AVIATION HISTORY Lecture 7: Flight Environments

Introduction  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.

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.

IONOSPHERE 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

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 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.

Stratosphere  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 Sun.

Stratosphere  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.

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.  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  Ionosphere is the layer of ionized gasses. It can be a conductor.  Ionosphere layer can act as reflector of radio waves.

Thermosphere  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 significantly.  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 encounter.  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 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.

TEMPERATURE  Temperature affects aircraft performance and is critical to some operations.  High temperature reduces air density and reduces aircraft performance.  Temperature can be related to cloud formation, turbulence, and thunderstorms.  Temperature in the cold air can be critical to icing.

What are the common bad weathers that could be faced by aircraft?

Aviation is Weather Sensitive  Thunderstorms  Turbulence  Aircraft Icing  Clouds/Restricted Visibility

Thunderstorms

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 aircraft.  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 control

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 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.  Avoid by at least 20 miles any thunderstorm identified as dangerous

Aircraft Icing

 Icing is the accumulation of ice on the exposed surfaces of aircraft when flying through super cooled water drops.  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 colder.  Aircraft icing is one of the major weather hazards to aviation. WHY????

Effect of the icing  Can reduce the aircraft efficiency.  Can make aircraft loss of control.  Can affect the aircraft engine performance.  Cause an aircraft loss of radio communications.  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 communications

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 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  To prevent ice from forming.  Electrical systems for keeping critical areas free of ice.

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

Turbulence

 Turbulence is one of the most unpredictable of all the weather phenomena that are of significance to pilots.  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 possible.  Get weather reports before and during flights  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 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.