MrRalphMan Posted February 7, 2008 Author Share Posted February 7, 2008 Seaplanes work because the air displaced by the engine/prop creates forward thrust against the water. This means that the plane moves forward, because it is moving against the medium it's pushing against. No that would be a boat.. What happens when it takes off? I'm amazed this is still going... Doesn't matter if the belt tracks the plane's air speed, wheel speed etc, as long as the plane is pushing at the air (prop or jet) then it's going to gain air speed.. Thus take off,, Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 No that would be a boat.. What happens when it takes off? I'm amazed this is still going... Doesn't matter if the belt tracks the plane's air speed, wheel speed etc, as long as the plane is pushing at the air (prop or jet) then it's going to gain air speed.. Thus take off,, How can it gain speed if the forces in use counteract each other? It can't move from a standstill. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 What did I just say above, the conveyer is NOT set to go at a high speed; one that would be fast enough to overpower the engines. It's ONLY going as fast as the plane is moving forwards. As said this just spins the wheels it isn't enough to stop the engines from pushing the plane forwards!! Yes, it is. Thats the whole idea. The conveyor moves at a speed that is the same as the plane so if the plane speeds up 1 m/s then so does the belt, in the other direction. Explain to me how the plane accelerates? Quote Link to comment Share on other sites More sharing options...
DamanC Posted February 7, 2008 Share Posted February 7, 2008 Great thread Quote Link to comment Share on other sites More sharing options...
AndrewOW Posted February 7, 2008 Share Posted February 7, 2008 Righto. I'm going unsubscribe to this now, as it's filling my email up, but before I do I'll put this to you: The only way I can think that the plane won't take off is if the conveyor belt moves FASTER than the plane can fly at full speed, ie. 500mph etc. I voted 'no' at the start, but during this very entertaining discussion, I've been persuaded that I should've answered 'yes' instead. Then again, I may have been right all along Quote Link to comment Share on other sites More sharing options...
Soop Dogg Posted February 7, 2008 Share Posted February 7, 2008 FFS........ This is my last post on this topic, you can argue the toss all you like.... I am not getting into a disscussion on this with people that have read a few books on Aeroplanes(including Thomas Cook holiday brouchers), surfed the net for rubbish info and who's Aircraft experience is limited to Holidays to Spain! 1. I'm glad that's your last post on the topic because you're starting to rant. 2. I studied for 3 years in the Royal Air Force to get my qualifications in Electronics & Aerospace Engineering. Only part of this is even relevant here, because it's such basic physics that the aircraft CAN and WILL move forward. (Thus the wings will be able to generate the lift required for take-off) I'm not talking as one of your people whose "Aircraft experience is limited to Holidays to Spain", so let's get past that, shall we? When you do your tests on engines, the point there is that they're strapped down and so prevented from moving forward. All the energy developed by the engine is dissipated into the rig holding it down. Like I said before, if the conveyor was going the wrong way - even at a million mph, this would only cause the wheels to spin the wrong way. (Albeit, incredibly fast) The engine wouldn't have to produce the thrust required to do 1 million mph PLUS its' take-off speed to be able to take of - it'd still go forward as normal and the wheels would simply turn backwards at a speed of 1million mph MINUS the take-off speed at the point of take-off. Because the wheels are not actually connected in any way to the propulsion mechanism of the aircraft, this means the aircraft speed is independant of the speed that the wheels are turning. Like I explained in post #135, the aircraft will take off with the wheels stationary if the conveyor is going the same direction as the aircraft at the take-off speed. When we run, we have to push against the ground to move forward, i.e. in your treadmill argument, the thing that we push against is moving. That goes for a car too. But the aircraft is pushing against air - and that's not moving at all. And by the way - you're the first propulsion engineer (if you're actuially an engineer and not a fitter) that I've heard try to equate their experience to having expertise in the field of aeronautics. (FFS...) Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 1. I'm glad that's your last post on the topic because you're starting to rant. 2. I studied for 3 years in the Royal Air Force to get my qualifications in Electronics & Aerospace Engineering. Only part of this is even relevant here, because it's such basic physics that the aircraft CAN and WILL move forward. (Thus the wings will be able to generate the lift required for take-off) I'm not talking as one of your people whose "Aircraft experience is limited to Holidays to Spain", so let's get past that, shall we? When you do your tests on engines, the point there is that they're strapped down and so prevented from moving forward. All the energy developed by the engine is dissipated into the rig holding it down. Like I said before, if the conveyor was going the wrong way - even at a million mph, this would only cause the wheels to spin the wrong way. (Albeit, incredibly fast) The engine wouldn't have to produce the thrust required to do 1 million mph PLUS its' take-off speed to be able to take of - it'd still go forward as normal and the wheels would simply turn backwards at a speed of 1million mph MINUS the take-off speed at the point of take-off. Because the wheels are not actually connected in any way to the propulsion mechanism of the aircraft, this means the aircraft speed is independant of the speed that the wheels are turning. Like I explained in post #135, the aircraft will take off with the wheels stationary if the conveyor is going the same direction as the aircraft at the take-off speed. When we run, we have to push against the ground to move forward, i.e. in your treadmill argument, the thing that we push against is moving. That goes for a car too. But the aircraft is pushing against air - and that's not moving at all. And by the way - you're the first propulsion engineer (if you're actuially an engineer and not a fitter) that I've heard try to equate their experience to having expertise in the field of aeronautics. (FFS...) But the plane can't move off from a standstill so this arguement carries no weight either surely? Everytime it accelerates, the runway moves backwards so keeping the plane in the same place. In this way, the plane is held back as an engine on a dyno would be. If the plane can't advance up the runway then how does it gain speed and so build up the resistance from air required for lift? Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted February 7, 2008 Share Posted February 7, 2008 Excellent thread. More of the same please. Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 7, 2008 Author Share Posted February 7, 2008 How can it gain speed if the forces in use counteract each other? It can't move from a standstill. The force of the belt acts against the wheels. If the wheels were driven as in the Dyno example, then it would be going no where. The plane is pushing against the air, the air is not going backwards at the same speed as the belt... So the plane pushes itself forwards... The wheels on the other hand are doing twice as much work as normal, but as they are NOT driven, they do not impeed the plane. Quote Link to comment Share on other sites More sharing options...
Soop Dogg Posted February 7, 2008 Share Posted February 7, 2008 1. Think of yourself on a 'threadmill'.... either running or on rollerskates. I'm sorry mate - a 'THreadmill' is (and I'm guessing here) probably something to do with needlework. (which certainly isn't my area of expertise - especially not on rollerskates.) I do wish you'd stay on topic and not try to relate everything to whatever strange hobbies you might have.... Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 7, 2008 Author Share Posted February 7, 2008 But the plane can't move off from a standstill so this arguement carries no weight either surely? Everytime it accelerates, the runway moves backwards so keeping the plane in the same place. In this way, the plane is held back as an engine on a dyno would be. If the plane can't advance up the runway then how does it gain speed and so build up the resistance from air required for lift? Gaz, are you just winding us all up? Quote Link to comment Share on other sites More sharing options...
johnnyknox Posted February 7, 2008 Share Posted February 7, 2008 The force of the belt acts against the wheels. If the wheels were driven as in the Dyno example, then it would be going no where. The plane is pushing against the air, the air is not going backwards at the same speed as the belt... So the plane pushes itself forwards... The wheels on the other hand are doing twice as much work as normal, but as they are NOT driven, they do not impeed the plane. Exactamondo! This is the answer...you started this thread so you have now concluded the answer..Thank you Quote Link to comment Share on other sites More sharing options...
Alex Posted February 7, 2008 Share Posted February 7, 2008 Gaz, are you just winding us all up? By christ I hope he is... Someone bring a treadmill and an RC plane to JAE or TOTB lol Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 The force of the belt acts against the wheels. If the wheels were driven as in the Dyno example, then it would be going no where. The plane is pushing against the air, the air is not going backwards at the same speed as the belt... So the plane pushes itself forwards... The wheels on the other hand are doing twice as much work as normal, but as they are NOT driven, they do not impeed the plane. We have to assume the wheels travel the same distance as the plane. This is because they are connected. If we are agreed on this and also that the forward motion of the plane is counteracted by the runway, then how can the plane accelerate and so create the lift needed to take off? Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 Gaz, are you just winding us all up? By christ I hope he is... Someone bring a treadmill and an RC plane to JAE or TOTB lol Quote Link to comment Share on other sites More sharing options...
tbourner Posted February 7, 2008 Share Posted February 7, 2008 Yes, it is. Thats the whole idea. The conveyor moves at a speed that is the same as the plane so if the plane speeds up 1 m/s then so does the belt, in the other direction. Explain to me how the plane accelerates? Are you under the impression the conveyer is measuring the planes speed with respect to the conveyer, or it's speed with respect to the Earth? If it's with respect to the Earth, then your theory creates a paradox; the non-movement of the plane meaning the conveyer doesn't move, which means the plane moves - loop to end. If it's with respect to the conveyer it's an increase to infinity because as soon as the plane starts to move the conveyer will move, but the plane's movement will mean it's always faster than the conveyer, so it will speed up until infinity. All this however, still relies on the car principle, since the engines are pushing on the air and not the conveyer, it's all irrelevant. Quote Link to comment Share on other sites More sharing options...
Supra Pilot Posted February 7, 2008 Share Posted February 7, 2008 [quote=MrRalphMan; A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off and why? QUOTE] The old adage, RTFQ... Read the f---ing question... There is no mention of wheels at all... You bring wheels in the equation then yes, the goal post is moved, and yes indeed, you are correct... as the wheels have no bearing on the test! I'm not the one getting hot and bothered about this... I fully understand the question and giving an answer to the exact nature of the question being presented. Read back everything I have said, I am simply basing my facts on a stationary object as people seemed to be having a problem with a simple aerodynamic situation. The question also never says anything about foward movement. If anything blame the flaw of the question! No need to get excited gents..... Quote Link to comment Share on other sites More sharing options...
tbourner Posted February 7, 2008 Share Posted February 7, 2008 We have to assume the wheels travel the same distance as the plane. This is because they are connected. Yes. If we are agreed on this and also that the forward motion of the plane is counteracted by the runway, No, why is it? then how can the plane accelerate and so create the lift needed to take off? Because the energy used to make the plane accelerate is not affected by the planes method of attachment to the ground. BTW, I'm not singling you out, you just seem to have the best arguments to go against. Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted February 7, 2008 Author Share Posted February 7, 2008 We have to assume the wheels travel the same distance as the plane. This is because they are connected. If we are agreed on this and also that the forward motion of the plane is counteracted by the runway, then how can the plane accelerate and so create the lift needed to take off? They travel the same distance as the plane as they are attached, but like my soop's wing mirrors. But they can rotate a different distance. **Edit** Just wanted to make it clear that my mirrors are not attached to the plane. That would be silly. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 Are you under the impression the conveyer is measuring the planes speed with respect to the conveyer, or it's speed with respect to the Earth? If it's with respect to the Earth, then your theory creates a paradox; the non-movement of the plane meaning the conveyer doesn't move, which means the plane moves - loop to end. If it's with respect to the conveyer it's an increase to infinity because as soon as the plane starts to move the conveyer will move, but the plane's movement will mean it's always faster than the conveyer, so it will speed up until infinity. All this however, still relies on the car principle, since the engines are pushing on the air and not the conveyer, it's all irrelevant. I'm basing this on the movement of the conveyor being directly proporitional to the speed of the plane moving along it. Yes, infinite values can be mentioned because of the concept of the problem. That is where I'm coming from. The plane simply can't move in this problem as every time it tried to accelerate the runway moves backwards to compensate. No movement = no take-off. Quote Link to comment Share on other sites More sharing options...
johnnyknox Posted February 7, 2008 Share Posted February 7, 2008 I'm basing this on the movement of the conveyor being directly proporitional to the speed of the plane moving along it. Yes, infinite values can be mentioned because of the concept of the problem. That is where I'm coming from. The plane simply can't move in this problem as every time it tried to accelerate the runway moves backwards to compensate. No movement = no take-off. Search youtube Gaz, it's been proven that the plane will take off. Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 Search youtube Gaz, it's been proven that the plane will take off. The whole site or have you got a link that hasn't already been posted in this thread? Quote Link to comment Share on other sites More sharing options...
Ric Posted February 7, 2008 Share Posted February 7, 2008 Search youtube Gaz, it's been proven that the plane will take off. I'm leaning to think that the plane will take off now, but those experiments on you tube are seriously flawed hardly scientific at all i think there's no way to test for example the take-off of a 747 or something therefore the question is until COMPLETELY proved is unanwserble Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted February 7, 2008 Share Posted February 7, 2008 I'm leaning to think that the plane will take off now, but those experiments on you tube are seriously flawed hardly scientific at all i think there's no way to test for example the take-off of a 747 or something therefore the question is until COMPLETELY proved is unanwserble Best post so far. At the end of the day, all of this is IMHO. We can't prove it, only argue about it. I'm quite enjoying playing devils advocate here actually Quote Link to comment Share on other sites More sharing options...
Ewen Posted February 7, 2008 Share Posted February 7, 2008 Forget speed for a minute. Put a chalk mark on the belt, and a corresponding mark on the ground next to the belt, and a corresponding mark on the plane. When all this stuff kicks off, the belt moves right ? The chalk mark will move from its point marked on the ground. Lets say it moves 100m. It can only move at the same time as the plane, and as stated the plane moves in the opposite direction...so the chalk mark on the plane is now also 100m away from the chalk mark on the ground, but 200m away from the chalk mark on the belt. So the plane has moved forward. Now add speed, and more distance. the chalk marks on the belt and plane get further apart, but the distance from the chalk mark on the plane and ground, and from the chalk mark on the belt and the ground are always equal. The plane will move further away from the chalk mark on the ground, accelerate and take off. Again. Quote Link to comment Share on other sites More sharing options...
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