777 down.

[AtoZ]

if the plane could creep forward on idle speed then increasing the speed of the conveyer would eventually drive it backwards.

friction and tyre deformation cannot be dismissed if we move from the strict question set by the op and move to noseall's statement.

thrust would have to be increased above idle to stay still or move forward once again.

 

[tim west]

i saw thunderbirds and they went to the sun to save some other spaceship... they made it back ok..

You got me there, there's no argument I can put to counter that, you are completely correct.

the acting from alan tracey was brilliant in that episode.. worth an oscar

Can't agree with that, I thought he was a bit wooden.

 

[AtoZ]

i saw thunderbirds and they went to the sun to save some other spaceship... they made it back ok..

You got me there, there's no argument I can put to counter that, you are completely correct.

the acting from alan tracey was brilliant in that episode.. worth an oscar

Can't agree with that, I thought he was a bit wooden.

i thought that was supposed to be method acting and it was the director pulling the strings....

sorry..

 

[AtoZ]

i went backwards while moving forwards on a childs windsurfer due to lack of thrust and action of tide
thats a little like the conveyer problem.

 

[megawatt]

Blondini wrote:

It doesn't matter what the aircraft is. The hypothetical conveyor runway is moving backwards and no matter how fast the aircraft travels relative to the conveyor surface, the conveyor matches to the wheelspeed of the aircraft. The aircraft engines are exerting a forward thrust, but the conveyor is exerting an equal and opposite reverse thrust against the aircraft solely through the rolling resistance of the aircraft wheels.The aircraft therefore cannot move forward relative to it's own position in space and can gain no airspeed. If it did move forward relative to it's own position it would mean the hypothetical conveyor wasn't matching the wheelspeed.

This definitely gets the prize for the post which has given me the best laugh in 2008 thus far.

I'm not sure what you do for a living Blondi but you certainly ain't an aircraft engineer

The aircraft engines are exerting a forward thrust.

Correct, the thrust is applied to the airframe.

The conveyor is exerting an equal and opposite reverse thrust against the aircraft solely through the rolling resistance of the aircraft wheels.

Nope, the conveyor isn't exerting any thrust at all to the airframe with the brakes off it is simply spinning the wheels. As I've already said, as the engine thrust is increased the aircraft will react as normal ... Only difference will be the speed of the wheels.

The aircraft therefore cannot move forward relative to it's own position in space and can gain no airspeed

Total nonsense I'm afraid.

True if you believe that aircraft reach take off velocity by driving the wheels though

MW

 

[empip]

Airframe by Boeing
Engines by Rolls-Royce
Micro-chips by Sum Ting Wong Electronics Ltd.

Thanx to 'skiesfull' at the rumour mill.

 

[blondini]

I shan't give up on you Megawatt

The following aren't my words. I've just cut and pasted from a couple of avaition sites.

On takeoff, the two major retarding forces are rolling resistance and aerodynamic drag.

Rolling resistance. Rolling resistance is determined by tyre pressure, aeroplane mass, and the surface characteristics of the movement area. Up to a point, rolling resistance may be welcome during landing, but unexpected rolling resistance on take-off can lead to a decision to abort the take-off, or possibly an over-run accident.

 

[Richardp]

I shan't give up on you Megawatt

Do you mean that he's worth saving ?

 

[megawatt]

Rolling resistance. Rolling resistance is determined by tyre pressure, aeroplane mass, and the surface characteristics of the movement area. Up to a point, rolling resistance may be welcome during landing, but unexpected rolling resistance on take-off can lead to a decision to abort the take-off, or possibly an over-run accident.

What they are getting at here Blondini is resistance to forward travel i.e. flat tyres, binding brakes, bogged down in sand (water), soft tarmac etc etc.
If the runway happens to moving towards the aircraft at the same time the aircraft is being powered by the engines there is no increase to inertial drag ... the wheels will simply spin faster

As I keep saying ... Try it out, this is easy to prove with a couple of models and a conveyor belt.

MW

 

[joe-90]

That's not exactly true. If you roll downhill on a bicycle you will achieve a greater speed than if you roll down hill on roller skates. There is a definite connection between wheel size and speed. Have you ever seen a top-fuel dragster take off? The wheels become taller and thinner, and at a certain speed they will self destruct.

 

[securespark]

i went backwards while moving forwards

Surely that means you were going backwards not forwards then??

 

[blondini]

What they are getting at here Blondini is resistance to forward travel

MW

 

[megawatt]

If you want to quote me fella ... Quote me accurately and in the context I posted ... Otherwise your posts become meaningless.

Joe: You're probably right but it doesn't affect the outcome of my post.

Fact is, the aircraft will take off and the pilot will be unaware of the conveyor ... Assuming the wheel bearings survive

MW

 

[AtoZ]

i went backwards while moving forwards

Surely that means you were going backwards not forwards then??

you are right, horatio i aint

if a sailing ship travels forward at say 2 knots but it is against a tide runing at 4 knots then the ship would drive forward but still lose ground.
thats what happened to me
i can wind surf but the sail was not big enough, and the wind not strong enough to get back to the beach.

i was moving forward because i did move pass things in the water. very strange.
i had to jump off and swim with it to get back in.
i was slaughtered at the end and in quite a bad way.

i read somewhere that the english used a run of water like this near the solent to help defeat the spanish armada.

 

[dave.m]