Wow thats an easy one. The plane will take off...end of story..

Think of the plane landing on a running treadmill, when the plane hit the treadmill it doesn't just stop. The wheels are just spinning faster then if it were to land on normal ground. The plane can just power up and take back off.
Its no different then if the plane started from a stand still.

That's a good way to look at it - and see that you are wrong <img src="/forums/images/graemlins/lol.gif" alt="" />

If I land a glider at 60 miles per hour (ground speed)on a conveyor that is moving in reverse 60 miles per hour - I go nowhere...technically i will eventually go backwards if the conveyor does not change speed.

Same principle as a hook and rope on an aircraft carrier. The static force (if thats the right term) applied to the hook is equal to or greater than that of the plane - stopping it in its tracks.

Yeah thats if you have a glider. <img src="/forums/images/graemlins/lol.gif" alt="" />

Actually, the plane would eventually stop (relative to the ground) due to wind resistance, but the plane would not roll backwards, because the bearings are frictionless. The plane would stay stationary with the wheels rolling at 60 MPH.

The friction of the wheel bearings won't be zero, but relative to the thrust of the engine they might as well be just about zero. The friction of the wheel bearings and air-mass resistance are the only things preventing forward movement of the aircraft (gravity could also be mentioned, but it's really a component of that wheel bearing friction), while the engine thrust (much more force) would pull the aircraft by grabbing the air (the air is unaffected by the conveyor) and pulling forward. The wheel bearings just need to be able to handle high speed. In most cases, aircraft wheel bearings (themselves) can handle quite high speeds.

It may take a bit more time (rolling resistance would have a small yet negligible effect), but if the conveyor were the length of a runway, the aircraft would fly.

OK Phil. I read that post.


This is where that dude with all the newtons is DEAD WRONG

The treadmill CANNOT make an opposing force Unless the wheels of the airplane are chocked, braked, or the like.


The conveyer STILL cannot act on the airplane.

Heres the way I see it in my mind in the VERY begining of the start.

Everything at rest, no movement anywhere, and magic treadmill.

You apply 100% throttle to your airplane, and your airplane pushes the AIR thats not connected to the treadmill. Airplane moves foward a fraction of an inch, and the treadmill says OHHHH Hell no airplane STOP!!!!! so it goes backwards, BUT the wheels slip, and the treadmill says Ohh no.... I cant stop this plane from pulling itself foward across me no matter HOW fast I run in either direction!!!!

The plane will normally accelerate foward as the treadmill will match the speed in the exact opposite direction.

How do you state that the treadmill will STOP the plane from accelerating in relation to the air?

I will be going to my folks house up north one of these weekends.

They have a fancy treadmill.

I will buy a cheap RC plane.

The experiment wont be perfect obviously...I can't control the speed relative to the plane, there will be wind kicked up from the treadmill...blah blah.

But I'll bring the vid cam and try to make my point - you say it doesnt matter how fast the treadmill is spinning - it will take off - so maybe we'll start there. Maybe I'll put something over the extra tread to keep the wind down - since it won't be moving forward anyway <img src="/forums/images/graemlins/pfft.gif" alt="" />

And I will post the whole thing on YouTube and settle this for the entire world once and for all. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Good. Be sure the model plane has good wheel bearings similar to what a normal plane would have. I can't believe you still can;t see the thing you are overlooking.

<img src="/forums/images/graemlins/lol.gif" alt="" />
Damn it, my day job is beackoning. You guys don't pay me to sit and type Physics arguments. I'll be back tonight...

I truly never thought I'd ever use my Physics classes from college again. I'm an Econ guy! You're killing me here...

Phil-
If your logic were to hold up, then this scenario would be applicable.
- You taxi down the runway for takeoff in your 152. Two-thirds of the way you have to cross a section of the runway that is actually a treadmill, let's just say it's 50' long X the width of the runway, perfectly recessed flush with the runway.
By using your theory, if the treadmill was going the same speed as your ground speed, your plane would instantaniously stop....
No way! The RPMs at each wheel would increase, but the plane would coast right over the treadmill like it wasn't even there. You may get some skidding when you hit the treadmill, or a chirp when you get to the other side, but that'd be the extent of it.
Under these conditions, because you're trying to take off which requires accelleration, the force driving the plane is the powerplant which is pulling air, not momentum or inertia.