Just wondering

[Sancho]

A conundrum for all.

You have an aeroplane sat on a huge conveyor belt. The conveyor belt is computer controlled such that its speed is always the same as that of the aircraft - only backwards. I.e. If the aircraft is moving forwards at 10mph (relative to a fixed point on the ground), then the conveyor will move backwards at 10mph. Will the aircraft be able to take off?

Assumptions:
1. The aircraft is otherwise normally capable of flying just fine, and the pilot is normally capable of flying this aircraft just fine.
2. The conveyor belt runway is more than long enough that if the belt didn't move the aircraft would have ample room to achieve take-off. There are no obstructions that would affect a normal take-off.
3. The runway is at sea level, the air is still, and the conditions are perfect.

OK, so, will it fly or not? Please explain your answers if possible.

[Rustinho]

A conundrum for all.

You have an aeroplane sat on a huge conveyor belt. The conveyor belt is computer controlled such that its speed is always the same as that of the aircraft - only backwards. I.e. If the aircraft is moving forwards at 10mph (relative to a fixed point on the ground), then the conveyor will move backwards at 10mph. Will the aircraft be able to take off?

Assumptions:
1. The aircraft is otherwise normally capable of flying just fine, and the pilot is normally capable of flying this aircraft just fine.
2. The conveyor belt runway is more than long enough that if the belt didn't move the aircraft would have ample room to achieve take-off. There are no obstructions that would affect a normal take-off.
3. The runway is at sea level, the air is still, and the conditions are perfect.

OK, so, will it fly or not? Please explain your answers if possible.

Assuming a spherical aeroplane in a vacuum, with a frictionless conveyer belt, no.

[ROMEROTECH]

The thrust of an airplane engine pushes against the air, not the ground therefore it matters not how fast the belt is moving. It will take off no probs.

[g3po]

No it wont take off because it is in fact not moving relative to the fixed point in the ground therefore will not be moving through the air. Thats if I understood the question right.

[puddlesurfer]

The thrust of an airplane engine pushes against the air, not the ground therefore it matters not how fast the belt is moving. It will take off no probs.

Yarp - I concur, the wheels on an aircraft are passive the prop/jet pushes the plane, it takes off due to bernouli's princeiple when the air passing over the curved upper surface of the wing is moving faster than the Flat(ish) underside creating lower pressure above the wing and higher pressure under -lifting the plane

[yoshie]

'O' dear HLS has officially died on it's arse.


http://www.hiluxsurf.co.uk/showthrea...=conveyer+belt

[Vultch]

No, there is no air speed, the aircraft is stationary with respect to its surroundings (including the air around it) thus no airflow over the wings - no lift or flight

[MWS]

Yarp - I concur, the wheels on an aircraft are passive the prop/jet pushes the plane, it takes off due to bernouli's princeiple when the air passing over the curved upper surface of the wing is moving faster than the Flat(ish) underside creating lower pressure above the wing and higher pressure under -lifting the plane

The aircraft remains stationary. Lift will only occur if the wings are travelling forward through the air.....So, no, the plane will NOT take off....Cheers....Mick.

[Rustinho]

The thrust of an airplane engine pushes against the air, not the ground therefore it matters not how fast the belt is moving. It will take off no probs.

Yarp - I concur, the wheels on an aircraft are passive the prop/jet pushes the plane, it takes off due to bernouli's princeiple when the air passing over the curved upper surface of the wing is moving faster than the Flat(ish) underside creating lower pressure above the wing and higher pressure under -lifting the plane

Think about what you're saying there...

http://www.grc.nasa.gov/WWW/k-12/airplane/forces.html



Consider the diagram for a moment. The forces parallel to the ground are irrelevant because the conveyer belt is moving such that any forward motion of the aircraft is counteracted.

The weight of the aeroplane is keeping it on the conveyer belt (good old F=ma).

The only upward force on the aeroplane is the normal reaction which all objects encounter in a situation where they are stationary and under the influence of gravity.

Lift
To overcome the weight force, airplanes generate an opposing force called lift. Lift is generated by the motion of the airplane through the air and is an aerodynamic force. "Aero" stands for the air, and "dynamic" denotes motion. Lift is directed perpendicular to the flight direction. The magnitude of the lift depends on several factors including the shape, size, and velocity of the aircraft. As with weight, each part of the aircraft contributes to the aircraft lift force. Most of the lift is generated by the wings. Aircraft lift acts through a single point called the center of pressure. The center of pressure is defined just like the center of gravity, but using the pressure distribution around the body instead of the weight distribution.

Since the aircraft is stationary (ie any forward thrust from the engines is counteracted by the movement of the conveyer belt) it is not travelling through air, therefore no lift is generated, hence the aeroplane does not take off.

[ROMEROTECH]

Myth Busted!!

http://mythbustersresults.com/episode97

[Sancho]

'O' dear HLS has officially died on it's arse.


http://www.hiluxsurf.co.uk/showthrea...=conveyer+belt

Why do you have to be such a miserable sack of shit?

I was just harking back to those days and thinking that most of the people that contributed to that thread had moved on and that we could have a bit of fun by getting some of the newer members into that debate again, but Mr Self-Righteous had to jump in and #### on everyone's chips again.

There's no apostrophe in a possessive 'its' by the way.

[Sancho]

I'm glad to see that NASA refer to gravity as 'weight'. They're really on top of things.

[Maverick]

There's still some of us old farts here that can remember that it wasn't a debate but a s t storm last time.

By the way the plane does take off, because the prop will create a difference in air pressure, that will cause an airflow over the wings, causing an air pressure difference, causing lift.

[Sancho]

There's still some of us old farts here that can remember that it wasn't a debate but a s t storm last time.

By the way the plane does take off, because the prop will create a difference in air pressure, that will cause an airflow over the wings, causing an air pressure difference, causing lift.

What if it's got a jet engine and it's at the back so doesn't blow air over the wings?

[Maverick]

What if it's got a jet engine and it's at the back so doesn't blow air over the wings?

It will create an air pressure difference at the rear, which will pull airflow over the wings, thus causing an aire pressure difference, thus causing lift.