Will it fly(don't answer too fast)?

[Delta_]

I'm just hoping that the conveyer has a good brake, cause when the plane runs out of gas it still won't go anywhere.

Why will it not go anywhere?  Give me a good explanation and i will believe you.  No one saying the aircraft will not take-off has given a reasonable explanation yet.

I have given my explanation in a simple description above, i can put more detail but peoples' heads will explode for sure.

[Chris_F]

I'm just hoping that the conveyer has a good brake, cause when the plane runs out of gas it still won't go anywhere.

Reread the question in the literal sence, not what you may think it says.

I've re-read the sentance a dozen times and here's what I think he's saying:  airplane starts, conveyor moves in opposite direction, airplane gains ground speed and air speed, airplane takes off, conveyor is still moving, airplane flies around and runs out of gas, conveyor still moving, matching plane's speed, airplane impacts the ground and stops instantly...  the conveyor, in order to match the plane's speed, must also stop instantly.  Hence a very good brake.

[61_OTU]

I've reached a conclusion which makes me agree with the takeoff contingent, which makes me really annoyed as I didn't think it would takeoff.

Imagine a stongman pulling a plane (Analogous to the jet engines).

As soon as the plane starts to move a conveyor under the plane only (not under the man) starts to turn to match the forward speed of the plane. The strongman has to contend with greater resistance due to friction in the wheel bearings, but can theoretically continue to pull the plane forwards. The wheels turn faster relative to the speed of the strongman, but the plane moves forwards.

Given sufficient time and thrust the plane could reach takeoff speed, but probably not pulled by a strongman

[Chris_F]

If it's difficult imagining a plane taking off under these conditions instead imagine the opposite: a plane landing under these conditions same conditions.  The plane is moving realtive to the air and REALLY fast relative to the belt.  It lands, does a touch and go, and takes off again.

Now have the plane touch down on the belt, slow down a little, then floor the throttle and take off again.  Can the plane take off or is it now doomed to the ground?  It can take off again since it is pushing against the air and not the ground.

Now imagine a car with wings.  The car touches down and when it tries to take off it only pushes against the belt.  It can't take off again because it can't gain airspeed due to the moving belt.  The plane however can push against the air itself and can gain airspeed to take off.

[TacitBlue]

That answer has been rephrased at least a hundred times.
And rightfully so, it is correct.

[bbstackerf]

Reasons can be given all day as to why it will take off. But all the babble is bending the rules in the given situation. The question is simple as it it stated. The the plane occupies the same geo position on the face of the planet - it's not going to get lift under the wings. Thus, it's not going to fly.

In simple easy to understand english:
If the aircraft overcomes the speed of the conveyor it will move forward through the air which causes a vacuum over the top of the wing, thus creating lift and it will fly. If does not, it will fall off the a$$ end of the conveyor.

Assuming power is gradually applied to the conveyor causing it to move faster under the aircraft, and the aircraft is powered up in order to keep the same position on the conveyor relative to the ground - which is the assumption made by the question - you've taken out the most basic ingredient in flight - lift.

No lift, no flight.

Try it this way. Grab a piece of plywood, jump on a tread mill, turn up the treadmill to the fastest setting. Feel anything tugging at the sheet of plywood? No? Gee, think maybe because you're not getting any lift?


Keni

[SilverFox441]

Keni, you're missing the point.

You, or a car, apply thrust through your contact with the ground or throught the treadmill. You're ability to move forward is based on the contact patch and the thrust applied.

A plane move based on reaction with the air, not the ground. What happens to the conveyor it immaterial.

Anyone who doubts that the plane will lift off should ask themselves what happens aboard an aircraft carrier. If a CVN is travelling at 30 KTS does a plane have to reach normal takeoff speed plus that 30 kts? Of course not...all that mattes is the planes airspeed, not it's groundspeed.

[Chris_F]

Reasons can be given all day as to why it will take off. But all the babble is bending the rules in the given situation. The question is simple as it it stated. The the plane occupies the same geo position on the face of the planet - it's not going to get lift under the wings. Thus, it's not going to fly.

No, the question as stated merely says the speed of the conveyor matches the speed of the plane, only in the opposite direction.  If the plane makes 100 knots airspeed the conveyor, as the problem is stated, moves 100 knots in the opposite direction.

Initially I assumed as you did: the conveyor moves whatever speed is necessary to keep the airplane stationary relative to the earth.  But upon re-reading the scenario I believe you find that this is not stated, only strongly implied (hence the riddle).

[H]

Do you know what....
Every now and again I come across a grope group of Folks who seem to thoroughly enjoy a good-old argument for the sake of a bleedin' argument....
...a bit like the Oprah Winfrey Show*...
...Aeroplanes, wheels, conveyor belts, catapults, etc....I just  can't stand the stress... ... ...!LOL...!*...another reason why I don't have a bloody television set... ... ...!

Now, Mr. Fozbury, I know you have enough electronic background to know that a television is just a 'monitor' with an rf tuner; welcome to the Simviation Talk Shows!

Try it this way. Grab a piece of plywood, jump on a tread mill, turn up the treadmill to the fastest setting. Feel anything tugging at the sheet of plywood? No? Gee, think maybe because you're not getting any lift?

Aside from the fact that the plywood is already lifted, to properly represent the original scenario it would need its own, ungrounded power. What you present makes the bearer the source of motive power; unless he/she has their own viable wings, propeller or a forceful enough jetstream emitting from their butt (inflammable or otherwise), they are relying upon their little feet pushing on the ground -- something they can't do with a conveyor/treadmill belt in the way (until they can get back up after they're flipped off the back end of it)!

[Delta_]

Try it this way. Grab a piece of plywood, jump on a tread mill, turn up the treadmill to the fastest setting. Feel anything tugging at the sheet of plywood? No? Gee, think maybe because you're not getting any lift?

Aircraft have wheels.  Try this put some roller skates/blades on and jump on a treadmill.  Other than friction in the bearings the treadmill will not pull you back.  Just hold onto the side railings and you can put the treadmill on full speed and still pull yourself forward.

[Chris_F]

[quote]
Aircraft have wheels.

[Delta_]

You still go forward of course!  The force generated from the rockets is independent of the wheels, just like pulling yourself forward.

[Felix/FFDS]

[quote]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 opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

[bbstackerf]

Ok, ok. I get it.

But nobody pointed out to me the disclaimer saying 'variable logic' was involved.

I was answering under the assumption that the conveyor situation basically was a distraction and we were talking about what would otherwise just be a jet sitting still taking off.

Keni

[eno]

Ok, ok. I get it.

But nobody pointed out to me the disclaimer saying 'variable logic' was involved.

I was answering under the assumption that the conveyor situation basically was a distraction and we were talking about what would otherwise just be a jet sitting still taking off.

Keni

You're right ........ the conveyor is a distraction  ;D