You could say it that way, but it would take a shitload of power to get that fast, probably something we haven't come up with yet. Then again we don't own giant runway sized treadmills. This is still a really wierd question.
you people are confusing thrust with lift. the jet engines would produce thrust, the wheels would roll forward, however the the 'treadmill' would counter the forward roll and cause the jet to stand still. If the jet is standing still, lift will not be produced, and will therefor not become airborne. as long as ATG's 'treadmill' proplerly counters the forward movement of the jet, you could ride it full throttle until the tanks are empty.
the friction between the wheels and the tarmac is what provides the traction required for acceleration, now a mag-lev jet, that might be interesting.
the friction between the wheels and the tarmac is what provides the traction required for acceleration, now a mag-lev jet, that might be interesting.
Hence my post.
edit:holy shit we got like 150 replies in 1 day
edit:holy shit we got like 150 replies in 1 day
chaosdragon001 wrote:
There's the original question. Now, I'm not really on anyone's side, but here's my argument.ATG wrote:
A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).
Will the plane be able to take off?
Aircraft need wind flowing over the wings to provide lift, correct? Now take a normal aircraft, sitting on the runway. If it were to take off, it would have to create some sort of thrust to get it down the runway, namely the engines. You would still need some groundspeed to provide enough airspeed to provide lift. An aircraft requires some groundspeed to take off, because.. well.. it just doesn't jump into the sky and fly like a Harrier or a heli.
When you place a plane onto said treadmill, which apparently compensates for ground speed in the opposite direction (refer to original post) you would still need to build groundspeed to take off, if the conditions were perfect and there was no wind. Thus, it would not take off. Jet engines provide thrust to move an aircraft along the ground to generate lift, therefore said treadmill would prevent it from taking off.
That's my 2 cents on it.
(Someone really needs to send this to mythbusters and record te episode if it comes on)
Not bad for a 15 year old huh?
Last edited by chaosdragon001 (2006-12-26 22:14:17)
I have a small electric plane. Anyone have a treadmill?
Oh, boy. What fun what fun. Answer is YES, the plane WILL take off. The original premise is that the plane is on a treadmil the length of a runway, and would move with the wheels.
The problem most people, including a lot of other pilots, forget are the follwing.
1. Liftoff is dependant on the lift of the wings.
2. Lift on the wings is dependant on airflow over the wings.
3. Airflow over the wings is usually caused by the engine forcing the plane forward through the air.
4. The engine (propellor) moves the plane through the air by pushing against the air.
Now, do you see the ground or the wheels anywhere on that list? The wheels are idle. neutral. Look at it in reverse. If you put a plane on a treadmil, tie the plane to a standpoint like a tree, then get the treadmill up to 120mph, does the plane take off? NO. The little wheels are spinning their little rubber souls off, BUT THE WINGS ARE NOT MOVING. no airflow over the wings means no lift.
If you take the situation given, the propellor will start to move the plane, say 5 mph forward. The treadmill starts to move 5mph in the opposite direction. The poor little wheels are moving at 10 mph, since the plane is still pulling the wheels forward. If you apply the brakes to the wheels, all bets are off, but as long as the wheels stay idle, then the treadmill has no effect on the plane other than to cause the wheels to move twice as fast.
Just to prove the point, a couple of pilots bought a toy rubber band-powered plane, got to a treadmill, turned the treadmill on, wound up the rubber band, held the place against the treadmill, and let go. Result? Plane took off with no trouble.
The problem most people, including a lot of other pilots, forget are the follwing.
1. Liftoff is dependant on the lift of the wings.
2. Lift on the wings is dependant on airflow over the wings.
3. Airflow over the wings is usually caused by the engine forcing the plane forward through the air.
4. The engine (propellor) moves the plane through the air by pushing against the air.
Now, do you see the ground or the wheels anywhere on that list? The wheels are idle. neutral. Look at it in reverse. If you put a plane on a treadmil, tie the plane to a standpoint like a tree, then get the treadmill up to 120mph, does the plane take off? NO. The little wheels are spinning their little rubber souls off, BUT THE WINGS ARE NOT MOVING. no airflow over the wings means no lift.
If you take the situation given, the propellor will start to move the plane, say 5 mph forward. The treadmill starts to move 5mph in the opposite direction. The poor little wheels are moving at 10 mph, since the plane is still pulling the wheels forward. If you apply the brakes to the wheels, all bets are off, but as long as the wheels stay idle, then the treadmill has no effect on the plane other than to cause the wheels to move twice as fast.
Just to prove the point, a couple of pilots bought a toy rubber band-powered plane, got to a treadmill, turned the treadmill on, wound up the rubber band, held the place against the treadmill, and let go. Result? Plane took off with no trouble.
No, no, no. Groundspeed has absolutely NOTHING to do with whether the plane takes off. The ONLY thing that matters is airspeed.chaosdragon001 wrote:
You could say it that way, but it would take a shitload of power to get that fast, probably something we haven't come up with yet. Then again we don't own giant runway sized treadmills. This is still a really wierd question.
I have a friend that has a treadmill and I have a small electric plane. If some of you want I will test it and post a vid too prove either way.......
Wow this is still being argueed? This is basic elementary aerodynamics/ fluid mechanics/ physics.
nuff' said
Oh, please do.viper313 wrote:
I have a friend that has a treadmill and I have a small electric plane. If some of you want I will test it and post a vid too prove either way.......
And sorry about my plane only having 1 wing...I am not an artist
Salright, still a thing of beauty.
But do you think it is correct?
It does make sense, yes, but we haven't seen it for real so it's anyboy's game.
I'm waiting for the video.
I dont think the video is going to be very reliable... ratio of friction to weight could be different on both planes, ratio of weight vs engine power, etc...
as someone said previously, we need to get the Myth Buster guys on this asap.
lol @ this thread attaining 7 pages in one day.
As said above, the plane will take off since the the jets on the wing, not the wheels on the ground, provide power. The movement of the ground would have little effect on the plane's take off. It might take a little more power than usual to over come the extra friction, but in the end it would take off.
As said above, the plane will take off since the the jets on the wing, not the wheels on the ground, provide power. The movement of the ground would have little effect on the plane's take off. It might take a little more power than usual to over come the extra friction, but in the end it would take off.
And it would require the model plane to match the speed of the tread mill and overcome the friction of the wheels before it reaches the back end of the mill. My guess is we will have a video of a plane sailing off the back end of a tread mill, potentially destroying whatever is behind it in the process (depending on the size of the plane and the power of it's engine.)bobby177 wrote:
I dont think the video is going to be very reliable... ratio of friction to weight could be different on both planes, ratio of weight vs engine power, etc...
Last edited by mcgid1 (2006-12-26 23:17:04)
Yea... who has Mythbuster's email? (send them the thread too... lol)
Done and done.
Any questions?
(Data derived from Wikipedia, Flight Simulation software formulas, and Physics 101)
Last edited by GotMex? (2006-12-26 23:28:31)
what is
the Mythbuster thing?
?ATG wrote:
Done and done.
the Mythbuster thing?
Yup. I emailed them as soon as I saw the suggestion.
What my picture was getting at with the FBD but I didn't wanna use numbers and formulasGotMex? wrote:
http://img155.imageshack.us/img155/2762 … illjy0.jpg
Any questions?
(Data derived from Wikipedia, Flight Simulation software formulas, and Physics 101)
Kung Jew is gonna love this.