will it take off?

[NewToy]

Just one or two more questions so I can get this straight.
Have you ever tried to push your tractor by hand on level pavement? I know it took 6 guys just to budge mine. I'm guessing 300 Lbs of force. Arent these rubber tires just like the ones on aircraft.
How much force do you think it would it take to push a Cessna 150, DC3, or 727 on pavement?

You must have a giant tractor or it has the brakes dragging. I can push mine (2600 lbs) easily by myself on level pavement. Never could get it going fast enough for takeoff though.
PS- The plane will fly.
John

 

[MossRoad]

So, in laymans terms it means that no matter how fast the convyer moves backwards the plane WILL move forwards due to it being drawn forward through space/air. No matter how fast the convyer goes and how fast the wheels spin the plane will gain forward movement through the air at it's normal speed and will take off.

I think my head hurts, fizzle, fizzle, pop!

The problem with this is, if the conveyer picks up speed to match the spinning tire, it never did its job of matching the speed in the first place. It was playing catch up, not exact match.

Splain that one, Lucy.

 

[MossRoad]

Just one or two more questions so I can get this straight.
Have you ever tried to push your tractor by hand on level pavement? I know it took 6 guys just to budge mine. I'm guessing 300 Lbs of force. Arent these rubber tires just like the ones on aircraft.
How much force do you think it would it take to push a Cessna 150, DC3, or 727 on pavement?

When I worked at the aiport, I frequently moved 10 passenger twin engine turboporps around the hangars by hand. I weighed 135 pounds. Airplanes do not weigh that much and have really good wheel bearings, as well as really smooth tread on their tires, usually just rain groves.

We could move a DC3 with an 18HP wheelhorse lawn tractor and a 727 with about 4 or five guys pushing each landing gear. The problem with a 727 is not getting it going, but getting it stopped when you get there! That's why you need a large tug with lots of weight and good brakes or the plane powered up to apply hydraulic pressure to the brakes. The mass gets rolling really easy and keeps on rolling.

 

[BillyP]

Nope. As soon as you push the model plane forward with your finger, its wheels are turning faster than the surface speed of the small conveyor. You, in effect, have cheated.

Nope, the wheels can't turn faster than the conveyor because the conveyor kicks into turbo boost overdrive and keeps up.

And the tires are made of a super non skid resistant high performance guaranteed to have 100% traction Firestone 500 Finger Plus and made especially for model airplanes on a super responsive magical conveyor belt

 

[Steve_Miller]

Sense we were having so much fun debating the finner points of tire pressure in the other thread....

i thought this would be kinda fun...

a plane is standing on a movable runway( something like a conveyor).as the plane moves the conveyor moves but in the opposite direction.the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

the question is

will the plane take off or not?

(ps its been debated to death on other forums, its always fun to see how people present the theory behind there answer)

Answer me this one then, if the plane was doing 200MPH flying thru the sky with the landing gear down and you put this magical conveyor under the wheels, would the plane and conveyor fall out of the sky or would the wheels just spin at 400mph. Unless this magic conveyor is moving ground, sky, air, landscape or whatever else you desire it's going to keep flying until the propellent (jet, prop, rocket,etc) is removed from the equation.

a plane is standing on a movable runway( something like a conveyor).as the plane moves the conveyor moves

I guess my question is what exactly does the conveyor move? If someone can put a definition on this, the question will answer itself.

Steve

 

[DieselPower]

The problem with this is, if the conveyer picks up speed to match the spinning tire, it never did its job of matching the speed in the first place. It was playing catch up, not exact match.

Splain that one, Lucy.

That's just the point that had me originally thinking it would not lift off. Then the light bulb went off. There are two different points. The ground and air space. A plane is not made to move over ground (though it does) it is made to move through space. Doesn't matter what you put under it. The convyer plays no part in the plane lifting off. It is not propelled on the runway/convyer by driven wheels like a car. It is propelled through space by a propeller/jet engine. The plane moves through the air as a result of the reaction between the prop/jet and the "air" and not ground.

Think of it this way. If you had a crane 20,000 feet high and you lifted a plane up to this point and dropped it, it would fall to earth directly under the point it was lifted to. If you now start that plane up and drop it, it will now fly away because it is pulled through the air by its engine propultion system. Now, attach your magic convyer to the crane and lift it to 20,000 feet and drop it. The plane and convyer will fall to earth. Redo this but now with the plane's propultion system running. The convyer will fall to earth and the plane will be propelled off and forward of the convyer.

 

[755inNY]

Nope. As soon as you push the model plane forward with your finger, its wheels are turning faster than the surface speed of the small conveyor. You, in effect, have cheated.

And another
The problem with this is, if the conveyer picks up speed to match the spinning tire, it never did its job of matching the speed in the first place. It was playing catch up, not exact match.

Splain that one, Lucy.

MossRoad, You seemed to be stuck on the conveyor matching the speed of the wheels when the scenario states that the conveyor matches the speed of the plane. Splain that one.

 

[755inNY]

okay - this is my last post on this topic.

I fully agree that if the plane moves it flies. It all comes down interpretation of the conveyor...if it is matching the planes speed (not the wheels...but the speed) then I would argue that it is stopping all movement of the plane. Naturally, this is impossible

So what happens to all the thrust if the plane isn't moving? Well what happens to it if the brakes are on? The thrust can't overcome the friction of the brake/tires.

So...if the thrust moves the plane and the magic conveyor is NOT able to exactly counter forward speed of the airplane then it will fly.

If this fictional and magic conveyor can exactly counter the speed of the airplane then the airplane does not move nor fly.

Based on all the posts here - I think everyone would agree with those last two statements - it all comes down to what this fictional conveyor is capable of!

I don't agree with either of the last 2 statements.

 

[gizmo]

The conveyor is doing nothing but spinning the wheels. The prop will still pull the plane through the air regardess of how fast or even what direction the conveyor moves and the plane will fly.

Nothing complicated about this. Don't read too much into it and it makes sense.

I am a pilot and an engineer and I have argued this scenario about a dozen times now.

 

[NewToy]

The conveyor is doing nothing but spinning the wheels. The prop will still pull the plane through the air regardess of how fast or even what direction the conveyor moves and the plane will fly.

Nothing complicated about this. Don't read too much into it and it makes sense.

I am a pilot and an engineer and I have argued this scenario about a dozen times now.

The no fly contingent will have to have a conveyor to prove it to them. Since they believe the plane will not move the conveyor need only be large enough to accomodate the footprint of the landing gear. Also, it won't need all the magical speed matching properties, we can spin it at twice the speed the airplane could ever go and the plane would still take off.
John