do helicopter push down air or lift thru the air?

Answer 1

Air passing over the top of the airfoil produces aerodynamic force The shape of the airfoil causes a low pressure area above the airfoil according to Bernoulli's Principle, and the decrease in pressure on top of the airfoil exerts an upward aerodynamic force. Pressure differential between the upper and lower surface of the airfoil is quite small - in the vicinity of 1 percent. Even a small pressure differential produces substantial force when applied to the large area of a rotor blade.
A helicopter flies for the same basic reason that any conventional aircraft flies, because aerodynamic forces necessary to keep it aloft are produced when air passes about the rotor blades. The rotor blade, or airfoil, is the structure that makes flight possible. Its shape produces lift when it passes through the air. Helicopter blades have airfoil sections designed for a specific set of flight characteristics. Usually the designer must compromise to obtain an airfoil section that has the best flight characteristics for the mission the aircraft will perform.
Airfoil sections are of two basic types, symmetrical and nonsymmetrical.

Symmetrical airfoils have identical upper and lower surfaces. They are suited to rotary-wing applications because they have almost no center of pressure travel. Travel remains relatively constant under varying angles of attack, affording the best lift-drag ratios for the full range of velocities from rotor blade root to tip. However, the symmetrical airfoil produces less lift than a nonsymmetrical airfoil and also has relatively undesirable stall characteristics. The helicopter blade (airfoil) must adapt to a wide range of airspeeds and angles of attack during each revolution of the rotor. The symmetrical airfoil delivers acceptable performance under those alternating conditions. Other benefits are lower cost and ease of construction as comparedto the nonsymmetrical airfoil.

Nonsymmetrical (cambered) airfoils may have a wide variety of upper and lower surface designs. The advantages of the nonsymmetrical airfoil are increased lift-drag ratios and more desirable stall characteristics. Nonsymmetrical airfoils were not used in earlier helicopters because the center of pressure location moved too much when angle of attack was changed. When center of pressure moves, a twisting force is exerted on the rotor blades. Rotor system components had to be designed that would withstand the twisting force. Recent design processes and new materials used to manufacture rotor systems have partially overcome the problems associated with use of nonsymmetrical airfoils.
Distribution of pressure over an airfoil section may be a source of an aerodynamic twisting force as well as lift. A typical example is illustrated by the pressure distribution pattern developed by this cambered (nonsymmetrical) airfoil:
The upper surface has pressures distributed which produce the upper surface lift.
The lower surface has pressures distributed which produce the lower surface force. Net lift produced by the airfoil is the difference between lift on the upper surface and the force on the lower surface. Net lift is effectively concentrated at a point on the chord called the Center Of Pressure.
When the angle of attack is increased:
Upper surface lift increases relative to the lower surface force.
Since the two vectors are not located at the same point along the chord line, a twisting force is exerted about the center of pressure. Center of pressure also moves along the chord line when angle of attack changes, because the two vectors are separated. This characteristic of nonsymmetrical airfoils results in undesirable control forces that must be compensated for if the airfoil is used in rotary wing applications.
The pressure patterns for symmetrical airfoils are distributed differently than for nonsymmetrical airfoils:
Upper surface lift and lower surface lift vectors are opposite each other instead of being separated along the chord line as in the cambered airfoil.
When the angle of attack is increased to develop positive lift, the vectors remain essentially opposite each other and the twisting force is not exerted. Center of pressure remains relatively constant even when angle of attack is changed. This is a desirable characteristic for a rotor blade, because it changes angle of attack constantly during each revolution.

Answer 2

Does an aeroplane wing cause a downward displacement of air? I think the answer is no. Could a helicopter lift off if the blades are in a horizontal position? Probably not.
Helicopter blades act like propeller blades, which deflect a large downward or backward amount of air. Lift is not really being created. Birds fly in this manner. Watch the wing beat of a fly in slow motion. The wing moves backwards and forwards and swings from the top edge to an angle of say, 45°. As it sweeps forward it pushes down a mass of air. This increases the pressure on the underside of the wing. There is clearly no aerofoil section to a fly's wing.

Answer 3

In conventional aircraft, the wing profile (called airfoil) is designed to deflect air efficiently downward. This downward deflection causes an opposite lifting force on the wing (described by Newton's third law) and a lower pressure on the upper surface, higher pressure on the lower surface. This pressure difference integrated over the airfoil area causes a net lift. However, the more the lift of the airfoil, the more drag that is caused (induced drag by creating wingtip vortices). A helicopter makes use of the same principle, except that instead of moving the entire aircraft, only the wings themselves are moved in a circular motion. The helicopter's rotor can simply be regarded as rotating wings, from where the military name of "rotary wing aircraft" originates.
Turning the rotor generates lift but it also applies a reverse torque, which would spin the helicopter fuselage in the opposite direction to the rotor if no counter-acting force was applied. At low speeds, the most common way to counteract this torque is to have a smaller vertical propeller mounted at the rear of the aircraft called a tail rotor. This rotor creates thrust which is in the opposite direction from the torque generated by the main rotor. When the thrust from the tail rotor is sufficient to cancel out the torque from the main rotor, the helicopter will not rotate around the main rotor shaft.

Answer 4

Both actually.
The rotor blades are simply rotating airfoils, like a wing. The shape of the blade causes lift through Newtons third law - every action has an equal and opposite reaction. The "action" of the downflowing air on the trailing edge of the blade causes the "reaction" of pushing the helicopter up.
The blades also cause lift through the low pressure caused by the faster airflow on the top of the blade (relative to the air underneath the blade). The low pressure area over the blade, in laymans terms, sucks the blade up, essentially creating lift.

So as I said...both!

Answer 5

It does both, it is still an ongoing argument whether most of the lift is created through displacement of the air (pushing air down) or through Bernoulli's principle (faster airflow over the top of airfoil reduces pressure creating lift). It is generally taught and accepted that about 70-85% of lift is created through Bernoulli's principle but this has not yet been proven and some say that most of the lift is created through the displacement of air.
But almost everyone agrees that both are factors in the creation of lift.

Answer 6

The rotating helicopter rotor blades lift the weight of the helicopter just as the wings lift the weight of an airplane.

It took about ten days of three-hours a day classroom lectures to explain everything that happens when a helicopter is in flight. I have 2000 hours of helicopter pilot time since then to prove that they really can fly.

Dan Dantzler
Radclif/Fort Knox, KY

Answer 7

It pushes the air with a downward force. This downward deflection causes an opposite lifting force on the rotor blade (described by Isaac Newton's third law) and a lower pressure on the upper surface, higher pressure on the lower surface.

Answer 8

the rotor blades create lift in the same way that the wing of a conventional aircraft creates lift tolift the aircraft into the air wings on a737 or cessna etc are known as fixed wing and on a helicopter are referred to as rotory wing . so as both types of wings create lift answer is lift thru the air

Answer 9

Don't be embarrassed if you don't understand these concepts. A lot of people don't understand it, even some of those who work with the science every day! (recall the song, "Rocket Man") ;) I'm going to give you a link to Georgia State University's hyper-physics lab. It has some great illustrations of Newton's laws of motion. The link I will give you takes you to detailed information about how collisions work. There's even a calculator to allow you to figure out exactly what happens when matter collides. Particle collision physics is very relevant to your question about propulsion in space. Here's a more specific answer to your question: Essentially, inside a rocket engine, you have oxidized rocket fuel exploding and colliding with the interior of the rocket engine, which directs/vectors it as exhaust out of the rocket. The molecules of the rocket fuel combustion are making "elastic collisions" with the inside of the rocket. Study the information and tutorials at the link below, and you should understand the physics better. As for "wings" on spacecraft, they are only for when the vehicle returns to Earth to allow it to glide like a glider (also for stabilization with its assent, as with the Space Shuttle). Rocket fuel (propulsion) of some sort moves the spacecraft in 3 dimensions in space: pitch, roll, and yaw. Momentum from the massive liftoff from the Earth is conserved throughout the voyage, and continues to move the spacecraft until another force (such as using control rockets to change course) is applied. Orbits around planets are actually "free falls"; the spacecraft is in a continuous fall, but moving so fast that it orbits the planet instead of crashing into it. In addition to collision physics inside the rocket engine, space travel today is really just a massively complex trick of force, acceleration, momentum and gravity. I hope I was helpful. Have a good day.

Answer 10

It does several things. When it is close to the ground (ground effects) it actuall pushes air down into a cushion. when it escapes ground effects it is strictly lift just like a fixed wing aircraft. The wing just happens to be moving independantly of the craft motion. Helos have very complicated movements/effects. If you want to learn more check out:
http://travel.howstuffworks.com/helicopter1.htm