AstroGimp01
Space Marshal
Flying is all about relative wind over the wing, ground speed is irrelevant.
View: https://www.youtube.com/watch?v=f7u1jzjFL8s
'Gimp
'Gimp
Please put this to rest for me (argument amongst friends)
- Thread starter Callahad
- Start date
Shadow Reaper
Space Marshal
No. I didn't say anything like that. Do you even have high school physics? What I said is entirely correct.
The hypothetical says the belt and wheels match speed, so the plane is not moving forward or back. In this instance, the only wind moving over the wing is generated by the engine, (unless there are other very unusual variables not in the text) and if that wind is blowing across the wing, it can produce enough lift for takeoff.
i think i might have done a class or two more then you because : as soon as the propeller starts pulling the belt and the wheel CAN NOT MATCH SPEED because the wheels are free
so has soon as the propeller starts pulling the wheels will spin faster if you make the belt go faster the wheels will just spin faster in reaction to it
the movement forward generated by the propeller wont stop
its the same thing as if your standing on the belt in roller blade and holding the side you can make the belt go as fast as you want its not harder to hold on only difference is the weels spin faster
its the moovement forward that provide the lift under the wings the belt does nothing to stop that movement because the propeller is acting like your hand on the rails pulling the plane forward until it reach takeoff speed
the wings only care about lift they dont care about how fast the ground under them is moving the only way that plane wont take off is if the pilot forgot to take off the BRAKES
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Bigcracker
Space Marshal
Take off speed helps but is not the major contributing factor. As long as the engine has power and gets lift and the wings of the aircraft generate a good enough laminar flow you should be able to take off just fine. In WW2 aircraft carriers would sail directly into the wind to help planes take off from a crowded deck. So it shouldnt really matter if you're on a treadmill or not.
The speed of the wheels can only be in one case the same as the speed of the belt, that is when the aircraft stands still. When the aircraft is moving forward, the speed of the belt always is half the speed of the wheels, assuming that the friction of the wheel bearing is zero.
Shadow Reaper
Space Marshal
That's a good answer, but you answered a different question than the one atop this thread. If in an hypothetical someone stipulates very specifically a certain set of conditions, you are not answering their question by supplying a new set of conditions.
Th proper answer is really to say that the above in its current form is a Conceptually Confused Question that has no correct answer. It suffers critical reference failure by speaking vaguely that the belt is designed go move at the same speed a the wheels, but technically it does not say the belt moves at the same speed as the wheels.
If the belt and wheels are not moving at the same speed, I suppose again you might stipulate that the wheels are dragging, and the plane moves forward, but you are not answering the question that was asked, but instead one of your own choosing.
the question is flawed because it is physicly not possible to have the belt and the wheels turn at the same speed once the propeller is engaged .....so no one can answer the question in that form
so one has to look at the intent of the question and i do beleave the intent was to know if a plane would take off from a conveyer belt if the conveyer belt matched the take off speed of the plane and the answer to that question is YES the plane would take off
also i seriously doubt you will ever have a sufficient amount of prop wash to provide enough lift under the wings to permit a plane to do a Vertical take off unless you turn the prop on their axes like an osprey but then its not the wings that provide the lift but the propellers
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ArmoredCarbon
Space Marshal
The plane could take off just fine because the speed the wheels spin doesn't factor into the speed of the airplane. All planes produce thrust by acting on the AIR around them. The largest source of drag is also from the air, part of why plane wheels are so small is to reduce drag from the wheels even further. The conveyor belt could spin at several hundred Mph and a plane would still be able to take off just fine. The plane could just as easily have low friction skis and still take off from the conveyor belt.
Let's throw in some Fake numbers:
The Car pulls the belt with a force equal to 1000kg=CarForce.
The Plane is also accelarating with a force equal to 1000kg=PlaneForce.
On first glance this looks like a balanced System,
which would be true, if the plane would be atached to the Belt,
but it actually stands on Weels, so a huge part of that CarForce is lost, let's say 80%. (A plane behaves like a Bobycar when it comes to it's weels)
So now we look at the more accurate Numbers::
CarForce=1000kg* (100% - 80%) = 200kg
PlaneForce=1000kg
And this System is havily in favour of the Plane, also keep in mind, the faster the Plane gets, the more lift will be generated and therfor the Friction will be further reduced, resulting in even less backwards accelearation of the plane.
The Car pulls the belt with a force equal to 1000kg=CarForce.
The Plane is also accelarating with a force equal to 1000kg=PlaneForce.
On first glance this looks like a balanced System,
which would be true, if the plane would be atached to the Belt,
but it actually stands on Weels, so a huge part of that CarForce is lost, let's say 80%. (A plane behaves like a Bobycar when it comes to it's weels)
So now we look at the more accurate Numbers::
CarForce=1000kg* (100% - 80%) = 200kg
PlaneForce=1000kg
And this System is havily in favour of the Plane, also keep in mind, the faster the Plane gets, the more lift will be generated and therfor the Friction will be further reduced, resulting in even less backwards accelearation of the plane.
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Shadow Reaper
Space Marshal
Sure it is. They turn at the same speed whenever horizontal V=0, is when the engine is off or if the plane is tied down. Given the flawed form of the question, both these are decent answers, but i think we can agree, there re no correct answers because of the flaws in the question.
Disclaimer: I like it when things explode or catch fire
Okay, let's take that theoretical question and let the Math do it's magic. (This time with real Numbers) (Do you know the Blog "What if?")
The plane as requested is a Boeing 747, with it's 4 Engines it can Accelerate with the Power of 1103.2kN (KiloNewton)
As mentioned earlier we will lose a huge amount of Force to friction (which causes other Problems, but let's ignore that for the moment)
The Weels of this Plane can be assumed to be similar to Truck weels, so we can use their Numbers to Calculate the Rollresistance of a 747. (The Force that is slowing down the 747)
Rolling resistance coefficient of aTruckweel on Aspahlt = 0.01
When Empty a 747 weigghs 184567kg which equals to a downward force of ~ 1810kN
So the actual Rollresistance of an empty Boeing 747 is 18,1kN [1810kN * 0.01]
Obvisuly, that's far less, than the 1103,2kN of output from the Engine.
In fact, we need to amplify these 18,1kN by the Factor of ~61 to balance it out.
Simpliest way would be, to pull the Belt 61 times harder, than the 747 is accelerating.
To do that we need something, that is able to pull the Belt with a Force of 67295.2kN
That is a Force equal to the weight of 6 ,862 kT that's the weight of roundabout 900 Auroras!
So to hold the 747 in place only by Friction we need to atach 900 Auroras to a Belt, and throw them down a Cliff.(let's ignore the air resitence here)
This would produce enough rollresistance to counter the 4 Engines of a Boeing 747 standing on that Belt.
If this sounds reasonable to you, i would like to remind you to the fact, that the Weels will create so much heat in the process, that they will catch fire, if they don't the rubber will be ripped apart by the centrifugal force, and flying around like Bullets.
Once the Weels are gone, we switch over from rollresistance to friction which means, the 747 is accelerating backwards, which would instantly kill the Pilot of the Boeing (Like a Car crashing into a Wall at very high speed)
The undercarriage would break away, as it's not build to survive this huge amounts of force., so the Boeing is now sliding on it's Belly with some big holes in it's wings.
Wait Wings, Airplanes carry their fuel in the Wings, which propaly means, we have pirced Fueltanks and a quickly heating up belly...
Yep, I'm pretty shure, that Boeing won't take off, it will lose it weels be pierced by it's undercarriage and finaly catch Fire.
PS: please don't try that at home.
PPS: Is anyone amazed of how strong that belt must be to not be ripped apart by the weight of 900 Auroras?
I have had my RC plane lift off without moving forward in a strong wind.
The treadmill is irrelevent. Air speed over the wings = lift. Subject closed.
The treadmill is irrelevent. Air speed over the wings = lift. Subject closed.
As someone who works on aircraft for a living.... Yes, it will take off, assuming that the bearings/axles/wheels do not fail due to having a significantly higher speed. Wheels mean nothing for an airplane, hence why some have skis or floats. Ground speed means nothing as long as it can get air lift it's wings. Just the other day we had a high wind warning and I got to watch a cessna 172 come it at with a major headwind what would be at most walking speed, which is way under the "take off ground speed" But plenty for it to float. STOL bush planes are another great example, as they can take off in 20 feet or less (someone posted a video up there about this). What would be fun is watching a STOL vs a 50 foot treadmill set to about 75mph, and assuming it can be held from rolling backwards, it would take off in only a slightly increased distance, and we're talking a foot or less extra distance, mostly due to friction. You can test it at home with a small RC airplane (one that has wheels) and a regular treadmill, assuming you don't hit the control panel posts, it will take off no problem.
Honestly, why are you all still discussing this? The answer is yes. A couple people got it wrong, which is amusing, but no matter how you look at it the answer is the same... yes. "But tire speed..." still yes. "But the belt matching speeds..." still yes. "But the curvature of the earth... " still yes. "But, theory of relativity, is the plane moving or the planet..." FFS, still yes! The plane can take off... If you don't get it, please stop trying and move on.
Also, YAY! It's my home. Bush pilots up here sure are a nutty bunch. I tell you what though, they sure have some amazing stories when you get them drunk in a bar. If you ever have the chance, buy one a beer and just let the stories flow.
Also, YAY! It's my home. Bush pilots up here sure are a nutty bunch. I tell you what though, they sure have some amazing stories when you get them drunk in a bar. If you ever have the chance, buy one a beer and just let the stories flow.
That plane is the Piper Super Cub, not a bad way to spend $150,000+. It's what bush pilots rub off to late at night. Mainly, because it can do just whats in the video. They are amazing planes but I have never seen one take off that short. I doubt that plane is stock.
