A jet plane on a large treadmill

[DBdude]

34 pages debating a poorly worded question

The answer depends on the assumptions you make.
You can’t keep the plane stationary without applying brakes.

Frictionless brakeless wheels make the treadmill irrelavent. In such a case, with the engines off, the treadmill can run forward or reverse 10,000mph and the plane does not move. It also does not take off since the engines are off, it’s not moving, and hence no lift.

When you add the condition that the treadmill keeps the plane from moving through space, you necessarily assume brakes are being applied to counteract the engine thrust. Whether the treadmill moves or not, the brakes keep the plane from taking off.

ASS U ME

now you have done it

the whole thing boils down to the air speed of the air flowing over the wings

if the jet is stationary then it will not take off

if the jet wings get enough lift from movement it will fly.

for example, if take off speed for the jet is 100 mph and the plane is moving 100 mph forward and the treadmill is moving 100 mph the other way, then the wheels are moving at 200 mph and the jet lifts off

see myth busters

[iceman]

Maybe it's like a cool built-in treadmill so it's flush with the ground and they can just push (or yes, pull) the plane onto it. You know how expensive that thing would be? Yikes.

If you put a jet plane into a frictionless lap pool, would it swim?

[k2skier112]

The jet engines don't push the ground, they push on the air, atmosphere. The plane will move regardless of what it's sitting on

[iceman]

Well then the front wheels would fall off the treadmill and it would be a mess (unless of course it was my patented hyper-expensive in-ground jet-sized treadmill of course). That's why the lap pool is such a good idea. The water puts the engines out and everyone can just hang out and drink a few beers or whatever.

[mcski]

Will the poo stay on the treadmill when the toilets in the lavatories get flushed?

[jono]

Yes. But if you use a powerful enough treadmill it will blow the tires out and light the magnesium wheels on fire and then the poo streak and the rubber treadmill surface will all burn together. So yeah, the pool would be better.

[Gepeto]

Yea, but then you got those that pee'd - in the pool (nasty fukers)

is the pool chlorinated? And if it is, does it affect the density of the water in a substantive way and impact velocity

[stuckathuntermtn]

The jet engines don't push the ground, they push on the air, atmosphere. The plane will move regardless of what it's sitting on

Assume a plane on floats going up river. It could only take off from a river if the engine can push the plane faster than the river. Assuming the river is the treadmill, if the river keeps going faster and faster and the plane's power goes up, how would it achieve any airspeed? It would be up on step, it's effective ground speed would go up, however it's airspeed would remain at zero (or a little greater if there's a headwind).
If it didn't matter how fast the treadmill was moving in the opposite direction, an aircraft would never get stuck in mud or slush or snow.

That Mythbusters thing was BS. Some of their stuff is a little too over-thought while missing some important oversights.

You guys should talk to some actual pilots.

[zartagen]

Will the poo stay on the treadmill when the toilets in the lavatories get flushed?

Depends. Northern or Southern hemisphere?

[Svengali]

^^ frictionless floats?

[Ted Striker]

Assume a plane on floats going up river. It could only take off from a river if the engine can push the plane faster than the river. Assuming the river is the treadmill, if the river keeps going faster and faster and the plane's power goes up, how would it achieve any airspeed? It would be up on step, it's effective ground speed would go up, however it's airspeed would remain at zero (or a little greater if there's a headwind).

In your scenario the airplane's ground speed remains at zero as well.

Its waterspeed would equal the flow of the river.

The difference between a river - or any body of water - and a hard surface is friction.

[DBdude]

That Mythbusters thing was BS. Some of their stuff is a little too over-thought while missing some important oversights.

You guys should talk to some actual pilots.

that's why I brought it up - the plane is moving. they didn't prove anything

[Harry]

Are there sharks in the pool ? That might make a difference.

[DJSapp]

You guys should talk to some actual pilots.

Yes, pilots understand that their planes don't fall out of the sky when the wheels go up. The wheels are a low friction platform. The engines drive against the air.

Your float plane argument assumes that the force from the water is somehow equal to the friction force of a wheel rolling on concrete. It is not.

[Ted Striker]

Are there sharks in the pool ? That might make a difference.

or a sharknado!

[jono]

... a wheel rolling on concrete.

This treadmill gets more unique with every page.

[wyeaster]

i probably missed it but has the helicopter on a treadmill problem been addressed yet?

[jono]

I thought that one involved putting the helicopter in a box or something. Shirley, on a treadmill it should be a gyrocopter?

[wyeaster]

ok what about a helicopter on a treadmill ON A DOCK FLOATING IN THE MIDDLE OF THE OCEAN???

[abraham]

i probably missed it but has the helicopter on a treadmill problem been addressed yet?

Put a helicopter on a fan. The fan spins at the same speed as the rotor blades but ok the opposite direction. Does it take off?

[Core Shot]

I think you put Schroedinger’s cat in a helicopter, in a box.

[wyeaster]

Put a helicopter on a fan. The fan spins at the same speed as the rotor blades but ok the opposite direction. Does it take off?

damn you

[jono]

Put a helicopter on a fan. The fan spins at the same speed as the rotor blades but ok the opposite direction. Does it take off?

This might be the one where the pilot gets super dizzy and pukes into the box--possibly killing the now-certainly-dead cat.

[east or bust]

Put a helicopter on a fan. The fan spins at the same speed as the rotor blades but ok the opposite direction. Does it take off?

is the helicopter's blinker fluid at the correct level?

[stuckathuntermtn]

Put a helicopter on a fan. The fan spins at the same speed as the rotor blades but ok the opposite direction. Does it take off?

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