Helicopter Physics Series - #3 Upside Down Flying With High Speed Video - Smarter Every Day 47

Hey, it's me Destin. Welcome back to Smarter Every Day. So last week I described collective pitch control for a helicopter, I described cyclic pitch control for a helicopter, and I also described anti-torque pitch control. But this week we're going to combine them all and describe something called collective-cyclic pitch mixing. It's pretty cool, and it's basically how every helicopter pilot flies, including Carl in this case.

The way I'm gonna describe this to you is by setting up and showing you a high-speed video clip of Carl flipping the helicopter over and flying inverted. [rotor noise] You're about center of the frame, maybe a little less right there. [rotor noise] [rotor noise] That's gonna be good. It's pretty interesting, because if you think about it he's having to use both collective and cyclic to make the sweep, go up, and then he's going back to negative collective. [music] And then he's balancing it up there with cyclic all the time. So you can see he's never using one particular input. It's always a variation of both.

OK, so if you didn't really understand what was going on there, I asked Carl to do something else for us. I asked him to mount a camera on the back of his helicopter looking at the swashplate, and then take a normal flight so you could see the collective-cyclic mixing, but here's a couple of things to keep in mind. At the top of the screen you're going to see the rotors, and at some point, it's gonna look like the rotors are bending. That's actually not happening. What you're seeing there is something called the rolling shutter effect. The second thing you're gonna see is it looks like the rotor shaft is speeding up and slowing down wildly. That has to do with the frame rate of the camera. That's called aliasing. If you want to know what aliasing is, just click this box over here and I'll explain that to you in greater detail. [electronic servo sounds] [music] [music]

OK, I've been getting a lot of comments on these videos about whether or not an actual helicopter can do these types of maneuvers. And the answer is yes, and no. Helicopters can do this if they're designed for it; however, you're limited by the meat servo sitting in the seat. A human can only take so much acceleration. So how do you scale up what you're seeing on this RC helicopter to a real helicopter? Before they flew a space shuttle into space, they had to do a wind tunnel test on it somehow, right?

Well, it gets complicated, but there's a term called similitude, and similitude has to do with the geometric, kinematic, and dynamic similarity between a small-scale object and a full-scale object. Engineers do this all the time, especially aerospace engineers. So anyway, go look at the wiki link I'm gonna put below and read up on similitude so you can understand it. I will tell you this: it has something to do with continuum mechanics, which is by far the hardest course I've ever taken in my life.

So if you must know, there's a city in Florida named Destin, and the thrift store there is the coolest place on earth for me personally. Anyway, next week's video will blow your mind. It's really complicated, but it's really interesting, so if you can understand it, you're doing pretty good, but it blew my mind. It's gonna blow yours too. Have a good one, and get Smarter Every Day.

[Captions by Andrew Jackson] Captioning in different languages welcome. Please contact Destin if you can help.