flying low makes aircraft too close to the
clouds. This may make it hard for the pilot to
see.
 Flying low means more bug and insects on the
wind shield which again can make it hard for
the pilot to see in front and reduce visibility.
Flying High
4. To avoid collisions with another aircraft
 The high altitudes are also great for
separation of flights to avoid collisions.
 At high altitudes (above 29,000 feet)
planes are required to have at least 2000
ft of vertical separation (it is usually
1000 ft when below 29,000 ft).