Will it take off?

[Garrick]

Re: Will it take off?

^ very well put. i don't know how many times it needs to be repeated in different ways before people start understanding. i have a hard time believing this is such a popular argument on the internet.

[MJDub]

Re: Will it take off?

And something else for people to consider if they still don't understand that: if you hold the brakes and put the engine to full throttle, you're not taking off the ground. The only thing that is different between holding the brakes and being on a conveyor belt is the wheels moving. Moving wheels do absolutely nothing.

[threehills]

Re: Will it take off?

^ very well put. i don't know how many times it needs to be repeated in different ways before people start understanding. i have a hard time believing this is such a popular argument on the internet.

Cause mythbusters shows the plane taking off. But its a crock because they don't set up the experiment correctly.

[unkownartist]

Re: Will it take off?

Let me bring my piloting expertise into this one (yes I'm a private pilot).

Say you were about to take off and you had a wind that was going parallel to the runway. Conventional wisdom would say that you would want to take off with the wind, no? But conventional wisdom doesn't apply to aerodynamics. You want to take off into the wind (a headwind) because air resistance is what gets the airplane off the ground. Since there is more wind/air coming over the leading edge of the wing (i.e. what creates lift), even though you're technically not going as fast with relation to ground speed, the air speed is all the matters. So if you were to takeoff with the wind (a tailwind), you would need to be going much faster ground speed wise to get the same amount of air over the leading edge of the wings, and unless you're taking off on the space shuttle landing strip, you would probably run out of runway before you got to rotation speed (speed the airplane can lift off the ground and climb).

So going back to this "conveyor belt" idea, there is no way that this would work with any conventional aircraft because while your wheels may be spinning like you're going 150 knots, your airspeed is essentially 0. The engine does provide some air over the wings (in a propeller plane for example) but nowhere near the amount and speed of air that is needed to get the plane off the ground. You need forward motion.

the expert has spoken...nuff said

[srbbnd]

Re: Will it take off?

I work at a University just called the aviation department. They said there is no way this would work. There is no indicated air speed and no angle of attack was the terminology they used. However, if there was a giant fan in front of the plane this could work...

[toasty]

Re: Will it take off?

Let me bring my piloting expertise into this one (yes I'm a private pilot).

Say you were about to take off and you had a wind that was going parallel to the runway. Conventional wisdom would say that you would want to take off with the wind, no? But conventional wisdom doesn't apply to aerodynamics. You want to take off into the wind (a headwind) because air resistance is what gets the airplane off the ground. Since there is more wind/air coming over the leading edge of the wing (i.e. what creates lift), even though you're technically not going as fast with relation to ground speed, the air speed is all the matters. So if you were to takeoff with the wind (a tailwind), you would need to be going much faster ground speed wise to get the same amount of air over the leading edge of the wings, and unless you're taking off on the space shuttle landing strip, you would probably run out of runway before you got to rotation speed (speed the airplane can lift off the ground and climb).

So going back to this "conveyor belt" idea, there is no way that this would work with any conventional aircraft because while your wheels may be spinning like you're going 150 knots, your airspeed is essentially 0. The engine does provide some air over the wings (in a propeller plane for example) but nowhere near the amount and speed of air that is needed to get the plane off the ground. You need forward motion.

Well, I'm satisfied with that answer. Thanks.

[progpopey]

Re: Will it take off?

Surely the two would just cancel each other out and the plane would be stationery going neither forwards or backwards and certainly not anywhere near flying!

[jamesalvarez]

Re: Will it take off?

Let me bring my piloting expertise into this one (yes I'm a private pilot).

Say you were about to take off and you had a wind that was going parallel to the runway. Conventional wisdom would say that you would want to take off with the wind, no? But conventional wisdom doesn't apply to aerodynamics. You want to take off into the wind (a headwind) because air resistance is what gets the airplane off the ground. Since there is more wind/air coming over the leading edge of the wing (i.e. what creates lift), even though you're technically not going as fast with relation to ground speed, the air speed is all the matters. So if you were to takeoff with the wind (a tailwind), you would need to be going much faster ground speed wise to get the same amount of air over the leading edge of the wings, and unless you're taking off on the space shuttle landing strip, you would probably run out of runway before you got to rotation speed (speed the airplane can lift off the ground and climb).

So going back to this "conveyor belt" idea, there is no way that this would work with any conventional aircraft because while your wheels may be spinning like you're going 150 knots, your airspeed is essentially 0. The engine does provide some air over the wings (in a propeller plane for example) but nowhere near the amount and speed of air that is needed to get the plane off the ground. You need forward motion.

lol - air speed does matter, it is confusing but if you have a long enough runway then the plane can take off. The conveyor belt will only cause a tiny amount of extra friction due to the increased wheel rotation in contact with the ground.

forget what the wheels are doing its what's confusing. the jet engines creates a pressure difference in the -air- which causes them to pull the plane forward due to -air- friction. like a submarine uses a turbine in water. the forward motion is created from a force on the air not the ground. so a forward motion would be generated and the plane can rise.

think of the behaviour of wheels that are not connected to an engine, if you lift the airplane up, set the conveyor on full and put it down again, for a second the wheels will just spin with the airplane still, (then friction as a force on the wheels would slowly cause cause the plane to accelerate backwards). This what would happen without a jet engine on. If you put the engines on full, the plane would start moving forward.

the wheels on an airplane are just there to support the plane and lower friction for taking off and landing and maybe they drive it slowly round the airport? dunno but they are not used for flying!

if the aviation department got it wrong then they probably didn't get the question. it is pretty confusing and i would certainly not blame anyone for not getting it at first

[MJDub]

Re: Will it take off?

Edit to my post:

"...the air speed is all that matters."

[jamesalvarez]

Re: Will it take off?

Edit to my post:

"...the air speed is all that matters."

yeah, and whatever the conveyor belt does , it doesn't effect the air speed the airplane can -still- generate!

[MJDub]

Re: Will it take off?

yeah, and whatever the conveyor belt does , it doesn't effect the air speed the airplane can -still- generate!

I think we're on two different pages here. Forward motion/air resistance is what generates air speed. It isn't generated by the plane or the plane's engine per se, although the engine propels the plane forward so it can get the air resistance the wings need to lift the plane off the ground.

Unless the conveyor belt is coupled with a wind tunnel to give the wings the air they need, the plane is grounded.

[jamesalvarez]

Re: Will it take off?

im not saying the airplane would rise vertically, it would look like a normal takeoff, just with a conveyor belt udnerneath - the engine generates air velocity on the wings by being attached to the airplane, pulling the airplane through the air. a plane doesnt take off by using its wheels to generate forward motion, it uses engines to drag the plane through the air.

[Steve Graham]

Re: Will it take off?

the plane ISNT moving along the converyor belt, it is basically stationary in this argument

[Garrick]

Re: Will it take off?

if the conveyor belt somehow generates equivilent wind speed of inflight wind speed, then yes, the plane would take off vertically but to maintain a stable take off and not move backwards or forwards would be friggin hard to impossible. i get what you're saying though, james... in this particular case, i think we were assuming nothing is generating wind speed for the plane to rise thus making it impossible to really take off.

[miketpoto]

Re: Will it take off?

Why is this so difficult to grasp?