Airplane and Belt Conveyor

[ThreeWheels]

This is more enjoyable that I first thought, thanks.

OP what say you?

I say, thank you, that's the purpose of this discussion.

As to the answer, some of you are correct, and others are not.
I won't end the thread prematurely.
If this thread remains active, the answer will be revealed at Spyder Quest in September of 2015.
Provided, of course, that I have enough beer.............................................. ........

[Bob Denman]

This was a heckuva lot more fun, than I originally thought...

Thanks!

[jcthorne]

I wonder how many forums have had this very same question asked and how many hours have been devoted to arguing about it.

It takes time to explain the laws of physics to those uneducated in the subject. They are not always easy concepts to understand. And this riddle tires to throw an irrelevant curve ball into the mix. Your answer may have explained it better than I did.

[Bob Denman]

But... Once in a while; the Pig DOES learn to whistle!

[vided]

[ARtraveler]

I hope this is technical enough for the Technicality Police.

I will watch this one. Don't feel like math this morning.

[spydaman60]

I say, thank you, that's the purpose of this discussion.

As to the answer, some of you are correct, and others are not.
I won't end the thread prematurely.
If this thread remains active, the answer will be revealed at Spyder Quest in September of 2015.
Provided, of course, that I have enough beer.............................................. ........

you and bridgett missed farkle bingo last year and that would be the perfect spot for the answer steve. ps. i won't ask where you and bridget were!

[aeroshots]

Not going to Spyderfest so I'll summarize my view and close with this.

Even if said plane requires forward motion to create lift, i.e. not VTO capable it will still take off. It will move forward due to its thrust being independent to its wheels. Again, the conveyer runway will match the rotation speed of the wheels into infinity or until the airplane reaches take off speed. Then airborne.

If the conveyer were successful in its attempt to keep the plane motionless, then grounded I say, GROUNDED. Unless of course the headwind were equal to the take off speed of said plane then the plane would hover above the conveyer and thumb its nose at said naughty conveyer runway for delaying its scheduled departure time and inconveniencing the passengers.

My personal conclusion is Yes and No.
I'm 100% confident in my conclusion.

[Yazz]

Arggg! Aeroshots, we posted at the same time, saying the same thing different ways. You said it better!

Leaving this in through...

Take a piece of lined paper and cut it in half lengthwise. Hold the paper under your lower lip and blow. That is the principle of lift which gets airplanes in the air and keeps them there.

[Bob Denman]

Paper cut on my lower lip now...
As I leak blood onto my collar; I'm left to ponder flight...

[ottawa-rider]

The plane will take off when its AIRSPEED reaches what the pilot call V2 or take-off speed.

The speed of the conveyor or its direction will not affect the plane's ability to reach that speed since it is not attached to the conveyor.

As has been said above, the only force acting on the plane is from the thrust of its prop or jet engine.

The only impact of the counter rotating conveyor will be a small amount of friction.

[ottawa-rider]

Seems like we are all tripping over each other trying to say the same thing.

[jonnysevel]

The counter direction conveyer has no effect once the engines are providing enough thrust to overcome rolling resistance of the wheels. It cannot 'counter' the forward acceleration that is the direct effect of the rearward acceleration of the air through the engines. This is nothing like a car that uses the wheels to generate the forward thrust.

Absolutely correct! not a case of relative motion.. If the wheels were providing the propulsion then that would be a different story

[jaherbst]

A plane is standing on a runway that can move (some sort of belt conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

NO

Jack

[bruiser]

The airline will charge passengers a fee for the conveyor.

The aircraft will become airborne as long as the engine(s) provide enough reaction force, thrust, to overcome aircraft weight, thrust to weight ratio, and forward speed to provide wing lift. The overall effect of the conveyor is nil.

[Bob Denman]

Let me see if this is the right way of looking at this...
The Turbines are providing their thrust against the atmosphere...
The conveyor is working against the speed attained by the wheels...

While there are opposing forces working hard; they're not opposing each other...
It should (might, maybe, sort of, could...) take off; once the wings are providing enough lift...

I need some Aspirin, and a handgun!

[ARtraveler]

Let me see if this is the right way of looking at this...
The Turbines are providing their thrust against the atmosphere...
The conveyor is working against the speed attained by the wheels...

While there are opposing forces working hard; they're not opposing each other...
It should (might, maybe, sort of, could...) take off; once the wings are providing enough lift...

I need some Aspirin, and a handgun!

Please fax me some Aspirin. I will see what else I can find.

[Yazz]

A plane is standing on a runway that can move (some sort of belt conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

No or yes...

The conveyer belt is moving as fast backwards as the plane is moving forwards, which means the plane has it's engines spooled up but it's going nowhere.

The plane has to reach the proper airspeed to take off, not how fast the wheels are going, or the thrust output, but how much air is flowing over the wings.

Refer back to blowing on a piece of paper, make sure you have parental guidance.

This may be a trick question. Something about a light plane and strong headwinds, in that case, it can be done.

[BajaRon]

I wish I'd gotten in on this earlier. But you guys have it nailed as it is airspeed, not ground speed that creates lift.

If takeoff speed is reached at 100 mph AIR SPEED, the plane could actually achieve liftoff at zero ground speed in a 100 mph wind. Of course it could not maintain it without forward thrust because once it left the ground the wind would begin to push it backwards (ground speed) which would reduce air speed to below the needed 100 mph to maintain sufficient lift to keep the plane in the air.

Very clever though. Pointing the reader to a ground speed question when the answer lies in the arena of air speed. I love it!

[jcthorne]

No or yes...

The conveyer belt is moving as fast backwards as the plane is moving forwards, which means the plane has it's engines spooled up but it's going nowhere.

The plane has to reach the proper airspeed to take off, not how fast the wheels are going, or the thrust output, but how much air is flowing over the wings.

Refer back to blowing on a piece of paper, make sure you have parental guidance.

This may be a trick question. Something about a light plane and strong headwinds, in that case, it can be done.

Your first sentence contradicted itself. Either you say the plane is moving forward under power (correct) or you say it is NOT moving forward (incorrect for this scenario).

The air is flowing over the wings based on the aircraft's speed relative to the earth. And that is the same as without the conveyor. The conveyor is detached from the plane and does not act on it. Makes no difference HOW fast the conveyor belt is moving, it does not affect the speed of the plane.

[bruiser]

F=ma

Basic physics. If the aircraft is static, that is, no forward motion, then it remains static. However, if you add thrust or acceleration as a constant, then the aircraft will move forward because force is overcoming mass creating velocity. If that force is great enough and constant to overcome the mass (aircraft) then lift will be achieved. The only constant force acting to keep mass in place is gravity. Gravity acts in only one direction, down. By providing rearward thrust, the mass has to move forward, overcoming the downward acceleration of gravity.

If you are running on a treadmill, your mass is constant to the speed of the treadmill because the downward force of gravity is holding you in position so you don't move forward. Now, if someone comes from behind and pushes you forward with enough force to overcome gravity you will move forward (probably falling on your face) regardless of the speed of the treadmill. If you increase the speed of the treadmill, but don't increase your pace relative, force from the treadmill will propel you backwards because that force is great enough to overcome mass.

[Magdave]

Turn the plane around on the runway. It will take off in half the time. Assuming the runway rolling direction is 1 way of course.

[Magdave]

Your first sentence contradicted itself. Either you say the plane is moving forward under power (correct) or you say it is NOT moving forward (incorrect for this scenario).

The air is flowing over the wings based on the aircraft's speed relative to the earth. And that is the same as without the conveyor. The conveyor is detached from the plane and does not act on it. Makes no difference HOW fast the conveyor belt is moving, it does not affect the speed of the plane.

In the original scenario the plane speed = 0. The relative motion to the earth below the wing tips is 0

[ARCTIC]

In the original scenario the plane speed = 0. The relative motion to the earth below the wing tips is 0

The treadmill would instantly go to Infiniti mph as the plane pulled itself forward by the propeller as it overcame the initial pullback of the friction created by the wheel bearings beginning to spin. Not sure what kind of drag a greased axle could create but the treadmill would probably break at some point less than infinity and the tires and bearings on the plane might last longer than the treadmill. If BRP manufactured the treadmill it would overheat and go into limp mode long before it created issues for the airplanes tires

[Explorer]

1. The plane will take off.
2. The air speed and true ground speed will be the same.
3. The conveyor will have to be almost as long as a runway.
4. At lift off the conveyor will be moving at the lift off speed, of the plane, but the wheels will be spinning at 2X that speed.
5. Of course the tires may blow or the wheel bearings seize, due to the heat generated by 2X normal rotation of the wheels. In which case, "Houston We Have A Problem".
Roger