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Would the plane take off?

imported_Nigma Mar 21, 2006

  1. Fantastic!

    particularly enjoyed seeing who the pilot is..!
     
  2. bainsyboy

    bainsyboy Guest

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    Risking a ban here but i really dont give a f----------------- End this thread now as its s--------------------t except for the pics of ladys,
    new question i have been up the pub since 4 and am now writing on the audi sport forum, is this a guinesss book of records? or shall i just go to bed and switch Brian from big brother fame on itv play off? as his annoying
     
  3. bainsyboy

    bainsyboy Guest

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    look at that time of posting this



    I really should be in the S.A.S as im a man's man ( i never have understood that, does that mean im gay or f-------------------k hard )
     
  4. bainsyboy

    bainsyboy Guest

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  5. scoTTy

    scoTTy Active Member

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    [ QUOTE ]
    Risking a ban here but i really dont give a f----------------- End this thread now as its s--------------------t except for the pics of ladys,

    [/ QUOTE ]
    Surely the simple answer is if you don't want to read it then ignore the thread. /ubbthreads/images/graemlins/noidea.gif

    p.s. Does anyone else think the above post may have been a little influenced by the demon drink? /ubbthreads/images/graemlins/lol.gif
     
  6. TDI-line

    TDI-line Uber Post Whore Team Floret Silver quattro Audi A3 Black Edition TDi

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    Bainsy...

    [​IMG]
     
  7. jdp1962

    jdp1962 Grumpy Old Moderator Staff Member Moderator Team V6 TFSI Owners Group Gold Supporter Team Tornado Audi S4 quattro Black Edition s tronic

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    [ QUOTE ]
    [ QUOTE ]
    Risking a ban here but i really dont give a f----------------- End this thread now as its s--------------------t except for the pics of ladys,

    [/ QUOTE ]
    Surely the simple answer is if you don't want to read it then ignore the thread. /ubbthreads/images/graemlins/noidea.gif

    p.s. Does anyone else think the above post may have been a little influenced by the demon drink? /ubbthreads/images/graemlins/lol.gif

    [/ QUOTE ]

    Speaking as one who has been known to post when pi$$ed before (never a good idea), I would have to say yes.
     
  8. S3Si

    S3Si Member

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    Funny vid Neil! Think TDI-line needs a little more practise in the pilot seat though, maybe he was distracted by a stewardess... /ubbthreads/images/graemlins/smirk.gif
     
  9. bainsyboy

    bainsyboy Guest

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    They should give you more time to edit, that way i could have removed those posts above.
     
  10. TDI-line

    TDI-line Uber Post Whore Team Floret Silver quattro Audi A3 Black Edition TDi

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    Never mind BB, everyone knows this thread has run it's course.

    [​IMG]
     
  11. treblesykes

    treblesykes Member

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    your conveyor is to short, it needs to be runway length (not heathrow obviously)
     
  12. NEiLS3LK51

    NEiLS3LK51 Member

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    It's more than long enough to prove the plane doesn't move forwards under thrust.
     
  13. Except that a chain belt, and wheels that are cogs that interlock with it, is going to present an enormously greater friction, resistance and coupling of the wheels with the surface below, compared to what was actually proposed, Ie normal smooth plane tyres and a conveyor belt (the asusmption being the conveyor belt offers no more resistance or friction that the normal runway surface)

    ;-)
     
  14. NEiLS3LK51

    NEiLS3LK51 Member

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    So you do agree with what I have been saying since page 3, the plane must skid forwards If it has any chance of getting to takeoff speed?

    The increased friction was to model the tyres as ideal, demonstrating that frictionless bearings do transfer a countering force to the plane under thrust.
     
  15. [ QUOTE ]
    I can't believe you guys have spent 12 pages discussing something which is obvious to a GCSE physics student...and that I've just added to it.

    [/ QUOTE ]

    I concur /ubbthreads/images/graemlins/mad.gif

    But for the record here's my twist on things...

    The friction doesn't matter.

    The thrust doesn't matter.

    The wheel bearings don't matter.

    The tyres don't matter.

    The speed of the wheels doesn't matter and neither does the speed of the belt... they cancel each other out which means, at the end of the day and 12 pages of complete guff that...
    ... go on...
    ... yeah that's it...
    ... nearly there...
    ... brain hurting yet?...
    ... got it!

    THE PLANE IS STANDING STILL!!!

    The single point that most people who have argued their own case are missing is that... the plane is actually standing in the same position it started in.

    The speed of the floor is irrelevant, the speed of the wheels is irrelevant. The plane has not moved a damn millimetre! Well maybe one or two but that is nowhere near enough to create enough air flow over the wings to provide sufficient uplift.

    It's an interesting argument and a bit of a brain tickler but most of you have second-guessed yourselves into 12 pages of rubbish! /ubbthreads/images/graemlins/tongue.gif

    No offence /ubbthreads/images/graemlins/wink.gif

    T /ubbthreads/images/graemlins/smile_smoking.gif
     
  16. scoTTy

    scoTTy Active Member

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    So are you saying that on an aircraft carrier, instead of the hook that holds the plane down whilst they go to full throttle, they could just have a conveyor belt instead?!?! Somehow I don't think so.

    I agree wheel speed is irrelvant (I posted about skids on sea planes earlier) but I don't see why you think this would stop the plane moving forward.

    Either you're missed the point or you're just baiting.

    /ubbthreads/images/graemlins/noidea.gif
     
  17. [ QUOTE ]
    So are you saying that on an aircraft carrier, instead of the hook that holds the plane down whilst they go to full throttle, they could just have a conveyor belt instead?!?! Somehow I don't think so.

    I agree wheel speed is irrelvant (I posted about skids on sea planes earlier) but I don't see why you think this would stop the plane moving forward.

    Either you're missed the point or you're just baiting.

    /ubbthreads/images/graemlins/noidea.gif

    [/ QUOTE ]


    'Baiting'... hahaha, not at all.

    On an aircraft carrier though...?? /ubbthreads/images/graemlins/confused.gif

    No, you've totally missed the point there I think. Even there the planes actually move forward and need airflow over the wings to lift off...

    On an aircraft carrier there is limited space... the hook is used to allow planes to build up maximum thrust in order to allow them to achieve maximum speed in the space available... hence achieving maximum possible airflow over the wings and thus giving uplift etc. etc. Quite how that has any relevance to the original problem posed I do not know! /ubbthreads/images/graemlins/wink.gif

    As the original question states...

    [ QUOTE ]
    the conveyor belt senses the speed of the plane's wheels and moves at exactly the same speed in the opposite direction

    [/ QUOTE ]


    So the amount of thrust etc. does not matter because the wheels moving forward faster than the conveyor moving backwards is the only thing that governs whether or not the plane will actually go anywhere... and since the conveyor cancels out all forward motion provided by the engine with backward motion of the 'exactly the same' magnitude (as stated in the question)... the plane won't move!

    Forget bearing friction etc. etc. It will be minimal anyway, and forward motion due to the thrust gained as a result of it will be neglibible and nowhere near enough to allow the plane to achieve flight.

    I'm sorry if I sound caustic now but come on, this is getting ridiculous... it's child's play!

    Basic physics, remember?

    This problem is a typical example of how people (usually intelligent people actually) think far too much and read way too far into things... and I don't really care so forget it, debate over... /ubbthreads/images/graemlins/grin.gif

    T
     
  18. scoTTy

    scoTTy Active Member

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    You don't sound caustic, just patronising.

    [ QUOTE ]
    the wheels moving forward faster than the conveyor moving backwards is the only thing that governs whether or not the plane will actually go anywhere... and since the conveyor cancels out all forward motion provided by the engine with backward motion of the 'exactly the same' magnitude (as stated in the question)... the plane won't move!

    [/ QUOTE ]

    This is where I disagree. I don't see that the conveyor cancels out the forward motion. It simply causes the wheels to rotate faster.

    This may explain better than I can. HERE

    Or this :

    [ QUOTE ]
    ......

    It was an interesting argument, but as things progressed, more rational heads prevailed, pointing out that the airplanes do not apply their thrust via their wheels, so the conveyor belt is irrelevant to whether the airplane will takeoff. One guy even got one of those rubber band powered wood and plastic airplane that sell for about a buck, put it on the treadmill someone foolishly donated to the Lounge years ago, thinking that pilots might actually exercise. He wound up the rubber band, set the treadmill to be level, and at its highest speed. Then he simultaneously set the airplane on the treadmill and let the prop start to turn. It took off without moving the slightest bit backwards.

    [/ QUOTE ]

    or this :

    [ QUOTE ]
    OK, let's figure out why the airplane will fly.

    We'll use Manfred again. Although we're bringing him forward into the 21st Century, we'll still let him use the 65 hp J-3. It doesn't really matter what airplane he flies, but he got used to the J-3 while he was demonstrating downwind turns and this one happens to have lifting rings on the top of the fuselage. It's also been modified with a starter so no one has to swing the prop.

    Manfred's in the airplane. Old Hack has the Army-surplus crane fired up and he's picking up the J-3 and Manfred and carrying them over to Runway 27, which has been transformed into a 3,000-foot conveyor belt. It is a calm day. The conveyor drive is programmed so that if Manfred can start to move in the J-3, if he can generate any airspeed or groundspeed, the conveyor will move toward the east (remember Manfred and the J-3 are facing west) at exactly the speed of the air/groundspeed. Because the wind is calm, if Manfred can generate any indicated airspeed, he will also be generating precisely the same groundspeed. Groundspeed, of course being relative to the ground of the airport surrounding the conveyor belt runway. So, the speed of the conveyor belt eastbound will be the same as Manfred's indicated airspeed, westbound.

    Manfred does his prestart checklist, holds the heel brakes, hits the starter and the little Continental up front clatters to life. Oil pressure comes up and stabilizes and Manfred tries to look busy because the eyes of the world are upon him, but all he can do is make sure the fuel is on and the altimeter and trim are set, then do a quick runup to check the mags and the carb heat. He moves the controls through their full travel and glares at the ailerons, doing his best to look heroic, then holds the stick aft in the slipstream to pin the tail and lets go of the brakes.


    Baron of the Belt

    So far the J-3 has not moved, nor has the conveyor. At idle power, there's not enough thrust to move the J-3 forward on a level surface, so Manfred starts to bring up the power, intending to take off. The propeller rpm increases and the prop shoves air aft, as it does on every takeoff, causing the airplane to move forward through the air, and as a consequence, forward with regard to the ground. Simultaneously the conveyor creaks to life, moving east, under the tires of the J-3. As the J-3 thrusts its way through the air, driven by its propeller, the airspeed indicator comes off the peg at about 10 mph. At that moment the conveyor is moving at 10 mph to the east and the tires are whirling around at 20 mph because the prop has pulled it to an airspeed, and groundspeed, of 10 mph, westbound. The airplane is moving relative to the still air and the ground at 10 mph, but with regard to the conveyor, which is going the other way at 10 mph, the relative speed is 20 mph.

    Manfred relaxes a bit because the conveyor cannot stop him from moving forward. There is nothing on the airplane that pushes against the ground or the conveyor in order for it to accelerate; as Karen -- one of our techies here at the Lounge -- put it, the airplane freewheels. In technical terms, there is some bearing drag on the wheels, but it's under 40 pounds, and the engine has overcome that for years; plus the drag doesn't increase significantly as the wheel speed increases. Unless Manfred applies the brakes, the conveyor cannot affect the rate at which the airplane accelerates.

    A few moments later, the roaring Continental, spinning that wooden Sensenich prop, has accelerated the J-3 and Manfred to 25 mph indicated airspeed. He and the airplane are cruising past the cheering spectators at 25 mph, while the conveyor has accelerated to 25 mph eastbound, yet it still has no way of stopping the airplane's movement through the air. The wheels are spinning at 50 mph, so the noise level is a little high, but otherwise, the J-3 is making a normal, calm-wind takeoff.

    As the indicated airspeed passes 45 mph, groundspeed -- you know, relative to where all those spectators are standing beside the conveyor belt -- is also 45 mph. (At least that's what it says on Manfred's GPS. Being brought back to life seemed to create an insatiable desire for electronic stuff.) The conveyor is also at 45 mph, and the wheels are whizzing around at 90 -- the groundspeed plus the speed of the conveyor in the opposite direction.

    Manfred breaks ground, climbs a few hundred feet, then makes a low pass to see if he can terrify the spectators because they are Americans, descendants of those who defeated his countrymen back in 1918.


    It's All About Airspeed



    (Don't try this at home!)

    While the speed of the conveyor belt in the opposite direction is superficially attractive in saying the airplane cannot accelerate, it truly is irrelevant to what is happening with the airplane, because the medium on which it is acting is the air. The only time it could be a problem is if the wheel speed got so high that the tires blew out.

    Put another way, consider the problem with the J-3 mounted on a hovercraft body (yes, similar things were tried about 30 years ago). The hovercraft lifts the airplane a fraction of an inch above the conveyor belt, and so no matter how fast the conveyor spins, it cannot prevent the propeller -- acting on the air -- from accelerating the airplane to takeoff speed. It's the same with wheels rolling on the conveyor belt. Those wheels are not powered and thus do not push against the belt to accelerate the airplane. Were that the case, the vehicle could not reach an airspeed needed to fly, because then the conveyor, the medium acted upon by the propulsive force, would be able to negate the acceleration relative to the air and ground.

    I'm reminded of the New York Times editorial when Robert Goddard's rocket experiments were first being publicized. The author of the editorial said that rockets can't work in space because they have nothing to push against. It was laughably wrong, ignoring one of Sir Isaac's laws of physics that for every action there is an equal and opposite reaction. Here the propeller is pushing against the air, as it does every time an airplane takes off. How fast the airplane is moving over the surface on which its wheels rest is irrelevant; the medium is the magic. On a normal takeoff -- no conveyor involved -- if there is a 20 mph headwind, Manfred and the J-3 will lift off at 45 mph indicated airspeed; but relative to the ground, it is only 25 mph. Should the wind increase to 45 mph and if Manfred can get to the runway, he can take off without rolling an inch. His airspeed is 45 and groundspeed is zero. It is not necessary to have any groundspeed to fly, just airspeed. Conversely, if Manfred has a lot of runway and nothing to hit, and takes off downwind in a 25 mph tailwind, the propeller will have to accelerate the airplane to a zero airspeed, which will be a 25 mph groundspeed, and then on to a 45 mph airspeed, which will have him humming across the ground at 70 mph. The speed over the ground, or a conveyor belt, when an airplane takes off is irrelevant; all that matters is its speed through the air, and unless the pilot sets the brakes, a moving conveyor belt -- under the freely turning wheels -- cannot stop the process of acceleration.


    [/ QUOTE ]

    No doubt you won't read it all. If you do please let me know where it's wrong....otherwise I'll accept the apology that's coming. /ubbthreads/images/graemlins/smirk.gif
     
  19. johnnywb

    johnnywb Member

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    Ok, when we're in the pub and a question such as this arises (well maybe not quite as controversial as this but hey), and we can't agree on the right answer, we text our friends at AQA - Any Question Answered. So i text them the exact question at the start of the thread. Their response is below; (bear in mind you have to have a degree to work for them apparently, so it's not jsut anyone off the street, lol)

    AQA:
    "Lift consists of the sum of all the fluid dynamic forces on a body perpendicular to the direction of the external flow approaching that body. AQA thinks that in this scenario, the plane will not have any forward motion. No lift will be generated and therefore the plane will not take off."

    They have also previously offered helpful advice such as 'AQA demands the boys stay for another' in response to 'should the boys go and do some work, or stay for another drink?'
     
  20. TDI-line

    TDI-line Uber Post Whore Team Floret Silver quattro Audi A3 Black Edition TDi

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    Nice work Johnny. /ubbthreads/images/graemlins/beerchug.gif

    Have another pint. /ubbthreads/images/graemlins/wink.gif

    [​IMG]
     
  21. scoTTy

    scoTTy Active Member

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    [ QUOTE ]
    bear in mind you have to have a degree to work for them apparently, so it's not jsut anyone off the street, lol

    [/ QUOTE ]

    /ubbthreads/images/graemlins/laugh_roll.gif

    As a degree holder myself, I know that this fact is an irrelevance when applying common sense. /ubbthreads/images/graemlins/lol.gif
     
  22. scoTTy

    scoTTy Active Member

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    p.s. Do you get your £1 back if they're wrong?
     
  23. /ubbthreads/images/graemlins/blush2.gif

    Apology tendered...

    Airspeed... that bloody smartarse Newton!

    Oh well, I guess I am human then /ubbthreads/images/graemlins/tongue.gif

    That AQA thing is FUNNY! /ubbthreads/images/graemlins/grin.gif
     
  24. scoTTy

    scoTTy Active Member

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    [ QUOTE ]
    /ubbthreads/images/graemlins/blush2.gif

    Apology tendered...

    [/ QUOTE ]

    /ubbthreads/images/graemlins/beerchug.gif

    [ QUOTE ]
    this is getting ridiculous... it's child's play!

    [/ QUOTE ]

    [ QUOTE ]
    Basic physics, remember?

    [/ QUOTE ]

    [ QUOTE ]
    This problem is a typical example of how people (usually intelligent people actually) think far too much and read way too far into things...

    [/ QUOTE ]

    /ubbthreads/images/graemlins/tongue.gif /ubbthreads/images/graemlins/wink.gif
     
  25. Ok... you got me... I'm a prize tw@t!

    /ubbthreads/images/graemlins/blush2.gif
     
  26. treblesykes

    treblesykes Member

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    the wheels and conveyor mean nothing, thrust pushes weight of plane along, plane doesnt need wheels when in the air so why do they affect it in the ground? only a solid connection with ground such as a hook or rope would have any affect
     
  27. johnnywb

    johnnywb Member

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    [ QUOTE ]
    [ QUOTE ]
    bear in mind you have to have a degree to work for them apparently, so it's not jsut anyone off the street, lol

    [/ QUOTE ]

    /ubbthreads/images/graemlins/laugh_roll.gif

    As a degree holder myself, I know that this fact is an irrelevance when applying common sense. /ubbthreads/images/graemlins/lol.gif

    [/ QUOTE ]

    Too true! Not sure about getting he £1 back if they're wrong. Hang on i'll just text them and ask....

    lol
     
  28. foolish3uk

    foolish3uk Member

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    my ten pence worth is the plane will take off as mentioned above air speed and not ground speed is the key, after all the bloody thing isnt ancored at the rear!
     
  29. The Slug

    The Slug Active Member

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    what was the max load for the conveyor btw??
     
  30. neversaydie

    neversaydie Post Whore

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    have the passengers on this plane got a refund of easyjet for not taking off yet?

    ffs
     
  31. Stringster

    Stringster Missed gear

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    [ QUOTE ]
    have the passengers on this plane got a refund of easyjet for not taking off yet?

    ffs

    [/ QUOTE ]

    No, but they are entitled to a free cup of tea to go with their £10 sandwich...
     
  32. TDI-line

    TDI-line Uber Post Whore Team Floret Silver quattro Audi A3 Black Edition TDi

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    Bump.

    [​IMG]
     
  33. CJ A4

    CJ A4 Active Member

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    Wonder what sort of runway strip she has?
     
  34. hop2407

    hop2407 Active Member

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    [ QUOTE ]
    Wonder what sort of runway strip she has?

    [/ QUOTE ]

    Yeah.... and I bet she's an 'aeroplane blonde' /ubbthreads/images/graemlins/tongue.gif /ubbthreads/images/graemlins/wink.gif
     
  35. Hop your first smiley has his tongue out, whats that all about??

    so,

    A Blonde is standing on a runway that is made of a large conveyor belt. BainsyBoy spots her and approaches. The Blonde starts to run, but as they both move forward, the conveyor belt senses the speed of her and Bainsys heels and moves at exactly the same speed in the opposite direction. She starts to flap her arms up and down wildly. Will the Blonde escape his clutches?

    Note - for the purpose if this thought experiment, if 'motivation' is considered an issue, it is assumed that BB has the horn.

    /ubbthreads/images/graemlins/angel.gif
     
  36. CJ A4

    CJ A4 Active Member

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    I don't think any amount of resistance or even any natural laws of physics are useful when measuring this scenario especially when you have to take into account the bainsy horn factor!....eeewwww /ubbthreads/images/graemlins/vomit.gif
     
  37. hop2407

    hop2407 Active Member

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    [ QUOTE ]
    Hop your first smiley has his tongue out, whats that all about??

    [/ QUOTE ]

    So if you got the chance with her - all you would do is look at it ?? ..... eeeerm - think not !!! /ubbthreads/images/graemlins/woohoo.gif /ubbthreads/images/graemlins/tongue_out.gif /ubbthreads/images/graemlins/froggie_red.gif

    [ QUOTE ]
    so,

    A Blonde is standing on a runway that is made of a large conveyor belt. BainsyBoy spots her and approaches. The Blonde starts to run, but as they both move forward, the conveyor belt senses the speed of her and Bainsys heels and moves at exactly the same speed in the opposite direction. She starts to flap her arms up and down wildly. Will the Blonde escape his clutches?

    Note - for the purpose if this thought experiment, if 'motivation' is considered an issue, it is assumed that BB has the horn.

    /ubbthreads/images/graemlins/angel.gif

    [/ QUOTE ]

    /ubbthreads/images/graemlins/laugh_2.gif /ubbthreads/images/graemlins/laugh_2.gif - Mint....
     
  38. TDI-line

    TDI-line Uber Post Whore Team Floret Silver quattro Audi A3 Black Edition TDi

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    BUMP!
     
  39. A4Andy

    A4Andy Quattro-tastic. Not half.

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    Christ.

    It will not take off. Thrust has no relevance in this equation.

    Airflow over the wing causes an area of low pressure above the wing, the wings shape facilitates this. The area under the wing has normal pressure so the wing is “sucked” up into the low pressure.

    Engines on a plane are used to propel it forward through the air, forcing air over the wings and creating the aforementioned areas of low pressure.

    If there is not enough airflow over the wing the pressure variance is not great enough to sustain lift and the craft enters into a stall; this has nothing to do with stalling the engines.

    So, regardless of ground speed if there is no flow over the wing there is not lift and it cannot take off.
     
  40. hop2407

    hop2407 Active Member

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    PMSL.... Here we go... The battle of the threads....
     

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