Would the plane take off?

[tropical_fishy]

New experiment.

Don't actually do this, you'll hurt yourself.

You need:
Rollerskates, helmet, treadmill, yourself, and a friend.

Strap on the skates and helmet and get on the treadmill. Turn on the treadmill.

You'll remain pretty much stationary. But you have thrust. Have your friend push you. You are moving forward! Your skate wheels and the treadmill don't factor into the speed at which your friend can push you!

The wheels and treadmill are irrelevant! Your friend can push you no matter how fast things are moving.

This analogy only works if as my friend pushes me and I pick up speed, the treadmill speeds up to match my new speed.

Please play again.

[magman007]

I see where i was wrong, and when flying today, i considered the problem, and retract my statement of it not being able to take off.

Consider this, the plane is still able to run down the runway, whether the wheels are turning or not, that doesnt matter. Its like spin in paintball, it doesnt do a damn thing. LEts put it this way, i was flying backwards today, how you may ask?

I was doing slowflight in a dirty configuration (for non pilots thats pitching up to just above stall speed in landing configuration) the wind was string enough to effectively put me in a hover/ -2 or 3 kts ground speed. I was effectively flying, because there was still wind going over the wings, just i was not traveling forewards.

Now, that conveyor belt can run as fast as it wants, in a perfect world, the jet would not have to over come its own weight on the wheels, if it could do that in a real world, then you could pull a 747 around on a string. but you cant.

so assuming the wheels are turning 100% effortlessly, the wheels will just rotate faster and faster as the jet pushes its way forewards, allowing air to flow over the wings effectively generating lift.

is there any sort of advantage to this conveyor style? NO. Because your TO distance is still the same. you still need to achieve your airspeeds before you pitch back for your climb out speed.

get it q?

[BD_Paintball]

My friend who is a senior at Purdue majoring in Aeronautical/Astronautical Engineering said it will not take off, and I believe him. he said it will not gain any air speed and it wont have any lift at all. he also game me this equation "L=.5*cl*rho*U^2*s. U is wind velocity. If U = 0, L=0, L is lift force, cl is lift coeficient, rho is air density, U is freestream velocity, and s is wing span"

i win

[tropical_fishy]

I see where i was wrong, and when flying today, i considered the problem, and retract my statement of it not being able to take off.

Consider this, the plane is still able to run down the runway, whether the wheels are turning or not, that doesnt matter. Its like spin in paintball, it doesnt do a damn thing. LEts put it this way, i was flying backwards today, how you may ask?

I was doing slowflight in a dirty configuration (for non pilots thats pitching up to just above stall speed in landing configuration) the wind was string enough to effectively put me in a hover/ -2 or 3 kts ground speed. I was effectively flying, because there was still wind going over the wings, just i was not traveling forewards.

Now, that conveyor belt can run as fast as it wants, in a perfect world, the jet would not have to over come its own weight on the wheels, if it could do that in a real world, then you could pull a 747 around on a string. but you cant.

so assuming the wheels are turning 100% effortlessly, the wheels will just rotate faster and faster as the jet pushes its way forewards, allowing air to flow over the wings effectively generating lift.

is there any sort of advantage to this conveyor style? NO. Because your TO distance is still the same. you still need to achieve your airspeeds before you pitch back for your climb out speed.

get it q?

The only thing you haven't explained is exactly how you're going to overcome physics. The problem says that no matter HOW FAST your wheels are spinning-- freewheeling-- the conveyor is going toexactly match that speed. I'm not convinced I'm right-- but no one has explained how exactly this plane is going to overcome 0 net movement.

[neppo1345]

My friend who is a senior at Purdue majoring in Aeronautical/Astronautical Engineering said it will not take off, and I believe him. he said it will not gain any air speed and it wont have any lift at all. he also game me this equation "L=.5*cl*rho*U^2*s. U is wind velocity. If U = 0, L=0, L is lift force, cl is lift coeficient, rho is air density, U is freestream velocity, and s is wing span"

i win

You don't win...its common sense that if an airplane has no airspeed there is no lift...this has nothing to do with the problem at hand...

The wheels and the runway have no effect on the system as a whole because they are virtually frictionless...

[neppo1345]

The only thing you haven't explained is exactly how you're going to overcome physics. The problem says that no matter HOW FAST your wheels are spinning-- freewheeling-- the conveyor is going toexactly match that speed. I'm not convinced I'm right-- but no one has explained how exactly this plane is going to overcome 0 net movement.

Yes, the wheels will be spinning at exactly the same speed as the conveyor...there is very little friction here...

Once the massive jet engines overcome this tiny amount of friction, the rest of the thrust will go towards accelerating the jet towards takeoff velocity...

[BD_Paintball]

You don't win...its common sense that if an airplane has no airspeed there is no lift...this has nothing to do with the problem at hand...

The wheels and the runway have no effect on the system as a whole because they are virtually frictionless...

no i win b/c i gave you scientific proof that it will not take off!!

[neppo1345]

no i win b/c i gave you scientific proof that it will not take off!!

You gave me scientific proof that it will not fly as long as it's not moving forward...

I'm telling you it's going to move forward despite the conveyor belt...so your fact only proves that it will fly...

[BD_Paintball]

You gave me scientific proof that it will not fly as long as it's not moving forward...

I'm telling you it's going to move forward despite the conveyor belt...so your fact only proves that it will fly...

how is it going to move forward if the conveyor belt is moving the other way the same speed as the plane is going? if the conveyor belt is matching the speed of the plane but in the opposite direction it will just sit there.

[magman007]

no i win b/c i gave you scientific proof that it will not take off!!

but you didnt

[BD_Paintball]

but you didnt

L=.5*cl*rho*U^2*s. U is wind velocity. If U = 0, L=0, L is lift force, cl is lift coeficient, rho is air density, U is freestream velocity, and s is wing span"

[Army]

The plane flies.

It has forward movement regardless of the belt. The belt will match the forward speed. Regardless of how fast the belt moves, the plane will continue to accelerate to flight speed.

There will be lots of rubber tire chunks all over...but it will be flying!

Think this way: the plane is already flying with wheels up, just very low and against the travel direction of the belt. It does not matter the belt speed, the plane flies. Now put the gear down. Does the plane instantly stop? No, it is still at flight speed. The plane does NOT get it's forward thrust/movement from any drive system to the wheels. Forward movement is independant of the belt.

Picture a car on a Dynomometer, the wheel thrust powers the drums the wheels are sitting on. The faster you spin the car wheels, the faster the Dyno turns, but the car can go nowhere since its "road" rolls as fast as it does. Put that same car back on the Dyno with the motor off but now the DYNO making the car wheels roll....and light the RATO pack now strapped to the roof. Where is the car going to go? Yup, airborne.

Independant thrust negates the speed or direction of the belt.

I am right. You are wrong. Worship me.

[UTDragun]

Well I just hope he does what Miscue says and turns to major in liberal arts

Im a mechanical engineer and I still got it right.

[neppo1345]

Yeah...considering that I'm an aerospace major as well...that equation looks sorta familiar, even in it's butchered form...i can spit out some more "science" if you want, but it's not going to make any difference.

It's one of those things you just have to get...if you don't have a decent math/physics/flight background you just wont get it...

I sure hope I never end up "flying" in anything he designs...

[Miscue]

Well I just hope he does what Miscue says and turns to major in liberal arts

Im a mechanical engineer and I still got it right.

Graduate of Howard R. Hughes College of Engineering right here... although who has what education is irrelevant in solving this problem. Just means you have less of an excuse to go about it the wrong way.