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.