Will it fly(don't answer too fast)?

[OTTOL]

[OTTOL]

Like I said, unless this scenario is differant to the one I know, I think it is worded wrong. There is supposed to be no suggestion of movement from the conveyer belt. Just that there is a belt with the potential to do so.......

 Nope! I know that you address this further on the next page or so but, just to clarify, this is a question of mechanical theory not syntax. There are variations of this scenario and I actually copied it directly from someone else (as opposed to re-typing it incorrectly) but all of the elements are as intended.

Holy crap, 5 pages for a simple yes or no question?

......heck, you ain't even "gottin'" close to beating this dead horse yet! For some real entertainment, listen to a bunch of professional pilots argue about it for 63 days (and counting) and 45 pages worth! If you don't have the time or patience to read it all, skip to post number 646 for some insight. The only factor that he's missing (that I think would further clarify the issue) is VELOCITY (or it's irrelevance with regard to specific dynamic factors).

http://forums.flightinfo.com/showthread.php?t=66860

[eno]

I've still been ignored  :'( :'( :'( :'(

CAR ON CONVEYOR

d=drive wheel.

         0--d  50mph--->
----------------------------------- groundspeed= 0/windspeed =0
         <-----  -50mph

The drivewheel acts on the ground therefore the conveyor.

PLANE ON CONVEYOR      p= prop t= thrust


       <---t =80mph             0--0P   80mph-->
---------------------------------------------------  groundspeed=80mph/ windspeed=80mph
                                   <---- 80mph

It's thrust that gives the aircraft forward motion and as the thrust is acting on the AIR not the GROUND any the direction of the conveyor is irrelevent unless the direction of the conveyor is in the same direction as the aircraft in which case the takeoff distance would be halved.

The car will never move as the thrust is being provided by the drivewheel which acts on the ground ..... the same as a man on a treadmill.

That should confuddle you lot.

[H]

I've still been ignored  :'( :'( :'( :'(
CAR ON CONVEYOR
d=drive wheel.
         0--d  50mph--->
----------------------------------- groundspeed= 0/windspeed =0
         <-----  -50mph
The drivewheel acts on the ground therefore the conveyor.
PLANE ON CONVEYOR      p= prop t= thrust
       <---t =80mph             0--0P   80mph-->
---------------------------------------------------  groundspeed=80mph/ windspeed=80mph
                                   <---- 80mph
It's thrust that gives the aircraft forward motion and as the thrust is acting on the AIR not the GROUND any the direction of the conveyor is irrelevent unless the direction of the conveyor is in the same direction as the aircraft in which case the takeoff distance would be halved.
The car will never move as the thrust is being provided by the drivewheel which acts on the ground ..... the same as a man on a treadmill.

I didn't ignore you, just overlooked you (and many others -- too much to read through). However, our posts compliment each other.

I came in on this way too late -- not about to read everything. However, as variously said, flight is determined by the airflow around the wings. The only thing the ground (in this case, conveyor belt) does is stop the plane from falling any lower until it has enough lift to go higher. The main confusion here, though, is in relation to the forward propulsion to create that lift. The plane's propulsion is in direct relation to the air, not the ground, and it will start moving forward no matter how fast the conveyor belt is moving. That's why the prop driven version is called, in the U.S., an airplane -- not a groundplane. Most ground vehicles use wheels or tracks for propulsion, thus having a direct relation to the ground below for their propulsion. Those that are propelled by props, jets or sails -- providing they have enough air power available -- wouldn't be stopped in this cirumstance, either.

[TacitBlue]

Why is this hard to understand? I had the answer before I read the first reply. Eno and Craig have explained it very well so I won't even bother. All I'll say is that the Wheels have nothing to do with the aircrafts ability to fly, forget the wheels.

Actually, I've just come up with an idea. Everyone meet me at the airport in an hour, I have to go find a big-ass conveyor belt.

[Omag 2.0]

Look, I'm still not convinced it will take off. For one, it would be the mother of all STOL devices... And I still don't see no conveyorbelts on American aircraftcarriers... They still use a catapult. I'd say that's proof enough!  ;D

[eno]

Look, I'm still not convinced it will take off. For one, it would be the mother of all STOL devices... And I still don't see no conveyorbelts on American aircraftcarriers... They still use a catapult. I'd say that's proof enough!  ;D

STOL would only be effective if the conveyor went in the same direction as the takeoff direction.

[Delta_]

The conveyor belt is doing nothing to slow the aircraft down other than creating more friction in the wheel bearings.

The aircraft's wheels spin freely from the jet engine.  This means that the conveyor belt is not directly opposing the thrust of the jet engine.  The conveyor belt is generating no opposing force on the aircraft other than friction in the wheel bearings.  The friction is no where near enough to slow the aircraft noticeably never mind significantly.  

If we ignore friction from the wheel bearings you will be left with an ideal model (easier to understand and solve problem).  This means that you could run the conveyor belt at 50kias and not even turn the engine(s) on and the aircraft will not move an inch.  It will simply spin the wheels at 50kias.  Now if you start the engine(s) and set the thrust at a typical amount for take-off, the aircraft will move forward, even though the conveyor belt is moving the wheels in the opposite direction.  

Say the aircraft can take-off at 80kias this means the conveyor will be moving at 80kias in the opposite direction.  This also means the wheels will be spinning at 160kias forwards.  The aircraft will continue to move forwards because the conveyor belt is generating no force to oppose the thrust.

If the conveyor belt speed was changed and set to 20x times the aircraft speed.  Assuming the aircraft is not damaged from the speed the wheels are spinning, it will still take-off.  It will just spin the wheels 20x faster in the opposite direction, still generating no force against the aircraft.

Omag you said about the aircraft carrier.  The reason the catapult system is used is to speed the aircraft up quicker than the jet engine can, hence decreasing take-off distance.  The system is not attached to the wheel but to the front landing gear frame.  It will pull the aircraft.  

Using a conveyor belt on the aircraft carrier will not work because it will just spin the wheels really fast and not actually move the aircraft.

[Craig.]

Which delta is what Eno and myself eno especially have been trying to say for the past 5 pages but have been ignored.

[Fozzer]

Holy crap, 5 pages for a simple yes or no question? heheheheeh oh no.

This thread is an ideal reason for the drug companies to design more effective headache tablets... ...!

Paul....having a lie-down in a darkened room... ...!

[Saitek]

Paul - you are following this thread fine.  :P

[Fozzer]

Paul - you are following this thread fine.  :P

Do you know what....
Every now and again I come across a grope group of Folks who seem to thoroughly enjoy a good-old argument for the sake of a bleedin' argument....
...a bit like the Oprah Winfrey Show*...

Whenever there is a chance of an argument brewing I quickly leg-it... ...!
LOL...!

Paul...
...Aeroplanes, wheels, conveyor belts, catapults, etc....I just  can't stand the stress... ... ...!
LOL...!


*...another reason why I don't have a bloody television set... ... ...!

[OTTOL]

I stopped buying TV sets years ago.

Everytime I'd get home and open the box, there'd always just be one in there!!

[Chris_F]

[quote]Look, I'm still not convinced it will take off. For one, it would be the mother of all STOL devices... And I still don't see no conveyorbelts on American aircraftcarriers... They still use a catapult. I'd say that's proof enough!

[Marlin]

[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 opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?