1. Lecture 6: Flight Environments
AVIATION HISTORY
Lecture 6: Flight Environments

2. Earth's atmosphere What are the Importance of 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.
Earth is a the bottom of an ocean of air.
Dynamic layers of air interact with the Earth's surface and the Sun's energy to produce the phenomenon of weather.

3. Atmosphere Layers
The 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
IONOSPHERE

4. 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.
Practical: 1km = aprox. 3,281ft

5. 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.
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.

6. Mesosphere Ionosphere
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.

7. The space shuttle orbits in the thermosphere of the Earth.
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.

8. Weather & Aviation

9. 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.
commercial jetliner at a high altitude (>30,000 feet) there is hardly any significant weather.

10. Aviation is Weather Sensitive
Thunderstorms
Turbulence
Aircraft Icing
Wind Shear

11. Thunderstorms How do you avoid weather you can’t really see?
Notes & Definition
Ceiling: The maximum height above sea level in STANDARD AIR attainable by an aircraft under given conditions
Thunderstorms

12. Thunderstorms is a violent storm of thunder and lightning.
Thunderstorms are usually accompanied by hailstone , strong winds, and heavy rain.

13. 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
Lightning strikes of aircraft are common. The probability of a lightning strike is greatest when the temperature is between -5ºC and 5°C. If the airplane is in close proximity to a thunderstorm, a lightning strike can happen even though the aircraft is flying in clear air. Lightning strikes pose special hazards.
Structural damage is possible.
The solid state circuitry of modem avionics is particularly vulnerable to lightning strikes. Electrical circuits may be disrupted.
The possibility of lightning igniting the fuel vapor in the fuel cells is also considered a potential hazard. Can cause fire

14. 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.
Hailstones are capable of inflicting serious damage to an airplane.
Encountered at levels between 10 and 30 thousand feet.
Also encountered in clear air outside the cloud as it is thrown upward and outward by especially active cells.
Can damage the aircraft and flight controls lead to incidents or accidents.
The thunderstorm contains vast amounts of liquid water droplets suspended or carried aloft by the updrafts.
This water can be as damaging as hail to an aircraft penetrating the thunderstorm at high speed.
The heavy rain showers associated with thunderstorms encountered during approach and landing can reduce visibility and cause retraction on the windscreen of the aircraft, producing an illusion that the runway threshold is lower than it actually is.
Water lying on the runway can cause hydroplaning which destroys the braking action needed to bring the aircraft to a stop within the confines of the airport runway.
Hydroplaning can also lead to loss of control during take-off.

15. Turbulence Associated with thunderstorms
Extremely hazardous - potential to cause overstressing of the aircraft or loss of control.
Vertical currents - can displace an aircraft up or down vertically as much as 2000 to 6000 feet. The greatest turbulence occurs in the vicinity of adjacent rising and descending drafts.
Gust loads can be severe enough to stall an aircraft flying at rough air (maneuvering) speed or to cripple it at design cruising speed.
Maximum turbulence usually occurs near the mid-level of the storm, between 12,000 and 20,000 feet and is most severe in clouds of the greatest vertical development.
Severe turbulence can be expected up to 20 miles from severe thunderstorms and will be greater downwind than into wind.
Severe turbulence and strong out-flowing winds may also be present beneath a thunderstorm.
Microbursts can be especially hazardous because of the severe wind shear associated with them.
Turbulence

16. 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.

17. 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.
THUNDERSTORMS: A violent storm of thunder and lightning, often accompanied by rain and sometimes hail.
Many times you have to make decisions involving thunderstorms and flying.
Don't attempt to fly under a thunderstorm even if you can see through to the other side. Turbulence under the storm could be disastrous.
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.
Don't fly without airborne radar into a cloud mass containing scattered embedded thunderstorms. Scattered thunderstorms not embedded usually can be visually circumnavigated.
Do avoid by at least 20 miles any thunderstorm identified as severe or giving an intense radar echo. This is especially true under the anvil of a large cumulonimbus.
Do clear the top of a known or suspected severe thunderstorm by at least 1,000 feet altitude for each 10 knots of wind speed at the cloud top. This would exceed the altitude capability of most aircraft.
Do remember that vivid and frequent lightning indicates a severe thunderstorm.
Do regard as severe any thunderstorm with tops 35,000 feet or higher whether the top is visually sighted or determined by radar.

18. Aircraft Icing

19. 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.
Icing at high altitudes is not as common or extreme as it can be at low altitudes. When it does occur, the rate of accumulation at high altitudes is generally slower than at low altitudes. Rime ice is generally more common at high altitudes than clear ice, although clear ice is possible. Despite the composition of cirrus clouds, severe icing is generally not a problem although it can occur in some detached cirrus. It is more common in tops of tall cumulus buildups, anvils, and over mountainous regions. Many airplanes that operate above 25,000 feet are equipped with deice or anti-ice systems, reducing even further the dangers of icing.

20. Effect of the icing 1. Can reduce the aircraft efficiency.
Aircraft’s efficiency reduce because lift decrease, thrust decrease while weight and drag increases.

21. 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)

22. 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.

23. Protection from Icing De-icing: To remove ice after it has formed
Anti-icing: To prevent ice from forming.
The process of spraying a glycol solution on the wings of an aircraft to prevent the formation of ice during inclement weather conditions

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

25. Anti-icing Electrical systems for keeping critical areas free of ice.
Many airplanes that operate above 25,000 feet are equipped with deice or anti-ice systems, reducing even further the dangers of icing.

26. 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

27. Wind Shear

28. 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.
Wind Shear (a sudden change in the wind speed & direction that can cause aircraft lose in control)
Wind shear is a violent downdraft of the wind that can occur around the edges of thunderstorms. A few decades ago, it was thought to have caused a number of serious accidents. During the 1980s and 1990s, NASA led a large research effort to identify how wind shear happens end to test technologies like Doppler radar that can predict wind shear & warn pilots. Today aircraft are equipped with these forward-looking sensors that alert pilots to wind-shear hazards.
Wind shear is encountered in an area where two winds moving in opposite directions "rub" or mix together. This shear zone creates small eddies and whirling masses of air that move in various directions. This generates tremendous turbulence. Some wind shears are predictable, but others may occur unexpectedly. Getting caught in wind shear can be devastating to an aircraft, especially if the wind shear occurs close to the ground. Currently airports are being outfitted with wind shear alarms that warn controllers and pilots of the potential windshear existence within runway takeoff and landing corridors.
MAKING AIR TRAVEL SAFER Many airports now have wind shear detection equipment near the ends of runways to warn aircraft if it is too dangerous to land.

29. 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.

30. 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.

31. 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 ).
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

32. 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.

33. 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.

34. 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.

35. 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.

36. 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 ft of vertical separation (it is usually ft when below 29,000 ft).