Will it Fly??

[Lowell]

Try looking at it like this:

The airplane moves forward from thrust at 10mph, the runway goes aft at 10 mph and the airplanes wheels are turning over at 20 mph.  Lets assume liftoff speed is 70 mph.  Then when the airplane is going 70 mph forward, the runway treadmill is going aft at 70 mph and the airplanes wheels are rotating at 140 mph, and the airplane flies away.

 

[Tom]

Where does the lift come from  ???

Carson, my money is still on Don, but I can't match your bet. Does that mean I lose my $1? 

 

[Ned]

The wheels are free wheeling, not powered, and have no bearing on the forward motion of the airplane.  It's forward motion comes from the propeller acting on the air which is not coupled to the treadmill or the wheels.  The lift comes from the forward motion through the air, just like a normal runway takeoff.

If the wheels had zero friction, then as the runway moves backward, the wheels would turn but inertia would keep the airplane stationary relative to the air.  The propeller turning then would pull the airplane forward as usual.  Replace the propeller with a rope attached to a winch off the far end of the runway and as the rope pulls the airplane forward, it will eventually take off, regardless of the wheels and the moving runway.

 

[carson]

Tom, I'll have mercy on you. I prefer to play with big-league guys  ;D ;D ;D

No offense, you are still my hero. 8)

carson FL

 

[Tom]

Thanks for the financial relief Carson.

I'm just glad that some of the folks around here weren't flying all those commercial planes I've been on  ;D

 

[Tom]

Sounds like a sailboater's physics. Here's a visualization of that theory  ;D

Oops, wasn't Chet a sailboater  :-[

 

[Ned]

Sailboats don't work on wind, they work on beer

 

[Tom]

Plus some rearward thrust from the effects of the beer  ;D

 

[Tom]

From the experts at NASA: airplane lift.

 

[Chet18013]

I found this question on NikonCafe, a photography forum I frequently visit. I thought it would be fun to see what happened in the RVForum when it was asked here. So far, the NikonCafe has had over 4000 views of the thread and 160+ posts discussing it.

I think one of thei NikonCafe forum members did the best job of stating his reasons on why it would fly.Following is his answer. It is sure the answer I'll bet on!

See: HERE then scroll down to post #60.

Anyhow, it's been fun watch the thread progress, both here and at the NikonCafe. Hope you have enjoyed it.

Chet18013

 

[Karl]

O.k. Guys, I've changed my mind. I was thinking about driving in winter in Wisconsin on ice, and the light came on. The treadmill is just like a sheet of ice; virtually no resistance, which is why it's difficult to start/stop/turn. But an airplane doesn't depend on the wheels turning to move forward, and it will accelerate as fast as if on concrete and will eventually take off and fly.

 

[Ned]

Exactly what I said in my last message on the topic.

Chet, the car can't possibly average 60mph for the 2 miles.

 

[KodiakRV]

...My previous answer was after an evening of food and drink with the neighbors, and that's my excuse

Is this the kind of thing you full-timers sit around the campfire talking about at night?    ;D 

 

[Ned]

Nah, we talk about black water tanks and those not present.

 

[Karl]

Exactly what I said in my last message on the topic

Yabut I was having my after-lunch nap when you posted it.

 

[Ned]

That's what you get for sleeping on the job.

 

[John From Detroit]

Sorry, Frank, but no.  If you're on a treadmill, you don't feel any air moving past you, and neither would the airplane.  Ergo, no lift.  Get on a treadmill, get running at a comfortable speed and stick your hands out and see if you feel any air pressure.

At the speeds you move, this is true

At the speed a plane can move, You will feel air moving past you, in fact. I just realized something.

The plane wheels will not turn AT ALL unless the plane is moving through the air, Thus the treadmill will NOT MOVE unless the plane is moving through air, We are talking a standard tarmac runway here.  THERE IS NO POWER TO THE WHEELS.

So unless the plane is moving through the air, the wheels are NOT TURNING

 

[Tom]

So unless the plane is moving through the air, the wheels are NOT TURNING

Does that mean that the wheels do turn when the plane is airborne  ???

 

[Lowell]

This was a fun problem to think through, anyone have more of these?

 

[John From Detroit]

For a time tom, yes they do, for a time, then they stop

I'm not quite being honest when I say there is "NO" power to the wheels

There are brakes  (kind of negative power)