## How Does an Airplane Fly? The Physics of Flight

written by: Andrea Campbell • edited by: Carly Stockwell • updated: 9/30/2014

Just over 100 years ago, gliders were suspect and no one could foresee how a passenger vehicle could fly. Now, although millions of people travel by air every year, most don’t know exactly how a huge hunk of metal (a jumbo jet is 800,000-plus pounds) is able to leave the ground. The marvel of physic

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### From the Cockpit to the Exit Doors

The body of a plane is bullet-shaped for good reason. This cuts down on the friction of the air against it. It is called the fuselage. The bottom section of a plane is the hold, and is available for baggage and cargo. The windowed passenger cabin is where travelers sit and the pilots sit in their cockpit. The kitchen area is a pass-through configuration called the galley. In jumbo jets, there is usually a sitting area apart from the seats called the lounge. The passenger cabin is typically divided into first- and second-class seats and of course there are small bathrooms—one toilet for every forty-six passengers in economy class, and one toilet for every eleven seats in first class.

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### Gateway Activities

A special truck pumps jet fuel into the wings, and a storage tank for petrol is in the hold.

You can hear the luggage being moved on a conveyor belt (and perhaps onto a pallet), then into the aircraft’s cargo.

When the airline doors close, the cabin becomes airtight and the air conditioning hisses into service.

A type of “push-back" tractor often moves the plane away from the gate.

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### Flight Physics

Notice that jet wings are curved on top and flat on the bottom (cambered). The plane’s speed forces the air to move and the wing shape causes the air to move faster over the wing than under it, producing a lift. The faster air pulls up and the slower air pushes down. That’s physics—the science of matter, energy, force and motion, how they relate and their reactions.

Eighteenth-century Swiss mathematician, Daniel Bernoulli, discovered this phenomenon and wrote about it in 1738 in his book, Hydrodynamica. He knew that the faster a fluid moves, the lower its pressure. The air acts like a liquid. There is less pressure above the wing than under it, and the plane is forced upward.

The flaps on the back of the wing and slats along the front make the wing curve and dynamics that much longer.

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### Up, Up and Away

Prior to takeoff, two powerful engines are engaged, one on each wing. A significant fan sucks air into the front engine compressor. The air is squeezed through a series of increasingly smaller fans and forced into a compression chamber. This forced air is mixed with jet fuel, ignited and burned; consequently, a hot gas rushes out, turning the turbine and providing forward thrust. The turbine spins the compressor fan.

The captain pushes the throttle forward and additional fuel is sent to the engines, making them roar. When the plane reaches 160 miles per hour, the captain raises the elevators on the tail that force the tail down and the nose of the plane lifts up.

Air rushing from the back of the engines moves the plane forward in thrust. The surrounding air slows the plane down in a force called drag. Thrust has to beat drag. Lift from the wings carries the jet upward. Earth’s gravity pushes the jet down. The airplane lift is winning the fight over gravity.

The landing gear withdraws into the belly of the plane.

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### Sailing Along

To make a turn, the captain engages the ailerons on the wings. When an aileron goes up the wing goes down; when one wing points down, the other points up and a tilt is formed whereby the rudder and tail fin are put into action by the captain who is controlling the turn.

When the airplane reaches cruising altitude the flaps are pulled in, the engines settle into a hum and the pilot may use autopilot if indicated. The speed can typically be 515 miles per hour.

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Air traffic controllers in airport towers or a centralized hub use radar so they can be aware of where each plane is, what direction it is traveling and how close it is to other aircraft. Radar uses light waves that the eye cannot see, and somewhat like the sonar that fishes use, the radar beam hits an object and bounces back. A sensor picks it up. Other sophisticated software and the airline transponder information (a device on the plane that transmits location code) helps to identify each aircraft.

In the near future, satellites will replace radar with its Global Positioning System (GPS) information and communication.

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### Flight Tidbits

• Those large, bulb-shaped objects hanging under the wings are called canoe farings because they are boat-shaped. Inside are the bulky mechanisms that extend and retract the flaps and slats during flight.

• The air over a wing accelerates so quickly that it actually reaches the back of the wing before the air below the wings.

• The flight numbers flying west and south are odd numbers, and when traveling east and north, flight numbers are even numbers.

• All airplanes have a red light on their left or portside wing tip. There is also a green light on the right, or starboard wing tip. In addition, a flashing white light typically makes planes easier to see at night.

• Air pressure inside a cruising airplane actually expands the fuselage slightly like a balloon making it taut. Doors and windows are inset a few millimeters from the fuselage so they will then expand to be flush with the plane body during flight.
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### Barbecue Wings, Anyone?

According to David Blatner, author of The Flying Book, “Jet engines are very reliable because there are few moving parts…When testing a new engine design, manufacturers strain it to the limits by shooting whole dead chickens into the moving blades at 180 mph (to simulate a bird getting sucked in at takeoff or landing), blasting torrents of water and ice into the engine, and even detonating dynamite inside it to ensure that broken fan blades won’t pierce the engine’s exterior shell."

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### Try This

Put your hand out a car window and raise your fingers against the oncoming wind—this is called raising the angle of attack in aviation terms, and the more you raise the angle, the more lift you get and the faster your hand goes up. This is the same phenomenon when you raise a wing’s angle; or pointing the nose of an airplane up.