Originally posted by caitekins: Christi, thanks for providing some links.
-rational-, I think it's time to accept that this is all a moot point because the way the MB see it, they busted the specific myth they set out to bust. COULD a plane take off from a conveyor belt. From how they explained it, people were convinced that it couldn't possibly happen. Well, it did. That myth was confirmed.
What you're talking about, -rational- is different, I think. What you're asking is: could you create a situation where it wouldn't take off? Maybe. Maybe not. I don't pretend to have the expertise to say yes or no. However, it's a different beast. You're taking the original intent of the myth and tweeking it. Your idea is one that, it sounds like, will not be revisited.
Finally, stop insulting almost everyone who disagrees with you. It doesn't help you make your point...quite the opposite. Calling them gibberish, idiots, morons, contentless posts or posters isn't what the situation calls for.
I think you need to bear in mind what this thread is about, please read the opening post which contains the classic wording of the myth which has a much greater scope than the mythbuster's test.
And you say the myth is confirmed, surely you the myth was busted? The myth as I recall was that the plane could be held back by the belt. It is very difficult to tell from your post what you mean. You need to be clearer in your comments.
I am not constructing anything that is not contained in the wording of the myth as described in the OP. I don't understand how you can think I am creating something outside of the context of the myth in the OP.
I don't call people names simply if they are stupid, only if they are stupid yet think they are clever, or they decide to initiate abuse or are wilfully contradictory.
Roofingguy is an example of someone who takes a contrary position to me, but does so with intelligence and decorum and I have always responded in kind.
I don't see a point in arguing your fuzzy logic since you will never change your ways of thinking. I can now see what kind of person you are. Just arguing for the sake of arguing.
After 245 pages, the only two arguing against everyone else is you and javaman. Both of you primarily only post in this particular thread it seems.
BTW in real life, we take airspeed through pitot tubes. So it won't matter if the plane is on wheels, or ski's or whatever. You are the one who wants to put speedometer/tachometer on the wheels.
As far as I am concerned, and apparently many others as well, MB tested the correct 'myth.' You have not convinced me otherwise.
Hello all, this is my first time here and first post.
Hopefully I won't get slammed by some of the intense flaming/counter-flaming that has gone on here, or I will simply abandon this website and stick to just watching (and laughing) at the show when it airs. Please be nice.
So, because I really don't want to read TWO HUNDRED AND FOURTY FIVE PAGES of posts to "get caught up", I'll just re-iterate a point that has probably already been made several times, or at least hope to clarify it.
As for my backround, I was in the US Air Force for five years and completed the EAUC course (Enlisted Aircrew Undergraduate Course) out of Sheppard Air Force Base in Witchita Falls, TX. My father-in-law is a retired commercial pilot of 22 years.
My point is that BASIC physics says lift is needed for the aircraft to "take off". No amount of conveyor belt speed or realistic engine speed will push enough air over the WINGS to create "lift" which was only mentioned in the episode ONCE by the PILOT who made the same argument I am making! LIFT IS THE ONLY WAY AN AIRCRAFT GETS OFF THE GROUND PEOPLE! NO AIR OVER WINGS, NO LIFT! NO LIFT, NO FLIGHT!
"Lift" happens when enough air is moving above and below the wings that a high pressure zone is created below the wings and a low pressure zone is created above the wings. This in turn "lifts" the wing (and thus aircraft) vertically in an attempt to equalize the pressure difference, a simple force of nature. The purpose of the prop engine (or any engine for that matter) in the aircraft has NOTHING TO DO WITH THE WHEELS/TIRES (as they just attempt to cancel out the ground's friction)! The engine is the machinery used to move the aircraft forward at a high enough speed to get the pressure difference on the wings.
How is the prop engine in front of the aircraft or the conveyor belt below the aircraft going to create enough of a pressure difference alone on the wings to increase the aircraft's altitude?
It's not.
And I agree with what someone said a few pages ago (or so) that the aircraft was moving forward WAY faster than the truck was pulling the tarp out from under the aircraft, thus it had a forward velocity and could create lift under the wings as described above.
My father-in-law and I sort of chuckled to ourselves when I asked the television set, "Have they heard of the concept of lift?"
Originally posted by -rational-: How come it is the people with experience of flying who make the most stupid posts on this subject?
I thought saintj858 was bottom of the class and now you prove otherwise.
I suggest before you post again on this subject that you read at least 5 pages of this thread so you can see just how stupid you are being.
I will help you out though, you are assuming that the conveyor belt will keep the aeroplane stationary, but it won't except under special circumstances which I have detailed on page 140. I wouldn't worry about the explanation there though because you haven't reached even the first rung of understanding the problem.
Harsh, unnecessary, and irrelevant. Your opinion of me doesn't affect the blatant fact that lift = flight.
Your instantaneous jump to hurling insults and speaking in a childish tone, the "Nuh-uh!" tone, just proves your ignorance.
No one disputes that airflow over the wings creates lift. That is not the issue. You are assuming the plane is prevented from moving forward, but it isn't!
The belt cannot stop the forward movement of the plane except under very special circumstances and with forward movement comes airflow and lift.
This message has been edited. Last edited by: mod_ivy,
Originally posted by -rational-: Oh Gawd, we have the ultimate idiot. So stupid yet so confident of their position.
You are in for such an embarrassing few days as you gradually begin to understand the problem and begin to realise what a twit you are.
No one disputes that airflow over the wings creates lift. That is not the issue. You are assuming the plane is prevented from moving forward, but it isn't!
Repeat after me
The belt cannot stop the forward movement of the plane except under very special circumstances and with forward movement comes airflow and lift.
Quoting Javaman:
quote:
Originally posted by Javaman: Oh, third-grade discussion then? Boo! Hoo! Teacher, [-rational-] called me names!
If you choose to be childish, fine. If you would like to act like an adult, then maybe you could take my word for it that I am not just arguing for the sake of arguing. There is a very valid point to what I am saying and just because you and a few others can't open your minds enough to consider what I am saying doesn't mean I am just looking for an argument.
Your last sentence was phrased MUCH better and *gasp* you actually made a point! I will read page 140 but I thought the original, very basic point of the myth was that forward-moving plane + backward moving conveyor belt = lift regardless, which according to lift is wrong.
Don't bother, you are not up to understanding the explanation on page 140.
You need to read the earlier posts in this thread which deal with the very basics of the problem, basics which you still don't understand.
The belt CANNOT stop the plane from moving forward EXCEPT under very special circumstances that you need not consider for now, and as the plane will move forward it will fly.
You should read the single post thread at the top of this forum in which Dan Tapster ( the MB producer) claims the MBs got it right, it covers some of the basic issues which alas I suspect are still above your level of understanding.
Originally posted by -rational-: Don't bother, you are not up to understanding the explanation on page 140.
You need to read the earlier posts in this thread which deal with the very basics of the problem, basics which you still don't understand.
The belt CANNOT stop the plane from moving forward EXCEPT under very special circumstances that you need not consider for now, and as the plane will move forward it will fly.
You should read the single post thread at the top of this forum in which Dan Tapster ( the MB producer) claims the MBs got it right, it covers some of the basic issues which alas I suspect are still above your level of understanding.
You're still being extremely rude and resorting to insults, and that's entirely unnecessary so I'm asking you to stop.
I do understand your post(s) on 140 and the point you guys are making, that there will be forward movement because the belt can't stop the acceleration.
I also admit that the massive wall of text (or wall of equations) are a bit much for me atm.
So answer some questions for me so I can go back to grunting, drooling, and beating my computer with a wooden club:
1) How fast would the belt have to be going for the aircraft to not gain forward momentum (in a natural environment) or is that irrelevant? Why?
2) How much thrust would the aircraft's engine(s) have to be providing (against the backwards momentum of the belt) to gain enough forward momentum and wind past the wings to create enough lift to increase the aircraft's altitude?
dbgoldberg you made a common mistake. You are measuring the speed of the plane relative to the speed of the conveyor belt. As this myth is worded the speed of the conveyor belt is almost irrelevant. The fact that the plane is moving forward on the belt does not mean that it is moving faster than the belt. The speed of the plane is its airspeed. On a windless day that will equal its forward speed relative to the ground. In the show the conveyor belt was moving backwards at 25 mph and the plane was moving forward at 25mph. The planes speed relative to the belt was 50mph but that is not part of the myth. Carefully read the original myth. It clearly states the speed that the plane is moving forward matches the speed that the conveyor belt was moving backwards. Here is one simple question to show you that they measured the sped of the plane in the correct manner. When was the last time you checked your tire speed when you took off?
-rational- is really an alright guy, he does get a little hopped up about this subject, and he can't spell "airplane" for beans
dbgoldberg323, the speed of the belt is irrelevant. The reason is that rolling resistance is a constant. In other words the force back by the belt is the same whether you are going ten miles an hour or one hundred miles an hour. The answer to number 2 therefore is the amount of thrust needed would be equal to the amount of thrust without the treadmill, in either case the rolling resistance is the same.
The only way a belt can keep a plane back is if it can accelerate at a very high rate for a continuous period of time, but that was not the question for this myth. It was a speed matching question.
I know it seems counter-intuitive that the treadmill would have no effect on the plane. All you have to do is google rolling resistance (which is the only force the belt can put on the plane) and you will see that it is so.
I believe the frame of reference is the issue causing these debates. We have two groups from what I see: A.) Velocities of the plane and belt referenced to a static point (usually ground)
B.) Velocity of the plane referenced to the belt, and the velocity of the belt referenced to the ground. So one frame of reference is moving at all times when the experiment is being executed.
Is this a pretty fair assessment of the debate going on here?
Originally posted by saintj858: I believe the frame of reference is the issue causing these debates. We have two groups from what I see: A.) Velocities of the plane and belt referenced to a static point (usually ground)
B.) Velocity of the plane referenced to the belt, and the velocity of the belt referenced to the ground. So one frame of reference is moving at all times when the experiment is being executed.
Is this a pretty fair assessment of the debate going on here?
I think you're on to something.
I think I was trying to say that the airplane relative to ground wouldn't go anywhere if the tarp was pulled back at the same speed that the airplane was moving forward because air is relative to the ground, not the tarp. (This is where my "no forward speed = no lift" argument came in which is obviously accepted.)
You guys were saying that the tarp (unless you pulled the tarp backwards at the airplane's forward speed +1 increment) would not EVER prevent the airplane from moving forward (because of math), thus it would eventually move forward, gain speed, gain a pressure differential, lift, and flight.
Yes, that is right the tarp cannot stop the plane from taking off. In fact it would be very hard for the plane NOT to move forward once his throttle is pulled back. The moving tarp provides so little resistance that the pilot would have to try not to move forward. Once he pulls that throttle out he is going to move forward.
And the key question of the myth was "Could the treadmill keep the plane from taking off" Since the pilot obviously wants to take off, he will.
It is a misinterpretation of the myth to think that the plane cannot move forward. If you are a pilot please answer this question: When moving down the runway for take off do you measure your velocity by wheel speed or air speed?
Originally posted by Subductionzone: Yes, that is right the tarp cannot stop the plane from taking off. In fact it would be very hard for the plane NOT to move forward once his throttle is pulled back. The moving tarp provides so little resistance that the pilot would have to try not to move forward. Once he pulls that throttle out he is going to move forward.
And the key question of the myth was "Could the treadmill keep the plane from taking off" Since the pilot obviously wants to take off, he will.
It is a misinterpretation of the myth to think that the plane cannot move forward. If you are a pilot please answer this question: When moving down the runway for take off do you measure your velocity by wheel speed or air speed?
Okay, very good then.
However for the question, what would be the reading on the airspeed indicator then? It connects to ram air pressure from outside the aircraft and compares it to non-moving air pressure outside the aircraft. Wouldn't it say that there wasn't enough air speed for lift or take off, considering the very slow speeds the aircraft would be moving forward on the backwards moving tarp?
Or are you saying it would continuously gain speed and then gain lift because the tarp wouldn't provide enough friction or backwards momentum to slow or stop the aircraft from moving forward regardless of the speed of the tarp? (10 mph backwards or 1,000 mph backwards, either way the aircraft would still move forwards eventually, and gain speed and lift)?
Originally posted by -rational-: Don't bother, you are not up to understanding the explanation on page 140.
You need to read the earlier posts in this thread which deal with the very basics of the problem, basics which you still don't understand.
The belt CANNOT stop the plane from moving forward EXCEPT under very special circumstances that you need not consider for now, and as the plane will move forward it will fly.
You should read the single post thread at the top of this forum in which Dan Tapster ( the MB producer) claims the MBs got it right, it covers some of the basic issues which alas I suspect are still above your level of understanding.
You're still being extremely rude and resorting to insults, and that's entirely unnecessary so I'm asking you to stop.
I do understand your post(s) on 140 and the point you guys are making, that there will be forward movement because the belt can't stop the acceleration.
I also admit that the massive wall of text (or wall of equations) are a bit much for me atm.
So answer some questions for me so I can go back to grunting, drooling, and beating my computer with a wooden club:
1) How fast would the belt have to be going for the aircraft to not gain forward momentum (in a natural environment) or is that irrelevant? Why?
2) How much thrust would the aircraft's engine(s) have to be providing (against the backwards momentum of the belt) to gain enough forward momentum and wind past the wings to create enough lift to increase the aircraft's altitude?
Well now that you are asking questions instead of making illogical and smug assertions we can communicate sensibly.
1) IF one assumes that this is a thought experiment and we can have indestructible materials in the wheels and belt etc the belt can go at ANY speed ( short of light speeds ) and the aeroplane will still move forward and take off. It is NOT the speed that is important, but acceleration. The only thing that can keep the plane stationary is an ACCELERATING belt! I repeat, an ACCELERATING belt. Remember if something is accelerating then forces are present from F= ma.
2) I suspect that you don't understand what momentum is, so I would suggest you avoid the term as you are misusing it. As the belt CANNOT exert large forces through the wheels except in very special circumstances then the aeroplane does not have to develop any thrust above normal.
Right I am now going to reveal to you where your misunderstanding of the myth originates and perhaps you can relate this back to your father in law as well and you can both share your embarrassment.
Consider the following.
If the belt was covered in ball bearings would you think that the plane would have any difficulty in taking off?
I hope the answer to that question is no. And then you have to consider the following, being on wheels is just like being on a surface covered in ball bearings ( unless the wheels are being accelerated )
Now perhaps you realise why the belt CANNOT exert large horizontal forces on the aeroplane body and why the aeroplane will take off as normal in almost all circumstances.
Tarp friction = constant friction regardless of backwards speed (breaks not on, tires not glued to tarmac) Propellers = forward acceleration Acceleration = increase in speed Increase in speed = more air over wings More air over wings = lift lift = I lost argument. :P
Well, -rational-, it didn't take a week, but a few hours.
I'm not going to spend the time typing up what you guys have already said but consider it understood.
Grrrr... so... dumb... I hate you -rational-. Being that right isn't...right.
--edit--
Yes, you explained it perfectly in that one.
I will reveal this information to my father-in-law and you can consider us two more educated individuals.
Originally posted by saintj858: I believe the frame of reference is the issue causing these debates. We have two groups from what I see: A.) Velocities of the plane and belt referenced to a static point (usually ground)
B.) Velocity of the plane referenced to the belt, and the velocity of the belt referenced to the ground. So one frame of reference is moving at all times when the experiment is being executed.
Is this a pretty fair assessment of the debate going on here?
You are about 240 pages behind in the debate.
This very issue was identified as a key issue at the start of this thread.
Originally posted by -rational-: Now perhaps you realise why the belt CANNOT exert large horizontal forces on the aeroplane body and why the aeroplane will take off as normal in almost all circumstances.
I must say, it's refreshing, and has greatly improved my impression of you (like that ever really matters on the internet, but whatever), to see you arguing the "will fly" position just as strenuously as you argue your "no fly" scenario.
quote:
Originally posted by dbgoldberg323: Grrrr... so... dumb...
Don't feel too bad, almost everyone on the internet had the same initial conclusion you did until they stopped and thought about it.
Originally posted by saintj858: So is it fair to say that you are in the B category rational?
If you read my posts on the last two pages you will see that I reference this issue repeatedly and that some of my posts are devoted to little else and the reasons why the B option is the only sensible interpretation. You may have noticed my reference to cars with wings etc which all relate to this issue.
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