How do helicopters hover?

Question

How do helicopters hover?

Answer 1

they are sucked into the air by means of a vacuum caused by the shape of the blades. Not something you would like the engine to fail on!

Answer 2

I'm not a professional in helicopters but the rotor blades create the lift not wings like as on a plane.  The pilot uses the cyclic or "stick" and the rotor blades move in the direction the cyclic is moved. (Forward-the chopper moves forward. Back-the chopper moves back. Left-the chopper moves left. Right-the chopper moves right, and etc.) During a hover, the pilot maneuvars the cyclic to keep the chopper from moving at all.  Airplanes have to constantly be moving because it is the airflow over the wings that provides lift.  In helicopters, air being thrusted down by the main rotors provides lift whether the helicopter is stationary or not.  The pilot uses another control known as the collective to adjust the angle that the rotor blades hit the air.  For example on a fan the blades are always angled, providing the air, but if they were not, the fan would not blow air very hard.  When the collective is raised the angle is increased and the rotor blades "get a bigger bite of air" thus creating more lift.  The opposite happens when the collective is lowered.  The other main controls are the anti-torque pedals which have the same effect on the tail rotor as the collective does on the main rotor.  Used to yaw the chopper and keep the torque from the main rotors from spinning the helicopter itself.  The pilot cobines the effects of all these controls to keep the helicopter in a hover.  It's not easy.  The pilot must tend to all these controls at once.

Answer 3

http://www.minihelicopter.net/howdohelic...

magic

Answer 4

the helicopter blades are pushing up at the same force gravity is pushing the helicopter down therefore counteracting the force and hovering.

Answer 5

gravitational thrust

Answer 6

With all due respect to Pompeyre who answered earlier , my understanding / explanation is simpler . Aircraft wings , helicopter blades work on the same principle . The shape of the aircraft wing / helicopter rotar is such that the airflow over the top of the wing is greater than the flow over the underside , causing "lift ".  Ask any pilot , my late father flew in Bomber Command in Lancasters , and was on his second "Tour" when the war ended . DJC.

Answer 7

By remaining horizontal the main rotor gives the lift whilst the tail rotor prevents the helicopter from spinning

Answer 8

To put it simply, the aerofoil shape of the rotor blades passing through the air at speed gives the helicopter lift. This lift factor is governed by the pilot via his collective lever. The more he pulls it up the more lift the rotors generate. Once the lift factor is equal to the Helicopters weight it will hover.

Answer 9

by switching the fan on and making it go really really fast

Answer 10

By pushing a volume of air down at such a rate that the resulting upward reactive force is exactly equal to the weight of the craft.

Answer 11

here are some videos for you to review:

http://rotorwingflight.com/videos/listid...

An excellent FREE book on helicopters is here:

http://www.faa.gov/library/manuals/aircr...

Answer 12

the key to the helicopter hovering are the RPM of the rotor. the RPM of the rotor enable the blades to move forwards /aka fly/ while the helicopter may stay in one position...

Basically this is the only difference from the planes. - the blades are moving fast enough to provide lift but the helicopter remains  in one place. the plane has to move with its wings.

Answer 13

Imagine that we would like to create a machine that can simply fly straight upward. Let's not even worry about getting back down for the moment -- up is all that matters. If you are going to provide the upward force with a wing, then the wing has to be in motion in order to create lift. Wings create lift by deflecting air downward and benefiting from the equal and opposite reaction that results

A rotary motion is the easiest way to keep a wing in continuous motion. So you can mount two or more wings on a central shaft and spin the shaft, much like the blades on a ceiling fan. The rotating wings of a helicopter are shaped just like the airfoils of an airplane wing, but generally the wings on a helicopter's rotor are narrow and thin because they must spin so quickly. The helicopter's rotating wing assembly is normally called the main rotor. If you give the main rotor wings a slight angle of attack on the shaft and spin the shaft, the wings start to develop lift.

In order to spin the shaft with enough force to lift a human being and the vehicle, you need an engine of some sort. Reciprocating gasoline engines and gas turbine engines are the most common types. The engine's driveshaft can connect through a transmission to the main rotor shaft. This arrangement works really well until the moment the vehicle leaves the ground. At that moment, there is nothing to keep the engine (and therefore the body of the vehicle) from spinning just like the main rotor does. So, in the absence of anything to stop it, the body will spin in an opposite direction to the main rotor. To keep the body from spinning, you need to apply a force to it.

The usual way to provide a force to the body of the vehicle is to attach another set of rotating wings to a long boom. These wings are known as the tail rotor. The tail rotor produces thrust just like an airplane's propeller does. By producing thrust in a sideways direction, counteracting the engine's desire to spin the body, the tail rotor keeps the body of the helicopter from spinning. Normally, the tail rotor is driven by a long drive shaft that runs from the main rotor's transmission back through the tail boom to a small transmission at the tail rotor.