Can the Plane Take-Off?

[DonRotolo]

Originally Posted by Wayne Doenges

end the thread

What, and spoil all the fun?

OK, here's a variant: Put wheels on a rocket (say, a Saturn V) and a veryical conveyer belt- will it go up?

Of course it will. So will the airplane. The force of the propulsor (propeller, jet engine, rocket engine) is what moves the plane - wheels are irrelevant to flight (ever hear of a ski plane, or a PBY?)

Don

[Protronie]

Originally Posted by Wayne Doenges

Mythbusters proved that the plane can take off. Nuff said, end the thread

This thread will NEVER die!

What if the plane was jet powered instead of a prop plane?
Say like a MD-80 with the engines mounted on the tail... no air would be pushed over the wings... so no take off.

(that should be good for 100 post at least )

[Graham Donaldson]

But still, the thrust created by the jet engine would move the plane forward, thereby pushing air over the wings. The wheels, same as a prop plane, would just spin faster.

[whytheheckme]

Originally Posted by robotcanuck1676

But still, the thrust created by the jet engine would move the plane forward, thereby pushing air over the wings. The wheels, same as a prop plane, would just spin faster.

Indeed, instead of the groundspeed of the wheels being, say, 100MPH, they would simply be 200MPH, with the motion forward as an observer at 100MPH.

Think about a vertical lift takeoff plane. It has thrusters that hold it in the air before it takes off, and is able to do so. Having supports down with wheels at the end (essentially frictionless, compared to the amount of force we are talking about here), doesn't matter. They will just spin faster as the jet is propelled forward.

-Jacob

[EricH]

Originally Posted by Protronie

This thread will NEVER die!

What if the plane was jet powered instead of a prop plane?
Say like a MD-80 with the engines mounted on the tail... no air would be pushed over the wings... so no take off.

(that should be good for 100 post at least )

As I said earlier, the wheels have nothing to do with it. The plane moves forward and takes off.

Here's something to think about...on my Aero Design team, we coated our axles and wheels with graphite. LOTS of graphite. 4 layers of pencil lead on the axle easily, put some graphite powder inside the wheel, rub the stuff inside the wheel onto the axle. Just before each flight, put a little more powder in.

Would we have done that if the wheels had anything to do with takeoff, other than keeping the prop off the ground and letting the plane move without resistance? No.

[Rick TYler]

Originally Posted by Protronie

Yes but... the thrust from the prop pulls the plane forward so air rushes over the wings to produce lift.
Would the prop-wash alone be enough to produce the required air moving over the wings flight surface in order to produce the lift needed?

No, it doesn't. The prop wash can give a little extra lift, but it's trivial compared to the speed of the aircraft.

Why is this even a three-year question? Assume the airplane is sitting still on a frictionless surface with its wheels spinning at an infinite speed. This is pretty much the situation described in the "conveyor belt" scenario. When thrust is applied, the airplane with infinitely-fast wheels will still take off, right? The rotational speed of the wheels is irrelevant (as others have said -- ski and float planes still work).

By the way, some people have invoked bearing friction to explain why the airplane won't move. If you want to bring real-world physics into this, there is no way to design an runway-sized conveyor belt that would respond instantly to the speed of the aircraft. Inertia and control loop delay would mean that the thought problem isn't possible. If you invoke bearing friction, you have to design an inertia-less conveyor.

[Waiakea12]

I think that it all depends on the size, Power, and overall weight of the plane. The "runway" size also matters.

WHAT ABOUT THE FIGHTER PLANES THAT CAN TAKE OFF AND LAND VERTICALLY AS WELL AS HORIZONTALLY? DOES THIS APPLY TO THEM??

(Don't kill each other over this one!!! lol)

P.S.- I'm a little bit late in this thread, sorry.

[EricH]

Originally Posted by Waiakea12

I think that it all depends on the size, Power, and overall weight of the plane. The "runway" size also matters.

WHAT ABOUT THE FIGHTER PLANES THAT CAN TAKE OFF AND LAND VERTICALLY AS WELL AS HORIZONTALLY? DOES THIS APPLY TO THEM??

(Don't kill each other over this one!!! lol)

P.S.- I'm a little bit late in this thread, sorry.

Actually, plane size doesn't matter. The thrust amounts are calculated to lift each plane type. See, plane weight and size are taken into account when planning for power (thrust is the technical term on aircraft). There is always power to spare--that is, the plane will be able to take off at maximum weight, guaranteed, or the mechanic or designer is looking for a new job.

But yes, the runway size matters. The Mythbusters started with a conveyor that was too short for their R/C plane, and it went off...

And I already suggested the VTOL aircraft. That's cheating!

[BigWhiteYeti]

If any of you have watched Mythbusters recently, they proved it can be done! Think about it. Planes derive their power from propellers or jets, each of which move air. This forces the plane forward relative to the air, not the ground. The wheels are free-spinning, so they will move twice as fast when the plane takes off upon reaching its take-off airspeed. Airspeed and groundspeed are totally different principles.

As for the Mythbusters, they pulled a really long mat with a pickup and had an ultralite take off successfully. Look it up!