*light blue touch paper*

Will the plane take off?

  • Yes

    Votes: 52 49.1%

  • No

    Votes: 54 50.9%
  • Total voters
    106
  • Poll closed .
Status
Not open for further replies.
Its a simple answer, but requires thought. The question is intentionally vague, and I reckon its designed to test people's ability to overcome their initial instincts.

The plane will take off.

The plane takes its power and acceleration from the wing-mounted engines.

The wheels are not driven, they are free spinning.







If you don't believe that, then by your logic it stands to reason that when a plane lands, if the wheels are not spinning, as soon as it touches down it comes to an immediate halt.
 
The wheels are completely irrelevant: what I don't get is how if it's moving forward-but-not, how is enough air being pulled past the wings to get it to lift off? Let's assume for a moment that 'lift off' means 'lift off and STAY UP'. I mean, when a plane normally lifts off, I imagine the air staying still and the place drags itself through the air, thus generating lift. If the plane isn't actually going anywhere...

...but then, I don't actually know anything about how it works.
 
Sulkdodds said:
The wheels are completely irrelevant: what I don't get is how if it's moving forward-but-not, how is enough air being pulled past the wings to get it to lift off? Let's assume for a moment that 'lift off' means 'lift off and STAY UP'. I mean, when a plane normally lifts off, I imagine the air staying still and the place drags itself through the air, thus generating lift. If the plane isn't actually going anywhere...

...but then, I don't actually know anything about how it works.
Click to expand...
I think you are letting those who are wrong confuse you. The plan IS moving. Period. The jets/propellers of the plane are causing it to move. And yes I'm pretty sure that's how flying works.
 
Yes, it's moving, but it can't possibly be getting enough air to take off from just the propellers sucking in. Otherwise we'd launch planes by clamping them down, firing up the engines then releasing the clamps.

Maybe?
 
Sulkdodds said:
Yes, it's moving, but it can't possibly be getting enough air to take off from just the propellers sucking in. Otherwise we'd launch planes by clamping them down, firing up the engines then releasing the clamps.

Maybe?
Click to expand...
The propellers aren't just sucking in... Honestly I don't know where you are getting these random ideas from :P

A plane taking off normally off a normal runway is doing the exact same thing as the plane in our scenario, except the wheels are spinning twice as fast. That's it. No "the plane is moving but it's not" No nothing. Done.
 
Sulkdodds said:
Yes, it's moving, but it can't possibly be getting enough air to take off from just the propellers sucking in. Otherwise we'd launch planes by clamping them down, firing up the engines then releasing the clamps.

Maybe?
Click to expand...
no, that's not how it works. The plane has to get enough speed so that there is a fast current of air flowing under the wings (this creates lift). Since the atmosphere is (for the most part) stationary in relation to the ground, to be moving fast through the air the plane has to be moving fast in relation to the ground.

All the conveyor belt would do is reduce the planes acceleration a bit, in proportion to the coefficient of friction between the plane and the conveyor belt.

So in short the plane would eventually take off, it would just take longer.
 
The plane is still moving as if it were taking off normally. The tries and the converyor belt have nothing to do with anything in this. It will speed up and take off as if it was on a normal runway.
 
Sulkdodds said:
Yes, it's moving, but it can't possibly be getting enough air to take off from just the propellers sucking in. Otherwise we'd launch planes by clamping them down, firing up the engines then releasing the clamps.

Maybe?
Click to expand...
Jets fly so much faster than prop planes because they create thrust with a powerful push. The air being pushed is irrelevant to lift. The air in front of the plane is more important as that is what the wings ride on. The motion of the air being sucked in by the engines is not integral to the generation of lift.

On prop planes lift is partly created by the huge propeller swirling around physically pushing air over the wings, and accounts for maybe 50% of lift which is why you see final model planes with prop engines spanning most of the wing depending on the capacity of the plane.

What you said is somewhat correct, but instead of clamps, jetliners use breaks in the landing gear to hold it while thrust is built up to take off speed. Engine speed is not altered from throttle up to fly-by-wire.

Fighter jets on the other hand have no landing gear brakes (not in the same sense as jet liners, but they do have small brakes otherwise they would roll about on their own, obviously) and use hooks when taking off and landing from carriers, but rely strictly on pilot control manipulation from runways.


Teta_Bonita said:
no, that's not how it works. The plane has to get enough speed so that there is a fast current of air flowing under the wings (this creates lift). Since the atmosphere is (for the most part) stationary in relation to the ground, to be moving fast through the air the plane has to be moving fast in relation to the ground.

All the conveyor belt would do is reduce the planes acceleration a bit, in proportion to the coefficient of friction between the plane and the conveyor belt.

So in short the plane would eventually take off, it would just take longer.
Click to expand...
You are completely mistaken. If lift were being generated by the engines the plane would take off almost immediately. It would not take longer to lift off because there is nothing hindering the thrust system.

The wheels move independantly of the rest of the plane and have no effect on whether it gets off the ground or not.
 
Dumb Dude said:
The plane is still moving as if it were taking off normally. The tries and the converyor belt have nothing to do with anything in this. It will speed up and take off as if it was on a normal runway.
Click to expand...
This man has the correct logic.

You get a cookie.
 
Vegeta said:
The propellers aren't just sucking in... Honestly I don't know where you are getting these random ideas from
Click to expand...
They obviously are, because otherwise the plane would never even start accelerating. They are sucking in/dragging the plane forwards. In a sense, they are 'climbing' the air, like a rock-climber climbs a rock-face.

Taking this analogy further, if said rockface is moving downwards, rock-climber is not actually moving upwards. He is not getting anywhere.

So the question is: how can a plane lift off if it is moving nowhere in relation to the largely-stationary air?

I would believe you, except you don't make any sense!

EDIT: So Z, from what you said it sounds like a prop plane would be able to take off (albeit not much) but a jet plane wouldn't?
 
Sulkdodds said:
They obviously are, because otherwise the plane would never even start accelerating. They are sucking in/dragging the plane forwards. In a sense, they are 'climbing' the air, like a rock-climber climbs a rock-face.

Taking this analogy further, if said rockface is moving downwards, rock-climber is not actually moving upwards. He is not getting anywhere.

So the question is: how can a plane lift off if it is moving nowhere in relation to the largely-stationary air?

I would believe you, except you don't make any sense!

EDIT: So Z, from what you said it sounds like a prop plane would be able to take off (albeit not much) but a jet plane wouldn't?
Click to expand...

Did you read my post?
 
Sulkdodds said:
EDIT: So Z, from what you said it sounds like a prop plane would be able to take off (albeit not much) but a jet plane wouldn't?
Click to expand...
In this situation the type of engine is meaningless, they both will take off, but in practice prop planes need much less distance to leave the ground pound for pound of thrust as they are designed to coerce lift.

Think of jets as gliders with rockets attached.
 
Assuming the aircraft achieves sufficient lift (dependent on the air density, the aircraft's velocity and the wing area) it will take off.

As people have already said, the aircraft does not rely on wheels for it's propulsion therefore how fast they are travelling (in this case twice as fast as at normal lift-off) does not affect the aircraft's ability to take-off.

(i think this is the first time i've used my Aeronautical Engineering degree since i graduated in 1998, and all to answer a question on a gaming forum!?!)
 
So the very fact that it's going at high speed means air gets pulled under the wings? How does that work?

(This isn't a rhetorical question. I don't get it.)
 
Sulkdodds said:
So the very fact that it's going at high speed means air gets pulled under the wings? How does that work?

(This isn't a rhetorical question. I don't get it.)
Click to expand...

The air's not being "pulled under the wings" it's the wings that are travelling through the air, propelled by the aircraft's engines.

Edit:- think about it this way. You've got a toy car sat on a treadmill. You turn on the treadmill, and the car starts to move backwards (they'll probably also be some movement of it's wheels). Next you take hold of the toy car and begin to push it foward - this force you're applying is effectively the same a the force of the aircraft's engines, so the harder you push, the faster the car goes, and the more forward speed it has independant of the speed and direction of the treadmill or the car's wheels.
 
_Z_Ryuken said:
Realize however, the wheels are still supporting the weight up to the point of lift off, and there's an increased chance the bearings will fail. If the bearings fail the wheels will grind to a stop and the plane will not lift off.
Click to expand...
Lol, caveat. Well played.


If you had some sort of CAR WITH WINGS that could accelerate enough using just the drivetrain (not some sort of jet power), then this winged car would never leave the ground.
 
Sulkdodds said:
So the very fact that it's going at high speed means air gets pulled under the wings? How does that work?

(This isn't a rhetorical question. I don't get it.)
Click to expand...
That's the "barn door" wing effect......flat wings do that, "collecting air under them" (raming it under by moving foward)

A proper wing actually works by it's shape, the upper surface is longer than the lower, equal air is split across top and bottom, the upper air has to spread out more because of the longer distance (travels faster) and is therefore less dense, the higher pressure under the wing than above the wing means it moves upwards into the "vacuum" of course, it's constantly moving with it......like a donkey following a carrot tied to a pole on it's back.
 
Griz said:
The air's not being "pulled under the wings" it's the wings that are travelling through the air, propelled by the aircraft's engines.
Click to expand...
Okay. But the wings aren't travelling through the air, surely? The air is still (ish) in relation to the ground. And because of the conveyor-belt, the plane's wings are still (ish) in relation to the ground...

The people who actually know anything about it are probably right. I just don't get how it works is all.

EDIT: Yeah, I know how the wings create lift Shorty. But how come they're collecting air if they aren't, effectively, going anywhere? To go back to John's treadmill analogy, you're running on a treadmill with a big net held above your head. You're trying to use the net to catch a ball or something hanging from the cieling, except you're not allowed to move your arms. So you can't catch it because you're not getting any closer to it. That's a huge oversimplification...but... D:
 
MuToiD_MaN said:
Lol, caveat. Well played.


If you had some sort of CAR WITH WINGS that could accelerate enough using just the drivetrain (not some sort of jet power), then this winged car would never leave the ground.
Click to expand...

I think I saw a video once (in my high school aviation class) where a plane's landing gear had failed right at the end of the runway and it just kind nose dived into some kind marsh. :/
 
The wings ARE moving through air. It takes off as normal as if it was on a normal runway. Same speed. The conveyor belt and tires mean NOTHING.
 
Sulkdodds said:
Okay. But the wings aren't travelling through the air, surely? The air is still (ish) in relation to the ground. And because of the conveyor-belt, the plane's wings are still (ish) in relation to the ground...

The people who actually know anything about it are probably right. I just don't get how it works is all.

EDIT: Yeah, I know how the wings create lift Shorty. But how come they're collecting air if they aren't, effectively, going anywhere? To go back to John's treadmill analogy, you're running on a treadmill with a big net held above your head. You're trying to use the net to catch a ball or something hanging from the cieling, except you're not allowed to move your arms. So you can't catch it because you're not getting any closer to it. That's a huge oversimplification...but... D:
Click to expand...

Take a look at my treadmill analogy above - it should make it a little clearer.
 
Sulkdodds said:
Okay. But the wings aren't travelling through the air, surely? The air is still (ish) in relation to the ground. And because of the conveyor-belt, the plane's wings are still (ish) in relation to the ground...
...That's a huge oversimplification...but... D:
Click to expand...

No. This is a huge oversimplification:

Thrust for a jet is like a giant hand holding the plane, but all it can do is throw it in the direction it's pointed.

Thrust for a prop plane is like a giant hand, same as the jet, but the hand is weaker and needs help from the propeller (to create lift by pushing air around the wings). (:

If you look below, you will find an even greater simplification. o_0;;
 
Of course not. If the plane doesn't move, it doesn't get any lift. No lift, no flying.
 
Steve said:
Of course not. If the plane doesn't move, it doesn't get any lift. No lift, no flying.
Click to expand...
Heh, a bit late in the game eh. The trick is, the plane is indeed moving as fast as it normally would.

And Sulks, you need to read closer, I said the plane wasn't JUST sucking in air. Not that it wasn't sucking in air. It is.

And you still don't get it, rofl. Why do you keep thinking the plane is standing still. I keep telling you, you say you know, and then you suddenly forget or something.
 
IF IT WERE ASSUMED TO BE TRUE that the plane was not moving relative to the real ground (more accurately, the stationary air) then yeah no takeoff.

But that can't possibly be the case, as Mr. MS Paint over here has ... uh ... clearly illustrated.
 
We'll never really know until somebody builds it.
 
Actually, we will. Read the thread. There's nothing "magical" about this scenario that can't be predicted. The conveyor and wheels do nothing to hinder the planes takeoff. Think about it.


I'm currently making a flash movie that shows the process. (A narrated one!)
 
Steve said:
Of course not. If the plane doesn't move, it doesn't get any lift. No lift, no flying.
Click to expand...
gif6mi.gif

Recoil Enterprises 2006®
 
Thanks for ignoring my posts. I already said that the plane was moving.

You people are dumb for thinking it couldn't take off, and dumb for ignoring my posts.
 
vegeta897 said:
The conveyor and wheels do nothing to hinder the planes takeoff. Think about it.
Click to expand...
Well there is, because they have to be spinning twice as fast when it attains take of speed as normal.

Obv there is more drag than normal, but it's not a lot compared to the overall force foward.

And if the where so stiff that it did have an effect the plane wouldn't move anyway........remember it's tracking the speed of the plane.
 
If a plane is on a conveyor that moves backwards at the same speed as the plane goes forward then the plane is standing still.

If the conveyor is NOT moving at the same speed as the plane, IE the plane is moving forwards then the plane takes off.

According to the question, the conveyor has a system that matches it to the planes speed, ie the plane does not move forwards. Ie it can't take off.

What am I missing?
 
MaxiKana said:
If a plane is on a conveyor that moves backwards at the same speed as the plane goes forward then the plane is standing still.

If the conveyor is NOT moving at the same speed as the plane, IE the plane is moving forwards then the plane takes off.

According to the question, the conveyor has a system that matches it to the planes speed, ie the plane does not move forwards. Ie it can't take off.

What am I missing?
Click to expand...
The wheels rotate freely and the conveyor moves backwards whilst the plane moves fowards. (think of moving your hands in opposite directions with a pencil in between, the pencil being the wheel)

A plane isn't powered by it's wheels......
 
dammit, I voted yes before yes was cool. I'm a trend setter!
 
I can pick a large amount of people in this thread that deserve my name more than me.
 
MaxiKana said:
If a plane is on a conveyor that moves backwards at the same speed as the plane goes forward then the plane is standing still.

If the conveyor is NOT moving at the same speed as the plane, IE the plane is moving forwards then the plane takes off.

According to the question, the conveyor has a system that matches it to the planes speed, ie the plane does not move forwards. Ie it can't take off.

What am I missing?
Click to expand...

The speed at which the ground is moving relative to the aircraft has absolutely nothing to do with the aircraft's ability to take-off. The only thing that matters is the speed at which the wing travels through the air (or the speed at which air travels over the wing). And since the air speed is dependent on the the aircrafts propulsion, and that the aircraft's propulsion is independent of it's wheels, the speed and direction of travel of the ground and/or the aircrafts wheels is inconsequential.
 
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