AVIATION HISTORY

Lecture 6: Flight Environments

Earth's atmosphere The Earth's atmosphere is a thin layer of

gases that surrounds the Earth.

What are the 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.

IONOSPHERE

Atmosphere LayersThe Earth’s atmosphere is divided into 5 layers-troposphere 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

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 feet-160’000 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

ThunderstormsThunderstorms 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.

Also known as “air pocket” Air pocket: a small area where the air is less

dense or where there is a downward air current, and which makes an aircraft lose height suddenly.

How to avoid thunderstorm and turbulence? Get weather reports before and during

flights Weather radar displays will show areas

of turbulence to note or to avoid. 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 icing2. Can make aircraft loss of control Ice forming on the rudder, elevator aileron, brakes

& landing gear could make aircraft loss of control3. 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

De-icing: To remove ice after it has formed

Anti-icing: To prevent ice from forming.

De-icing

De-icing is the process of removing snow & ice from an aircraft surface.

Anti-icing Electrical systems for keeping critical

areas free of ice.

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

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 wind-shear hazards.

Many airports now have wind shear detection equipment near the ends of runways to warn aircraft if it is too dangerous to land.

VIDEO = "Cruel Skies"

This special video looked at the role of bad weather in disasters, and toured the US Aviation Weather

Centre in Kansas City, Missouri to see how information on weather is

transmitted to pilots in the sky.

Why do Airplanes Fly at High Altitudes? 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 High1. 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 High2. 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

5. 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).