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Helicopter Physics Series – #5 Autorotation = NO PARACHUTE! – Smarter Every Day 50

September 29, 2019


Hey it’s me Destin.Welcome back to Smarter Every Day.
We’re right in the middle of a series on helicopters and we’re gonna talk to you about.. What is this called?
(son) Parachute. A parachute.
So in airplanes, the pilot can have a parachute so if anything
goes south he can jump out and he can parachute to safety.
Do you want to test the parachute real quick? (son) Yeah I’ll do it.
OK we’re gonna use the parachute off the balcony here. Check this out. Daddy’s gonna throw it. You ready? Parachute man… in the ocean. 1…2…3… Oh man! [laugh] We just gave the parachute man to our neighbours. So think about this.
Let’s say we’re in a helicopter and we’re up high and all of a sudden we run
into trouble when we run out of engine power and we start to fall.
So we’ve got this weight and it’s suspended by this rotor system.
Now if we’re smart about it we can change the pitch on our blades to
spin up our rotors really really fast. And then we have kind of like a
pinwheel or a windmill effect. And if we’re really smart, right at the last minute,
right before we hit the ground, we can change the pitch on those
blades to provide lift. So we’re back driving our rotors and then right at the last
minute we’re using them to decelerate, right before we hit the ground.
This is a manouver called autorotation, and this has kept helicopter pilots alive
for many many years. In fact, they’ve even done autorotations from 40,000 feet. So a helicopter basically has a built-in parachute.
But with a helicopter you’ve got this rotating disc right in front of you.
So my question is, what happens if you lose power at altitude. So this battery he just put in, what if it dies.
So what happens Carl? (Carl) If you lose power in a helicopter you can autorotate.
Alright. So Carl’s gonna demonstrate autorotation and
we’ll get an idea for what happens. You’re getting Smarter Every Day. Alright so what exactly are we about to do here? (Carl) We’re gonna demonstrate autorotations.
I’m gonna take you up a couple of hundred feet up in the air shut the motor off, and fly it all the way
to the ground without power. (Destin) Sounds like a genius idea to me.
(Carl) [laughs] Let’s do it. (Destin) You know… This is expensive right?
(Carl) Yeah [ rotor noise ] Alright so where you at? How high? (Carl) Aah this is probably about 300 feet. Three and I’m gonna turn the motor off right now, and we’re coming in without power.
(Destin) On a very expensive helicopter.
(Carl) Oh yeah.
(Destin) So there’s no power right now. (Carl) No power at all. (Destin) So why did that happen? What did you just do?
(Carl) We’re turning the pitch of the blades down, and as the helicopter is falling down, the air being forced through by gravity spins the blades.
(Destin) So it’s like a windmill?
(Carl) It’s like a windmill.
(Destin) So helicopters are a whole lot safer than I thought. I’m gonna be honest with you I’m not very impressed though cause it was right side up the whole time.
[laughs] (Carl) Let’s do it upside down.
(Destin) W..w..wait dude. I’m joking dude. (Carl) Aah. Let’s do it!
(Destin) He can do it.
(Carl) Let’s do it! I am not responsible for what’s about to happen. [rotor sounds] You don’t have to do it if you don’t want to.
(Carl) [laugh] (Destin) Are you upside down already?
(Carl) Oh yeah. (Carl) Here we go. We’re gonna flip upside down. (Destin) So you have an unpowered..
(Carl) Power is off
(Destin) helicoper upside down.
(Carl) Correct. (Destin) This makes perfect sense. Holy cow. [laughs] (Carl) There we go.
(Destin) That is messed up man. Alright so helicopters are a whole lot safer than I thought, and if you want to see more about how they work look at this video series that we’re making, how to control helicopters. This is Carl. I put his info in the description. Please subscribe. Later. Where’s my thinking hat? I need my thinking hat.
[laughs] [ Captions by Andrew Jackson ] Captioning in different languages welcome.
Please contact Destin if you can help.

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