Will the plane take off?? Finally going to be answered.***

[squeak9798 5,000+ posts]

that is assuming both the treadmill and the plane are traveling in the same direction. think of the moving sidewalks in the airport. they move you at about 3mph, give or take. if you get on the sidewalk and stand still you are moving forward at 3mph. if you walk in the same direction of travel as the sidewalk at 3mph, you effectively double your speed and move 6mph. But if you walk in the opposite direction of travel from the sidewalk at 3mph, your forward movement and the sidewalk's backward movement negate each other and you have a net velocity of 0mph.

And in your scenario our feet,the things in contact with the conveyor belt, provide the force for our movement. THIS IS NOT THE SAME CASE AS WITH AN AIRPLANE. The airplane's force is provided by it's engine, NOT it's wheels.

To correlate this to your example, let's pretend we are facing backwards on the airport conveyor......so it is traveling at 3mph in the opposite direction we are heading. However, instead of walking on the conveyor belt, we are wearing roller skates, and our "force" or "thrust" is provided by our friend (standing on solid ground) pulling us with a rope. If he pulls us at 3mph in the opposite direction of the conveyor belt, will we move ?? The answer is YES, WE WILL, at approximately 3mph.

This case I present is equivalent to an airplane on a conveyor belt. Your example of us just "walking backwards" is NOT, because an airplane's thrust is NOT provided by it's wheels.

the plane would be traveling opposite the direction of the treadmill, so the velocities would negate each other and the plane would have an effective velocity of 0mph (in relation to the surroundings)

Wrong.

 

[IamDeMan 5,000+ posts]

i think that people are trying to over complicate this problem.
say you are running on a treadmill. the treadmill belt is moving backward at the same velocity you are running forward, and in relation to your surroundings, you are not moving. your velocity is ZERO. obviously you are not gaining airspeed. this is the same situation that the airplane would be in on a conveyor runway. The plane would fail to gain velocity and airspeed, thus preventing aerodynamic lift.

now if you were on the treadmill and you ran the same direction as the treadmill belt, you would be doubling your speed (until you fell off), which would double the airspeed that you would gain by running without the aid of the treadmill. this would work for a plane because you could halve the runway length needed to attain liftoff speed

Wrong. No resistance is present to keep the plane from moving. The wheels will spin faster.

 

[Acidburn 5,000+ posts]

Isn't that something of a modified F22? I know there's a lot more than meets the eye, but aren't they somewhat on the same platform?

no

 

[rollerdj 10+ year member]

i think that people are trying to over complicate this problem.
say you are running on a treadmill. the treadmill belt is moving backward at the same velocity you are running forward, and in relation to your surroundings, you are not moving. your velocity is ZERO. obviously you are not gaining airspeed. this is the same situation that the airplane would be in on a conveyor runway. The plane would fail to gain velocity and airspeed, thus preventing aerodynamic lift.

now if you were on the treadmill and you ran the same direction as the treadmill belt, you would be doubling your speed (until you fell off), which would double the airspeed that you would gain by running without the aid of the treadmill. this would work for a plane because you could halve the runway length needed to attain liftoff speed

you are correct... if this was a CAR. but it's not. where does a airplane (any kind) get it's power from????? not the wheels. the wheels (the only part that makes contact with the treadmill) is just along for the ride. they don't push, pull, anything. therefor, the plane is going to move weather the treadmill moves or not.

 

[mapolley07 10+ year member]

i think i understand it now. i was thinking about it more in terms of a car rather than a plane, which threw me off. it would be much more difficult, however to launch an airplane in this manner. I think that having the plane on a conveyor, but moving in the same direction as the conveyor would be very effective, because the conveyor speed would add to the plane's thrust thus doubling the speed in half the distance, and would launch the plane in a runway 1/2 as long.

is that thinking correct? and then the plane could land on the conveyor that is going the opposite direction of travel because it could slow down while making little forward progress?

 

[93EXT 10+ year member]

a conveyor with the plane would cause the wheels to go backwards while the plane went forward, right? I don't think it would double the speed, now a cable launcherand a aircraft carrier on the other hand that grabs the body of the plane instead of making contact with the tires... //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Acidburn 5,000+ posts]

i think i understand it now. i was thinking about it more in terms of a car rather than a plane, which threw me off. it would be much more difficult, however to launch an airplane in this manner. I think that having the plane on a conveyor, but moving in the same direction as the conveyor would be very effective, because the conveyor speed would add to the plane's thrust thus doubling the speed in half the distance, and would launch the plane in a runway 1/2 as long.
is that thinking correct? and then the plane could land on the conveyor that is going the opposite direction of travel because it could slow down while making little forward progress?

no, the conveyor's effect on the plane is negligible in all regards until the brakes are applied

 

[IamDeMan 5,000+ posts]

i think i understand it now. i was thinking about it more in terms of a car rather than a plane, which threw me off. it would be much more difficult, however to launch an airplane in this manner. I think that having the plane on a conveyor, but moving in the same direction as the conveyor would be very effective, because the conveyor speed would add to the plane's thrust thus doubling the speed in half the distance, and would launch the plane in a runway 1/2 as long.
is that thinking correct? and then the plane could land on the conveyor that is going the opposite direction of travel because it could slow down while making little forward progress?

No but you are getting there. Just like going in opposite direction has no effect, neither will it going in the same direction except maybe in the beginning where what little friction the wheels provide has a slight effect. Otherwise, you will just reach a point right before lift off where the wheels stop spinning because the plane has matched the speed of the tread. the treadmill has no real effect no matter which way it moves.

 

[joetama 5,000+ posts]

If object 'A' is moving a 1mph left and object 'B' is moving at 1mph right (relative to a stationary object (ground) the difference in the speed between them is 2 mph. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Kind of like two object heading at each other, car 1 is moving at 50 mph car 2 moving at 50 mph hit head on = car 3 hitting a brick wall at 100 mph... //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[squeak9798 5,000+ posts]

i think i understand it now. i was thinking about it more in terms of a car rather than a plane, which threw me off. it would be much more difficult, however to launch an airplane in this manner. I think that having the plane on a conveyor, but moving in the same direction as the conveyor would be very effective, because the conveyor speed would add to the plane's thrust thus doubling the speed in half the distance, and would launch the plane in a runway 1/2 as long.
is that thinking correct?

No.

Again, the wheels just freely spin.

If you tried to launch an aircraft from a conveyor belt traveling in the same direction at exactly the same speed.....the plane's speed would NOT be affected (again, wheels = have no affect on the thrust of the plane). The wheels would simply not spin.

and then the plane could land on the conveyor that is going the opposite direction of travel because it could slow down while making little forward progress?

Again, no. The wheels would just spin twice as fast while the plane was trying to land. The wheels (other than brakes) have no affect on the planes deceleration either (other than friction, which is minute).

 

[rollerdj 10+ year member]

i think i understand it now. i was thinking about it more in terms of a car rather than a plane, which threw me off. it would be much more difficult, however to launch an airplane in this manner. I think that having the plane on a conveyor, but moving in the same direction as the conveyor would be very effective, because the conveyor speed would add to the plane's thrust thus doubling the speed in half the distance, and would launch the plane in a runway 1/2 as long.
is that thinking correct? and then the plane could land on the conveyor that is going the opposite direction of travel because it could slow down while making little forward progress?

no, all that would do is just lower the friction gererated by the wheels. the only good way to shorten take-off distance is by taking off into the wind. thats why on a aircraft carrier, when they start doing takeoffs, why turn into the wind. more wind under the wings, more lift.

 

[mr Tibbs 10+ year member]

To correlate this to your example, let's pretend we are facing backwards on the airport conveyor......so it is traveling at 3mph in the opposite direction we are heading. However, instead of walking on the conveyor belt, we are wearing roller skates, and our "force" or "thrust" is provided by our friend (standing on solid ground) pulling us with a rope. If he pulls us at 3mph in the opposite direction of the conveyor belt, will we move ?? The answer is YES, WE WILL, at approximately 3mph.

This did it for me, I now understand.

NG, maybe you can try to explain things like this rather than just call people idiots and look like a bigger idiot doing said idiot calling.//content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

 

[Acidburn 5,000+ posts]

no, all that would do is just lower the friction gererated by the wheels. the only good way to shorten take-off distance is by taking off into the wind. thats why on a aircraft carrier, when they start doing takeoffs, why turn into the wind. more wind under the wings, more lift.

Bingo. It's all about air speed.

 

[rollerdj 10+ year member]

This did it for me, I now understand.
NG, maybe you can try to explain things like this rather than just call people idiots and look like a bigger idiot doing said idiot calling.//content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

but it's so fun calling people idiots. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[mapolley07 10+ year member]

okay, i realize that a treadmill going in the opposite direction would not help the plane slow down on landing, but essentially you can reduce the land area of the airport because the plane can act like it is landing on a 3,000 foot runway when it is only on less than 800 feet, gives more braking time while reducing the ground distance the plane has to travel.

for takeoff, if the plane needs and airspeed of 150 miles per hour, the plane can have thrust of 75 mph rolling on a 75mph forward conveyor, then hit its brakes and achieve the rest of the necessary velocity almost instantly, because the conveyor velocity would then add to the thrust from the plane? is that more correct? the plane would have to lock the wheels in place though to prevent rolling