Aviation

“ Heavier-than-air flying machines are impossible.” — Lord Kelvin, 1892

http://en.wikipedia.org/wiki/Aviation

History of Aviation• The modern age of aviation began with the first human lighter-than-

air flight on November 21, 1783, in a hot air balloon designed by the Montgolfier brothers

• The practicality of balloons was limited because they could only travel downwind

• It was immediately recognized that a steerable balloon was required

• Jean-Pierre Blanchard flew the first human-powered ballon in 1784 and crossed the English Channel in one in 1785

• In 1799 Sir George Cayley set forth the concept of the modern airplane as a fixed-wing flying machine with separate systems for lift, propulsion, and control

• While there are many competing claims for the earliest powered, heavier-than-air flight, the most widely-accepted date is December 17, 1903 by the Wright brothers, who had solved the age old problem of controlling a craft in flight

• The widespread adoption of ailerons made aircraft much easier to manage

• Only a decade later, at the start of World War I, heavier-than-air powered aircraft had become practical for reconnaissance, artillery spotting, and even attacks against ground positions.

• Aircraft began to transport people and cargo as designs grew larger and more reliable

• In contrast to small non-rigid blimps, giant rigid airships became the first aircraft to transport passengers and cargo over great distances

• The best known aircraft of this type were manufactured by the German Zeppelin company

• The most successful Zeppelin was the Graf Zeppelin. It flew over one million miles, including an around-the-world flight in August 1929

• The dominance of the Zeppelins over the airplanes of the that period, which had a range of only a few hundred miles, was diminishing as airplane design advanced

• The "Golden Age" of the airships ended on May 6, 1937 when the Hindenburg caught fire killing 36 people.

• Although there have been periodic initiatives to revive their use, airships have seen only niche application since that time.

• Great progress was made in the field of aviation during the 1920s and 1930s, such as Charles Lindbergh's transatlantic flight in 1927

• One of the most successful designs of this period was the Douglas DC-3 which became the first airliner that was profitable carrying passengers

• By the beginning of World War II, many towns and cities had built airports, and there were numerous qualified pilots available

• The war brought many innovations to aviation, including the first jet aircraft and the first liquid-fueled rockets

• After WW II, especially in North America, there was a boom in general aviation, both private and commercial, as thousands of pilots were released from military service and many inexpensive war-surplus transport and training aircraft became available

• Manufacturers such as Cessna, Piper, and Beechcraft expanded production to provide light aircraft for the new middle class market

• By the 1950s, the development of civil jets grew, the first widely-used passenger jet was the Boeing 707, because it was much more economical than other planes at the time

• Since the 1960s, composite airframes and quieter, more efficient engines have become available

• The most important lasting innovations have taken place in instrumentation and control

• The arrival of Global Positioning Systems, satellite communications, and increasingly small and powerful computers and LED displays, have dramatically changed the cockpits of airliners

• Pilots can navigate much more accurately and view terrain, obstructions, and other nearby aircraft on a map or through synthetic vision, even at night or in low visibility

• On June 21, 2004, Spaceship One became the first privately funded aircraft to make a spaceflight, opening the possibility of an aviation market capable of leaving the Earth's atmosphere.

• Meanwhile, flying prototypes of aircraft powered by alternative fuels, such as ethanol, electricity, and even solar energy, are becoming more common and may soon enter the mainstream, at least for light aircraft

• http://www.youtube.com/watch?v=1NCOPLEJOl0

Straight and Level Flight

• In order for an airplane to fly straight and level, the following relationships must be true: – Thrust = Drag – Lift = Weight

Thrust

• An aerodynamic force that must be created by an airplane in order to overcome the drag

• Airplanes create thrust using propellers, jet engines or rockets

• In the figure above, the thrust is being created with a propeller, which acts like a very powerful version of a household fan, pulling air past the blades.

Drag• An aerodynamic force that resists the motion of an object moving

through a fluid (air and water are both fluids).

• If you stick your hand out of a car window while moving, you will experience a very simple demonstration of this effect.

• The amount of drag that your hand creates depends on a few factors, such as the size of your hand, the speed of the car and the density of the air. If you were to slow down, you would notice that the drag on your hand would decrease.

• If you've ever wondered why, after takeoff, a passenger jet always retracts its landing gear (wheels) into the body of the airplane, the answer is to reduce drag. The pilot wants to make the aircraft as small as possible to reduce drag.

• Weight– Every object on earth has weight (including air). A 747

can weigh up to 870,000 pounds (that's 435 tons!) and still manage to get off the runway

• Lift– Lift is the aerodynamic force that holds an airplane in the

air, and is probably the trickiest of the four aerodynamic forces to explain without using a lot of math

– On airplanes, most of the lift required to keep the plane aloft is created by the wings

– A principal concept in aerodynamics is the idea that air is a fluid.

Air is Fluid

• a principal concept in aerodynamics is the idea that air is a fluid

• Like all gases, air flows and behaves in a similar manner to water and other liquids

• Even though air, water and pancake syrup may seem like very different substances, they all conform to the same set of mathematical relationships

• In fact, basic aerodynamic tests are sometimes performed underwater

• Another important concept is the fact that lift can exist only in the presence of a moving fluid

• This is also true for drag. It doesn't matter if the object is stationary and the fluid is moving, or if the fluid is still and the object is moving through it

• What really matters is the relative difference in speeds between the object and the fluid

• Neither lift nor drag can be created in space (where there is no fluid)

• This explains why spacecraft don't have wings unless the spaceship spends at least some of its time in air.

• The space shuttle is a good example of a spacecraft that spends most of its time in space, where there is no air that can be used to create lift

• However, when the shuttle re-enters the earth's atmosphere, its stubby wings produce enough lift to allow the shuttle to glide to a graceful landing

How Lift is Created

• Lift is a force on a wing immersed in a moving fluid, and it acts perpendicular to the flow of the fluid. (Drag is the same thing, but acts parallel to the direction of the fluid flow).

How Airplanes fly video

• Dot Video – 19 min

• Aerodynamics of Flight – 7 min

• How to throw a boomerang – 8 min

• Why boomerangs come back – 3 min– Gyroscopic precession – 3 min– How boomerangs come back – 3 min