I have heard takeoff distance isn't even increased with an upstream takeoff in a float plane.The show will be worth watching just to see the details of how they did it- how do they match the speed of the aircraft with the conveyor etc... and how did they manage a quarter mile moving conveyor belt within budget constraints???Best Regards, Donny :-waveFLYing? It's cool. Trillions of birds and insects can't be wrong.

>>Remove the analogy of a treadmill and a wheeled aircraft. In its place put a float plane and a rushing river. Prevailing winds make it necessary to depart "upstream". Will the float plane take off? Yes. Why? Because the propulsion system of the aircraft is completely independant of the ground surface (unlike a car). In this example the river may have more effect on the A/C, as there is much more friction involved, but in the end the plane will have no trouble reaching V1 (80 - 110 kts) in spite of the river.<

>plane is not going to get in the air if a treadmill is>matching the speed of it's wheels. Yes, but why bother to consider such a case, it is totally uninteresting from the physics point of view and completely misses the main thrust of the problem. It is in fact a 'trick' question. In my opinion someone made a mistake in relaying this puzzle and this is how it originated.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

Right, the question should not be whether or not it can fly, but instead "Can a treadmill stop a normal powered plane if it has free spinning wheels". That is the question that people need to look at. For anyone discussing lift and takeoff speed.... stop. Nobody is arguing the basics of flight :)If we put a 747 on a treadmill and add enough power to get it to taxi at 10 knots on a normal runway, then set the treadmill spinning 10 knots... is the treadmill going to hold a 747 in place? I think the engines will win out easily :)

Thank god for bandwith, eh Tom!JimCYWG

>Right, the question should not be whether or not it can fly,>but instead "Can a treadmill stop a normal powered plane if it>has free spinning wheels". That is the question that people>need to look at. I agree. But it is far more sexier to ask whether it will fly than if it can be stopped. ;)Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

Okay, let's try a different angle on this, if we put the plane on the treadmill, on idle, so it won't go forward, then move the treadmill backwards, the plane (no matter what anyone says) WILL go backwards along the treadmill. Okay, now we bring the engines up to taxi at the speed of the treadmill, the plane will not move forwards suddenly, it will stop, and sit stationary until we either add more power, or speed up the treadmill, in which case the plane has to go backwards again until more power is added. Keep doing this until the plane is taxiing at 80 Knots, the treadmill is also doing 80 Knots, and the plane will still be on the treadmill stationary, Unless you add more power to make it move again.The analogy of 2 people walking by the side of the treadmill doesn't work here, they aren't 'on' the treadmill, erego they are not affected by it, the aircraft is fully on the treadmill so it's own weight comes into play as well.Also the guy from the show said that the pilot and entire flying club got it wrong. My guess would be that most pilots used in that capacity have a physics degree, you used to need it to get into the RAF here in UK, don't know if that's the same now though.

Your answer, and other similar answers, are wrong because they ignore the fundamentals of physics. Newton's Law states that F = M * MwhereF = forceM = MassA = acceleration.Therefore the acceleration is given by:A = F / MThe force on a aircraft is F = T - D - RwhereT = Thrust (from the engines)D = Aerodynamic DragR = Resistance (at the wheels)If the aircraft is stationary and Thust is applied then it must accelerate unless R = T. If it accelerates it must move forwards and not remain stationary. The only way it can remain stationary under all conditions is if R = T - D. There is absolutely no known physical mechanism that can make the Resistance at the wheels exactly equal to Thrust minus Drag. Your argument fails because it implies that the Thrust is set exactly equal to the Resistance and not to the maximum Thrust. In that case the aircraft would remain stationary and not achieve any speed, and certainly not 80kts. Observing an aircraft taking off shows that the maximum Thrust is much greater than the Resistance.

>the plane will not move forwards suddenly, it will stop, and>sit stationary until we either add more power, or speed up the>treadmill, in which case the plane has to go backwards again>until more power is added. Keep doing this until the plane is>taxiing at 80 Knots, the treadmill is also doing 80 Knots, and>the plane will still be on the treadmill stationary, Unless>you add more power to make it move again.Unfortunately it is a completely fallacious argument and shows complete lack of understanding of basic forces involved in this experiment. But I am not going to counter it - 'mgh' did it very well above.>Also the guy from the show said that the pilot and entire>flying club got it wrong. My guess would be that most pilots>used in that capacity have a physics degreeOh no they don't. Pilots most often have very rudimentary education. Actually pilots, engineers or computer programmers are usually worst "professionals" in correctly answering this question. Fortunately I have not yet met a physicist with at least M.S. that would get it wrong.Michael J.

John...<>EXACTLY .. I'm glad you could detect the important concept of my analogy. The reason the analogy was chosen is to pound into your head the FACT that the power source for the airplane is ALSO NOT (except for a very tiny degree) on the treadmill (once you do a free body diagram of the system). In BOTH cases (the silly problem of the airplane and the equally silly analogy at the gym) a minor force is felt from the treadmill system. The guys beside the treadmill get a tiny load rearward, which they completely ignore. Similarly, inertia and friction provide a minimal load to the propellor/air system...which the airplane completely ignores.Bob

"Back to the original issue since I've never commented on it before, and I'm not sure if I've got the scenario right, but a plane is not going to get in the air if a treadmill is matching the speed of it's wheels. You have to have "positive" speed passing over the wings surfaces to generate lift, forward motion or really fast wind, simple as that. I don't know how this is an argument.I disagree. You are implying that the wheels provide the forward motion the aircraft needs to take-off. They don't. The aircraft's propulsion system is entirely independent of the wheels, and the treadmill could be spinning at 1000 miles an hour and the aircraft would still move forward and take off providing that the wheels could spin at that velocity without melting...a whole nuther can of worms! :-)bt

BT,Please be careful. This is a trick question completely unrelated to our original problem. His requirement "treadmill is matching the speed of the wheels" can't be satisfied by a flying airplane (you can work out simple algebra to see it). Again, like I was trying to point out - this is a version of the problem totally unrelated to the question "if an airplane can take off". Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

>The analogy of 2 people walking by the side of the treadmill>doesn't work here, they aren't 'on' the treadmill, erego they>are not affected by it, the aircraft is fully on the treadmill>so it's own weight comes into play as well.Yes, it does. Assuming a normally powered airplane with a jet or prop, the force from the engine(s) acts on the air, not on the treadmill. A person jogging on a treadmill has their feet hit the treadmill itself and will stay in one spot. All the running force is ON the treadmill itself. A car on a treadmill will also have the wheels acting ON the treadmill itself. A jet will put force on the air AROUND the treadmill, not act on it itself. Grab your sneakers and run on the treadmill... you stay in one spot, right? Or course! Next, put on some roller skates with well oiled wheels, and strap a rocket to your back... think about this.. what is different? Which one is closer to simulating a plane on a treadmill?

This is totally related to our origional problem. The treadmill is matching the speed of the wheels. Simple math won't work. Albert Einstein is scratching his head. Tom, you got to get into the discussion. Forget the bandwidth man.JimCYWG

>This is totally related to our original problem. The>treadmill is matching the speed of the wheels. No, it is NOT.Depends what you are interested in - whether the airplane will take off from a moving treadmill (regardless how it is moving) or whether you insist on "trd. matching the speed of the wheels". If you insist on the latter then the speed of wheels is VA+VT (VA - air speed, VT - treadmill speed). In order for VA+VT to be equal VT the VA must be zero - the only algebraic solution - so the airplane can't fly by a simple mathematical trick. It is as if someone said "you can't cook a steak on a cold grill" - this is a correct statement but it doesn't prove that you can't cook a steak on a grill, if you want to cook it you have to remove restriction that grill must be cold. The same way the sentence "airplane won't takeoff from a treadmill that matches the speed of the wheels" is correct - but it doesn't mean that airplane won't take off - because during such takeoff no such artificial speed matching will occur. Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg