Would It Take Off?
Discussion
fozzi said:
The thrust never reaches the conveyor belt... it pushes the plane forward - then the wheels spin faster to compensate.
Theory = take off
It's got you fozzi
You are being drawn into the conundrum.
The plane speed is relative to the environment - powered by the jet
The conveyor and the wheels then enter an eternal struggle of speed matching - but meanwhile the plane moves forward in its environment and takes off.
fozzi said:
"tracks the plane speed and tunes the speed of the conveyer to be exactly the same"... e.g. the plane is not moving relative to the surroundings, hence no airflow, no lift, no take off!
If the plane were not moving relative to the surroundings, ie zero ground speed, then by definition of the original question the conveyor would be matching this zero speed and itself not moving !?!
As soon as the engines start to give any thrust the plane would move forwards relative to the surroundings, the convyor would move backwards at the same ground speed as the plane moves forwards, thus making the plane's wheels spin at double their normal speed, BUT HAVING NO EFFECT ON THE PLANE'S FORWARD MOTION OTHER THAN A TINY BIT MORE ROLLING DRAG.
The plane's forward thrust comes from the engines moving air and is totally independent of the ground. You could make the conveyor move as quickly as you wanted in the opposite direction to the plane's motion and the plane would still move forwards through the air, thus gaining the lift it requires to take off.
>> Edited by thegreenhell on Saturday 4th March 12:52
The conveyor and the aircrafts' wheels cancell each other out.
Lift can only be created by air passing over the wings creating low pressure.
The air must pass over the wings at the normal rate and this can only happen if the aircraft is actually moving through the air.
It will not take off.
Lift can only be created by air passing over the wings creating low pressure.
The air must pass over the wings at the normal rate and this can only happen if the aircraft is actually moving through the air.
It will not take off.
Then what prevents the thrust from moving the plane?
Imagine a motorbike and sidecar on a long road.
The bike is on normal road...the sidecar is on a coveyor belt built in to its half of the road.
The conveyor is running *and will match the speed of the bike*.
The bike moves off - the sidecar follows the sidecar wheels are moving really fast though
The jet thrust is not related to the plane wheels
The bike movement is not related to the sidecar wheels
Imagine a motorbike and sidecar on a long road.
The bike is on normal road...the sidecar is on a coveyor belt built in to its half of the road.
The conveyor is running *and will match the speed of the bike*.
The bike moves off - the sidecar follows the sidecar wheels are moving really fast though
The jet thrust is not related to the plane wheels
The bike movement is not related to the sidecar wheels
stovey said:Wheels spin freely, ergo they can't transmit an opposing force into the airframe to hold the engine back. She takes off every single time we discuss this. Airframe must be getting a bit tired by now
The conveyor and the aircrafts' wheels cancell each other out.
Lift can only be created by air passing over the wings creating low pressure.
The air must pass over the wings at the normal rate and this can only happen if the aircraft is actually moving through the air.
It will not take off.
the wheels are connected to the under-carriage
the under-carriage is connected to the fuselage
the fuselage is connected to the wings
the wings are connected to the engines
and that's what it all about...
fire engines up, get thrust, plane moves forward... on it's wheels!!!!!!!
no drive shafts, but thrust IS directed through wheels until the plane is in flight... otherwise all the jumbos in the testing bay at heathrow, with their brakes on, would vtol up into the sky.
>> Edited by fozzi on Saturday 4th March 13:02
the under-carriage is connected to the fuselage
the fuselage is connected to the wings
the wings are connected to the engines
and that's what it all about...
fire engines up, get thrust, plane moves forward... on it's wheels!!!!!!!
no drive shafts, but thrust IS directed through wheels until the plane is in flight... otherwise all the jumbos in the testing bay at heathrow, with their brakes on, would vtol up into the sky.
>> Edited by fozzi on Saturday 4th March 13:02
fozzi said:
the wheels are attached the under-carriage
the under-carriage is connected to the fuselage
the fuselage is connected to the wings
the wings are connected to the engines
and that's what it all about...
fire engines up, get thrust, plane moves forward... on it's wheels!!!!!!!
no drive shafts, but thrust IS directed through wheels until the plane is in flight... otherwise all the jumbos in the testing bay at heathrow, with their brakes on, would vtol up into the sky.
No! All that the wheels on the aircraft are for is to stop the fuselage from scraping along the tarmac as the jet engines push it along!
stovey said:
The conveyor and the aircrafts' wheels cancell each other out.
Lift can only be created by air passing over the wings creating low pressure.
The air must pass over the wings at the normal rate and this can only happen if the aircraft is actually moving through the air.
It will not take off.
Correct, IF you've made the mistake of assuming the wheels are doing the forward thrust, which they don't on all the aircraft I know. If they did then your right. But the jets which do the pushing push against the air, and have no interaction with the conveyor belt. There are two systems at work...wheels against belt and jets against air. The confusion is that the question does not mention how the aircraft is being moved forward. I hate ambiguity, I'm a scientist. PLEASE re-write the question properly.
fozzi said:
the wheels are connected to the under-carriage
the under-carriage is connected to the fuselage
the fuselage is connected to the wings
the wings are connected to the engines
and that's what it all about...
fire engines up, get thrust, plane moves forward... on it's wheels!!!!!!!
no drive shafts, but thrust IS directed through wheels until the plane is in flight... otherwise all the jumbos in the testing bay at heathrow, with their brakes on, would vtol up into the sky.
>> Edited by fozzi on Saturday 4th March 13:02
You need to think that through mate. thrust isn't throught the wheels, its through the jets. the reason they dont vtol is that the thrust is being counteracted by the friction of the braked tyres against the tarmac. if the jets were put on full throttle(and not just idling in the test bay)then the thrust might overcome the friction and the tyres would be dragged along the ground leaving skid marks. Unless the friction of the tyres on ground is greater than the friction of the brakes in which case the wheels would turn.
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