Question: Will the plane fly? (warning: nerdy)
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Originally Posted by iBlueVirus
Plus, I thought we have established wheel speed and plane speed in relation to ground is irrelevant. 
Originally Posted by iBlueVirus
A runway is needed for a plan to take-off, is not to get speed on plane vs ground. The reason for it is by doing so the plane would gain MORE air speed than just props/jets alone.
But the forces are still applied only from the props or jets, no planes any of us know about have drivelines to their wheels
My statement would be true in a no wind situation.
Originally Posted by psoper
Not true- the air speed must have the wind vector added to it from it, so if you are going north at 10 mph (ground speed) with a wind from the south at 10 MPH you would technically have air speed =0, whereas if you had an air speed of 10 mph in those conditions, your ground speed would be 20 mph.
So what you are saying is that jets/props alone would generate enough aerodynamic forces on the wings provide enough lift for the plane to fly?
If that is the case, it's not physic I don't understand, it's the current technology I don't (or didn't rather). I had no idea that jets/props alone can generate so much power (thrust vector). Which has been my question all along, or rather unable to accept the fact that they do generate enough aerodynamic forces.
If that is the case, it's not physic I don't understand, it's the current technology I don't (or didn't rather). I had no idea that jets/props alone can generate so much power (thrust vector). Which has been my question all along, or rather unable to accept the fact that they do generate enough aerodynamic forces.
Originally Posted by psoper
Jets and props both impart force to the airframe by displacing air from in front of the plane to the rear, the reason that it "takes a runway" is that this force has to be applied over time to do the work of accellerating the plane to exceed its stall or minimum take-off speed where the aerodynamic forces on the wings provide enough lift for the plane to fly. But until that point, the thrust vector from the engine is the dominant force acting on the plane, with the force of gravity in equilibrium with the force of the wheels against the runway.
Last edited by DetailAddict; Jan 25, 2006 at 04:40 PM.
I don't think I was/am thinking that wheel or ground speed would contribute to take-off...
Originally Posted by psoper
But other than keeping the plane from falling to the ground, the wheels do not apply any force effecting the accelleration of the plane (unlike the case of a car or bicycle, which is where most people arguing this, and even you still Leo- seem to be losing their minds).
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Originally Posted by iBlueVirus
I just don't know if jets/props alone can generate enough air speed on the WHOLE plane for it to take-off.
That's all.
I agree, there is NOTHING ELSE!!! So the only way for the plane to take off in this situation is that the props/jets would generate enough aerodynamic forces on the wings provide enough lift for the plane to fly. So do they?
Originally Posted by psoper
I'm only saying there is NOTHING ELSE that can make the plane accellerate to the rate where it will take off.
That's all.
That's all.
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No the props and jets only provide thrust on the airframe, accellerating it forward so that the airspeed over the wings creates the aerodynamic forces. It's a subtle difference, but the lift is dependant on the air speed, not on the engines, although it is the thrust from the engines that propel the plane to the required speed.
Damn I am such a slacker!! I should be working right now. 
Alright!! We are getting somewhere (are we?)! So props/jets alone do not provide enough aerodynamic forces. However, in this case, they do move the plane forward, and yes, it's moving.
Question, where is this airspeed is coming from? As I stated, I was on the threadmill yesterday, I didn't feel any wind...
You actually stated VERY well and VERY clear. Thanks!
Which would generate enough aerodynamic forces on the wings provide enough lift for the plane to fly.
Alright!! We are getting somewhere (are we?)! So props/jets alone do not provide enough aerodynamic forces. However, in this case, they do move the plane forward, and yes, it's moving.
Originally Posted by psoper
No the props and jets only provide thrust on the airframe, accellerating it forward
Originally Posted by psoper
so that the airspeed over the wings creates the aerodynamic forces.
Originally Posted by psoper
It's a subtle difference, but the lift is dependant on the air speed, not on the
engines,
engines,
Originally Posted by psoper
although it is the thrust from the engines that propel the plane to the required speed.
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Originally Posted by iBlueVirus
Question, where is this airspeed is coming from? As I stated, I was on the threadmill yesterday, I didn't feel any wind...
But a freewheeling plane will not be subjected to that constraint, because its thrust is applied against the air, not against the treadmill.
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BTW, BlueVirus,
I think you're imagining a very short conveyer in this example. Think of it as a conveyer the length of a regular runway. The simple fact is that the speed or direction of the conveyer impose no singificant force on the frame of the aircraft because the wheels are free spinning. Therefore the airplane is free to accelerate just as if it was on a regular stationary runway. This has nothing to do with the engines providing enough airflow over the wing to generate lift. Rather the engines apply thrust to the air around it, accelerating the airplane to take-off speed just as they do under regular take-off conditions. THE MOVING RUNWAY HAS NO EFFECT ON THE PLANE.
I think you're imagining a very short conveyer in this example. Think of it as a conveyer the length of a regular runway. The simple fact is that the speed or direction of the conveyer impose no singificant force on the frame of the aircraft because the wheels are free spinning. Therefore the airplane is free to accelerate just as if it was on a regular stationary runway. This has nothing to do with the engines providing enough airflow over the wing to generate lift. Rather the engines apply thrust to the air around it, accelerating the airplane to take-off speed just as they do under regular take-off conditions. THE MOVING RUNWAY HAS NO EFFECT ON THE PLANE.
I understand in a REAL situation no matter what you do, the plane will move forward and ground speed would be > 0 no matter what is under the plane. As someone has mentioned how a plane takes off from shore against wave.
but I thought in this THEORATICAL situation there is a moving runway under the plane and the plane stays staionary in relation to the ground. With the plane staying staionary, there is just no way for the plane cantake-off with just props/jets forces alone.
but I thought in this THEORATICAL situation there is a moving runway under the plane and the plane stays staionary in relation to the ground. With the plane staying staionary, there is just no way for the plane cantake-off with just props/jets forces alone.
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Originally Posted by iBlueVirus
but I thought in this THEORATICAL situation there is a moving runway under the plane and the plane stays staionary in relation to the ground.
Originally Posted by iBlueVirus
With the plane staying staionary, there is just no way for the plane cantake-off with just props/jets forces alone.
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Exactly... I don't see anywhere in the original problem where it says the plane is stationary. This is an assumption most people wrongfully jump to.
LOL! I think we've been arguing over different things. You guys are trying to convince others that the plane will take-off because it moves in relation to air. But it also moves in relation to the ground because wheel on a moving runway is irrelevant. Which I agree…
I've been arguing that props/jets alone do not generate enough air flow to lift the plane. It requires the plane to move in relation to the ground in order to gain enough air speed to take-off. Somehow I interpreted most of the replies saying that jets/props alone would generate enough air speed. LOL!!! This is just too damn funny!!!
I just wasted bunch of time at work!! YAY!! :banana:
I've been arguing that props/jets alone do not generate enough air flow to lift the plane. It requires the plane to move in relation to the ground in order to gain enough air speed to take-off. Somehow I interpreted most of the replies saying that jets/props alone would generate enough air speed. LOL!!! This is just too damn funny!!!
I just wasted bunch of time at work!! YAY!! :banana:
