The conveyor belt myth - poll

[Greg Bockelman]

Rats. Another one to the dark side.

What does wheel speed have to do with flying?

Exactly.

I say you need relative wind to fly.

Exactly

With a plane on a belt with a belt doing 5000 MPH, and the planes wheels are doing 5000 MPH to stay in the same spot, there is no relative wind except for prop wash.

And if the prop is turning at full takeoff RPM, just what exactly is holding the airplane back?

A maule might almost take off, a C-172 will not.

Sure it will. There is nothing holding it back.

To see if the test type plane will take off, try the same plane with no wheels attatched just sitting on the bare gear.

Sit the bare gear on cement, add full power & the test is about the same.

How do you come to that conclusion? Tho rolling and bearing friction of a spinning wheel comes nowhere close to the friction of NO wheels on bare concrete.

Gotta do better than that.

 

[SCCutler]

I am just trying to figure out where the 5000 mph came from...

 

[cwyckham]

Its not about whether the plane moves, but that the wheels will overheat and explode sending FOD through the wings and greatly increasing the friction by forcing the airplane to slide on the wheel-less gear.

But I believe the plane will move.

There seems to be much debate about the wheels (I think you mean tires?) overheating. However, I don't think that is what a tire speed rating is based on. Any spinning object wants to rip itself to peices. The only thing keeping your tires from ripping apart is the tensile strength of the rubber/plys, etc. If you spin a tire fast enough it will fail, even without any heating. The heating that will occur will weaken the tires a bit, but it's not the dominant factor.

 

[stingray]

There seems to be much debate about the wheels (I think you mean tires?) overheating. However, I don't think that is what a tire speed rating is based on. Any spinning object wants to rip itself to peices. The only thing keeping your tires from ripping apart is the tensile strength of the rubber/plys, etc. If you spin a tire fast enough it will fail, even without any heating. The heating that will occur will weaken the tires a bit, but it's not the dominant factor.

You still have to prove that you can get the wheels over 120kts at a minimum before anything will happen. The only way you can do that is get the plane to move over the belt surface faster than it is moving past the ground surface.

Dan

 

[gkainz]

I think the basic point to get a "yeah" or "nay" on is "can you get sufficient airflow over the wing to achieve lift" and to hell with the speed of the wheels/tires ...

 

[mikea]

You still have to prove that you can get the wheels over 120kts at a minimum before anything will happen. The only way you can do that is get the plane to move over the belt surface faster than it is moving past the ground surface.

Dan

Beene goh.

The problem statement says,

The conveyor belt speed increases to match the speed of the plane as the plane moves...

How can there be any speed to match if the plane isn't moving?

...and as been explained over and over and over what can the conveyor belt possible do to stop the plane from moving? Unless if comes with the optional aircraft arrestor cable attachment the conveyor can't stop the plane.

 

[stingray]

Beene goh.

The problem statement says, The conveyor belt speed increases to match the speed of the plane as the plane moves...



How can there be any speed to match if the plane isn't moving?

...and as been explained over and over and over what can the conveyor belt possible do to stop the plane from moving? Unless if comes with the optional aircraft arrestor cable attachment the conveyor can't stop the plane.

Original question: A plane is standing on a runway that can move (some sort of band 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?

That is why it makes it so hard to see it, increases is not in the question. Tires and wheels are not in the question. When you think increases it seems to imply "more than" it is not more than. Even though it is true just matching, the brain will see it as an increase (to some). When you just say exactly it implies the same. They get it wrong because they install things that are not there.

The belt is going the same speed as the plane.

The belt is increasing it's speed to that of the plane.

Both are correct, but one is trying to throw you off.

Dan

 

[Henning]

Original question: A plane is standing on a runway that can move (some sort of band 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?

That is why it makes it so hard to see it, increases is not in the question. Tires and wheels are not in the question. When you think increases it seems to imply "more than" it is not more than. Even though it is true just matching, the brain will see it as an increase (to some). When you just say exactly it implies the same. They get it wrong because they install things that are not there.

The belt is going the same speed as the plane.

The belt is increasing it's speed to that of the plane.

Both are correct, but one is trying to throw you off.

Dan

It can only throw you off if you have the brakes applied because the belt has no effect on the airspeed, and it's the airspeed that the prop and wings operate on, so as long as the rolling gear stays together, you just need enough excess HP to overcome the extra brearing drag which isn't very great. In otherwords, as long as the tires stay together, you'll fly.

 

[AuntPeggy]

What the heck, put teflon skids on the plane and be done with bearings and tires.

 

[EdFred]

I posed this question to my mother, who will grudgingly admit she doesn't know anything about algebra and physics, and wouldn't know a vector diagram or the quadratic equation if it was presented by Isaac Newton himself. Who I think she was classmates with incidentally.

Even she said "of course the plane will take off, the wheels don't move the plane, the propeller does."

Feel stupid yet?

 

[gprellwitz]

I posed this question to my mother, who will grudgingly admit she doesn't know anything about algebra and physics, and wouldn't know a vector diagram or the quadratic equation if it was presented by Isaac Newton himself. Who I think she was classmates with incidentally.

Feel dead yet? Because when she sees this, you WILL be! You have one of the nicest ad prettiest mothers I know, so don't go dissing her, you hear!?!

(I'm trying for a spot in the house at the next 6Y9 flyin! )

 

[tonycondon]

... if it was presented by Isaac Newton himself. Who I think she was classmates with incidentally.

haha ed. I dont think Diz would appreciate that!

 

[stingray]

It can only throw you off if you have the brakes applied because the belt has no effect on the airspeed, and it's the airspeed that the prop and wings operate on, so as long as the rolling gear stays together, you just need enough excess HP to overcome the extra brearing drag which isn't very great. In otherwords, as long as the tires stay together, you'll fly.

Throwing your trane/train? of thought off. Both statements are exactly the same.

Dan

 

[jesse]

The whole tire exploding crap is just what people made up instead of admitting they were wrong. It's a simple airplanes 101 question with a simple answer. You can try to complicate this all you want but in the end the airplane will take off.

So for those of you trying to say 'no' using the tire excuse. Just admit you didn't think about the aerodynamics properly from the start and quit trying to complicate a simple concept.

 

[Henning]

The whole tire exploding crap is just what people made up instead of admitting they were wrong. It's a simple airplanes 101 question with a simple answer. You can try to complicate this all you want but in the end the airplane will take off.

So for those of you trying to say 'no' using the tire excuse. Just admit you didn't think about the aerodynamics properly from the start and quit trying to complicate a simple concept.

Waaayyyyy back when in the first POA/treadmill thread (which IIRC you started), I brought up the tire issue, but I have always maintained that yes, the plane will fly as long as the tires hold out. Tires are not an excuse or circumvetion or anything else. They are a reality of high speed operations. If you haven't considered tires, then you haven't thought the entire situation thru. When setting speed records at Bonneville, tires are one of the greatest concerns. People have banded metal around them to keep them together, and extreme speed vehicles use billet aluminum wheels with a tread surface machined into them and no rubber at all.

The theoretical is always simpler than the practical as applied. Many things are theoretically possible, but we lack technological expetise to bring them into the practical realm. In this case it would be simple enough, band or eliminate the tires, or use a STOL aircraft where having the tires spinning at twice their liftoff speed would not pose a problem. To completely discount the issue though shows a lack of sophistry of thought.

 

[stingray]

Like this.

http://www.youtube.com/watch?v=Yn2jET1dcPY&feature=related

Dan

 

[jesse]

Waaayyyyy back when in the first POA/treadmill thread (which IIRC you started), I brought up the tire issue, but I have always maintained that yes, the plane will fly as long as the tires hold out. Tires are not an excuse or circumvetion or anything else. They are a reality of high speed operations. If you haven't considered tires, then you haven't thought the entire situation thru. When setting speed records at Bonneville, tires are one of the greatest concerns. People have banded metal around them to keep them together, and extreme speed vehicles use billet aluminum wheels with a tread surface machined into them and no rubber at all.

The theoretical is always simpler than the practical as applied. Many things are theoretically possible, but we lack technological expetise to bring them into the practical realm. In this case it would be simple enough, band or eliminate the tires, or use a STOL aircraft where having the tires spinning at twice their liftoff speed would not pose a problem. To completely discount the issue though shows a lack of sophistry of thought.

Sure Henning. I remember you bringing that up too. The thing is--if we could build a conveyor built that was 3000 ft long and had the capability of moving fast enough to blow up tires--we would just bolt on some tires that wouldn't blow up.

 

[AWACSEng]

Jesse, I think some of us, myself included, have confused the theory with what is practical. Could the plane take off? Theorecticaly yes, practicaly no. But like you said, if we could make the said conveyor, we could probably remedy the other issues. My question is this; what good does the conveyor do?

 

[Henning]

Sure Henning. I remember you bringing that up too. The thing is--if we could build a conveyor built that was 3000 ft long and had the capability of moving fast enough to blow up tires--we would just bolt on some tires that wouldn't blow up.

Exactly, but you would have to do something, you can't just ignore the issue because if you do and it comes down to a test with a wager, you can lose the wager over a side issue, but since it didn't fly, you lost anyway even though it would have had the tire not blown. I don't lose bets over stupid and unstipulated grounds.

 

[cwyckham]

...My question is this; what good does the conveyor do?

It helps pilots understand how aircraft actually work and lets them shed their preconceived notions based on years of driving cars. The more one understands about aircraft and how they work, the better once can respond to an unusual situation.

Also, it's fun.

 

[Henning]

Jesse, I think some of us, myself concluded, have confused the theory with what is practical. Could the plane take off? Theorecticaly yes, practicaly no. But like you said, if we could make the said conveyor, we could probably remedy the other issues. My question is this; what good does the conveyor do?

The ONLY thing the conveyor does is spins the wheels faster, that's it, the one and only effect the conveyor belt would have on the entire situation. Outside of that (and the extra "squirlyness" of ground handling on the roll), you would not notice the difference between taking off on a concrete runway or a conveyorbelt running opposite your direction. The friction of the belt/air interface increasing your headwind would probably bring the increased bearing friction to a wash.

 

[stingray]

Jesse, I think some of us, myself included, have confused the theory with what is practical. Could the plane take off? Theorecticaly yes, practicaly no. But like you said, if we could make the said conveyor, we could probably remedy the other issues. My question is this; what good does the conveyor do?

I think we are all in trouble if a tire can blow up at twice the speed of a short field takeoff. Somewhere in the neigborhood of 57 mph (C150 climb speed with obsticles). Tire speed no more than 114 mph. The plane will take off practicaly and theorecticaly and as Henning said you would not even notice the difference. You would probably notice a harder takeoff trying to takeoff downwind.

Dan

 

[Henning]

I think we are all in trouble if a tire can blow up at twice the speed of a short field takeoff. Somewhere in the neigborhood of 57 mph (C150 climb speed with obsticles). Tire speed no more than 114 mph. The plane will take off practicaly and theorecticaly and as Henning said you would not even notice the difference. You would probably notice a harder takeoff trying to takeoff downwind.

Dan

Well, there you go, we have now stipulated an aircraft. A 150 no real problem. Take my old Midget Mustang that I'd unstick over 80 and now the tires are doing over 160 which means the top of the tire is doing 320.

 

[Greg Bockelman]

which means the top of the tire is doing 320.

Which is irrelevant.