# plane question

Discussion in 'Off Topic [BG]' started by fr0me0, Jan 13, 2006.

1. ### fr0me0

Dec 7, 2004
A plane is standing on 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 opposite direction).

The question: Will the plane takeoff?

2. ### Vorago(((o)))

Jul 17, 2003
Antwerp, Belgium
no

3. ### fr0me0

Dec 7, 2004
i think it would still take off. I mean the conveyor would just spin the wheels backwards the wheels don't provide much drag on the plan cause the forward motion is from the thrust of the engine, not from the wheels themself.

4. ### canopener

Sep 15, 2003
Isle of Lucy
Where's Ray Salamon when you need him?

5. ### Gard

Mar 31, 2000
WInter Garden, FL
Vorago is correct.

In your scenario, the plane would never gain any forward speed at all, and without doing so, there will be no lift on the wings, the plane will just sit still.

6. ### Kelly LeeYeah, I'm a guy!Supporting Member

Feb 17, 2004
Marana, AZ, USA
The main thing an aircraft must have is "lift". It cannot get that unless the wings are moving through the air at sufficient speed to generate lift. Spinning the wheels to 10,000 mph will not give the aircraft any lift whatsoever. Sorry.

EDIT: Dang it Gard, you beat me to it!

7. ### SnoManWords Words Words

Jan 27, 2001
Charleston, WV

Huh

It takes upward lift caused by wind to get a plane off the ground.....not just making the wheels move....which is all what you originally proposed would do.

8. ### Gard

Mar 31, 2000
WInter Garden, FL
You'll have to settle for me for now, but I'm the son of a former USAF and Delta Air Lines captain, grew up spouting aeronautical equations.

V sub 1, V sub 2, V sub r....

...where's that geek smiley???

9. ### stedtale

Yep. No forward motion-or air moving over the wings-no lift, no fly.

10. ### fr0me0

Dec 7, 2004
ok put a model car on a treadmill and it goes backwards.

Now hold it with you hand it will stay motionless with little effort. it'll also be really easy to move it forward no matter how fast its spinning since the only drag you have to contend with is the slight drag on the axels since there's no drive train (like on a plane)

i think the thrust from a plane engine will be exactly like your hand since its a force external to the treadmill, I think the plane would move not matter how fast the conveyor was going.

11. ### SnoManWords Words Words

Jan 27, 2001
Charleston, WV
Wait Wait Wait!

you've worded your original question very poorly.

You're not asking it the plane will take off from the conveyor, you're asking if the plane will be able to move itself off the conveyor regardless of the conveyors speed.

Whether the plane will fly is irrelevant, you want to know if the plane will be able to move itself off of the conveyor.

Is that correct?

I'll have to think about my answer again if that's what you're trying to get at

12. ### fr0me0

Dec 7, 2004
its not actually my quesiton it was posted on another form I visit and has turned into a huge pissing match over there lol. The way I interpret the situation the spirit of the question is "will the plan be stuck in one spot or will it be able to move forward against the conveyor" wether or not the conveyor is long enouhg for the plane to get enough speed or not to take off is mute. More so the question is will the plane be able to move forward.

people say that since the conveyor is matching speed the plane won't go anywhere, but how can its speed effectivly produce drag on the plane since the wheels on the plane aren't used to generate forward motion, the engines do.

13. ### PaleMelanesian

Jun 23, 2005
N / East Texas
It'll just get really fast in a hurry.

Since the conveyor is matching the plane's thrust, the plane will sit still with its wheels spinning. At least, until the conveyor breaks or runs out of power, and then the plane goes, and it takes off. (or the conveyor is stronger, and the plane quits, and gets thrown off) I'd put my money on the plane being stronger at the limit.

Edit: Actually, the planes engine is fighting its own wheel friction. It's already known, for sure, that the engine can overcome THAT. Faster, faster, faster, conveyor goes boom, plane takes off.

14. ### fr0me0

Dec 7, 2004
like theoretically I guess i'tll never take off but I mean thats one hell of a conveyor since the only drag on the plane its producing is wheel friction.

15. ### Alex

^^^^^

I can't phrase it any better myself

16. ### UnsungZerosThe only winning move is not to play.

This is a situation where thrust vectoring would be nice to have.

17. ### SnoManWords Words Words

Jan 27, 2001
Charleston, WV
Ok, I have no physics knowledge....or any field of knowledge that pertains to this, I'm using just what I've picked up in my years.

I assume that the plane may be able to move forward if it's engines are able to create enough forward propultion to offset the drag caused by the wheels(which will be influenced by the wieght of the craft).

More-so, you would need to know the weight of the aircraft, the amount of surface contact from the tires, the hieght of the engines, the placement of the engines on the aircraft, the output force of the engines and possibly any variables caused by the material on the converyor belt.

A formula could probably be divised using those measurements to give an exact speed/thrust-amount needed for the plane to move forward on the conveyor.

I could be completely wrong....but I feel that I'm on the right track here

18. ### SnoManWords Words Words

Jan 27, 2001
Charleston, WV
and you can probably throw the word displacement somewhere into my variables also...something surely needs to be displaced.....

Dec 7, 2004