Does a steady tailwind “push” an airplane?

Clark1961 said:
Are you really asking about the difference between 4 point sources and a continuous system?
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Continuous system, there's some kind of magic **** there, LOL. Take a look at a 747 engine hazard diagram, engines 1&2 and 3&4 are blended together at about 50 ft and all four are blended together at a couple hundred.
 
GlennAB1 said:
Continuous system, there's some kind of magic **** there, LOL. Take a look at a 747 engine hazard diagram, engines 1&2 and 3&4 are blended together at about 50 ft and all four are blended together at a couple hundred.
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Okay, that's one case of ignoring reality for you. Here's your next opportunity: what is wake turbulence for $100 Alex.
 
Clark1961 said:
Okay, that's one case of ignoring reality for you. Here's your next opportunity: what is wake turbulence for $100 Alex.
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Is wake turbulence only felt directly below the path of an aircraft? No. I think you should research that a little further. Wake turbulence is created by wingtip vortices.

NASA credits Newton's laws, can't argue with that, but they have this nice little summary which backs what I've said:

Summary
Lift and drag are mechanical forces generated on the surface of an object as it interacts with a fluid. The net fluid force is generated by the pressure acting over the entire surface of a closed body. The pressure varies around a body in a moving fluid because it is related to the fluid momentum (mass times velocity). The velocity varies around the body because of the flow deflection
 
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GlennAB1 said:
Is wake turbulence only felt directly below the path of an aircraft? No. I think you should research that a little further. Wake turbulence is created by wingtip vortices.

NASA credits Newton's laws, can't argue with that, but they have this nice little summary which backs what I've said:

Summary
Lift and drag are mechanical forces generated on the surface of an object as it interacts with a fluid. The net fluid force is generated by the pressure acting over the entire surface of a closed body. The pressure varies around a body in a moving fluid because it is related to the fluid momentum (mass times velocity). The velocity varies around the body because of the flow deflection
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Are you insinuating that a moving fluid (i.e. airmass) exerts pressure/force on something contained within it, like an airplane? :eek:
 
GlennAB1 said:
Take a Cessna 172R for example. Numbers taken from Wikipedia. Wing area: 174 sq ft. That's roughly 25,000 square inches. Gross weight 2,450 lb., use 2,500 for convenience.
2,500 lb. ÷ 25,000 sq. in. = .10 lb./sq. in.

That's 1/10 of 1 psi average differential required to lift the aircraft.

A Boeing 747 works out to just over 1 psi average differential required at MTOW.
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Exactly. That differential is tiny compared to the atmospheric pressure of 14.7 PSI at sea level. The airfoil only has to alter the pressures over it a small amount.
 
PaulS said:
But in the grand scheme of things you are right, the AP is still part of the airmass it is travelling in. I think.
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You think right. A fish in a river moves with the flowing water, as does a swimmer who, if he swims across the river perpendicular to the current, will end up well downstream on the other side but won't feel any "push" on the upstream side of his body as he crosses. If he wants to arrive at a point directly across the river from where he started, he has to aim at the bit of water that will be at the desired point at the time he arrives there; he crabs across the river, and still feels no push on the side.

Gravity works only in the vertical. It has no horizontal effect on your airplane as it drifts with the wind.
 
GlennAB1 said:
Is wake turbulence only felt directly below the path of an aircraft? No. I think you should research that a little further. Wake turbulence is created by wingtip vortices.

NASA credits Newton's laws, can't argue with that, but they have this nice little summary which backs what I've said:

Summary
Lift and drag are mechanical forces generated on the surface of an object as it interacts with a fluid. The net fluid force is generated by the pressure acting over the entire surface of a closed body. The pressure varies around a body in a moving fluid because it is related to the fluid momentum (mass times velocity). The velocity varies around the body because of the flow deflection
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You think I should research it further? What an arrogant ass. You dream about pressure differential and ignore Newton. Why does a wing stall? is it because downflow is less than the aircraft weight? Of course it is. Why does a pressure drop occur? Is it because airflow is deflected down? Of course it is. Stop pretending to understand fluid dynamics and stick with being a mechanic/inspector.
 
Clark1961 said:
You think I should research it further? What an arrogant ass. You dream about pressure differential and ignore Newton. Why does a wing stall? is it because downflow is less than the aircraft weight? Of course it is. Why does a pressure drop occur? Is it because airflow is deflected down? Of course it is. Stop pretending to understand fluid dynamics and stick with being a mechanic/inspector.
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So, differential pressure has nothing to do with lift, but wing stall is related to pressure drop... think about that.
 
Dan Thomas said:
Exactly. That differential is tiny compared to the atmospheric pressure of 14.7 PSI at sea level. The airfoil only has to alter the pressures over it a small amount.
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Thank you.

Everyone should understand, that is not the sole producer of lift, I never implied it was (even if Clark assumed I did). When AOA increases, it also causes pressure on the wing lower surface to increase. Airfoil shapes complicate lift even more.

The old school reason for lift of a basic airfoil, that everybody was taught, was "for level flight", and that was usually stated in the description. It still holds true.
 
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