# how do the propellers on a helicopter actually make the vehicle able to fly?

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how do the propellers on a helicopter actually make the vehicle able to fly?

In: Engineering

The shapes of the rotor blades creates a zone of low pressure above the blades when spinning, “sucking” the helicopter upwards.

Wings provide lift when there’s air rushing around them.

Airplanes move the whole vehicle forwards and have their wings fixed.
Helicopters just spin their wings really fast around in circles.

Wings work by deflecting air downwards. As they push the air down, the air pushes the wing up.

Helicopter’s can also control how much tilt their wings have, causing it to push down more or less air depending on if they need to go more up or down.

~~You may have heard some wrongs stuff about the wing shape causing weird pressure effects (like sucking it up because of low pressure), but the main thing is how much air it’s deflecting. If it was only weird pressure effects, then planes would not be able to fly upside-down without falling out of the sky.~~
EDIT: turns out the bernoulli suction explanation is also a valid description, saying the same thing in different terms. Though I feel the deflection is explanation is more intuitive for the helicopter example considering how much more often they tilt the entire wing.

Air bounces off propeller blade, gets pushed down and according to Newton’s 3rd law there is a force generated that points up. [drawing](https://imgur.com/a/oBOQqeH)

These answers are not really correct.. I would suggest you just want a video about it on YouTube. I went to college for helicopter flight. There is a lot too it..

But I’ll try to simplify it, basically a wing creates pressure on the bottom side and reduces pressure on the top side. High pressure naturally goes to the low pressure side and takes the wing with it. The rotormast of a helicopter does the same thing.

It’s not done”weird pressure thing,” it is aerodynamics.

There are a few elements that need to work together to make a helicopter fly. The simplest is probably the big rotor on the top – this pushes air down and lifts the helicopter into the air. Once the helicopter is off the ground though, there is nothing to hold it straight, so the rotor spinning would start to make the body of the helicopter spin too.

To counteract this they put a second, smaller rotor at the back pointing sideways – when the torque from the main rotor tries to twist the body one way, the tail rotor pointing the other direction pushes in the opposite direction to balance out.

That gives you a helicopter that goes up and down, which is cool but not entirely useful.

The more complicated bit comes when you want to travel sideways – this is done by adjusting the pitch (angle) of the blades as they rotate. Changing the pitch of a blade changes how effective it is. So if you have the blade pitched to be effective when it is on the rear of the helicopter, and less effective when it is at the front, this will naturally lift up the back of the helicopter and cause it to move forwards. Reverse that so the blades are pitched to be more effective on the front and you will go backwards (and the same to the sides).

By manipulating the speed of the main rotor you can go up and down, by manipulating the pitch you can move forwards, backwards or side to side, and by manipulating the tail rotor you can rotate on the spot. Combine them all together and you can fly.