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Melkor Bloodaxe
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Posted - 2006.07.11 13:13:00 -
[61]
and how about this one: Your build a really BIG ventilator and place it in front of the aircraft. You apply the brakes of the aircraft and then turn on your very big ventilator producing a stable wind at 200 knots. As this head wind is greater than the rotating speed of the aircraft, the wings will produce enough lift to let the aircraft take off from the ground - but only as long as it is within the produced currents and the relative airspeed is maintained: This will require the aircraft to be kept on a leash, making this a 100 ton-kite ... ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:14:00 -
[62]
Originally by: Melkor Bloodaxe and how about this one: Your build a really BIG ventilator and place it in front of the aircraft. You apply the brakes of the aircraft and then turn on your very big ventilator producing a stable wind at 200 knots. As this head wind is greater than the rotating speed of the aircraft, the wings will produce enough lift to let the aircraft take off from the ground - but only as long as it is within the produced currents and the relative airspeed is maintained: This will require the aircraft to be kept on a leash, making this a 100 ton-kite ...
They call that a wind tunnel.
What about if the OP forgot the mention the engines were mounted backwards? ----------
Always Up To SomethingÖ |
Melkor Bloodaxe
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Posted - 2006.07.11 13:18:00 -
[63]
Edited by: Melkor Bloodaxe on 11/07/2006 13:20:14
Originally by: Crumplecorn What about if the OP forgot the mention the engines were mounted backwards?
In that case I would fire the mechanics for mounting the engines frontside backwards... But for the case. You would deffinatly NOT take off. I think... Never actually had problems where wing structures where facing the opposite direction... (which is the case for flying backwards.) There are some cases however where thrust inverters started working in full flight. None of the planes landed without total destruction... ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:19:00 -
[64]
Edited by: Crumplecorn on 11/07/2006 13:19:41
Originally by: Melkor Bloodaxe
Originally by: Crumplecorn What about if the OP forgot the mention the engines were mounted backwards?
In that case I would fire the mechanics for mounting the engines frontside backwards... But for the case. You would deffinatly NOT take off.
Unless you turned the plane around and used the treadmill acceleration thing......
Edit: Did the OP actually specify the aircraft had engines? ----------
Always Up To SomethingÖ |
Melkor Bloodaxe
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Posted - 2006.07.11 13:22:00 -
[65]
Edited by: Melkor Bloodaxe on 11/07/2006 13:22:27
Originally by: Crumplecorn Edited by: Crumplecorn on 11/07/2006 13:19:41
Originally by: Melkor Bloodaxe
Originally by: Crumplecorn What about if the OP forgot the mention the engines were mounted backwards?
In that case I would fire the mechanics for mounting the engines frontside backwards... But for the case. You would deffinatly NOT take off.
Unless you turned the plane around and used the treadmill acceleration thing......
Edit: Did the OP actually specify the aircraft had engines?
but since it was specified that the treadmill turned the opposite direction as the plane, that wouldn't work.
Engines? ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:25:00 -
[66]
Originally by: Melkor Bloodaxe Edited by: Melkor Bloodaxe on 11/07/2006 13:22:27
Originally by: Crumplecorn Edited by: Crumplecorn on 11/07/2006 13:19:41
Originally by: Melkor Bloodaxe
Originally by: Crumplecorn What about if the OP forgot the mention the engines were mounted backwards?
In that case I would fire the mechanics for mounting the engines frontside backwards... But for the case. You would deffinatly NOT take off.
Unless you turned the plane around and used the treadmill acceleration thing......
Edit: Did the OP actually specify the aircraft had engines?
but since it was specified that the treadmill turned the opposite direction as the plane, that wouldn't work.
Engines?
But he never said whether the treadmill would reverse direction if you turned the plane ----------
Always Up To SomethingÖ |
Melkor Bloodaxe
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Posted - 2006.07.11 13:26:00 -
[67]
Originally by: Levin Cavil An airplane is on a runway which is built like a huge treadmill. The treadmill moves in the opposite direction of the plane at the same speed as the plane. Will the plane ever take off?
But he said the opposite direction of the plane... ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:28:00 -
[68]
Originally by: Melkor Bloodaxe
Originally by: Levin Cavil An airplane is on a runway which is built like a huge treadmill. The treadmill moves in the opposite direction of the plane at the same speed as the plane. Will the plane ever take off?
But he said the opposite direction of the plane...
That doesn't mean it will change direction with the plane, it's just a way of describing the initial direction with respect to the plane. ----------
Always Up To SomethingÖ |
Melkor Bloodaxe
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Posted - 2006.07.11 13:33:00 -
[69]
Originally by: Crumplecorn
Originally by: Melkor Bloodaxe
Originally by: Levin Cavil An airplane is on a runway which is built like a huge treadmill. The treadmill moves in the opposite direction of the plane at the same speed as the plane. Will the plane ever take off?
But he said the opposite direction of the plane...
That doesn't mean it will change direction with the plane, it's just a way of describing the initial direction with respect to the plane.
but it doesn't say it doesn't either. ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:35:00 -
[70]
Originally by: Melkor Bloodaxe
Originally by: Crumplecorn
Originally by: Melkor Bloodaxe
Originally by: Levin Cavil An airplane is on a runway which is built like a huge treadmill. The treadmill moves in the opposite direction of the plane at the same speed as the plane. Will the plane ever take off?
But he said the opposite direction of the plane...
That doesn't mean it will change direction with the plane, it's just a way of describing the initial direction with respect to the plane.
but it doesn't say it doesn't either.
Well then, I guess we're stuck. ----------
Always Up To SomethingÖ |
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Melkor Bloodaxe
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Posted - 2006.07.11 13:37:00 -
[71]
damn.
Call CCP to reboot the server so we are not stuck anymore ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:40:00 -
[72]
CCP nerf treadmills plz ----------
Always Up To SomethingÖ |
Melkor Bloodaxe
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Posted - 2006.07.11 13:43:00 -
[73]
and airplanes too, they can take off from treadmills, so they are way overpowered.
Time to go home i think... ---
Originally by: HippoKing Since when is justified killing more fun than random killing?
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Crumplecorn
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Posted - 2006.07.11 13:45:00 -
[74]
CCP nerf missiles plz, the USAF are going around pwning everyone else because they have better planes and weapons. ----------
Always Up To SomethingÖ |
Levin Cavil
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Posted - 2006.07.11 14:22:00 -
[75]
Yes the plane has engines and no they are not mounted backwards. All relevant information is in the OP. ---------- <Kayosoni> I'm actually normal |
bsspewer
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Posted - 2006.07.11 15:02:00 -
[76]
Ok, let's change the situation a bit more for the slower folks..
A airboat is on a river that is flowing in the opposite direction. The airboat throttles up and the water underneath flows the same speed as the blades? Does the airboat move forward?
Yes. Same basic concept. The surface underneath is negated due to the force propelling it forward has no interaction with that surface. The interaction is with the wind and the air.
If you were in a boat pulling yourself upstream by a rope, will you move? Yes. Because the force propelling you forward has no interaction with the surface underneath you.
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Jernau Gurgeh
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Posted - 2006.07.11 15:16:00 -
[77]
Originally by: bsspewer
If you were in a boat pulling yourself upstream by a rope, will you move? Yes. Because the force propelling you forward has no interaction with the surface underneath you.
You would still have to work against the current.
There are 10 sorts of people in the world - those who understand binary, and those who do not. |
St Dragon
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Posted - 2006.07.11 15:39:00 -
[78]
Errm lets see considering that an aircraft needs a runway to gain the right takeoff speed, id say it has to be moving before it can take off.
So no the plane on this treadmill wont take off because it needs to be moving to generate lift.
All the engines do is move a plane fowards.
Its the wings that provide lift.
Here is some data to help thank you wikky
Lift
The mere fact a plane need a runway to take off pretty much points to what trully makes a plane fly if this was not so we would ahve planes taking off like Harrier Jump Jets. -----------------------------------------------
"Kill one man, and you are a murderer. Kill millions of men, and you are a conqueror. Kill them all, and you are a god." -- Jean Rostand |
Valeria Wolf
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Posted - 2006.07.11 15:55:00 -
[79]
Edited by: Valeria Wolf on 11/07/2006 16:14:56 First Id like to say why is anyone even answering this but then I look in the mirror and face the oddly compelling need to do so myself.
Quote: An airplane is on a runway which is built like a huge treadmill. The treadmill moves in the opposite direction of the plane at the same speed as the plane. Will the plane ever take off?
assuming that the plane moves forward at x and the treadmill is actually moving backward at -x. given the negation of forward speed you do not have any air moving over the wing in which to provide the lift necesary to make the plane fly. irrespective of prop or jet (ultralight models excluded) no forward motion equals no lift. Given your comparison to a treadmill it should be painfully obvious you simply dont go anywhere.
now having said all of that if you actually look at whats being said and compare it to "on the way to St Ides I met a man with seven wives..." sitting on the treadmill today has no bearing on wether or not the plane will ever fly. simply take the plane off the treadmill or turn the plane around and yes it will fly.
however lets go back to the authors several replies
Quote: If you still think the answer is no then think about a few things.
1. What moves an airplane foreward? A: Thrust from the engine (jet, prop, whatever)
2. What is the purpse of the wheels on the plane? A: To eliminate the friction between the runway and the airplane (so the plane and runway can operate at different speeds)
3. What would happen if you tried to rollerblade on a treadmill? A: Lots of things, you could stand still when it is at full speed, you could move foreward or back regardless of belt speed.
1 & 2 are a duh really but 3 is awkward for this comparison because you set the equal speed but opposite direction parameter in the first post. you have implied that the runway is moving although you have not specifically said so.
Quote: Edited by: Levin Cavil on 11/07/2006 09:47:22 The treadmill only moves in the opposite direction, it can't prevnt the plane from moving because the plane is not moved foreward with its wheels.
An airplane acheives foreward speed with a propeller or jet or some other source of thrust. The thrust generated by the engine and the resulting speed are what generates lift. The only relative speed that maters is the plane's speed relative to the air around it, not the ground speed.
and this is where we have a problem because a) if the treadmill is moving in an equal but opposite direction no the plane wont take off. notice the OP says "moves" not "is moving". b) because the treadmill can only move antidirectional to the plane then it shouldnt move at all (if its not self propelled) making it static because the plane does not use wheels for propulsion. as Levin says is pushes or pulls itself. simply take a piece of paper and slide it forward on your desk then hold the paper with your other hand while continuing forward push with the motion hand. thats the example you need.
and I simply cant let this one go - unless said plane is in a wind tunnel wind speed is ground speed during take off... but i think your refering more to the tires etc.
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Xeios
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Posted - 2006.07.11 16:13:00 -
[80]
Originally by: Valeria Wolf First Id like to say why is anyone even answering this but then I look in the mirror and face the oddly compelling need to do so myself.
Quote: An airplane is on a runway which is built like a huge treadmill. The treadmill moves in the opposite direction of the plane at the same speed as the plane. Will the plane ever take off?
assuming that the plane moves forward at x and the treadmill is actually moving backward at -x. given the negation of forward speed you do not have any air moving over the wing in which to provide the lift necesary to make the plane fly. irrespective of prop or jet (ultralight models excluded) no forward motion equals no lift. Given your comparison to a treadmill it should be painfully obvious you simply dont go anywhere.
now having said all of that if you actually look at whats being said and compare it to "on the way to St Ides I met a man with seven wives..." sitting on the treadmill today has no bearing on wether or not the plane will ever fly. simply take the plane off the treadmill or turn the plane around and yes it will fly.
however lets go back to the authors several replies
Quote: If you still think the answer is no then think about a few things.
1. What moves an airplane foreward? A: Thrust from the engine (jet, prop, whatever)
2. What is the purpse of the wheels on the plane? A: To eliminate the friction between the runway and the airplane (so the plane and runway can operate at different speeds)
3. What would happen if you tried to rollerblade on a treadmill? A: Lots of things, you could stand still when it is at full speed, you could move foreward or back regardless of belt speed.
1 & 2 are a duh really but 3 is awkward for this comparison because you set the equal speed but opposite direction parameter in the first post. you have implied that the runway is moving although you have not specifically said so.
Quote: Edited by: Levin Cavil on 11/07/2006 09:47:22 The treadmill only moves in the opposite direction, it can't prevnt the plane from moving because the plane is not moved foreward with its wheels.
An airplane acheives foreward speed with a propeller or jet or some other source of thrust. The thrust generated by the engine and the resulting speed are what generates lift. The only relative speed that maters is the plane's speed relative to the air around it, not the ground speed.
and this is where we have a problem because a) if the treadmill is moving in an equal but opposite direction no the plane wont take off. notice the OP says "moves" not "is moving". b) because the treadmill can only move antidirectional to the plane then it shouldnt move at all (if its not self propelled) making it static because the plane does not use wheels for propulsion. as Levin says is pushes or pulls itself. simply take a piece of paper and slide it forward on your desk then hold the paper with your other hand while continuing forward push with the motion hand. thats the example you need.
and I simply cant let this one go - unless said plane is in a wind tunnel wind speed is ground speed during take off...
This would be correct, however, because the wheels are free moving and the plane has so much thrust from the jet engines it wouldnt be left sitting on the spot at full power. It would take a very long runway but i think u will find the plane would take off.
Ofcourse as someone else mentioned earlier in the thread it wouldnt be doable because it would blow a tire and ud end up with a mess to clear up.
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Dark Shikari
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Posted - 2006.07.11 16:21:00 -
[81]
Here is your answer.
--Proud member of the [23]--
-WTB Platinum Technite, WTS Nanotransistors, Heavy Electron II, 100mn AB II- |
Valeria Wolf
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Posted - 2006.07.11 16:28:00 -
[82]
damn levin and his posts!!!
Quote: This would be correct, however, because the wheels are free moving and the plane has so much thrust from the jet engines it wouldnt be left sitting on the spot at full power. It would take a very long runway but i think u will find the plane would take off.
this assumes some forward motion - irregardless of how much thrust is coming from and engine it needs to be allowed to roll forward to gather lift speed. x-x = 0 no speed no lift no fly. if you cannot translate thrust into forward motion you simply dont go anywhere dont care how long you run it. Likewise there is a required threshold to reach a speed at which lift can be obtained. thus you not only have to have forward motion you have to have enough forward motion which you never acheive because again x-x = 0
the limiting parameter is "equal speed, opposite direction"
but as I said previously it depends on how much you want to read into the OP. if the treadmill is only propelled by the movement of the plane and is antidirectional the plane should take off normally because the plane tires dont grip they roll. and the runway cant move in the same direction as the plane.
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Drizit
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Posted - 2006.07.11 16:46:00 -
[83]
Edited by: Drizit on 11/07/2006 16:48:06 The only reason this would work is that the propellor/jets would act against the air and not the treadmill. You are pushing air backwards to create the propulsion rather than using force applied directly to the wheels to generate forward motion. A car would go nowhere since the force to move it forward is applied directly to the wheels.
This problem is similar to the paper plane against a fan idea. I wonder how many could answer that one correctly.
A paper plane is thrown against a fan. The fan is running at a speed that negates all forward speed of the paper plane but does not blow it backward either. How long would the plane stay airborne?
Edit: grammar. --
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Border201
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Posted - 2006.07.11 20:46:00 -
[84]
Originally by: Levin Cavil Yes the plane has engines and no they are not mounted backwards. All relevant information is in the OP.
Levin your not allowed to post any more riddles jokes, discussion topics or anything else that does not involve you blowing stuff up!
Originally by: Tuxford once tried to kick my brother when I had my pants around my ankle. Probably not my brightest moments.
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Anarlina
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Posted - 2006.07.11 21:13:00 -
[85]
Edited by: Anarlina on 11/07/2006 21:22:23 Edited by: Anarlina on 11/07/2006 21:17:57 To help explain this to those who still think the plane won't take off:
1) The treadmill is moving at the speed of the /plane/, not the plane's wheels. This is a fairly minor point.
2) Any 'force' the treadmill can apply to the plane itself is through the wheels and their friction. Free-spinning OR stationary wheels will only have friction creating problems for a thrust engine.
3) Force that the treadmill applies has to be based around the treadmill's acceleration. If the treadmill is currently constant speed, then there is zero acceleration, and zero force being applied to the plane's wheels via the treadmill. The problem here is that by assuming we apply force to the /wheels/ we apply force to the plane. Not true, we are simply encouraging the wheels to spin, but friction in the wheels will let a treadmill move a resting plane/vehicle backwards.
4) Force from friction in the wheel itself comes from the plane's weight, and is constant, despite the plane's speed. So the friction that a plane has to overcome with engines is the same on a treadmill as on a standard tarmac.
5) Assuming that the plane /is/ stuck in one spot on the treadmill, there is NO force coming from the treadmill... the plane is only facing the friction force, and is only using enough thrust to overcome that force alone.
6) Assuming that 1-5 are accurate, we know that a jet's engines are capable of overcoming the friction in the wheels. Once that happens, the plane begins to move forward. At this point, the treadmill can spin however fast it wants, but the friction force is overcome... and the treadmill does nothing but change the speed of the spinning tires.
7) As an interesting aside... you get an interesting effect if you accelerate the treadmill while the plane has the wheels unlocked and is not applying any thrust. If you accelerate quickly enough, you will see the wheels spin during the acceleration of the treadmill, and the plane will /stop moving backwards/. I have actually seen this effect on a smaller scale with things like model cars. The force the treadmill applies manages to overcome the friction of the wheels, and cause them to spin at the speed of the treadmill briefly. Similar friction concepts also help explain the 'dinner table' magic trick where you pull out the table cloth without disturbing the place settings too much.
Any more questions about this?
EDIT: Fixups for clarity.
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Ishen Villone
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Posted - 2006.07.12 00:15:00 -
[86]
Edited by: Ishen Villone on 12/07/2006 00:25:17 Quoted post since edited.
Anyway. Just ask yourself this to simplify everything:
Does the treadmill impart enough friction upon the wheels to counteract the considerable thrust provided by the engines? Remember: wheels are designed to spin relatively freely.
Since our treadmill is limited to the speed of the aircraft, we have to assume that it will not provide a retarding force equal to the engines. (because if the wheels were capable of this, no plane in the world would be capable of takeoff)
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Xziled
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Posted - 2006.07.12 04:20:00 -
[87]
i didn't read anything after the first page but it seems pretty obvious to me. there is no drive train or anything attached to the wheels on a plane, they are just free spinning. they will spin as fast as they want it doesn't matter. the wheels don't move the plane the thrust does. the ground can be moving at whatever speed and as the wheels will also be moving at that speed but as long as the engines are producing thrust it will move. just cause the ground is moving doesn't mean that the jets won't work.
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Sarleena
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Posted - 2006.07.12 04:39:00 -
[88]
Originally by: Drizit Edited by: Drizit on 11/07/2006 16:48:06 The only reason this would work is that the propellor/jets would act against the air and not the treadmill. You are pushing air backwards to create the propulsion rather than using force applied directly to the wheels to generate forward motion. A car would go nowhere since the force to move it forward is applied directly to the wheels.
This problem is similar to the paper plane against a fan idea. I wonder how many could answer that one correctly.
A paper plane is thrown against a fan. The fan is running at a speed that negates all forward speed of the paper plane but does not blow it backward either. How long would the plane stay airborne?
Edit: grammar.
Until the plane's forward motion stops. The fan doesn't provide windspeed, it provides acceleration away from it, and the plane has no constant forward thrust, only its initial velocity. If the fan is blowing at a speed that completely negates all forward movement of the plane, once the plane's forward movement stops, the fan would have to stop blowing, or the plane would start moving backwards, so the airflow would stop, and therefore the lift would die. Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the oth |
Marie Sklodowska
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Posted - 2006.07.12 04:58:00 -
[89]
Originally by: Sarleena
Until the plane's forward motion stops. The fan doesn't provide windspeed, it provides acceleration away from it, and the plane has no constant forward thrust, only its initial velocity. If the fan is blowing at a speed that completely negates all forward movement of the plane, once the plane's forward movement stops, the fan would have to stop blowing, or the plane would start moving backwards, so the airflow would stop, and therefore the lift would die.
What? Um, I do believe you have just made up stuff there..new physics for the win.
Def. WIND SPEED : Wind speed is the speed of movement of air relative to a fixed point on the earth.
Last I checked the air blowing from the fan moves relative to the earth. What you really mean is true airspeed, or speed of the plane relative to the earth with the wind factored in. In which case, your wrong again. If you assume the plane does not need forward thrust (or is able to maintain constant forward thrust magically) and the wind from the fan blows at the same speed the plane moves forward, you have zero transversal velocity and the plane hovers. Same concept as if you were to fly a real plane into a strong headwind. You have to throttle faster then the oncoming headwind to overcome it.
www.eve-search.com | www.eve-files.com |
Gothikia
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Posted - 2006.07.12 06:35:00 -
[90]
Edited by: Gothikia on 12/07/2006 06:35:58 The only airflow over the wings will be that generated by the prop. This will not work as the airfoil (wing) is the thing that generates the lift for the plane to enter the air. The aircraft requires that the AIRSPEED be at a certain point before it can take off otherwise the airfoil will stall. What the OP is talking about is the GROUNDSPEED of the aircraft. Thus the airspeed remains very low, well below Rotate speed for the plane (takeoff speed) which means the airfoil will not generate any lift.
The only way to get a plane to 'hover' is if magically the aircraft had a strong wind hitting the nose directly on center of the aircraft at say about 70 kts IAS on a Cessna 150. The ground speed will probably remain unchanged, but the airspeed would be high causing the airfoil to generate lift thus the aircraft hovers.
Its the very basics you get taught in RAF Cadet Flight School
Regeneration - Homosexuals more than welcome! |
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