Can the plane take off?

[RyderOCZ]

Simple answer is this...and think about it guys...come on.

 

The engines are pushing on the plane, it would push it forward no matter what the ground is doing beneath the wheels, period.

 

This example would just make the wheels spin twice as fast because the planes ground speed would = 2 x airspeed (no wind factor mentioned, this statement based on no head/tail wind )

[Guest LookBackX2]

Is the assumption that the plane has not and will not gain velocity taken into account?

 

I ask because regardless of the belt's speed or type/location of prop if propeller driven, the rate at which the wheels spin seems unimportant here.

 

As long as the plane is able to gain velocity, and as a result, airspeed.....why wouldn't it fly.

[krazypoloc]

No the plane will not gain any groundspeed or velocity no matter what.

[werdwerdus]

If we are talking about a jet aircraft, there is no air movement across the wing because the thrust of the engine is negated by the moving runway. Jet air craft will not take-off in this scenario.

 

Even if it is a prop, or turbo-prop, their may possible be enough air movement across the wing. I think this would only be possible on a twin engine though, as a single would only create air movement around the fuselage and only a small portion of the wing. An airplane with a propeller might be able to take off.

 

qft

[Guest LookBackX2]

So the airplane is tied down, or what? The only thing affecting it is the rpm of the tires. Pilots it woould be like having 1/2 the diameter landing gear. Twice the rpm. How does this change anything else involved if there aren't more stipulations?

[werdwerdus]

The RPM of the tires is irrelevant, since the RPM would necessarily increase without bound in this situation, which is not physically possible (the wheels and/or conveyor belt would eventually fail due to the extreme stresses of the high rpm/speed)

 

so theoretically we can assume the wheels and belt would keep increasing at an equal but opposite rate, therefore cancelling any effect they have on the airplane's ability to take off. THe only thing we have to consider then is that the airplane has an absolute velocity of Zero, and if we assume the airspeed is also Zero (which may be a wrong assumption, maybe there is extreme winds :-P) then the plane won't take off.

[Thraxz]

It comes down to how the speed is monitored. If it's measured at the wheel it'd exponentially increase speed until something broke (within seconds). The wheels would turn, then the conveyor would turn increasing the wheel speed which would in turn increase the conveyor back and forth in a positive feedback situation until something failed.

 

If it's measured as airspeed, it'd take off nicely.

[ReelFiles]

You're all reading way too much into it.

 

Everything has to to do with the conveyor belt canceling out the speed at which the plane tries go.

 

The plane is stationary

 

plane stationary = no wind

 

no wind = no lift

 

no lift = no fly

[3stars]

The plane is stationary

 

plane stationary = no wind

 

no wind = no lift

 

no lift = no fly

it really is this simple and it don't take no degree to fiugre it out neither.

[dr_bowtie]

are you guys still debating this topic...you losers need to get a life..

 

 

EDIT: if you google this topic you will see it's been a long going question...geez... there must be a million forums with the same topic post atleast once...

[radodrill]

ok...I wanted to keep my mouth shut, but radodrill....for having "passed the FE exam, and having 2 BS degrees in engineering," you don't have a firm grasp of physics.

...

I also have a BS in aerospace engineering and mechanics, the only difference between our degrees is that mine came from an accredited university not the shopping mall.

 

My degrees are from an ABET accredited program (BTW it isn't the university, but rather the degree program that gets the accreditation).

 

The boat example that you just gave is completely different than the airplane example. the water in a riverbed is naturally flowing downhill. the air doesn't naturally "flow" at speeds that will allow a plane to take off. (don't even start with hurricanes and tornadoes cause that is just being stupid.) In the question stated above, the situation is this:

 

immagine the there is a flagpole right next to the planes wingtip on the side of the conveyor belt. this flagpole is on solid ground....it doesn't move. the conveyor provides enough friction into the system to keep the plane stationary with respect to our flagpole. To possibly think that an engine mounted anywhere on a plane can move enough air across the wing, while the plane's groundspeed is zero, to cause the plane to lift off is crazy

 

The original question never states anything about friction; it merely states that it moves at the same speed as the aircraft; but in the opposite direction. Even in the case where the conveyor matches the rolling speed of the wheels; the plane would still be able to move wrt the flagpole you mentioned, the only thing is the wheels would spin very fast at an increasing rate; this is true because (from a stop; i.e. engines and conveyor at rest) the plane would have to start moving wrt the conveyor (and flagpole) before the conveyor would start moving; the rolling speed of the wheels and conveyor would reach infinitesimal speeds, but the plane would still be accelerating wrt the flagpole.

 

The boat example is in many ways similar to the aircraft; in particular that the "fluid" in which they operate isn't "linked" to the conveyor.

[ericgcollyer]

I have worked at an Airport before and my opinion is the plane would be able to take off under certain conditions. I have witnessed (with smaller plains of course) planes tied to the ground take off under high wind speeds. If the wind is blowing fast enough to push wind across the wings at >100% the necessary speed at which the plane takes off at, the plane could get off the ground rather easily. If there was no wind blowing the plane could not take off. Wind reduces the speed at which a plane takes off. Thats why planes always take off into the wind. Ever taken off and then made a 180 degree turn? Now you know why. Think about it. If you have to have wind moving over your wings at 70MPH in order to take off, if you already have a 35MPH headwind you are already halfway there. If the wind is a tailwind, then you have to go 105MPH in order to take off. The problem that I foresee is that if your engines are at full blast, and a strong headwind comes to get you off the ground you could be in trouble. Now your wheels are not keeping you from moving forward and you will gain forward speed too fast. This speed will cause an enormous amount of lift(due to the increased rate at which the wind is moving over the wings) and the plane's nose will rise. If it rises too much the wings will lose their lift and then the plane will stall.

 

It all depends on how you define take off. Will the plane be able to get off the ground? Yes. Will it be able to fly without stalling? We'll see...