Can the Plane Take Off ?

[Corey]

Everything would be at a standstill! (catch 22)

BINGO finally it has got home it is a paradox

[Fat Audi 80]

It may be worded badly but the words state that the conveyer matches the planes speed not the wheels therefore the plane stays stationary.

We can all assume this and that but the original wording is what was up for debate.

It says it matches the planes speed but in reverse so if the plane starts to move forwards at 10 mph initially then the conveyor will run at 10 mph in reverse, so the wheels of the plane will a combined speed of 20 mph relative to the earth....

Yes, the question is a superbly badly worded piece of tripe!!

But we are all still talking about it!

[Ross]

It may be worded badly but the words state that the conveyer matches the planes speed not the wheels therefore the plane stays stationary.

We can all assume this and that but the original wording is what was up for debate.

Then how can the conveyor be moving to match the planes speed if it's stationary? It HAS to mean the wheel speed, or else it contradicts itself because the plane's speed relative to the ground is zero when the conveyor is moving. It's a logically impossible system. And, there's no way for the conveyor to force the plane to stay stationary anyway. My last 0.02c on this thread, my head feels like it's gonna implode

[Sidspud]

If it was a Harrier jump jet it would take off! :mischeif:

[flossymeister]

I suspect Sidspud has got the right answer.

The problem with this whole debate is that "speed" is a useless term for projectile modelling, which is what this is effectively. You need vectors, which would give direction and therefore distance travelled by the plane. then we would know whether the plane is actually moving or not. If the plane does not move, then it does not fly. you cannot generate lift without air passing faster over the top of the wing than the bottom, which drags air from above down as well and generates lower pressure over the top of the wing. no wind (i.e when you are running on a treadmill) = no lift. However, if the plane can achieve take-off VELOCITY (NOT speed, as VELOCITY would then tell us where its going), then it will take off.

The original question is too ambiguous to be sure.

Would be interesting what SR71 has to say on this, since he is a pilot... :mischeif:

Tim

[hiltoa]

The plane takes off, period.

It produces thrust by shifting air, whether it be through a jet engine or with a prop. Its wheels just stop it from gouging big holes in the ground, they have nothing to do with propulsion, so the conveyor has no effect on the plane's movement, or ability to fly (except for a negligable increase in friction due to the wheels spinning faster than normal).

Ride a bike using pedals on a speed matching conveyor = no forward motion and a steady conveyor speed.
Ride a bike on a speed matching conveyor using a jet engine = lots of forward motion and an exponentially increasing conveyor speed.

Fin.

[AndyP]

Where's Jay when you need him?!!

The plane will take off though

[quattroTurbo]

Can't imagine it taking off. The thrust only moves it forward not up and if it can't travel forward because the moving runway prevents this then how can lift be generated. Very fast moving air has to travel over the wings to generate lift.

[A1QSHIP]

THE BLOODY PLANE TAKES OFF IF THE THRUST IS GENERATED BY THE ENGINE, IRRESPECTIVE OF THE WHEELS. YOU COULD MOUNT THE PLANE ON SKIDS AND IT WOULD STILL TAKE OFF! NEXT QUESTION PLEASE.

[MidnightBlueS2]

Now what about the 'Egg' and the 'Chicken' ?

[Ross]

Hmmm... you'd probably have to grease the runway too.

Do you think we could persuade the RAF to invest in a big conveyor belt to prove all those doubters wrong who expect the plane to sit there and go nowhere??

On a side note, what tv program was it on recently where they had a 747 with it's brakes full on, with full thrust it just sat there? Rather impressive... any chance of getting those brakes on teh S2?? C'mon BRY...

IIRC they mentioned that they could only hold the throttle open for x number of seconds, coz once the engines were up to speed the immence thrust would start tearing chunks outta the runway! A car then proceeded to drive behind it and get ripped to shreds...

Ross

[hiltoa]

I seem to vaguely remember a 2cv being blown over by thrust from a jet - was it an old topgear maybe?

[Bibby]

A plane is standing on a runway that can move (some sort of conveyer belt). 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?

Discuss.......



Well can it ?

The aircraft will only take off if there is airflow over the aerofoils (to generate lift) plus enough thrust to overcome gravity. If the aircraft is stationary (only the wheels moving) in relation to the ground, it will not take off under any circumstances, unless it's something like a Harrier as suggested by Sidspud.

If the aircraft is actually moving through the air (ie wheels moving twice as fast as the opposing conveyor belt) then it could take off, providing gravity is overcome by lift.

I can't understand all the confusion here, it's pretty simple aerodynamics.

Oh yeah, I'm a qualified aeronautical engineer.

[mreinders]

http://www.straightdope.com/columns/060303.html

[Ski]

Can it f**k. There is a reason why a place has wings.