Did we ever discuss it here? One of the pre-wipe topics I assume?

Its not even a brain teaser. No airflow across the wing no lift. Was rehashed yet again on "Ask a Pilot" on salon.com this week.

Didnt someone do a video for this with scale models?

A harrier jump jet would have no probs. But for a normal plane wouldnt it move forward regardless? Its pushing against air, all the wheels are doing is spin around, they dont contribute anything to forward motion, on a converyor belt theyd just be spinning much faster than normal. The engines push against air, not the runway.

edit: thinking about it, Id put a tenner on it taking off.

Also, you could just point the plane backwards, brakes and flaps on full, and spin the belt up to 300mph.

Wheels on planes are unpowered but have brakes.

Just to be completely off topic there was a couple of reports of people being stung by scorpions on US planes recently.

I wonder if they are going to make a movie about that.

not bitten by snakes then? lol

yeah of course it would take off, engines produce thrust and the wheels freewheel

Two conflicting opinions already......


:mrgreen:

All the conveyor belt is going to do is make the wheels spin a bit more - the plane will still take off.

In fact the conveyor belt can spin backwards at twice the speed that the plane moves forwards - the plane will still move forwards - its wheels will just be spinning a bit faster than normal.

(we do have to assume that the tires dont burst etc.. )

Quote from: maximusotterIts not even a brain teaser. No airflow across the wing no lift. Was rehashed yet again on "Ask a Pilot" on salon.com this week.

Dude its got you assuming the wrong answer - how is there going to be no airflow across the wing - its a plane not a car with wings.

Chris can you edit you first post to include the question - Im assuming it is this one....

Quote"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

Im not sure youre right there m8.

There has to be airflow across the wings for the plane to lift. The airflow is normally generated by forcing the plane to move through the air at a certain speed.

If the plane is on a runaway that is moving in the opposite direction at the exact same speed as the plane then the relative travel of the plane to the air will be zero; the plane will be motionless (think running on a treadmill) and there will be no airflow across the wings to generate lift from.

how is a moving floor going to stop the plane moving foward when the thrust is genereated by the engines moving air on the wings?

As you state a planes thrust comes from its engines and not the friction/drive of its wheels.

If the conveyor is travelling at an equal speed to the plane but in the opposite direction (treadmill) then no matter how much thrust the plane uses the conveyor will cancel out any movement.

how? the wheels are freewheeling, like a shopping trolley rolling down a hill

the belt could be doing mach 2 for all it matters, the plane will still accelerate and take off, yeah the wheel bearings might cook but thats a minor detail

when youre running on a treadmill do you get "wind blowing" into your face due to the speed at which youre traveling ?

Let me put it another way...
If you put the plane on a big "car" jack so that the wheels were not touching for the floor/conveyor or anything and stuck the engines on...would you take off ?