Would a plane take off on a tredmill?

[LinX]

although moving downward, its forward motion, in a downward direction causes it to slow as well. Once it reaches the ground, brakes and instilling "flaps-up" (causing downward pressure on the plane) slows it.

yes i agree, I'm just making a point here

[203Cree]

Actually, on small planes they use wheel brakes, on bigger planes they use thrust reversers and brakes. The flaps do not do much other than spoil the airflow over the wing to discourage lift.

Back to the subject at hand....feed the proper air flow at the plane, on the treadmill, or even w/o the treadmill, and i think it could get lift. I mean, it may be unheard of, but feed enough wind, head-on, at an airplane, and it could get off the ground. I dunno that its gonna go anywhere, but the formula still stands; get enough air moving over/under the wing of an airplane, and you have lift.

I think the real catch here is the engines. Im sure we could all come to agree that with enough airflow, the airplane will get lift. Not flight, but lift.

Now of you powered up engines to full speed.....there inlies the problem.

If the winf gust was so striong that it did indeed get the plane off the ground:
A) How far off the ground would the plane have to be for the engines to provide enough power to get it going in a forward and up direction?

B) If the engines provided enough power, in time, would the airplane "hover" then begin its forward ascent, or would the airplane need to be pointed in an "upward" direction?

Does anybody else think that this test could be done by simply dropping, or pulling a plane, behind another, powering up engines, then being released???

Wouldnt the principals still stand?? Gravity wuld be pulling it in a downward directiom, but power up engines, and drop it at about 40k feet...i think thats plausible.

So....runway, little to no wind, NO. Engines or not. Without proper airflow, the wheeld could spin and spin, but it aint going anywhere.

Feed it the proper airflow, yes, it could acheive LIFT. It might be an un-controlable lift, but nonetheless, LIFT.

You're WAAAAAYYYYYY overthinking this.

Thrust will provide forward momentum. So, the plane will push it's self forward no matter what the treadmill is doing beneath it. Even with no wind, there is still AIR, and the wings, or airfoils, will generate lift and the plane will take off.

On another note, and one not directed at ANYONE, just a general thingie....

How did this go from "Would-A-Plane-On-A-Treadmill-Take-Off" to "Would-A-Plane-On-A-Treadmill-Take-Off-If-It-Was-Underwater
-With-No-Air-Supply-While-Swimming-With-Great-White-Sharks-Backwards
-I'm-A-Physics-Major-And-Sumshit"?

If the original arguement wasn't silly enough, now we're adding more shit into the already simple equation in an effort to futher confuse those that are easily confounded, lol. BASTARDS!

[MikeW]

I know. Just helping out.

[MikeW]

But why is the treadmill even in the question? Could you not lift the plane off the ground , or even suspend it, and it still works??

I think the wheels have nothing to do with this.

But essentially, the runway, IS a treadmill.....


Now i get it......

[deevergote]

The motion of the treadmill has no bearing on the motion of the plane. The plane will move as if it were on stationary ground. The wheels will just spin faster.

[LinX]

On another note, and one not directed at ANYONE, just a general thingie....

How did this go from "Would-A-Plane-On-A-Treadmill-Take-Off" to "Would-A-Plane-On-A-Treadmill-Take-Off-If-It-Was-Underwater
-With-No-Air-Supply-While-Swimming-With-Great-White-Sharks-Backwards
-I'm-A-Physics-Major-And-Sumshit"?

If the original arguement wasn't silly enough, now we're adding more shit into the already simple equation in an effort to futher confuse those that are easily confounded, lol. BASTARDS!

Yeah, now thats a good question.

[deevergote]

I think I may have started that

If the wheels reached their limit and failed, the plane would not take off. I began adding in other factors.

[203Cree]

I think I may have started that

If the wheels reached their limit and failed, the plane would not take off. I began adding in other factors.

Well now you've opened a whole new bag of worms. Tire failure would be totally dependant upon aircraft model and total load. Avg. takeoff speed for, say a 747, is 180mph. So, tire speed at rotation would be 360 mph. There's a 560,000lb difference btwn a 747-8I empty and at max takeoff weight.

Empty, I bet those wheels and tires would hold up, since the load is decreased as forward motion and lift increases. Fully loaded, your rollout will take longer and you will accellerate slower, but you will maintain speeds for a longer distance. So the stress on the tires and wheels under those conditions would be exponentially higher than were it empty not only due to the higher gross weight but increased time on the ground.

I'm sure I could come up with an equation for how to figure the difference's in load vs. time on the ground vs. stress on the tires/wheels, but I quit trying to prove how smart I might be YEARS ago, lol, so I'll leave that one to someone else.

[owequitit]

But why would the wheels moving have anything to do with lift

Now if you had equivalent air being fed at the plane, at speed, yes, i think it would take off, but if you just sat it in a field and basically lifted it off the ground and acceleratted the engines, no i dont think it would take off.

Someone back me up or correct me anywhere they feel necesarry, but engines really wouldnt have anything to with this. Isnt it sheer wind velocity over the wings, causing lift??

I mean, if you could find a cliff high enough, could you, essentially, push a passenger 747, off that cliff and assuming winf velocity/sheeras were in proper order, etc etc, couldnt that plane, being piloted to do so, essentially, get lift??

Maybe not enough to get it up and away from the ground, but i mean at least enough to get it leveled out???

Thats how gliders work. Essentially. The only reason theyre flown to high alt's is so that they can get plenty of airtime. Scale it down. A model, styrofoam plane works the same way. Its small size only requires a small amount of resistance to gain lift. granted it isnt much, but it doesnt have engines. Shit, same rule even applies to paper planes. You give anything a wing that is proportionate to its body and it can, essentially, have lift. Not flight, "LIFT". I know, humans have tried it, and although they havent exactly soared across the sky, you could still "lower" or "float". You're still getting enough resistance to at least, slow gravity's pull...

Back to the subject at hand....feed the proper air flow at the plane, on the treadmill, or even w/o the treadmill, and i think it could get lift. I mean, it may be unheard of, but feed enough wind, head-on, at an airplane, and it could get off the ground. I dunno that its gonna go anywhere, but the formula still stands; get enough air moving over/under the wing of an airplane, and you have lift.

I think the real catch here is the engines. Im sure we could all come to agree that with enough airflow, the airplane will get lift. Not flight, but lift.

Now of you powered up engines to full speed.....there inlies the problem.

If the winf gust was so striong that it did indeed get the plane off the ground:
A) How far off the ground would the plane have to be for the engines to provide enough power to get it going in a forward and up direction?

B) If the engines provided enough power, in time, would the airplane "hover" then begin its forward ascent, or would the airplane need to be pointed in an "upward" direction?

Does anybody else think that this test could be done by simply dropping, or pulling a plane, behind another, powering up engines, then being released???

Wouldnt the principals still stand?? Gravity wuld be pulling it in a downward directiom, but power up engines, and drop it at about 40k feet...i think thats plausible.

So....runway, little to no wind, NO. Engines or not. Without proper airflow, the wheeld could spin and spin, but it aint going anywhere.

Feed it the proper airflow, yes, it could acheive LIFT. It might be an un-controlable lift, but nonetheless, LIFT.

Power up engines, give it such a gust of air that the plane gets "lifted" 100's of feet in the air...engine at full throttle...plausible.

Drop it from a substantially high distance, again, engines Full Throttle...I think, Plausible, even do-able.

You are over complicating a VERY simple problem. The problem in the original question was this:

Does the treadmill have the ability to prevent the takeoff?

The answer is no.

All a wing needs to produce lift is airflow. The wing can move through the air, or the air can move over the wing. Either way it does NOT matter. As long as air is circulating around the wing, it will produce lift.

We can circulate air in one of three ways.

1) The first, and the one most associated with airplanes is to provide a thrust, and thus propel the wing forward through the air. This causes the air to circulate around the wing, even though the air is not moving.

2) Move the air over the wing. This would be completely dependent on wind speed, which would essentially be the air flowing over a stationary wing. This is completely dependent on causes outside our control though, so this is not the preferred method. Besides, even a Cessna needs about 50MPH worth of airflow before it will generate enough lift to fly.

Where are you going to find 150MPH winds to get an airliner into the air safely? You aren't. So see method #1.

3) The third method is to move the wing around a central point, in a circular motion which essentially creates airflow over the wing, because the wing is moving through the air, albeit around and around instead of in a straight line. Helicopters use this method to produce lift, as do propellers, and compressor sections on turbine engines.

The helicopter isn't moving, and in the case of the propeller, or compressor section, neither is the airplane, but they are both able to produce thrust (lift that opposes drag) anyway.




So, in answer to your question, yes, it is possible to hover a 747, a Cessna, a helicopter, glider, ultralight, etc. The problem with anything other than a helicopter, or airplane such as the harrier, is that we would be dependent on the wind to do it. Since it is very hard to find wind that high, and there is a high degree of safety risk associated with winds that high, you probably won't see too many airplanes hovering. But it is possible.

Also, there is a TON of misinformation and incorrect terminology in this thread that is just driving me crazy.

1) Flaps are the big huge panels that extend down below the wing, and make the wing look as though the back is falling out.

If you look at the pic in my sig, the feathers at the back of the wing that you see hanging down are essentially the same as flaps.

These panels serve several functions, the first is to create more lift from a given wing. I won't go into how or why, because it can easily get beyond the scope of this thread, but they essentially create a shape that generates more lift, and they also increase the surface area of the wing.

They also create more drag. This allows the aircraft to slow down OR fly a steeper descent angle to the ground. In the case of big airliners, it also allows them to keep their turbine engines spooled up, since they take a long time to "rev."

"Spoilers" are the devices that pop out of the top of the wing, when the airplane touches down. These panels' purpose is to destroy the smooth airflow over the wing, thus greatly reducing or "spoiling" the lift being generated, and they also present more surface area to the airstream which increases drag. Since drag is bad, the airplane slows down. By destroying the lift, they also transfer more weight onto the wheels of the landing gear, thereby improving braking effectiveness, especially on a short runway, or at a heavy weight.

You have seen these "spoiler" panels on the roof of NASCARS when they spin out. They do the same thing. Destroy lift, and keep the car on the ground.

Here is a good example of what I am talking about:

http://www.youtube.com/watch?v=JrbHR8-TRwY

You can see the flaps extended throughout the video. They are the parts that have moved backward and downward, and hang below the wing.

The "spoilers" are the panels that extend upward when the airplane actually touches the ground. If you pay close attention, you can see the spoiler panels moving as the aircraft is flying. This is because they are used to improve roll control, so they actually serve two purposes.

Also, airplanes usually use a combination of reverse thrust (if it is available), wheel breaks, and aerodynamic braking when slowing down.

To illustrate the effectiveness of these techniques, it is possible to stop an airliner that weighs several hundred thousand pounds (a 737 at max landing weight weighs about as much as 50 CB7s), in a few hundred feet from almost 150 MPH. Conversely, it would take you several hundred feet to stop your CB7 from that speed. You most likely won't every experience a landing such as this, because it is quite uncomfortable, but it is possible.

**INSERT COOL YOUTUBE AIRPLANE VIDS HERE**

Here are a couple of the C-17 Globemaster III, this aircraft is really capable on short fields.

http://www.youtube.com/watch?v=nfI4gSz4RJk

http://www.youtube.com/watch?v=N2awzBWwr3Y

http://www.youtube.com/watch?v=xVHZzjRzgC4

Even "boring" airplanes can do it.

http://www.youtube.com/watch?v=vNDoo7wf42o

http://www.youtube.com/watch?v=_vJliayH6co

http://www.youtube.com/watch?v=nfI4gSz4RJk

To further prove the point that lift is generated on the basis of airflow, completely independent of groundspeed, here are some wind tunnel videos. This essentially creates lift using high airflow velocities over a fixed test model. The basic one is first.

http://www.youtube.com/watch?v=b_THe9JL_iw

Here are two more tests. Notice the little strings attached to the upper surface of the wing. These are called "tufts" and are used to be able to visually see the airflow over the wing. When the tufts reverse, or stand straight up, like in the second video (hard to see, but it is there), then the wing is "stalled" and is no longer producing lift and flying, because the air is not flowing properly.

http://www.youtube.com/watch?v=A3OEJtCE5kE

http://www.youtube.com/watch?v=4UjbGfXgct8

This one is just a good illustration of the airflow over the wing.

http://www.youtube.com/watch?v=OATTXmxQw-E

Here is a video of a guy that built one at home, and is testing the control surfaces on a wing section.

http://www.youtube.com/watch?v=6VeBzSkQ_7s

[owequitit]

Well now you've opened a whole new bag of worms. Tire failure would be totally dependant upon aircraft model and total load. Avg. takeoff speed for, say a 747, is 180mph. So, tire speed at rotation would be 360 mph. There's a 560,000lb difference btwn a 747-8I empty and at max takeoff weight.

Empty, I bet those wheels and tires would hold up, since the load is decreased as forward motion and lift increases. Fully loaded, your rollout will take longer and you will accellerate slower, but you will maintain speeds for a longer distance. So the stress on the tires and wheels under those conditions would be exponentially higher than were it empty not only due to the higher gross weight but increased time on the ground.

I'm sure I could come up with an equation for how to figure the difference's in load vs. time on the ground vs. stress on the tires/wheels, but I quit trying to prove how smart I might be YEARS ago, lol, so I'll leave that one to someone else.

Don't forget that part of the stress is taking a punishing when 500,000 lbs of airplane pile drives you into the runway and makes you spin from 0-150MPH is a fraction of a second after being in subzero temps for hours and hours on end.

Seriously, airplane tires are like 36-50 ply, and are aired up with nitrogen to a really high pressure.

[203Cree]

Don't forget that part of the stress is taking a punishing when 500,000 lbs of airplane pile drives you into the runway and makes you spin from 0-150MPH is a fraction of a second after being in subzero temps for hours and hours on end.

Seriously, airplane tires are like 36-50 ply, and are aired up with nitrogen to a really high pressure.

This I know my friend, this I know. Ever seen what one of those bad boy's does to a guy when it comes apart?

[owequitit]

This I know my friend, this I know. Ever seen what one of those bad boy's does to a guy when it comes apart?

No, but I can imagine, because I have seen them come apart...

Blender.

[2.2litrebeater]

back from the dead
http://dsc.discovery.com/video/?play...eId=1344511100
on mythbusters this wednesday, im saying itll fly

[owequitit]

back from the dead
http://dsc.discovery.com/video/?play...eId=1344511100
on mythbusters this wednesday, im saying itll fly

It will, because the treadmill has nothing to do with how an airplane works.

If the mythbusters don't get that result, they should be shot for being bad "scientists."

[Losiracer2]

yippeee! can't wait to watch.