ami asked in Cars & TransportationAircraft · 1 decade ago

what makes an airplane fly?

what are the things that make airplanes fly? and about how much does an airplane wheigh?

22 Answers

  • 1 decade ago
    Favorite Answer

    How does an Airplane Fly?

    I've answered this same question a couple of times, so I'll copy and paste the answer I gave then. Hope it helps. :)

    Forces on an Airplane in Flight

    The four aerodynamic forces that act upon an airplane in flight are lift (the upward acting force), weightgravity, the downward acting force), thrust (the forward acting force), and drag (the air resistance or backward acting force). These four forces are continuously battling each other while an airplane is in flight.

    Gravity opposes lift, thrust opposes drag. In order to take off, the aircraft's thrust and lift must be suffucient to overcome its weight and drag. In level flight at constant speed, thrust exactly equals drag and lift exactly equals the pull of gravity. To land, an aircraft's thrust must be reduced safely below its drag, as its lift is reduced to levels less than its weight.

    How an Airplane Generates Lift

    Lift is the aerodynamic force that counteracts gravity and holds an airplane in the air. Most of the lift required by an airplane is created by its wings, but a certain portion is also generated by other parts of the aircraft, such as the fuselage. But what actually causes the lift to be created?

    First, understand that air is a fluid, just like water, and that all fluids adhere to the same physical and mathematical principles. Next, realize that lift can only be generated when a fluid is in motion. For example, a wing must be passing through the air or the air must be moving around a stationary wing, one or the other. (The way it usually happens is that the wing is doing most of the moving, although the air may be moving too, at the same time.)

    Most airplane wings have a special, basic shape as viewed edge-on: their upper surfaces are curved and their lower surfaces are flatter. This shape is what works with the fluid motion of the air to create lift. As air moves around a wing, some goes over the top and some goes underneath. The air that goes over the curved upper surface undergoes two important changes: it is reduced in pressure (by the centrifugal force of flowing across the curved surface) and it is accelerated downward (as it leaves the trailing edge of the wing). The wing is forced into the region of reduced air pressure above the upper surface of the wing by the higher air pressure beneath the wing. Also, the downward acceleration of the air (downwash) at the trailing edge forces the wing upward.

    Since lift is dependant on the motion of the air, it increases as the speed of the air increases. Lift also increases (to a point) as the angle that the wing makes with the airflow (known as the angle of attack) increases. Past a certain point, however, increased angle of attack will cause the wing to suddenly lose its lifting ability, or stall.

    Control Surfaces and Maneuvering

    An airplane in flight moves around three axes of rotation: longitudinal axis, lateral axis, and vertical axis. These axes are imaginary lines that run perpendicularly to each other through the center of gravity of the airplane. Rotation around the longitudinal axis (the line from the nose of the plane to the tail) is called roll. Rotation around the lateral axis (the line from wingtip to wingtip) is called pitch. Rotation around the vertical axis (the line from beneath to above the plane) is called yaw. The pilot guides and controls the aircraft by controlling its pitch, roll, and yaw via the control surfaces. These include the ailerons, elevators, and rudder.

    Basic Control Surfaces on an Airplane


    The ailerons on an airplane's wings control roll around the longitudinal axis. They work together, simultaneously, tied to the control wheel, or stick, in the cockpit. When the control wheel is turned left, the aileron on the left wing goes up and the one on the right wing goes down. The opposite occurs when the wheel is turned right. But how does this make the airplane roll?

    The ailerons alter the lifting ability of the wings slightly. When an aileron is lowered, the lift on the outer portion of that wing increases, causing that wing to rise a little. When an aileron is raised, the lift on the outer portion of that wing is decreased slightly, causing that wing to drop a little. Since the ailerons on an airplane work together, their action causes the airplane to roll.

    aileron neutral, normal lift

    aileron lowered, increased lift

    aileron raised, decreased lift


    The elevators on the horizontal portion of the tail of an airplane control the pitch of the plane, or its motion around the lateral axis. They are also tied to the control wheel in the cockpit. When the wheel is pulled back, the elevators move upward, causing the tail of the plane to move downward and the nose to pitch upward. When the wheel is pushed forward, the elevators move downward, causing the tail of the plane to rise and the nose to pitch downward.

    The elevators work like the ailerons on the wings, in that they cause changes in the lift generated by the tail of the plane. Also, the elevators work together, simultaneously, like the ailerons, but they do not work in opposition to one another. Both go up when the control wheel is pulled back and both go down when the control wheel is pushed forward.

    elevator raised, reduced lift, tail goes down, nose goes up

    elevator neutral (centered)

    elevator lowered, increased lift, tail goes up, nose goes down


    The rudder on the rear edge of the vertical fin on the airplane's tail controls yaw around the vertical axis. It is connected to the pedals at the pilot's feet. Pushing the right pedal causes the rudder to deflect to the right. This makes the tail of the airplane move toward the left, causing the nose to move to the right. Pushing the left pedal makes the rudder deflect to the left, the tail moves to the right, and the nose points to the left.

    rudder left, tail right

    rudder neutral (centered)

    rudder right, tail left

    Although the rudder pedals and control wheel in the cockpit are not linked together, they must be used simultaneously to control the plane. The pilot guides the airplane by careful and precise movements of the control wheel and rudder pedals, as well as adjusting the thrust of the aircraft.

    How Does an Airplane Produce Thrust?

    Thrust is the force created by a power source that overcomes the airplane's aerodynamic drag (its resistance to passing through the air) and gives it forward motion. This force can either "pull" or "push" the aircraft forward, depending on the type of power source used. Common types include reciprocating (piston-powered) engines driving propellers, and jet engines.

    Reciprocating Engines with Propellers

    A reciprocating engine is an internal-combustion engine in which pistons moving back and forth act upon a crankshaft to create rotational movement. (This is the same type of engine that powers most family cars.) A mixture of fuel and air is compressed by the pistons, an electric spark causes the mixture to explode, driving the pistons downward. This motion is transferred to the crankshaft by connecting rods. The rotating crankshaft turns the propeller.

    A propeller is a type of airfoil (similar to a wing) that turns and accelerates air. As the blades of the propeller rotate they create lifting forces just as a wing does, only working in the horizontal plane instead of the vertical as with wings. Thus, the propeller creates a propulsive force perpendicular to its plane of rotation that moves the aircraft forward as a reaction. Props can either "pull" the aircraft from their position on the front of the wings or fuselage, or "push" it from behind, or both.

    Jet Engines

    A jet engine is any engine that ejects a jet or stream of gas or fluid, thereby obtaining thrust in reaction to the ejection force. A jet aircraft engine obtains oxygen from the atmosphere for the combustion of its fuel, creating thrust in reaction to the rapid exhaust of the combustion products. There are several types of jet engines. Some are briefly described below.


    A turbojet engine is a jet engine that incorporates a turbine-driven compressor to take in and compress air for the combustion of fuel. The exhaust from the combustion drives the turbine and creates the thrust-producing jet.


    A turbofan engine is a turbojet engine in which additional thrust is gained by extending a portion of the compressor or turbine blades outside the inner engine casing. These extended blades propel bypass air around the engine core, between the inner and outer engine casings. This air is not combusted but does provide additional thrust since it is compressed by the blades.


    A turboprop engine is a turbojet engine in which a portion of the exhaust energy is used to drive a propeller. The engine's thrust is therefore generated by a combination of the propeller's thrust and the jet exhaust from the engine.


    A ramjet engine is the simplest type of jet engine since it has no moving parts. The engine is basically a specially-shaped duct open at both ends, with the air necessary for combustion being compressed by the forward motion of the engine. Fuel is sprayed into the airstream and the mixture is ignited. The high-pressure air coming into the combustion chamber keeps the reaction from going back toward the inlet.

    Basic Ramjet Engine

    Ramjet engines cannot operate under static conditions. In order to function, they have to already be traveling through the air at slightly over the speed of sound. (The speed of sound is somewhat over 740 miles per hour at sea level.) This means that the aircraft using them must first get up to the required speed using some other type of propulsion, then start the ramjets. They can operate at up to five times the speed of sound.


    A scramjet, or "supersonic combustion ramjet", engine is similar to a ramjet, but is designed to operate at well over five times the speed of sound, or at hypersonic velocities. As with ramjets, aircraft powered by scramjets must first be brought up to required speed by some other means of propulsion. Unlike ramjets, which slow the supersonic airstream entering the inlet to subsonic speeds before combustion, a scramjet combusts the supersonic airstream without slowing it.

  • 4 years ago


    Source(s): Realistic Airplane Flight Simulator :
  • 5 years ago

    What makes airplanes fly are the four forces of flight, thrust, provided by the engines, propelling the airplane forward, lift pulling the airplane up, drag pulling the airplane back, and weight, or gravity pulling the airplane down. How much an airplane weighs, depends on the plane. Small 4 seater training planes, such as Cessna 172s weigh about 2000 pounds. Commercial planes, such as 747s, weigh about 430 tons.

  • Anonymous
    1 decade ago

    Looking at a big old jet plane kinda makes ya wonder how they get off the ground. The answer is foward motion and wings! If you can get a rock to skip over a pond what keeps it from falling into the water? Motion and shape of the rock. As the air moves over the top of the plane a suction takes place and lifts the plane off the ground. Now depending on wing size, shape, and length, you get performance. You cannot see the air you breathe but if you go underwater you find out really fast you need more air. That is how it is with airplanes. You cannot see the lift,but it is there.

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  • Bernoulli is not the total answer, remember a guy by the name of newton ?

    What makes an airfoil fly? thrust and angle of attack...

    "You’ve probably been told that an airfoil produces lift because it is curved on top and flat on the bottom. But you shouldn’t believe it, not even for an instant.

    Presumably you are aware that airshow pilots routinely fly for extended periods of time upside down. Doesn’t that make you suspicious that there might be something wrong with the story about curved on top and flat on the bottom?"

  • Anonymous
    1 decade ago

    Well, money for starters. Without that, they'd never get built or leave the ground ;>)

    The second reason is called aerodynamic lift created when air flows over the curved surface of a properly designed airfoil. This lift (suction above the wing, actually) is explained by the Bernoulli principle. Read here: .

    A small two seat airplane like a Piper Cub may only weigh 1,000 lbs or so while a Boeing 747 weights close to a million pounds fully loaded.

  • 1 decade ago

    The main component of an airplane are wings, which help an airplain to fly in the ocean of air. According to Bernoulli's principle: "As the velocity of the fluid increase, its pressure decreases." When pressure on upper surface of the wings is low and lower surface of wings the pressure is high then lift create. Acoording to nature, If high pressure is down and low pressure is up then high pressure try to meet low pressure, so that it does create lift.

  • Anonymous
    1 decade ago

    check out the explanation of Bernoulli's principle that makes an airplane fly and th angle of the wings flaps, aerofoils etc.. helps it :)

    full explanations too on the aerodynamics :)

  • 1 decade ago

    What makes an airplane fly??

    MONEY! And lots of it!

    I think lift has something to do with it too, but mostly it's money.

    Source(s): Personal Experience
  • 1 decade ago

    WOW great question!

    I had a pilot ask me the same question when I was in flight school and I was searching for my lift and thrust answers when he got a big grin on his face and said, "money."

    Looks like you have all the answers you need!

    Source(s): me
  • Anonymous
    1 decade ago

    Airplanes fly because people got tired of railroads, that's one .... and the other reason is that we have business meetings in London.

    Airplanes wheigh different amounts.


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