Will this plane take off?

[robert_s_hunter]

Originally Posted by yellowduc

didn't read through all of the posts, but wouldn't it technically depend on whether it was a prop plane or not? If it was a jet, then no air is moving over the wings, if it is a prop plan, then the prop is pushing air over the wings.

As long as it isn't force applied to the ground plane, the force WILL cause forward motion, irrespective of the means of applying it.

[robert_s_hunter]

Originally Posted by Gimpdiggity

Right...that's what I get out of the question...

I get out of it that the treadmill would effective act as some kind of tether that would keep the airplane in the exact same position relative to things around it at all times.

I get out of the question that there is NO WAY that the plane can achieve ANY forward momentum.

You're being held back by the assumption that the opposing force of the aircraft's engine is being applied against a moving ground plane.......

Ever heard of a wheel-driven airplane???

[Anthonyd5189]

The answer is NOOOOO.

Aircraft need wind moving across the wings to create lift. As stated in the first question the plane is stationary, therefore not moving and not creating any lift.


Now if the question was...If a plane was parked into the wind and a 70mph wind came along, could it take off(Im talking about a Cessna 152/172)? That answer would be yes.

[SAHTT]

In fact, given the technical facts of the riddle, the plane does take off.

What is hardest to overcome is allowing FOWARD MOVEMENT.

That's the hardest logic barrier to overcome because it isn't possible to explain it 'exactly' in laymen terms. Just look at the wheels like nothing more than bearings and the force of the propellers/jet engines as a completely different force unrelated to the ground. As long as something isn't holding the plane back [bearings have no friction aka no force] the jet engines don't know the ground "is moving".

What boggles the mind is trying to figure out how the plane takes off without having forward movement. What people seem to "leave out" is the plane DOES MOVE FOWARD, it's just that no matter how fast the belt spins in relation to the wheels the plane WILL MOVE FOWARD.

It's also important to realize this is hypothetical. It's impossible to make this scenario happen in the real world under these exact conditions. Notice I didn't say unbelieveably complicated/expensive, it simply won't happen.

Got it?

[Ershank]

yellowduc hit the nail on the head.

It really depends on if it's a prop plane or jet. Prop planes don't need to move to create lift under their wings. Now I doubt every prop plane could create enough lift to actually take off, but some could.

And we don't even need to mention harrier jets.

[SAHTT]

Another big help is picture the plan on a conveyer belt the size of a regular run way. That way you can visualize the plan actually picking up speed regardless of the belt moving and being able to take off.

If you try to visualize it with the size of a treadmill, which the riddle DOES NOT STATE, it is probably impossible realistically as the plan would just crash off the treadmill as soon as it got some foward motion.

It also DOES NOT MATTER WHAT KIND OF PLANE IT IS. As long as the plane has the ability to fly once in the air, [aka not a car with wings], it will take off on a long enough conveyer belt.

[WannaMoto]

http://www.avweb.com/news/columns/191034-1.html

Conveyer-Belt Runway


What I learned from Old Hack was that an updated version of a question aimed at confusing folks over relative measurements of airplane motion and the medium in which it operates had shown up on the Internet, and it was causing the fracas in the Lounge.

The question that has been going around is not particularly artfully worded, and I think that has caused some of the disagreements, but I'll repeat it as it is shown: "On a day with absolutely calm wind, a plane is standing on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. The conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction). Can the airplane ever take off?"

My comment: Notice that the question does not state that the conveyor's movement keeps the airplane over the starting position relative to the ground, just that it moves in the direction opposite to any movement of the airplane.

Initially, about a third of the folks here said that the airplane could not ever takeoff, because the conveyor would overcome the speed of the airplane and it could never get any airspeed. The rest said the airplane would fly.

The "It won't fly, Rocky" group said that the conveyor would hold back the airplane. They asked us to imagine a person running on a treadmill. As he or she sped up, the treadmill would be programmed to speed up, just as the conveyor in the problem, and the person would remain over the same locus on the earth, while running as fast as possible.

The argument was that if the airplane started to move forward, the conveyor program was set up to move the conveyor at exactly that speed, in the opposite direction, thus, the airplane would never move relative to the ground, and, because the air was calm, it could never get any wind over its wings. One of the analogies presented was the person rowing at three mph upstream in a river on a calm day. However, the current was flowing downstream at three mph, so the resultant speed with reference to the stream bank and air was zero, and thus there was no wind on the rowboat.

I watched and listened to the disagreement for a while and was fascinated to see that the argument seemed to split between those who had some engineering or math background, all of whom said the airplane would takeoff and fly without any problem; and those with some other background, who visualized the airplane as having to push against the conveyor in order to gain speed. Because the conveyor equaled the airplane's push against the conveyor, the airplane stayed in one place over the ground and in the calm air could not get any airspeed and fly.

It was an interesting argument, but as things progressed, more rational heads prevailed, pointing out that the airplanes do not apply their thrust via their wheels, so the conveyor belt is irrelevant to whether the airplane will takeoff. One guy even got one of those rubber band powered wood and plastic airplane that sell for about a buck, put it on the treadmill someone foolishly donated to the Lounge years ago, thinking that pilots might actually exercise. He wound up the rubber band, set the treadmill to be level, and at its highest speed. Then he simultaneously set the airplane on the treadmill and let the prop start to turn. It took off without moving the slightest bit backwards.

[SAHTT]

In this particular riddle, if the conveyer was moving BACKWARDS at INFINITE speed the plane would still take off. Try to get barriers of the real world out of your head and think 'bigger'.

[Ershank]

Oh, I thought it was a serious question as to if a plane could create lift while sitting still. The riddle is a little too ridiculous to acknowledge at first.

[Anthonyd5189]

Originally Posted by WannaMoto

It took off without moving the slightest bit backwards.

Rubberband plane and real plane...much different.

Prop planes can not take off unless they have air moving over their wings. Hence why planes measure their speed with airspeed and not ground speed. I dont know where someone thought that the prop alone can provide enough lift, but that is not true at all. Every plane I have flown hasn't taken off while donig a runup before taking off. That is also the reason planes take off into the wind...they can get a higher airspeed with a lower ground speed, using less runway to take off.

So...if the question is will it take off if the the ground is moving under the plane so as the plane is stationary to the point at which it started. It will NOT take off.

Now if the plane can get moving 55kts(Cessna 152) then it will take off. But if the ground is moving from underneath it, its going to take alot to get it moving that fast.

[Akheloce]

Well, the only thing holding it back would be if the bearings of the landing gear wheels, and the tires failed, because they are spinning 400 miles per hour, as the plane is moving forward at 200 mph. Take that out of the equation, and yes, it will fly. Or, perhaps, is the conveyor belt somehow creating a wind that is coming toward the airplane... in that case, the plane would take off sooner, because there is more relative wind (same reason planes take off into the wind). The only thing that would cause the plane not to take off is if you had a fan at the tail of the plane which increased wind at the same rate as the engines produced thrust.

[SAHTT]

Originally Posted by Anthonyd5189

Rubberband plane and real plane...much different.

Prop planes can not take off unless they have air moving over their wings. Hence why planes measure their speed with airspeed and not ground speed. I dont know where someone thought that the prop alone can provide enough lift, but that is not true at all. Every plane I have flown hasn't taken off while donig a runup before taking off. That is also the reason planes take off into the wind...they can get a higher airspeed with a lower ground speed, using less runway to take off.

So...if the question is will it take off if the the ground is moving under the plane so as the plane is stationary to the point at which it started. It will NOT take off.

Now if the plane can get moving 55kts(Cessna 152) then it will take off. But if the ground is moving from underneath it, its going to take alot to get it moving that fast.

Check out my posts Anthony to see if it can help your understanding. It is a difficult riddle at first.

[chaos14]

Originally Posted by yellowduc

a helicopter has a big enough prop to lift it vertically and enough power. I think that if a plane was built to allow a big enough prop, there is no way that you could keep it from taking off.

no a heliocopters blades are just little wings that spin they do blow air down but that is only a byproduct, the blades produce lift exactly like a wing. and no not even a big enough prop could create enough wind becasue the wind is not blowing uniformly backwards. if your a pilot you know why if your not then i am not going to write 30 pages out to explain it to you

the wording is bad on the OP and it leads to one of two conclusions the plane takes off or the plane stays still and in a fraction of a second the tires are spinning so fast that they blow up. the landing gears heats up and collapses a wing tip hits the runway, (that is now moving at an indescribable speed) falls to pieces launching thousands of gallons of fuel every where which are quickly ignited by the molten landing gear blowing up the plane the runway and every jackass standing next to it to see if the plane will take off

id like to think the OP was ment to be read as to lead to my first conclusion

[SAHTT]

Originally Posted by Akheloce

Well, the only thing holding it back would be if the bearings of the landing gear wheels, and the tires failed, because they are spinning 400 miles per hour, as the plane is moving forward at 200 mph. Take that out of the equation, and yes, it will fly. Or, perhaps, is the conveyor belt somehow creating a wind that is coming toward the airplane... in that case, the plane would take off sooner, because there is more relative wind (same reason planes take off into the wind). The only thing that would cause the plane not to take off is if you had a fan at the tail of the plane which increased wind at the same rate as the engines produced thrust.

Great post and absolutely true.

[TTsixxer]

OMFG the plane on the conveyer belt thread! hahahahahahaha!

The plane flies, whoever thinks otherwise is a complete dumbass that can't understand simple conceptual physics.