FINALLY! Mythbuster, Dec 12th, MUST WATCH!

[Xtrema]

http://community.discovery.com/eve/f...5321919039/p/1

Airplane Hour
(Weds., December 12 at 9 PM ET/PT)
Adam and Jamie find out if either of them can safely land a Boeing 747-400 on a runway in varying weather conditions. Meanwhile, Kari, Tory and Grant risk life and limb to investigate skydiving myths regularly featured in Hollywood action films. Is it possible to catch up with someone in freefall if that person jumps out a plane before you do? Can you really hold a conversation during freefall? And would you survive if you opened your parachute only a few feet off the ground? Finally, Adam and Jamie carefully navigate their way through a myth that has baffled everyone from web bloggers to pilots. If a plane is traveling at takeoff speed on a conveyor belt, and the belt is matching that speed in the opposite direction, can the plane take off? Extensive small-scale testing with a super treadmill and a nearly uncontrollable model airplane don't completely resolve the myth, so our flight cadets supersize the myth with help from a willing pilot and his Ultralight flying machine.

YES!

[Mibz]

Do people seriously think that the plane won't move forward? I'm unsure of the friction between the tires and belt so perhaps it won't be able to take off but it will definitely move forward.

[buh_buh]

its about time we solved this

[Tik-Tok]

I don't understand the myth. You require airflow, and high/low pressure ranges along the airfoil to create lift, how would a conveyer belt create this?

[alloroc]

Bernoulli's Theorem people.

no forward motion relative to the surrounding air = no airflow across the wings = no flight - unless they are contemplating doing this in a wind tunnel and blowing air across the wings at take off velocity.

[natejj]

I got 5 bucks that says the plane DOESNT take off. I've seen planes take off the back of trucks, but that is different.

[benyl]

^^ is thrust applied to the ground or the air?

OMG... hahahahaha...

It really isn't a myth. The plane will take off. It is all about relative air speed.

[benyl]

Originally posted by natejj
I got 5 bucks that says the plane DOESNT take off. I've seen planes take off the back of trucks, but that is different.

I will bet you $5 it does.

[natejj]

Originally posted by benyl


I will bet you $5 it does.

Lets just clarify something. Lets say once the plane is at full thrust, in place, on the conveyor belt, does the belt suddenly stop or something, and the plane shoots forward into the air? Or is the idea that the plane can point its nose upwards and shoot off forwards?

I dont want to start this whole argument over, because I dont claim to be an expert on the subject, I do work in the tower at an airport, so I know a bit about planes. But the theory behind lift is basically when a plane flies forward, the pressure about the wing, is lower then below the wing, so the wing moves toward the lower pressure area, up. If the plane is not moving forward, its relative airspeed is 0 (unless theres a wind) so I just dont think it will fly.

We on for 5 bucks?

[Tik-Tok]

Adam and Jamie find out if either of them can safely land a Boeing 747-400 on a runway in varying weather conditions. Meanwhile, Kari, Tory and Grant risk life and limb to investigate skydiving myths regularly featured in Hollywood action films. Is it possible to catch up with someone in freefall if that person jumps out a plane before you do? Can you really hold a conversation during freefall? And would you survive if you opened your parachute only a few feet off the ground?

Wow, their really gearing the show towards kids these days, aren't they?

Without having to use any cool toys that they always use...

1) Can you safely land a 747 during adverse weather - Highly unlikely, it would be a fluke if you can. BUSTED
2) Can you catch up with someone in freefall Obviously, how else do you think aerobatic skydiving teams do what they do? 50 people all jumping out of the plane at the same time? TRUTH
3) Can you hold a conversation during freefall Why not? you can hold a conversation on a windy day can't you? TRUTH
4) Will you survive if your chute opened a few feet off the ground? Depend how many feet a "few" are, but yeah, your aren't gonna live if they mean THAT few. BUSTED
5) Can an aircraft take off from a conveyer belt No chance in hell. BUSTED

There, I just saved you guys a 2 month wait, and an hour of your life.

[natejj]

Regards to Number 4-
http://www.msnbc.msn.com/id/17113222/

Its all about where you land... this guy survived a 14,000 feet jump with no chute.

[Tik-Tok]

Originally posted by benyl

It really isn't a myth. The plane will take off. It is all about relative air speed.

you just contradicted yourself.

The plane WON'T take off because of relative air speed. There's no air going around the wings.

Will a ram air hood scope make the same power on a dynamometer as it will going 100km/h on the road?

[Tik-Tok]

Originally posted by natejj
Regards to Number 4-
http://www.msnbc.msn.com/id/17113222/

Its all about where you land... this guy survived a 14,000 feet jump with no chute.

There's always exceptions to the rules, a few people have survived, wholly by accident.

[89coupe]

Originally posted by natejj


Lets just clarify something. Lets say once the plane is at full thrust, in place, on the conveyor belt, does the belt suddenly stop or something, and the plane shoots forward into the air? Or is the idea that the plane can point its nose upwards and shoot off forwards?

I dont want to start this whole argument over, because I dont claim to be an expert on the subject, I do work in the tower at an airport, so I know a bit about planes. But the theory behind lift is basically when a plane flies forward, the pressure about the wing, is lower then below the wing, so the wing moves toward the lower pressure area, up. If the plane is not moving forward, its relative airspeed is 0 (unless theres a wind) so I just dont think it will fly.

We on for 5 bucks?

But its thrust that is moving the plane foward, not its wheels. All I would be interested to know is if the thrust of Jet engines would be enough to overcome the gravity of the plane in relation with the drag created on the moving conveyor belt.

[benyl]

Originally posted by Tik-Tok


you just contradicted yourself.

The plane WON'T take off because of relative air speed. There's no air going around the wings.

Will a ram air hood scope make the same power on a dynamometer as it will going 100km/h on the road?

Again. Is the thrust being applied to the air, or the ground?

[Nav13]

Heres the thing though the plane will still require the same if not more room to take off on the conveyor belt. So if they are testing weather or not it will take off on a conveyor belt, the plane will simply move forward abit and then go onto normal tarmac and they might say it doesnt work? So unless they have a huge conveyor belt, like runway length size, I dont see how they are going to do this experiment? Guess I'll just have to wait and see.

[Strider]

The idea behind the myth isn't that the thrust will overcome the conveyor and allow the plane to free itself from the treadmill and take off...

The idea is that you can use a treadmill to let the plane develop the "speed" (and thus lift) that it needs to take off, which it obviously doesn't, because the plane is still in one place.

Originally posted by 89coupe


But its thrust that is moving the plane foward, not its wheels. All I would be interested to know is if the thrust of Jet engines would be enough to overcome the gravity of the plane in relation with the drag created on the moving conveyor belt.

[jibber]

The thrust from the engines move the plane through the air, and it's soley the wings that are resposible for creating the lift that opposes gravity. The plane won't take off unless the airspeed over the wing is high enough.

If the plane was held in place on a moving treadmill by a high-strength steel cable tether, with the engines off, the experiment's results would be the same. No air over the wing = no lift.

I think the desciption of the experiment isn't detailed enough. If they stop the treadmill when the plane is rolling at take-off speed, the plane would shoot forward, and it would leave the ground when the air going over the wings creates enough lift to get the plane off the ground. If they plan on holding the plane in place on a treadmill, by whatever means, it's going to go nowhere.

I'm in for $5 that the plane doesn't take-off if the experiment is as described in the OP.

[Strider]

Thrust is applied to the air, but it's the relative velocity of the air over the wing that creates the pressure difference (between the top surface of the wing and bottom surface) that causes lift.... The jets can thrust all they want, but unless there's air moving over the wing, it's not gonna fly.

I'll take your $5 bet!

Originally posted by benyl


Again. Is the thrust being applied to the air, or the ground?

[Hakkola]

Originally posted by 89coupe


But its thrust that is moving the plane foward, not its wheels. All I would be interested to know is if the thrust of Jet engines would be enough to overcome the gravity of the plane in relation with the drag created on the moving conveyor belt.

That is the logic I used when I decided the plane would take off, with enough thrust you could probably make a plane take off on blocks, which is basically the idea with the treadmill. The negative force will cause the wheels to keep from spinning, but that doesn't mean that the plane will not move forward. It will be like the plane is on skis instead of wheels.