Brainteaser - Input from Aerospace Engineers, Pilots etc. needed

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Posted: 2/3/2007 8:11:02 PM EDT

So the following question was posted on another message board I frequent, and it turned into a 10 page flame war with multiple bans and no answer.

"Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway. The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?"

Posted: 2/3/2007 8:12:15 PM EDT

[#1]

You'd really like to think that you're the first person to ask this wouldn't you?

ETA: The answer is no. Planes fly by the air moving over the wings, the speed at which the wheels turn has no bearing.

Posted: 2/3/2007 8:13:13 PM EDT

[#2]

how the hell are you gonna generate lift?

Posted: 2/3/2007 8:13:28 PM EDT

[#3]

It did the same thing on here, and no, it can not.

Posted: 2/3/2007 8:13:46 PM EDT

[#4]

Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

Posted: 2/3/2007 8:14:24 PM EDT

[#5]

Were you part of the multiple banned?

Posted: 2/3/2007 8:16:12 PM EDT

[#6]

Yes.

Some small additional "drag" would be present in the form of a marginal increase in the friction of the wheel bearings, but all other factors remain the same.

Anyone that tells you otherwise (and they will be along shortly) is a fucking moron.

Posted: 2/3/2007 8:16:27 PM EDT

[#7]

Flying comes from lift.
Lift is generated by airflow over a designed aerofoil. (Wing)
Airflow is not accomplished on a conveyor belt.
Without it you're just wearing out the wheelbearings...

-Edit-
Maybe I understood the question wrong..
Unless you mean that the belt moves the whole plane along.
If that's the case, I guess you could, as long as you can make it go fast enough.

Posted: 2/3/2007 8:16:31 PM EDT

[#8]

Need air moving over the wings to get it off the ground..

Posted: 2/3/2007 8:17:09 PM EDT

[#9]

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

That said, this question is not valid. A conveyor could not match the speed of the landing gear, as the landing gear provides no resistance. The thrust of the engines provides the forward force, the conveyor has no effect on thrust. The plane would move forward--generating lift--therefore the conveyor could not possibly match the speed of the wheels.

Posted: 2/3/2007 8:18:53 PM EDT

[#10]

Depends on the plane.

Posted: 2/3/2007 8:19:05 PM EDT

[#11]

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

The added thrust would only make the conveyer turn faster keeping up with the wheels. You would actually be controlling the speed of the conveyer with the planes throttle. The plane could not move forward and thus could not generate lift.

Posted: 2/3/2007 8:19:32 PM EDT

[#12]

Quoted:
Were you part of the multiple banned?

nope, didn't even post in the thread. i just want an answer.

Posted: 2/3/2007 8:21:42 PM EDT

[#13]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

The added thrust would only make the conveyer turn faster keeping up with the wheels. The plane could not move forward and thus could not generate lift.

No. "Forward" is a relative term. You do realize that people have taken off in planes without the wheels turning or the plane moving relative to a fixed object on the ground, right?

Some small planes cruise around 45knots. In a wind of that amount, you could simple hop in, pull back on the stick, and be airborne.

Posted: 2/3/2007 8:21:46 PM EDT

[#14]

Quoted:

Quoted:
Were you part of the multiple banned?

nope, didn't even post in the thread. i just want an answer.

What was the final consensus on your other board?

Posted: 2/3/2007 8:22:45 PM EDT

[#15]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

Negative. You're both wrong. If the plane is not moving forward, it will not take off, as there is no airflow over the wings to generate lift. The conveyor is keeping the plane stationary, thus no airflow.

Posted: 2/3/2007 8:24:27 PM EDT

[#16]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

Negative. You're both wrong. If the plane is not moving forward, it will not take off, as there is no airflow over the wings to generate lift. The conveyor is keeping the plane stationary, thus no airflow.

See my post above. I am a pilot, and without an understanding of this I would be outright dangerous behind the yoke.

Posted: 2/3/2007 8:24:38 PM EDT

[#17]

The answer is: Yes.

Posted: 2/3/2007 8:24:52 PM EDT

[#18]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

The added thrust would only make the conveyer turn faster keeping up with the wheels. The plane could not move forward and thus could not generate lift.

No. "Forward" is a relative term. You do realize that people have taken off in planes without the wheels turning or the plane moving relative to a fixed object on the ground, right?

Some small planes cruise around 45knots. In a wind of that amount, you could simple hop in, pull back on the stick, and be airborne.

Well, if it was setting on a conveyer with a headwind of whatever it needed be airborne, sure. but no mention of that here.

Posted: 2/3/2007 8:25:44 PM EDT

[#19]

Jet or Propeller?

Posted: 2/3/2007 8:26:32 PM EDT

[#20]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

The added thrust would only make the conveyer turn faster keeping up with the wheels. The plane could not move forward and thus could not generate lift.

No. "Forward" is a relative term. You do realize that people have taken off in planes without the wheels turning or the plane moving relative to a fixed object on the ground, right?

Some small planes cruise around 45knots. In a wind of that amount, you could simple hop in, pull back on the stick, and be airborne.

Well, if it was setting on a conveyer with a headwind of whatever it needed be airborne, sure. but no mention of that here.

The way the "riddle" is worded is flawed in the first place. The presumption is the plane is attempting to take off; i.e generate thrust.

The misnomer is the assumption that movement of the conveyor would cancel out the relative wind the airfoil sees. If the assumption, then planes with small wheels (wheels in which the bearings spun faster than x) would not be able to take off.

Posted: 2/3/2007 8:27:16 PM EDT

[#21]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

Negative. You're both wrong. If the plane is not moving forward, it will not take off, as there is no airflow over the wings to generate lift. The conveyor is keeping the plane stationary, thus no airflow.

Your statement about the conveyor keeping the plane stationary would be valid if the wheels provided any power. They do not. The plane will move foward, and take off.

Posted: 2/3/2007 8:27:17 PM EDT

[#22]

IF there is sufficient air moving over the wings, either from the plane moving or from a very significant wind, then YES. If there is NOT sufficient air moving over the wings, i.e. in normal conditions as you describe (the plan remains stationary relative to objects on the ground, is not a VTOL aircraft, and there is not a wind moving sufficient quantities of air), then ABSOLUTELY NOT.

PERIOD.

Prove me wrong if you can.

Edit: The way you are describing it seems to me to be, the plane is kept stationary relative to the earth by the movement of the conveyer belt cancelling the effect of the thrust. In which case, lacking sufficient wind, the plane would not take off.

Posted: 2/3/2007 8:27:20 PM EDT

[#23]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

Negative. You're both wrong. If the plane is not moving forward, it will not take off, as there is no airflow over the wings to generate lift. The conveyor is keeping the plane stationary, thus no airflow.

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

Posted: 2/3/2007 8:27:29 PM EDT

[#24]

Quoted:

Quoted:
Were you part of the multiple banned?

nope, didn't even post in the thread. i just want an answer.

What was the final consensus on your other board?

it's still ongoing. pretty evenly split, perhaps a slight edge to "won't take off."

Posted: 2/3/2007 8:28:52 PM EDT

[#25]

Quoted:

Quoted:
Were you part of the multiple banned?

nope, didn't even post in the thread. i just want an answer.

What was the final consensus on your other board?

it's still ongoing. pretty evenly split, perhaps a slight edge to "won't take off."

I think we need a poll so we can see how many rocket scientists think the plane can't take off.

Of course a numerical count is kind of meaningless - clearly we in the minority actually know what we are talking about

Two of us are pilots, what are the qualifications of the others?

Posted: 2/3/2007 8:29:22 PM EDT

[#26]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

Negative. You're both wrong. If the plane is not moving forward, it will not take off, as there is no airflow over the wings to generate lift. The conveyor is keeping the plane stationary, thus no airflow.

The plane is propelled referenced to AIRSPEED. Groundspeed means nothing. Any conveyor cannot keep the airplane down, unless the wheels are firmly connected with the belt.

Posted: 2/3/2007 8:30:10 PM EDT

[#27]

Quoted:

Well, if it was setting on a conveyer with a headwind of whatever it needed be airborne, sure. but no mention of that here.

Exactly. It's not a plane in a wind tunnel. It's a plane in still air on a conveyor belt.

Further, it wouldn't matter what the thrust:weight ratio was unless it stood on its tail and took off like a rocket, which is also outside the boundary of the question.

The plane is trying to accelerate horizontally. The conveyor cancels its speed perfectly. Therefore, the air at the top of the wings is still. It is not generating lift. It will not take off.

Posted: 2/3/2007 8:31:13 PM EDT

[#28]

Quoted:
The plane is propelled referenced to AIRSPEED. Groundspeed means nothing. Any conveyor cannot keep the airplane down, unless the wheels are firmly connected with the belt.

And all this time I thought my plane actually slowed down as I went up, since IAS falls. The GPS showing increased or stable groundspeed simply must be wrong.

Posted: 2/3/2007 8:31:45 PM EDT

[#29]

Quoted:

Quoted:

Well, if it was setting on a conveyer with a headwind of whatever it needed be airborne, sure. but no mention of that here.

Exactly. It's not a plane in a wind tunnel. It's a plane in still air on a conveyor belt.

Further, it wouldn't matter what the thrust:weight ratio was unless it stood on its tail and took off like a rocket, which is also outside the boundary of the question.

The plane is trying to accelerate horizontally. The conveyor cancels its speed perfectly. Therefore, the air at the top of the wings is still. It is not generating lift. It will not take off.

How?

The wheels do nothing to propel the aircraft. The prop/jets do all the movement.

Posted: 2/3/2007 8:32:47 PM EDT

[#30]

Quoted:

Quoted:

Well, if it was setting on a conveyer with a headwind of whatever it needed be airborne, sure. but no mention of that here.

Exactly. It's not a plane in a wind tunnel. It's a plane in still air on a conveyor belt.

Further, it wouldn't matter what the thrust:weight ratio was unless it stood on its tail and took off like a rocket, which is also outside the boundary of the question.

The plane is trying to accelerate horizontally. The conveyor cancels its speed perfectly. Therefore, the air at the top of the wings is still. It is not generating lift. It will not take off.

No. The problem as stated might presume that the conveyor speed would somehow cancel the movement of the relative wind, but as I stated above that is an incorrect assertion.

Posted: 2/3/2007 8:33:44 PM EDT

[#31]

Quoted:

Quoted:
Yes.

The wheels do nothing more than hold the airplane off the ground and allow it to move.
The thrust is what propels the aircraft forward, not the turning of the wheels like a car.

You are right. Why is this so hard for many to understand?

Negative. You're both wrong. If the plane is not moving forward, it will not take off, as there is no airflow over the wings to generate lift. The conveyor is keeping the plane stationary, thus no airflow.

The Wheels are freespining.

Once the aircraft is outputting the needed amount of trust, to get the wheel moving just the slightest bit, its off to the sky as long as it has enough trust to overcome the drag of the wheels with isn't much.

If the aircraft is standing still and wheels are standing still the conveyor is standing still, right?

When the aircraft moves forward the wheels spin counterclockwise at the rate of the aircraft speed, the conveyor belt moves and the same rate as the wheels and and the aircraft but in the opposing direction.

say the aircraft is going at 50 kph, the belt is going at 50 kph, the wheels will be turning at a rate of 100 kph, the aircraft is still going 50 kph.

Posted: 2/3/2007 8:33:52 PM EDT

[#32]

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

Posted: 2/3/2007 8:34:54 PM EDT

[#33]

Quoted:

Quoted:
The plane is propelled referenced to AIRSPEED. Groundspeed means nothing. Any conveyor cannot keep the airplane down, unless the wheels are firmly connected with the belt.

And all this time I thought my plane actually slowed down as I went up, since IAS falls. The GPS showing increased or stable groundspeed simply must be wrong.

You have decreased KE because you are increasing PE. Silly civie, flying aircraft with thrust less than weight! You will always slow down when climbing. You still haven't transitioned from glider school

Posted: 2/3/2007 8:35:58 PM EDT

[#34]

poll added per request.

Posted: 2/3/2007 8:36:22 PM EDT

[#35]

Quoted:

Quoted:
Were you part of the multiple banned?

nope, didn't even post in the thread. i just want an answer.

What was the final consensus on your other board?

it's still ongoing. pretty evenly split, perhaps a slight edge to "won't take off."

I think we need a poll so we can see how many rocket scientists think the plane can't take off.

Of course a numerical count is kind of meaningless - clearly we in the minority actually know what we are talking about

Two of us are pilots, what are the qualifications of the others?

I'm an Engineering Student and generally not a retard.

Those are my qualifications

Posted: 2/3/2007 8:36:38 PM EDT

[#36]

Damn!!! I've never seen poll results like these! Of course it wont take-off you numb skulls.

Posted: 2/3/2007 8:36:48 PM EDT

[#37]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

100% of the pilots here say you are wrong.

Posted: 2/3/2007 8:37:42 PM EDT

[#38]

One minor point, if the conveyor is causing the wheels to move, the aircraft would likely exceed max tire speed since tires would move at twice aircraft speed. The tires would overheat/rupture and cause the aircrafrt to crash before it could take off. Exceptions would be any aircraft that can become airborne before max tire speed is exceeded. Anything with a high thrust/weight ratio would probably work.

Posted: 2/3/2007 8:37:50 PM EDT

[#39]

Quoted:
So the following question was posted on another message board I frequent, and it turned into a 10 page flame war with multiple bans and no answer.

"Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway. The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?"

It's a poorly worded question. Is the movement of the belt relative to the wheels such that the wheels are not rotating? The phrase: "match the speed of the wheels, moving in the opposite direction" isn't exactly a precise description of what is going on.

Regardless, as the posters above stated, it's the air moving over the wings that is of importance.

Posted: 2/3/2007 8:37:53 PM EDT

[#40]

Quoted:

Quoted:

Well, if it was setting on a conveyer with a headwind of whatever it needed be airborne, sure. but no mention of that here.

Exactly. It's not a plane in a wind tunnel. It's a plane in still air on a conveyor belt.

Further, it wouldn't matter what the thrust:weight ratio was unless it stood on its tail and took off like a rocket, which is also outside the boundary of the question.

The plane is trying to accelerate horizontally. The conveyor cancels its speed perfectly. Therefore, the air at the top of the wings is still. It is not generating lift. It will not take off.

If the conveyor could stop the forward motion of the plane, you would be right. But it could not. The wheels of an aircraft do not provide resistance to forward motion.

Posted: 2/3/2007 8:38:23 PM EDT

[#41]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

100% of the pilots here say you are wrong.

100% of the pilots here don't understand the question, then. If there's no air moving over the wing, they're not going to fly. If the belt is keeping the plane stationary, there's no air moving over the wing. Simple as that.

Posted: 2/3/2007 8:39:07 PM EDT

[#42]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

As I have repeatedly said, the presumption that the aircraft cannot have more power than that which is used to "spin the wheels" is wrong.

I will grant you this - in still air, the plane must move in relation to any fixed point on the ground to generate airspeed in the first place. However, the speed at which the wheels turn has NO relevance whatsoever on airspeed. The "riddle" implies that one affects the other and is worded so poorly that the answer might as easily be "red".

This was stated best do far by TIMMAH who said "If the conveyor could stop the forward motion of the plane, you would be right. But it could not. The wheels of an aircraft do not provide resistance to forward motion."

The false assumption is that the conveyor could keep the plane stationary, which it cannot. I can the change the answer too, if I claim that gravity doesn't exist.

Posted: 2/3/2007 8:39:20 PM EDT

[#43]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

100% of the pilots here say you are wrong.

Don't see how being a pilot gives you any advantage with this riddle

Posted: 2/3/2007 8:40:15 PM EDT

[#44]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

100% of the pilots here say you are wrong.

100% of the pilots here don't understand the question, then. If there's no air moving over the wing, they're not going to fly. If the belt is keeping the plane stationary, there's no air moving over the wing. Simple as that.

What holds the plane relative to the air, keeping the airspeed 0 KTIAS?

Invisible rope?

Your mamma's garter belt?

The conveyor?

Posted: 2/3/2007 8:40:44 PM EDT

[#45]

Quoted:

Quoted:
So the following question was posted on another message board I frequent, and it turned into a 10 page flame war with multiple bans and no answer.

"Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway. The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?"

It's a poorly worded question. Is the movement of the belt relative to the wheels such that the wheels are not rotating? The phrase: "match the speed of the wheels, moving in the opposite direction" isn't exactly a precise description of what is going on.

Regardless, as the posters above stated, it's the air moving over the wings that is of importance.

i agree, it's poorly worded, but i didn't think i should change it.

Posted: 2/3/2007 8:40:58 PM EDT

[#46]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

"Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway. The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?"

Where in that question does it say that the plane will not move forward relative to a fixed object?

Posted: 2/3/2007 8:41:08 PM EDT

[#47]

No air flowing over wings = no lift = no flight.

Posted: 2/3/2007 8:41:51 PM EDT

[#48]

Quoted:

Quoted:

The wheels of an aircraft provide negligible resistance to forward motion. The plane would move forward, creating lift.

Imagine the wheels of an airplane as skids. They have nothing to do with moving the plane forward. They just hold the plane off of the runway.

The plane would not move forward. That's the whole point of the question; the conveyor belt keeps the plane where it is, regardless of its forward thrust. Its wheels will be spinning wildly, but it will have no airspeed. It will not take off.

All of you who are pilots should understand that you actually need air moving over the wing in order to take off, and you won't have that in this case.

100% of the pilots here say you are wrong.

Don't see how being a pilot gives you any advantage with this riddle

what Riddle?

If this is a riddle to you, you have already got it wrong.