Larger planes will have to generate more thrust and lift than smaller ones, for instance. It also matters how weight is distributed throughout the plane — an airplane must be loaded according to its center of gravity envelope. The center of gravity is the point at which if an aircraft were suspended, it would be balanced at that location. Having too much weight toward the nose, for instance, would move the center of gravity too far forward and make it difficult, if not impossible, for the plane to take off — you would not be able to lift the nose off the ground, and the airplane would not be able to climb.
It may not seem like it, but air takes up space and exerts weight. At sea level, a square inch column of air exerts As you go higher in the atmosphere, the density of the air decreases. For airplanes such as airliners that can fly at higher altitudes, this decreased air density means less resistance and helps the plane move faster and more efficiently. For other airplanes, however, such as single-engine piston-powered aircraft, a decrease in air density results in a less efficient engine.
Humidity refers to the amount of moisture in the air. More specifically, relative humidity measures what percentage of moisture is present relative to how much a given sample of air can contain. The higher the humidity, the more water is present in the air. Because aircraft rely on air to operate, higher humidity can cause their engines to function less efficiently.
Additionally, once the air becomes saturated, the water it holds can begin to condense into fog and clouds , which, of course, reduces visibility both on the ground and in flight. Much like humidity, weather can be a factor in how and where an airplane is able to fly. As air is warmed, it begins to rise, and cooler air moves in underneath to take its place. This movement of the air causes what are known as convection currents. Convection helps to create winds as well as other weather phenomena such as thunderstorms.
It can also be a cause of turbulence, which affects how bumpy a flight is. In addition to convection currents, several other factors can generate wind, such as:. Headwinds and tailwinds also affect the speed an airplane travels over the ground. The airplane essentially rides the stream of air, like a ship might ride an ocean current, and can reach its destination faster.
One passenger jet recently broke the transatlantic subsonic speed record for an airline by doing just that. Despite common fears about air travel, often generated by the rare sensationalistic news story, plane crashes are just that — rare.
The rudder works to control the yaw of the plane. The pilot moves rudder left and right, with left and right pedals. Pressing the right rudder pedal moves the rudder to the right. This yaws the aircraft to the right. Used together, the rudder and the ailerons are used to turn the plane. The elevators which are on the tail section are used to control the pitch of the plane. A pilot uses a control wheel to raise and lower the elevators, by moving it forward to back ward.
Lowering the elevators makes the plane nose go down and allows the plane to go down. By raising the elevators the pilot can make the plane go up. The pilot of the plane pushes the top of the rudder pedals to use the brakes. The brakes are used when the plane is on the ground to slow down the plane and get ready for stopping it. The top of the left rudder controls the left brake and the top of the right pedal controls the right brake.
If you look at these motions together you can see that each type of motion helps control the direction and level of the plane when it is flying. Sound is made up of molecules of air that move. They push together and gather together to form sound waves. Sound waves travel at the speed of about mph at sea level. When a plane travels the speed of sound the air waves gather together and compress the air in front of the plane to keep it from moving forward.
This compression causes a shockwave to form in front of the plane. In order to travel faster than the speed of sound the plane needs to be able to break through the shock wave. When the airplane moves through the waves, it is makes the sound waves spread out and this creates a loud noise or sonic boom. The sonic boom is caused by a sudden change in the air pressure. When the plane travels faster than sound it is traveling at supersonic speed. A plane traveling at the speed of sound is traveling at Mach 1 or about MPH.
Mach 2 is twice the speed of sound. Sometimes called speeds of flight , each regime is a different level of flight speed. This is very different than dealing with solid pellets for which only the bottom surface would deflect. The faster an airplane travels the more lift is generated.
Inclining the wing to the wind also produces more deflection and more lift. The wings of an airplane have adjustable flaps that can be extended or retracted. When extended, the flaps increase the deflection of the air and provide greater lift for takeoff and landing. This drawing away or pulling down of those air parcels from their neighboring parcels above is what creates the area of lower pressure atop the wing.
But another effect also accompanies this action: the higher airflow speed atop the wing. But as always, when it comes to explaining lift on a nontechnical level, another expert will have another answer. But he is correct in everything else. The problem is that there is no quick and easy explanation. Drela himself concedes that his explanation is unsatisfactory in some ways.
So where does that leave us? In effect, right where we started: with John D. This article was originally published with the title "The Enigma of Aerodynamic Lift" in Scientific American , 2, February How Do Wings Work?
Holger Babinsky in Physics Education , Vol. David Bloor. University of Chicago Press, Understanding Aerodynamics: Arguing from the Real Physics. Doug McLean. Wiley, You Will Never Understand Lift. Peter Garrison in Flying ; June 4, Culick; July Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. In Brief On a strictly mathematical level, engineers know how to design planes that will stay aloft.
But equations don't explain why aerodynamic lift occurs. There are two competing theories that illuminate the forces and factors of lift. Both are incomplete explanations.
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