Plane on a Treadmill

[CadetProgramGuy]

Umm not to nitpick, but your answer is in the negative.....

It's a power vector in the opposite direction the aircraft's engine power is being directed.

Actually it would take less effort to overcome friction on the treadmill than it would on a stationary surface since the treadmill would already be working toward breaking the friction of the wheels. 

Except the work being performed by the treadmill is in the opposite direction as the work being performed by the propeller. So, the treadmill isn't taking work away from the propeller, but adding to it's burden.

What I am failing to understand is for an aircraft to remain stationary on the treadmill at full power, the treadmill must be running at Mach 3ish.....(1700 MPH)

[N Harmon]

What I am failing to understand is for an aircraft to remain stationary on the treadmill at full power, the treadmill must be running at Mach 3ish.....(1700 MPH)

Think of it like this: Every second that 230 horsepower engine does 171.5 Kilojoules of work to make the plane go forward, meanwhile the treadmill is doing 171.5 Kilojoules of work to make the plane go backward. To argue that the plane goes forward is to argue against the conservation of energy.

Wrong, If you want to talk about friction then you have to isolate the wheels and the treadmill, as soon as the treadmill starts running it will try to break the friction of the wheels.  Just as a powered wheel tries to break the friction of the ground, the powered ground will try to break the friction of the wheel 

Breaking the friction usually means going from static friction to sliding friction. A rolling wheel is not sliding friction, it's static friction, so there is no friction to break. You may be thinking of the wheels' moment of inertia, and while the treadmill would help break the moment of inertia, that still translates as a negative force to the airframe.

[capchiro]

Nat, you must remember that all of the Physicists that the opposition want to mention were the very ones that said the bumble bee couldn't fly..  By complicating the original supposition, that the wheels and threadmill are going the same speed in opposite directions, they miss the whole premise.  The A/C is not moving in relation to the ground, ergo, no airspeed, no airflow, no lift, no flying..  It really is simple..Isn't it..  Given the parameters we have in the original question, we are right.  Adding exterraneous stuff that is not in the original is not allowed..  Geesh, it just doesn't get any simpler..

[CadetProgramGuy]

+1

Thanks capchiro!!  Exactly what I have been trying to say.

[Major Lord]

The argument that you are making for the non-flight side is that the treadmill will prevent the aircraft from accelerating.

No one in their right mind believes that the aircraft will take flight due to the AC/s wheels spinning at takeoff velocities if the airplane is not moving forward into the wind. (stop me if anyone in their right mind thinks it will leap off the runway)

The argument from the flight side is fundamentally that the aircraft will accelerate as a function of the thrust generated by the propeller, moving the airplane forward. Because the problem stipulates that the treadmill will change to match the velocity of the wheels, the forward motion of the aircraft plus the backwards motion of the treadmill determine the specific velocity (RPM) of the wheels, but not the forward velocity of the aircraft, which is primarily a result of the forces in play created by the propeller.

Yes, the additional drag created by the treadmill will act to slow the plane, through the minor additional frictional forces imparted by the treadmill working against the wheels, but unless the treadmill is going (as someone pointed out) Mach 2.8, the forces won't be enough to slow the plane.

This can't happen in this situation, because the problem stipulates that the treadmill can accelerate only to the velocity of the airplanes' wheels, which with any aircraft, will be well below Mach anything!

As the aircraft adds power, it begins to move forward ( although many of you doubt this apparently) and the treadmill accelerates to the velocity of the wheels. This does not substantially reduce the aircrafts' forward speed, but it sets up a loop of cause and causation: As the airplane picks up forward speed, the treadmill picks up rearward speed. No amount of treadmill force can effectively counteract the airplane's thrust, because the treadmills speed is limited to the absolute maximum velocity of the aircraft's forward speed, which determines the initial wheel RPM.

Imagine if this aircraft had ice skates, and it was trying to take off from a perfectly flat glacier sliding away in the opposite direction that the aircraft is attempting to accelerate. Do you think the glacier would prevent the airplane from accelerating? Can you construct an experiment that will do this?

The Mythbusters constructed both a model, using an actual home treadmill, and a toy aircraft. It took off. Since doubt was still present, they dragged a sheet of canvas across an airfield to replicate the treadmill, and had a light sport aircraft of some breed try and take off. It accelerated without problems and took flight perfectly.

You say it won't roll, we say it will. I will leave my $100.00 on the table and will walk around with a hole in my Ribbon rack where my Gen. CY award is supposed to sit if you can prove the treadmill will prevent takeoff. Absolutely no way in the real world can this happen. 

Major Lord

[lordmonar]

ok, let me ask this question. In order for the airplane to fly, you need lift.  Where is your lift created in this theory?

Okay.

The wheels must turn.....the orginal question says the wheels turn.  The treadmill's speed is set by the speed of the wheels.


How do the wheels turn on an air plane?

When the powerplant generates enough thrust to overcome inertia and the resistance of the bearings and the reisistance of the ground.....it moves the whole aircraft forward.  The wheels turn because the plane is moving forward.

As the plane gains speed it generates lift.

[CadetProgramGuy]

and I agree that if the airplane can create FORWARD movement it will fly.  No doubts about it.  but the question was for a treadmill and wheels.  No movement of the airplane.

[Swampfox]

Why is anyone taking the time to discuss this?  It's been done to death.  The treadmill has no effect on the plane.

S. Morgan

[N Harmon]

Why is anyone taking the time to discuss this?  It's been done to death.  The treadmill has no effect on the plane.

S. Morgan

Did you register on here just to post this?

[heliodoc]

^^^^^

What S Morgan said!! :clap: :clap: :clap: :clap: :clap:

[N Harmon]

Well, it beats discussing uniforms, that's for sure.

[heliodoc]

^^^^

There is that!!

[Major Lord]

Although the "will fly" group seems to outnumber the "won't fly" group, I don't think the question has been definitively  answered. ( Hey, until a few months ago, "reputable" scientists believed in man-made global warming and the benefits of the Acai Berry, whatever the heck that is!) We could just drop it, conduct an experiment, or find an expert that everyone would acknowledge as acceptable. ( fat chance!) Trial by Combat seems the only practical answer. We will take Chuck Norris, who do you guys want?

Major Lord

[Swampfox]

Why is anyone taking the time to discuss this?  It's been done to death.  The treadmill has no effect on the plane.

S. Morgan

Did you register on here just to post this?

No, but thanks for the warm welcome to CAP and exemplary mentoring.

[N Harmon]

No, but thanks for the warm welcome to CAP and exemplary mentoring.

Well, this is the only thread to be graced by your input. It is odd to see a new member jump into a 10 page thread, and declare it done to death while putting in his/her two cents.

It is more typical of people who have been here longer.

I might be interested in how you arrived at the conclusion that the treadmill has no effect on the plane, if it is a reason we have not touched on already. Or perhaps you have a better insight into one of the already discussed reasons?

[lordmonar]

No, but thanks for the warm welcome to CAP and exemplary mentoring.

Part of mentoring is that the Protoge (that's you) actually takes the time to listen to the advice of the mentor (that would be us).

So....begins the lesson.

If you are going to jump into a discussion that is long lived and has two very opposed view points.  Saying "Why are you arguing....you're wrong!" is NOT the way to gain friends and influence people.

Asking a question (even if it has been asked before) or adding some new information is always welcomed.  No one likes to be told that "they are wrong...shut up".....that is considered poor feed back.  Be specific, offer corrective advice and then observe if the person has learned from the feed back.

Thank you.....may return to your previously scheduled argument! 

[Swampfox]

No, but thanks for the warm welcome to CAP and exemplary mentoring.

Well, this is the only thread to be graced by your input. It is odd to see a new member jump into a 10 page thread, and declare it done to death while putting in his/her two cents.

It is more typical of people who have been here longer.

I might be interested in how you arrived at the conclusion that the treadmill has no effect on the plane, if it is a reason we have not touched on already. Or perhaps you have a better insight into one of the already discussed reasons?

Sorry, obviously not a good way to provide a first post.

I could be wrong but I was assuming that this forum is not the only source of information on the topic.

A quick search on Google, searching for "airplane treadmill argument" found 1,340,000 hits.  Please note that many of these multiple hits are copied from other sites making the number a little lower.  Also, please consider that the Google search engine probably stopped after the first 1,340,000 items were found.

For example:

http://www.airplaneonatreadmill.com/2008_01_01_archive.html

http://pogue.blogs.nytimes.com/2006/12/11/the-airplane-treadmill-conundrum/

http://blog.xkcd.com/2008/09/09/the-[stupid]-airplane-on-the-[stupid]-treadmill/

http://answers.google.com/answers/threadview?id=428718

http://www.airplaneonatreadmill.com/

http://boingboing.net/2008/01/28/mythbusters-tackles.html


Since I have seen this argument for many years now, I was surprised that it is still going on.  It has been done to death on aviation forums, physics classes, etc.  The answers are available.

Just curious, are there any pilots saying the airplane won't fly?

S. Morgan

[CadetProgramGuy]

yes there is, me for one.

One cannot prove to me that a stationary airplane will take off unless there is significant airflow over the wings to create lift.  The only way that can happen is if the airplane is moving forward - or - an outside source is providing the lift.   That was never in the premise of the original question.

[lordmonar]

yes there is, me for one.

One cannot prove to me that a stationary airplane will take off unless there is significant airflow over the wings to create lift.  The only way that can happen is if the airplane is moving forward - or - an outside source is providing the lift.   That was never in the premise of the original question.

Sorry...but it was a prmise in the original question.

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

The treadmill moves at the same speed as the wheels........HOW DO THE WHEELS MOVE?!?!?!

The only way for the wheels to move is for the aircraft to be propelled forward by the powerplant....i.e. thrust! 

[AirAux]

IF the treadmill has a powerplant that is moving the treadmill in the opposite direction as the powerplant is moving the AC and at the same speed, ergo, wheels are rolling at the same speed, the AC will not reach flying speed and will in fact be stationary to mother earth..