Helicopter Physics Series – #2 Chopper Control – Smarter Every Day 46
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Helicopter Physics Series – #2 Chopper Control – Smarter Every Day 46

November 4, 2019

Alright. This is totally easy once
you understand the physics. Watch this. Left, yep right, go back to the right. It’s easy! [unintelligible] flip. 1..2..3.. Yeah! Awesome! So, as a kid I spent many an hour in a book about the drawings of Leonardo Da Vinci. In particular his flying machines. Check out this medieval helicopter.
It looks like it would work, but you can’t really judge a book by it’s cover because there’s no way to provide counter torque to the body of the aircraft. Modern day helicopters do this by providing a counter torque rotor on a boom, a tail rotor. This works by stopping the rotation of the helicopter. But here’s what you haven’t thought about. You are, after all, applying a force to a free floating body,
which means that body wants to drift. So how does a helicopter
keep from drifting? We’re gonna take a journey. We’re gonna go from a top level knowledge of how helicopters work to a really deep understanding.
How you doing Mr Ledbetter? Hi, I’m Richard Ledbetter. I’m a docent at the National Air and Space Museum.
(Destin) Alright! So what do you have to show us today about how helicopters work.
(Mr Ledbetter) Well, I guess what we’re gonna talk about is kinda the main rotor system on a conventional helicopter, and the main rotor system basically provides both the lift and the control for the helicopter. And how we control the helicopter is by varying the pitch at each of the rotor blades. (Destin) So how do you vary the pitch on a helicopter when it’s rotating, when the blades are rotating? We use, on most helicopters, we use something called a swashplate, and essentially what a swashplate does, is it converts non-rotating to rotating control motion. We have two kinds of control for the helicopter, and for cyclic inputs, what happens is that that swashplate will just simply rotate forward or rotate aft, and that changes the input to each of the rotor blades, but for collective pitch what will happen is that swashplate will actually move up or down. That will actually change the pitch in both of those rotor blades at exactly the same time. (Destin) Ohh! OK I just learned something.
So in summary there’s three types of control. There’s collective pitch, there is cyclic pitch, and there’s antitorque. Of course antitorque is the rotor system on the back.
(Destin) So lets start with collective Carl. So what is this magical device right here? (Carl) This is the swashplate, and this is the source of all control for any helicopter. Any direction the swashplate moves, for the most part, the helicopter follows. So the collective is where you change the pitch of both blades, either up or down, and that pulls the helicopter up or down. You do not control the altitude of the helicopter by the speed of the blades. That stays the same.
(Destin) It’s translated up or down, and that controls how much of a bite of air the rotors take. Is that correct? (Carl) That is. Yep. Absolutely. And that’ll actually make the helicopter either go up or down. Or if it’s upside down, it’s backwards.
(Destin) Oh yeah, cause it’s upside down. Cause I’m a helicopter genius. [laugh]
(Carl) The tail rotor, just like the main blades never changes speed, so in order to control the thrust, we change the pitch on the blades, so it can push or pull in both directions.
(Destin) And the reason it does that, it’s basically a reaction torque to what’s going on up here. The blades are putting a torque into the body is that correct?
(Carl) Yep the act of spinning the blades makes the helicopter want to go the opposite direction. (Destin) Makes sense. Can you show me what cyclic pitch looks like now. (Carl) Cyclic pitch is where the swashplate tilts, and through the linkage controls the pitch of the blades and changes it every revolution to control the pitch and roll of the helicopter. (Destin) Give me cyclic pitch in this direction..
OK but then if I rotate it it’ll change as it goes around correct?
(Carl) It does change.
(Destin) So.. so.. that linkage rides on the swashplate and then pushes up on the side of the blade, and then that in turn changes the blade depending on where it is in the rotation of the rotor shaft right?
(Carl) Correct.
(Destin) Alright. And so, what does that do for ya? (Carl) That lets me flip it any way I want to. [laughs]
(Destin) That lets me do wizardry. [rotor noise] OK now you speak helicopter. And for the next few videos, prepare for your mind to be blown, but we’re going to be using these fundamental terms so get ready. Go ahead and subscribe so you can see this video series. It’s worth it. [rotor noise] [music] [ Captions by Andrew Jackson ] Captioning in different languages welcome.
Please contact Destin if you can help.

Only registered users can comment.

  1. Wait he said "Most helicopters use a swash plate" are the ones that dont use it co-axial or is there something even more complex and cool than a swash plate?

  2. I've been a big aviation buff for a long time so I mean this as a big compliment when I say your quick, simple visual explanation for how all of the controls work was an easier explanation than I've ever seen or read. Bravo!

  3. you really shouldn't stand that close to one of those. Recently a guy just as good at flying them as him cut half way through his neck and died

  4. Ok so if you see the rotor as a circle from above, cyclic pitch creates more lift in one area of the circle than another. This causes this area to rise, shifting the force keeping the helicopter flying from straight down to angled, so you can use it to get where you're going. g

    I kinda always knew this, I just couldn't imagine that we had tech that kept a rotor-blade that's changing pitch a hundred times a second from shaking to bits. I mean I can see that now we can, easily, but when the first heli's went airborne this wasn't the case.

  5. at about 2 minutes in, the red/white helicopter in the background, i got bored and looked it up, it's a bell 47B manufactured in 1947 and is currently sitting with an expired registration (expired 03/31/2013) with the registered owner indeed being the national air and space museum

  6. Collective pitch = W(up) and S(down)
    Cyclic pitch = Arrow keys (direction of tilting)
    Anti Torque = Q(left) and E(right)

    Yep, learned it all in GTA San Andreas

  7. Watching that little RC helicopter fly, all I could think about were dragonflies. Very erratic, very agile, and yet very precise.

  8. Hello I am a big fan of this channel,

    I would like to point out that, at minute 2:39, you guys are explaining that "You do not control the altitude of the helicopter by the speed of the blades." However, I found in The Complete Book of Helicopters by D. N. Ahnstrom (page 127) that you do control de altitude of the helicopter by the speed of the blades, could you please explain me what is going on, than you for your time!!!

  9. That Smithsonian guy sounds like he really knows is stuff, but if you watch him in mute he looks like he has no idea what he's talking about

  10. awesome video. I was really hoping he would have shown that kids hands on the controller. I wanted to see him doing those crazy moves on the joysticks.

  11. How I wish these videos were available wen I was attending the US Army Initial Entry Rotary Wing (IERW) Course (aka: Flight School) at Fort Rucker, AL.

  12. Ya and flip it any way I want to "slams" on the controls crazily and makes the funny I want to crash it face

  13. great tricks with that thing, But you cant do that with a real helicopter although you can do a flip in one if you have enough training i know i fly a chopper

  14. Superb guys.. special information I never know about this but now I came to know this..
    Well I like your helicopter toy.. how can buy this.. ?

  15. i had to watch this video to understand the 90 degree out of phase concept, because only here i saw that the rods for the pitch control are no aligned or directly under the blades. now all makes sense 😀

  16. At 3:25 you can see 2 linkages to the blades, but there are 2 other shorter linkages to the mast. I assume this tilts both rotors in the direction of motion? I've seen this in other helicopters at least: https://youtu.be/_QkOpH2e6tM?t=4m27s

  17. Destin, Destin, Destin,

    Directed here from another site. I am very disappointed that you did not show that to tilt the heli FORWARD, the AoA and, therefore maximum lift is on the RETREATING blade, NOT at the rear.

    Gyroscopic precession, then acting 90 degrees LATER in the rotation, lifts the tail. You can just barely see this at time 3:27. The retreating blade (on the left) increases AoA as the swash-plate tips forward.

    This is one of the most interesting aspects that ties the real world to understanding ALL of the fundamental principles of science to understand thing like this. The beauty of science is the way it all fits so nicely and plays so well together…when you fully understand and apply ALL relevant principles to things….

    Shame, Shame, shame.

  18. Here is my question. I have heard stories of rotor blades chopping through cockpits and killing pilots, but you make it seem as if the rotors dont tilt forward or back at all. Are these two different systems? Or am I just unable to understand.

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