Plane on a Treadmill

[tim_redd]

Re: CyBookie - Plane on a Treadmill

That's the difference between indicated airspeed, and true groundspeed.

Of course the whole system depends greatly on the treadmill being able to determine the amount of thrust, and hence how fast to turn. That's going to be the key part of the whole thing.

I think this is the key to the question, and we understood it differently. I thought the treadmill just matched the speed of the wheels, regardless of the thrust. In which case I think it would takeoff. But if the treadmill matches the speed of the thrust, and the groundspeed is zero, the plane obviously won't takeoff.

 

[cyadict]

Re: CyBookie - Plane on a Treadmill

I'm guessing that the plane won't be lifting off.

 

[cyfan964]

Re: CyBookie - Plane on a Treadmill

I think this is the key to the question, and we understood it differently. I thought the treadmill just matched the speed of the wheels, regardless of the thrust. In which case I think it would takeoff. But if the treadmill matches the speed of the thrust, and the groundspeed is zero, the plane obviously won't takeoff.

Exactly... it's more a question of wording. Everyone is aware of the fact that if the plane is not moving in relation to the ground, or more importantly the air, that it won't take off. I thought the question was based on wheel speed... which has no bearing at all on whether or not the plane flies, other than a small amount of easy to overcome friction.

 

[cytech]

Re: CyBookie - Plane on a Treadmill

My prediction is about 50% that the plane will take off due to failure of the treadmill. 40% the treadmill works and the plane doesn't take off. 5% the treadmill works and the plane takes off. And 5% something terribly bad happens that hasn't been predicted.

 

[ericlambi]

Re: CyBookie - Plane on a Treadmill

If this is posted, I am going all-in on WON'T take-off.

 

[jumbopackage]

Re: CyBookie - Plane on a Treadmill

I think this is the key to the question, and we understood it differently. I thought the treadmill just matched the speed of the wheels, regardless of the thrust. In which case I think it would takeoff. But if the treadmill matches the speed of the thrust, and the groundspeed is zero, the plane obviously won't takeoff.

Yes, but the speed of the wheels, at least while the plane is on the ground, is directly related to the amount of thrust being provided. The plane cannot move forward while the wheels are not moving in relation to the earth. If they are spinning, but only in relation to a treadmill, the forward velocity relative to the earth is still 0, and there will still be 0 lift as air (which is generally stationary in relation to the earth) will still be going 0 MPH over the wings. It doesn't matter where the forward thrust is coming from.

What is weird about this one is that how fast the wheels are turning during the test doesn't really have any relation to how fast they might turn under normal conditions. The wheels can go infinitely fast, with frictionless bearings, and the plane still won't go anywhere. All the engine(s) are trying to overcome, in this case, is the friction of the wheels turning.

 

[Wesley]

Re: CyBookie - Plane on a Treadmill

Option Three:It may only fly off backwards if the mooring cables break.

 

[cyfan964]

Re: CyBookie - Plane on a Treadmill

Does it make a difference if this is the plane?????



Just for the record this really exists.....

[ame=http://www.youtube.com/watch?v=y9633v6U0wo&NR]YouTube - Fairey Rotodyne[/ame]

 

[jumbopackage]

Re: CyBookie - Plane on a Treadmill

I'd say the odds are about 90% the treadmill fails, 9% the treadmill works and the plane stays put, and 17% everything works but Adam makes fun of Jamie's moustache.

 

[twittkop]

Re: CyBookie - Plane on a Treadmill

So MythBusters got a Big Treadmill, huh?

I agree, it will not take off, but what do I know.

From the previews, it looks like they got a treadmill that they are going to use as a runway for a model air plane, which will be able to take off. For their full scale approach, they got a really long tarp that they are going to pull with a truck.

This does sound like a great bookie event. There are enough people that would be on both sides of this issue.

There seems to be 2 different ways to test this myth:
1. Have the treadmill going the same speed the wheels are going.
2. Have the treadmill match the forward velocity of the plane relative to the ground.

In scenario 1, they will not be able to have the treadmill match the speed of the wheels because the velocity of the wheels is going to be the forward velocity of the plane relative to the ground + the speed they are running/pulling the treadmill. Assuming the plane is going to be able to move forward on the treadmill because of the thrust produced by the prop, this scenario is going to be busted because a + b never equals b if both a and b are greater than 0.

If scenario 1 is busted, scenario 2 is automatically busted because in scenario 1 the faster they run the treadmill, the faster the wheels are going to turn, which will be much less than the forward velocity of the plane.

I believe this myth is going to be busted for the same reason that people have already stated, the wheels on a plane are not the cause of the forward motion of the plane.

 

[jumbopackage]

Re: CyBookie - Plane on a Treadmill

From the previews, it looks like they got a treadmill that they are going to use as a runway for a model air plane, which will be able to take off. For their full scale approach, they got a really long tarp that they are going to pull with a truck.

This does sound like a great bookie event. There are enough people that would be on both sides of this issue.

There seems to be 2 different ways to test this myth:
1. Have the treadmill going the same speed the wheels are going.
2. Have the treadmill match the forward velocity of the plane relative to the ground.

In scenario 1, they will not be able to have the treadmill match the speed of the wheels because the velocity of the wheels is going to be the forward velocity of the plane relative to the ground + the speed they are running/pulling the treadmill. Assuming the plane is going to be able to move forward on the treadmill because of the thrust produced by the prop, this scenario is going to be busted because a + b never equals b if both a and b are greater than 0.

If scenario 1 is busted, scenario 2 is automatically busted because in scenario 1 the faster they run the treadmill, the faster the wheels are going to turn, which will be much less than the forward velocity of the plane.

I believe this myth is going to be busted for the same reason that people have already stated, the wheels on a plane are not the cause of the forward motion of the plane.

1. matching the speed of the wheels is going to result in the plane going nowhere. The wheels will just continue to go faster, while the treadmill will continue to go faster, and the plane will stay put. Dragging a tarp behind a truck won't be enough to prove this, though, IMO. The wheel acceleration is going to be exponentially faster than it would be under normal conditions.

2. The aircraft would take off, but the wheels would spin twice as fast while doing so. i don't think that's the point of the "myth" though. ANY forward velocity relative to the earth will result in the aircraft being capable of taking off at some point.

 

[jcats322]

Re: CyBookie - Plane on a Treadmill

If have to be missing something. My understanding is that plane will not be in motion. If that is the case there is no way it will takeoff.

 

[DMCYFAN]

Re: CyBookie - Plane on a Treadmill

Nobody actually thinks it will take off if the treadmill works (keeps the plane stationary relative to everything else) do they? I see what people are saying about the wheels spinning freely not being able to control the planes speed but is there anyone that thinks the plane would take off if is stationary? the funny thing about thinking about this is right after the plane would take off from the runway it would be in the air but not moving lol. Just floating there all because a runway was under it? lol come on seriously, no one believes this right?

 

[tim_redd]

Re: CyBookie - Plane on a Treadmill

Yes, but the speed of the wheels, at least while the plane is on the ground, is directly related to the amount of thrust being provided. The plane cannot move forward while the wheels are not moving in relation to the earth. If they are spinning, but only in relation to a treadmill, the forward velocity relative to the earth is still 0, and there will still be 0 lift as air (which is generally stationary in relation to the earth) will still be going 0 MPH over the wings. It doesn't matter where the forward thrust is coming from.

What is weird about this one is that how fast the wheels are turning during the test doesn't really have any relation to how fast they might turn under normal conditions. The wheels can go infinitely fast, with frictionless bearings, and the plane still won't go anywhere. All the engine(s) are trying to overcome, in this case, is the friction of the wheels turning.

On the contrary, if the wheels truly are frictionless, they should always match the speed of the treadmill, and they cannot provide a backwards force to negate the thrust.

On the free-body diagram, you have the thrust of the engines moving the plane forward, where is the force that negates this?

Plane moves forward and takes off.

 

[twittkop]

Re: CyBookie - Plane on a Treadmill

Does it make a difference if this is the plane?????



Just for the record this really exists.....

It could also be this airplane:

This is the BA609, a tilt rotor plane, which is produced by Bell Augusta Aerospace. This was initially a project by the military, but they gave up on it because they kept crashing it.

 

[ISUAlum2002]

Re: CyBookie - Plane on a Treadmill

Lift is created by the air on the top of the wing moving faster than air going below the wing (low pressure on top of the wing vs. high pressure below it). If you were to place the plane on a treadmill you're not moving any air over the wings. Just think of yourself running on one, do you feel a breeze the faster you run?? No, so the plane would definitely NOT take off...

Humans run using their legs. Planes do not move using their wheels as propulsion.

In your example, strap a jet engine on the back of the human running on the treadmill. Will the human move forward? The answer is yes. So the plane WILL take off.

I've only read the first page of this thread and its already ridiculous to see how many people believe the plane moves forward based on power from its wheels.

 

[ISUAlum2002]

Re: CyBookie - Plane on a Treadmill

It will not take off....case closed. ME grad with Thermodynamics classes taken.

That is very disturbing. Please don't get a job where you serve the public's interests.

 

[ISUAlum2002]

Re: CyBookie - Plane on a Treadmill

If this is posted, I am going all-in on WON'T take-off.

You'll lose a lot of credits.

 

[jumbopackage]

Re: CyBookie - Plane on a Treadmill

On the contrary, if the wheels truly are frictionless, they should always match the speed of the treadmill, and they cannot provide a backwards force to negate the thrust.

On the free-body diagram, you have the thrust of the engines moving the plane forward, where is the force that negates this?

Plane moves forward and takes off.

That's my point. The wheels aren't frictionless. There's no such thing as a frictionless bearing. The only way the treadmill can negate the thrust is by creating more friction with the wheels, by turning them faster. It could theoretically do this, but it's going to have to travel very fast to do so. Far faster than a tarp can be pulled by a truck.

I guess the answer is, in theory, the plane will not take off, given a fast enough treadmill. It's almost impossible to practically demonstrate this, however.

 

[jumbopackage]

Re: CyBookie - Plane on a Treadmill

Humans run using their legs. Planes do not move using their wheels as propulsion.

In your example, strap a jet engine on the back of the human running on the treadmill. Will the human move forward? The answer is yes. So the plane WILL take off.

I've only read the first page of this thread and its already ridiculous to see how many people believe the plane moves forward based on power from its wheels.

Put a SMALL jet engine (i.e. a model plane one) on the back of someone who is on rollerblades on a treadmill. Will the person move forward on a treadmill given that the treadmill can go, say 40 MPH?

That's what's up for debate here. The answer is "it depends". With enough friction and little enough thrust, the answer is no, he won't go anywhere. Obviously you can strap enough thrust onto someone to overcome the limits of the treadmill and the friction it's capable of generating through the wheels, but that's not necessarily the point of the test.