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#617175 - 28/12/06 03:23 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Madman, I fail to see how you reached the conclusion that there would be zero forward motion of the aircraft. The scenario says that the conveyor matches the speed of the plane, not the speed of the wheels. If the plane goes nowhere, the conveyor doesn't even turn. If the plane starts moving forward, the conveyor does start to turn but affects only the wheels. The plane is already moving, and is pushing air, not the surface.

Rinky, an aircraft taxis by pushing air, there is no drivetrain connected to the wheels, just steering at the nose wheel. The wheels are just there as an alternative to scraping the belly of the plane everywhere.

Madman again- the cats on a carrier are fairly irrelevant to the other discussion, but essentially they are a thrust enhancer. Perhaps the Navy could come up with a way to make jets take off of ships using thrust only, but the steam cats are fairly economical and very effective.

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#617176 - 28/12/06 03:25 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by NY Madman:
In this scenario there is no groundspeed.
And the Earth is flat.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617177 - 28/12/06 03:30 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by Paul H:
Quote:
Originally posted by TravelingFool:
[b]For the love of God... The plane would fly. Period.
Wow 7 pages and all we needed was you to answer it. Man that was easy.
:rolleyes:

An airplane requires wind speed (wings vs. wind), not ground speed (wheels turning on conveyor belt), to generate the lift. Turbines and props create thrust, which pushes the plane forward through the wind.

Without the conveyor belt, a plane generates speed through the wind as it moves forward, which means it ALSO generates it with respect to the ground.

Because (with the conveyor belt) everything remains stationary with respect to the wind (not the ground), your plane AIN'T taking off, no matter how fast the wheels turn.

If you think a plane can fly at 0 mph, think about this: A plane is moving at 500 MPH through the air, but suddenly (magically), you STOP it (to 0 mph) and, simultaneously, put a conveyor belt under it's wheels that is moving at 500 mph.

Do you think that plane is going to stay aloft at 0 mph windspeed but 500 mph wheel speed?[/b]
Paul, what you and so many others fail to realise is that without wind pushing the airplane itself backward at the same rate the engines push the plane forward, there will be forward motion. The airplane's engines are what are moving the airplan. NOT the wheels. You all are associating the wheels with the airplane's motion when in fact, they have nothing to do with the airplane's forward momentum. They are just moving at the rate that the engines are pulling them forward. The plane will still be pulled forward by the engines and not by the wheels.

The only way that a plane will remain stationary on the conveyor belt is if the plane was being propelled by the wheels and not the engines. The conveyor belt has no effect what-so-ever on the engines. It just moves the wheels.

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#617178 - 28/12/06 03:42 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


OK, free body diagram it is.



Forward motion will be attained whenever the thrust force is greater than the friction force (as stated above).

The only was the plane will stay stationary is if the force of friction between the wheels and ground is greater than the thrust. Period, end of story

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#617179 - 28/12/06 03:43 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Smith Offline
Member

Registered: 19/07/01
Posts: 2032
Loc: Winston-Salem, NC
Quote:
Originally posted by Paul H:
Quote:
Originally posted by Smith:
[b]
Quote:
Originally posted by RiNkY:
[b]

Stick a forward thrusting object on something that equally matches its forward thrust with rearward motion / thrust and it won't go anywhere.

My wife would disagree.[/b]
Yeah your wife mentioned that to me as well [Wave] [/b]
I just saw this you bastard. frown

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#617180 - 28/12/06 03:45 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by MattyX:

Rinky, an aircraft taxis by pushing air, there is no drivetrain connected to the wheels, just steering at the nose wheel. The wheels are just there as an alternative to scraping the belly of the plane everywhere.
I know that. But when an aircraft taxis the wheels rotate and the plane moves along the runway does it not. Or does the plane have that much power that it just makes long trails of rubber all over the airport without rotating the wheels? eek

What we are saying is - as the aircraft taxis and the wheels are rotating, the revolving runway / treadmill thingy is moving in the opposite direction ad the same speed. Hense the plane isn't moving anywhere with regards to anything not on the moving runway. Lets say a Tree at the side of the fucking runway. The plane may as well be sodding tied to the tree, because when it thrusts itself forward, the stupid dumbass treadmill - Which I wish wasn't there, but unfortunately is fucking there, keeps the plane static to the surrounding area. Hense no lift, hense no takeoff - regardless of if the plane is going 1mph in relation to the treadmill going backwards at 1mph or 1000mph.

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#617181 - 28/12/06 03:46 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Now for the bullet-

A bullet fired from gun (when the barrel is perfectly level) over tranquil ocean (for the purposes of creating the most perfect earthbound surface) will likely strike the surface of the water at exactly the same time as the bullet dropped from exactly the same height at the exact same time the other bullet was fired [huh?]. The lateral velocity of the bullet will not have any effect on or resistance to gravity, the bullet simply isn't that fast.

Now, I said "likely" not because I was unsure, but because the two bullets will encounter different conditions. The fired bullet will travel through more air than the dropped bullet and may encounter an updraft or downdraft. Were it possible to conduct this experiment in a perfect vacuum, the two bullets would strike the surface at exactly the same time, every time.

::edit to reply to Rinky::

Just because the conveyor is turning does not mean that the plane is not moving.

::ETA:: In fact if the conveyor is moving at all, it is because the plane is moving forward. The scenario calls to match the plane's speed, not its power or friction or any other imaginable thing.

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#617182 - 28/12/06 04:03 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


The plane would definitely be able take off.

100% certain

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#617183 - 28/12/06 04:08 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by tahoe_x:
The plane would definitely be able take off.

100% certain
I agree - But for that damn treadmill. I say we throw a spanner in the works and fuck up the treadmill, so the plane can take off and end this thread.

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#617184 - 28/12/06 04:10 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by Hawk:
How about this.....lets see if this can get to the ALR:

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?
Let me try to break what the question is down.

Plane standing on Runway.
Runway matches speed of Plane in opposite direction.

Point of Observer outside the Plane:
Plane appears as usual and takes off.

Point of Onboard Occupants:
Feeling the sensation of acceleration (cool) and the bumpiness of the runway and the separation and weightlessness (very cool) when the plane bobs up and down as it is continually accelerating and climbing until it reaches Cruise Speed and Altitude.

No other fact is included in the question, it is what it is.

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#617185 - 28/12/06 04:18 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by RiNkY:
Quote:
Originally posted by tahoe_x:
[b]The plane would definitely be able take off.

100% certain
I agree - But for that damn treadmill. I say we throw a spanner in the works and fuck up the treadmill, so the plane can take off and end this thread.[/b]
Do whatever you want to the treadmill, as long as your spanner wrench doesn't FOD the engine the aircraft will take off.

If the aircraft has 0 speed, the conveyor is not moving.

In order for the aircraft to attain any speed, it must be moving.

If the aircraft MOVES forward at one mile per hour, using jet propulsion or conventional propellers, the conveyor moves in the opposite direction at one mile an hour. The result of this is not a stationairy aircraft, it is a plane moving forwards at one MPH with its wheels turning at a rate of two MPH.

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#617186 - 28/12/06 04:19 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by RiNkY:
Quote:
Originally posted by tahoe_x:
[b]The plane would definitely be able take off.

100% certain
I agree - But for that damn treadmill. I say we throw a spanner in the works and fuck up the treadmill, so the plane can take off and end this thread.[/b]
Think of it this way. (read slowly...) The plane is sitting still on a treadmill that isnt turned on. Try to picture that for a second. Now.... Try to imagine something holding the plane in place.

Now, turn on the treadmill. What happens? The tires on the plane turn but the plane doesnt move. Do you understand that? Now, you are inside the plane and throttling up the engines. What does the airplane want to do?

If you understand that, then you have the answer. wink

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#617187 - 28/12/06 04:22 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


To simple Adam. Why would the plane appear to take off as per normal?

What you are saying is the same as saying, if we turned on the conveyor and span it up to say 100mph, but didn't bother to do anything with the planes engines - Just the conveyor on its own. The plane would stay in 1 place!!!

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#617188 - 28/12/06 04:27 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quoting from someone on CO 4X4 site who's quoting avweb:
Quote:
It was an interesting argument, but as things progressed, more rational heads prevailed, pointing out that the airplanes do not apply their thrust via their wheels, so the conveyor belt is irrelevant to whether the airplane will takeoff. One guy even got one of those rubber band powered wood and plastic airplane that sell for about a buck, put it on the treadmill someone foolishly donated to the Lounge years ago, thinking that pilots might actually exercise. He wound up the rubber band, set the treadmill to be level, and at its highest speed. Then he simultaneously set the airplane on the treadmill and let the prop start to turn. It took off without moving the slightest bit backwards.

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#617189 - 28/12/06 04:32 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Ok so let me get this straight....

If you belong to another forum, logically, the plane will take off ONLY if its shot out of a gun level with the ground at 27,000MPH? But on XOC, the above is BULLSHIT????

[LOL] !!!

MGJ

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#617190 - 28/12/06 04:34 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Just emailed: mythbusters@m5industries.com

Hopefully they look into this one and give it a try smile

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#617191 - 28/12/06 04:54 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
RiNkY- I bet Mythbusters won't even bother wasting their time on this one.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617192 - 28/12/06 05:07 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Quote:
Originally posted by RiNkY:
To simple Adam. Why would the plane appear to take off as per normal?

What you are saying is the same as saying, if we turned on the conveyor and span it up to say 100mph, but didn't bother to do anything with the planes engines - Just the conveyor on its own. The plane would stay in 1 place!!!
Well, Exactly! confused ?

If the conveyor were turned on and doing 100MPH and the Plane were stationary upon it, then consequently the tires are rotating at 100MPH, if thrust is therefore applied to the airframe through the engines the resulting action will be an equal and opposite reaction, Ie. Newtons Third Law, the plane will move through the AIR and eventually gain the speed required for takeoff.

Rog, this will be one of those slap yourself on the forehead moments for you and with the ability to get to 8+ Pages in a day, it is worth setting up a scenario Ie. Mythbusters to quelch this thirst for knowledge. wink

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#617193 - 28/12/06 05:12 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Anonymous
Unregistered


Lift is the force that directly opposes the weight of an airplane and holds the airplane in the air. Lift is generated by every part of the airplane, but most of the lift on a normal airliner is generated by the wings. Lift is a mechanical aerodynamic force produced by the motion of the airplane through the air. Lift acts through the center of pressure of the object and is directed perpendicular to the flow direction.

Lift is generated by the difference in velocity between the solid object and the fluid. There must be motion between the object and the fluid: no motion, no lift.

(too many years in the aerospace business I am afraid !!)

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#617194 - 28/12/06 05:51 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
*

Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by Scrabo:
Lift is the force that directly opposes the weight of an airplane and holds the airplane in the air. Lift is generated by every part of the airplane, but most of the lift on a normal airliner is generated by the wings. Lift is a mechanical aerodynamic force produced by the motion of the airplane through the air. Lift acts through the center of pressure of the object and is directed perpendicular to the flow direction.

Lift is generated by the difference in velocity between the solid object and the fluid. There must be motion between the object and the fluid: no motion, no lift.

(too many years in the aerospace business I am afraid !!)
I think we are in agreement regarding this hypothetical scenario.

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#617195 - 28/12/06 06:00 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by NY Madman:
Quote:
Originally posted by Scrabo:
[b]There must be motion between the object and the fluid: no motion, no lift.
I think we are in agreement regarding this hypothetical scenario.[/b]
But your hang-up is how motion through the fluid is achieved, right?

Motion through the fluid (air) is achieved by the engines pushing against the air around the plane, not by the wheels turning on the conveyor.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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#617196 - 28/12/06 06:13 PM Re: Know that if you do not post in this thread today the human race may cease to exist
Mobycat Offline
Member
*****

Registered: 12/09/00
Posts: 8374
Loc: the hue of dungeons and the sc...
Another way to look at it - a plane on water.

The water is most certainly not solid. Yet the plane takes off (if it has enough power to get up to speed).

The plane may take longer to take off going against current as opposed to with the current - but it will eventually.

I think...

My brain hurts. It's been WAY too long since I bothered with this stuff.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist

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#617197 - 28/12/06 06:18 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
*

Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by TravelingFool:
For the love of God... The plane would fly. Period.
I wouldn't bet my life on it... or your life.

Quote:
Originally posted by MattyX:
Madman, I fail to see how you reached the conclusion that there would be zero forward motion of the aircraft. The scenario says that the conveyor matches the speed of the plane, not the speed of the wheels. If the plane goes nowhere, the conveyor doesn't even turn.
You are wrong. In the scenario the conveyor speeds up and matches the thrust of the plane. As the pilot throttles down - which would normally cause the plane to move down the runway - the conveyor speeds up to match it. Thus there is no forward movement of the plane in the hypothetical scenario. The fuselage and the wings are not moving forward through fluid air. The forces of the air moving over the wings are not present in the hypothetical scenario.

If you were looking down from above (or anywhere for that matter) during this hypothetical scenario, the plane would appear to be not moving at all even though the the throttle is down and thrusters are going full blast. To an outside observer the plane would appear stationary.

Quote:
Madman again- the cats on a carrier are fairly irrelevant to the other discussion, but essentially they are a thrust enhancer. Perhaps the Navy could come up with a way to make jets take off of ships using thrust only, but the steam cats are fairly economical and very effective.
If the Navy could have done it, they probably already would have done so considering the amount of men that have died over the years by catapult accidents.

In order for a plane to achieve flight.. a flight where the pilots will not crash... the plane has to be moving in a forward direction to obtain the initial lift required to sustain the angle of attack to keep it climbing into the sky.

In the hypothetical scenario in this thread, there is no sound aerodynamics operating in which the nose can lift to obtain the proper angle.

A Harrier jet can lift itself vertically with it's technology, but if the pilot is not well experienced enough to know how to manuever the plane and the thrusters while in the air to obtain a proper angle, that plane will crash... even though it is already in the air. It will not obtain flight. Not viable flight where the occupants have a reasonable chance of living to see the next day.

Without forward motion, the lift it provides and the proper angle of attack... I would think the aircraft would stall and crash.

..............



"That's my story and I'm sticking to it...."

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#617198 - 28/12/06 06:54 PM Re: Know that if you do not post in this thread today the human race may cease to exist
NY Madman Offline
Member
*

Registered: 09/05/02
Posts: 5232
Loc: Florida
Quote:
Originally posted by XPLORx4:
But your hang-up is how motion through the fluid is achieved, right?
No, not at all.

I've been discussing this hypothetical scenario. In the scenario we have NO MOTION through the fluid of air.

In the scenario we only have the thrust from the engines.

Understand? Other vital components needed for flight are absent in the scenario.

Quote:
Motion through the fluid (air) is achieved by the engines pushing against the air around the plane, not by the wheels turning on the conveyor.
Yes.. but we are not moving in the scenario. There is no motion of the plane. The plane can be at maximum thrusters, but in the scenario the conveyor matches the force created by the thrust.

We still need the plane moving forward through the air to create the lift needed for flight.

Quote:
Originally posted by Mobycat:
Another way to look at it - a plane on water.

The water is most certainly not solid. Yet the plane takes off (if it has enough power to get up to speed).
Yes... the key there is the plane on the water is moving forward through the air. It makes no difference what surface is underneath the plane, as long as the plane moves forward and can create lift and the proper angle to obtain flight.

I'm saying engine thrust against the air behind the plane is not enough for flight if the plane is not moving forward through the fluid of the air.

Am I making myself clearer now.

I think these web sites will help....

http://www.grc.nasa.gov/WWW/K-12/airplane/factors.html

http://www.grc.nasa.gov/WWW/K-12/airplane/climb.html

Remember your vectors....

http://www.grc.nasa.gov/WWW/K-12/airplane/vectors.html

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#617199 - 28/12/06 07:17 PM Re: Know that if you do not post in this thread today the human race may cease to exist
XPLORx4 Offline
Member

Registered: 23/03/01
Posts: 1906
Loc: San Jose, CA
Quote:
Originally posted by NY Madman:
The plane can be at maximum thrusters, but in the scenario the conveyor matches the force created by the thrust.
There's where you've got force and thrust mixed up. The conveyor is only effective on the wheels of the aircraft. How can the conveyor counteract any thrust against the air around the aircraft?

As I said in an earlier post, the wheelbrakes on the aircraft could be locked on, but the engines (presumably on the wings) could be at full throttle, pushing the AIR. At this time, the aircraft has both zero airspeed and zero groundspeed. (The conveyor is also at zero).

Now imagine that you tie a big cable to the back of the aircraft so that it really can't go anywhere. Now imagine that someone walks up to the wheels of the aircraft and then tries to turn the tires by hand (simulating what the conveyor would interpret as forward motion). Let's say that they could somehow get those tires spinning at 100mph, so that the conveyor is also going 100mph, but in the opposite direction.

Now, you've got the tires spinning at 100mph, the conveyor moving at -100mph, and the aircraft, engines still at full throttle, pushing on the air, but the aircraft isn't going anywhere because it's secured by a rope.

What is counteracting the engine thrust against the air?

The answer: NOTHING is counteracting the thrust! Therefore, the aircraft moves forward through the fluid of air. As it does so, the tires accelerate, the conveyor accelerates negatively, but the surrounding air does not accelarate negatively, so the aircraft can build up enough airspeed to take off.
_________________________
4x4 in uppercase is $X$!!!
1997 R50: VG33E/RE4R01A/TX10/3.7/R200A/ARB/4.636/H233B/ARB/4.636/321150R15

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