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Will the plane fly?

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  • #31
    The wheels are NOT the driving force to get the air craft moving/flying, like you have in an automobile the jet thrust or the propellers are, the jet propulsion will push/pull the fuselage which in turn pull the wheels along the conveyer. The conveyer will in turn cancel out the "wheels only" not the forward movement of the air craft. The wheels have no effect on the forward movement of the air craft.

    Think of it this way
    same scenario
    you have one of your kids pull-toys. as long as you pull the string on the conveyer the toy will move forward.
    if you did the same with a wind up toy car, the car would sit still and the conveyer would equal out the force from the wheels.

    The Plane will fly.


    Now I have a Headache.
    Rich
    If you don't have Meguiar's in your hand
    DON'T TOUCH MY TRUCK

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    • #32
      Originally posted by Jeff Smith
      ...I did speak with one of our pilots about this this morning...
      I said to "Run this past one of your engineers".


      Originally posted by Jeff Smith
      ... It would depend on the Thrust-Weight ratio of the aircraft...
      No. If the aircraft had enough thrust to fly under any conditions it would only depend on having enough thrust margin to overcome friction in the landing gear (which is very, very small).


      Originally posted by Jeff Smith
      ...Is the question refering to aircraft currently inproduction. or is it a theoretical question based on the "possibilty" that an aircraft can do this.

      If it is asking about a currently produced aircraft, the answer would be no. Nobody is currently building an aircraft capable of this ...
      Everybody is currently building all their aircraft to be capable of this. If there were any aircraft without enough excess thrust to overcome 2x the rolling friction of its landing gear I sure wouldn't want to fly in it.


      Originally posted by Jeff Smith
      ...As for the possibilty is a plane being built specifically to do this. His thoughts were yes. But he did go on to say that he would never fly it. The stress loads on the aircraft so great that we really just don't have the manufacturing processes in place to build an aircraft to withstand them on a regular basis. At least not at this point in time...
      The only stress load increase would be from having to spin the tires 2x their normal speed.

      I haven't done the analysis but it seems ridiculous to think that landing gear/wheels/tires that have to accelerate from zero to landing speed practically instantly (on every landing) couldn't withstand simply spinning faster (with no hard accelerations).

      And the materials and manufacturing processes to do it are nothing special. It's purely a design issue (which is nothing special either).


      Originally posted by Jeff Smith
      ... After giving me the above food for though he then added the comment that In His Honest Opinon. Gold class was the best. ...
      Can't argue with him there.


      PC.

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      • #33
        Originally posted by Hannibal
        LOL

        It doesnt matter which way a conveyor belt moves under the planes wheels. The plane is not using the wheels to get it up to speed. The one thing to note is that the wheels will be moving at a higher velocity (airplane velocity + reverse conveyor speed= wheel velocity)

        Riddle me this: How is it that a certain plane can take off while floating on the surface of water?? Is it using paddles or something? NO, it is using accelerated air that is passed over the surface of the wing, and is essentially "pulling" itself using the wind created by the propeller.
        Brandon

        2007 Black Chevy Avalanche

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        • #34
          It won't fly.... Nuff said...
          Rangerpowersports.com
          Ranger72

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          • #35
            Posted by Hannibal....
            "Riddle me this: How is it that a certain plane can take off while floating on the surface of water?? Is it using paddles or something? NO, it is using accelerated air that is passed over the surface of the wing, and is essentially "pulling" itself using the wind created by the propeller"

            It's not the accelerated air from the propeller creating the lift, it's the air the whole wing is passing thru. The propeller provides the plane enough speed thru the air to create lift. Man......time for a beer!
            Black......the ONLY color!

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            • #36
              Originally posted by the other pc
              I said to "Run this past one of your engineers".


              No. If the aircraft had enough thrust to fly under any conditions it would only depend on having enough thrust margin to overcome friction in the landing gear (which is very, very small).


              Everybody is currently building all their aircraft to be capable of this. If there were any aircraft without enough excess thrust to overcome 2x the rolling friction of its landing gear I sure wouldn't want to fly in it.


              The only stress load increase would be from having to spin the tires 2x their normal speed.

              I haven't done the analysis but it seems ridiculous to think that landing gear/wheels/tires that have to accelerate from zero to landing speed practically instantly (on every landing) couldn't withstand simply spinning faster (with no hard accelerations).

              And the materials and manufacturing processes to do it are nothing special. It's purely a design issue (which is nothing special either).


              Can't argue with him there.


              PC.
              I think I'll stick to what he said. He has been a US Marine Test Pilot since before I got outta high school. I'd like to assume he knows what he is doing. As far as talking to an engineer, I'd rather have answer. Anywho. I am done with this. Above my pay grade.
              Jeff Smith

              Don't mistake my enthusiasm for experience.

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              • #37
                I don't think it will fly. While a plane may take off on water, the water isn't moving in an opposite direction underneath the plane like a conveyor belt. The plane's thrust would push off on the water creating an action-reaction effect, the plan gets force from the engine, it pushes off an goes

                However, when the plane's engines thrust up to take-off speed, the belt just moves equally and oppositely (sp?). The plane is moving, but it cannot get the reaction force to take off, insted the action and reaction forces are cancled out. While I think I am proving Newton's 2nd law, I dont think a plane can take off from a moving runway.

                Example, put a car on a dyno, its engine is providing force to the wheels and the ground is moving in opposite direction. It doesn't matter how far the car is going, wind wont drag on the car, its not moving.

                Funny thing is, You can be in your Buggati Veyron going 250, and not feel any wind resistance on a Dyno, so same effect with the plane. It wouldn't go anywhere.

                Even if there was wind to drag it, it would not contain the push-off needed to stay in flight.

                This is really making me think, I can prove myself wrong just as eaisly as I can prove myself right.

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                • #38
                  The engines push the air not the moving ground. Your examples are flawed in that you use something that needs the ground to be able to move. The plane doesn't need the ground it needs the air that it pushes to gain speed.
                  Quadruple Honda Owner
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                  • #39
                    Originally posted by Jeff Smith
                    I think I'll stick to what he said. He has been a US Marine Test Pilot since before I got outta high school. I'd like to assume he knows what he is doing. …
                    I think it’s safe to assume he does, in which case he must be interpreting the conditions of the question vastly differently. That’s the problem with ambiguously worded questions. Unless everyone works from the same set of conditions they won’t necessarily come up with the same answers (even if they are applying the physics correctly).


                    PC.

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                    • #40
                      Originally posted by the other pc
                      I think it’s safe to assume he does, in which case he must be interpreting the conditions of the question vastly differently. That’s the problem with ambiguously worded questions. Unless everyone works from the same set of conditions they won’t necessarily come up with the same answers (even if they are applying the physics correctly).


                      PC.
                      Yes, This question does leave alot of unanswered variables out. Regarding the Colonel, I have to give the man the respect he is due. Simply because he runs the whole V-22 Osprey Flight Test Program here. Uh, they sign my paycheck.

                      And with asking our Engineers anything, The answer would likely depend on what kind of engineer. We have production, structural, avionics, Flight Test. and 20 or so other types of engineers. We would likely pull 20 answers out of them.
                      Jeff Smith

                      Don't mistake my enthusiasm for experience.

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                      • #41
                        Originally posted by SiriusRIMZ
                        …While a plane may take off on water, the water isn't moving in an opposite direction underneath the plane like a conveyor belt. The plane's thrust would push off on the water creating an action-reaction effect…
                        The plane’s thrust doesn’t push off the water. It just pushes. A prop or jet accelerates air rearward. The action of “pushing” the mass or air rearward causes a reaction force that pushes the engine (and aircraft) forward.

                        Originally posted by SiriusRIMZ
                        …the plan gets force from the engine, it pushes off an goes…
                        That is correct, whether on the water or a conveyor, moving or not.


                        Originally posted by SiriusRIMZ
                        …However, when the plane's engines thrust up to take-off speed, the belt just moves equally and oppositely…
                        True, but since the belt exerts no force on the aircraft (assuming negligible rotational inertia and bearing friction) it has no effect on the aircraft’s reaction to engine thrust so the aircraft will move forward normally.


                        Originally posted by SiriusRIMZ
                        …The plane is moving, but it cannot get the reaction force to take off, insted the action and reaction forces are cancled out….
                        It can and will move due to the reaction force of engine thrust. There are no forces generated by the conveyor so it cannot cancel anything.


                        Originally posted by SiriusRIMZ
                        …Example, put a car on a dyno, its engine is providing force to the wheels and the ground is moving in opposite direction. It doesn't matter how far the car is going, wind wont drag on the car, its not moving. …
                        This is because a car’s thrust comes from applying torque to it’s tires, which in turn develops a reaction force at the contact patch on the pavement. Aircraft tires are freewheeling, not driven. The aircraft’s engine generates thrust at the exhaust. The conveyor has no effect.


                        Originally posted by SiriusRIMZ
                        ….Funny thing is, You can be in your Buggati Veyron going 250, and not feel any wind resistance on a Dyno, so same effect with the plane. It wouldn't go anywhere…
                        It is not the same for the plane. The plane doesn’t push against the pavement (or conveyor). The plane develops thrust in the air, not at the tires.


                        Originally posted by SiriusRIMZ
                        …Even if there was wind to drag it, it would not contain the push-off needed to stay in flight…
                        Thrust comes as a reaction to the action of accelerating mass rearward. For a prop it’s the mass of ambient air pushed by the blades. For a jet it’s the mass of ambient air brought into the intake, heated by combustion with fuel and then expanding from the outlet nozzle. For a rocket it’s the mass of gasses from combustion of fuel and oxidizer expanding from the outlet nozzle.

                        If there had to be something to “push-off” of rockets wouldn’t work in the vacuum of space.


                        Originally posted by SiriusRIMZ
                        …This is really making me think, I can prove myself wrong just as eaisly as I can prove myself right.
                        If you start with the same conditions and apply the laws of physics correctly you will always come to the same conclusion. That’s the beauty of physics.


                        PC.

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                        • #42
                          Originally posted by Jeff Smith
                          …And with asking our Engineers anything, The answer would likely depend on what kind of engineer. We have production, structural, avionics, Flight Test. and 20 or so other types of engineers. We would likely pull 20 answers out of them.
                          As I said above, “If you start with the same conditions and apply the laws of physics correctly you will always come to the same conclusion.”

                          When you to see engineers and scientists arguing over this sort of thing it’s usually because they’re assessing the conditions differently but it may be that somebody has the physics wrong. It happens. We’re human. Physics, i.e. nature and the universe, always works. So if somebody has it wrong it will turn up in the analysis or an experiment.

                          With any technology it’s best to ask somebody who has expertise, or at least some education, in that area. Not all engineers are trained in the same areas of technology or perhaps some who were trained went into other specialties and forgot it.

                          Obviously your best bet would be to talk to an aeronautical, aerospace, mechanical or flight test engineer. Any systems engineer should know it. A structural engineer will have learned it (but if they’ve only thought about static structures all their working life may have forgotten). Avionics guys? Well, about half the electronics guys I know are interested stuff outside the wires. The other half wants absolutely nothing to do touchy feely things like engines or airframes. Production engineers? All bets are off. They come form far too many backgrounds and there is way, way, way too much variation in their technical level to make any generalizations at all. Most Software engineers won’t even try; it’s a hardware problem.


                          PC.

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                          • #43
                            I have to quote my post which was the 4th reply to this thread...

                            Quote....
                            Put a skateboard on a conveyor belt, and push it with a stick...
                            Does it matter how fast the conveyor is going?
                            All that matters is how hard you push on the stick (jet engine)...


                            Quit thinking of the plane accelerating forward on the conveyor, think of it accelerating forward in the body of air surrounding it. All the wheels are doing is holding up the weight, not holding it back........

                            Most planes have a low power to weight ratio, but they will still overcome the rolling resistance of the tires sitting on the conveyor no matter how fast it turns. And it will accelerate forward in the body of air...
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                            • #44
                              Turn the equation around.

                              How can an airplane land on an aircraft Carrier when it is moving forward.
                              And yes you can land a plane without the arresting cable...


                              If a fly is flying in your car while your sitting still, and you nail the gas pedal, will the fly go forward with the car? NO! First reaction will be to hit the back window.
                              WHY? because the fly's movement is related to the air surrounding it, not the tires on the ground...
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                              • #45
                                Originally posted by Desertdawg
                                Turn the equation around.

                                How can an airplane land on an aircraft Carrier when it is moving forward.
                                And yes you can land a plane without the arresting cable...


                                If a fly is flying in your car while your sitting still, and you nail the gas pedal, will the fly go forward with the car? NO! First reaction will be to hit the back window.
                                WHY? because the fly's movement is related to the air surrounding it, not the tires on the ground...
                                Sorry DD, but you're examples are flawed. In the case of the aircraft carrier, the ship is moving at a constant speed and can be compensated for in the landing calculations of the pilot so that even though the ship is moving, the calculations can realign the ship's forward speed to equal "0." Think of two cars on the highway. The first car stays at exactly 60 mph. The second car can, by speeding up or slowing down, change the speed of the speed of the first car relative to itself. If car #2 is also going 60 mph, car #1 has a relative speed of 0 mph. If car #2 has a speed of 20 mph, then #1 has a relative speed of 40 mph. If car #2 is traveling at 75 mph, then #1 is moving backward at a speed of 15 mph relative to the motion of car #2

                                As for your fly, the car and everything in it, the occupants, the air and the fly all accelerate and decelerate almost instantaneously to each other. If you rapidly accelerate with the fly buzzing your ears, AT MOST the fly will move 1/2" or so before the air in the car and therefore the fly, also accelerate to match the speed of the car.

                                Your example of the fly (taken to the extreme) suggests that in a front end collision, the passengers should only move forward slightly until they bump the dashboard since they are traveling at a speed relative to the interior of the car.

                                Back to the treadmill... The plane does not rely on the wheels for motion, we all agree. HOWEVER, even if you take away the wheels and use skids, or pontoons (in the case of the seaplane), the plane is still permitted to move forward in space (air and ground) until lift velocity is reached AS LONG AS THE AIR SURROUNDING THE PLANE REACHES LIFT VELOCITY IN RELATION TO THE PLANES FUSILAGE. The treadmill prevents ANY forward motion of the aircraft therefore no lift is created.

                                The rocket in space is a nice, but misleading example. The force of the engine's thrust backward allows the rocket to travel forward, in relation to the space around it. Space itself is assumed to be motionless, with only the solid bodies within space having motion. Therefore in the motionlessness of space the rocket moves forward.
                                Don
                                12/27/2015
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