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#1
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On Fri, 09 Sep 2005 14:29:18 +0200, Thomas Borchert
wrote: Wings generally tend to have a curved suface. The upper surface has a greater arc or curvature than the lower surface. As the air flows across the surfaces of the wing, the upper surface air is forced to move faster than the lower surface air thus causing a pressure difference between the two surfaces. Forced by what? And how does your "theory" explain inverted flight? I don't buy it. BTW, this has been beaten to death in countless aviation newsgroup discussions. I once thought like you, because I was taught that way. It's still a bad theory. I suggest googling. Keywords might be: lift, flight, Bernoulli, Newton. He is describing the traditional airfoil theory which is correct. It is the most efficient method as it produces lift with minimal drag. That's what most people are taught. There is another mode that is related to the force of the air impacting on the bottom of the wing at high AOA producing lift as well. Think of your control surfaces. Your rudder control surface is symmetric, yet it produces horizontial components of force. IIRC, the Jeppesen books cover high AOA effects as well. Inverted flight is accomplished by the second of the two effects. They have to fly at a higher AOA relative to normal flight to compensate for the airfoil effect. Some aerobatic planes have symmetric airfoils for this reason. As AOA increases, the deflection takes more of a role. At stall, the deflection is suffcient for the airfoil effect to be interfered with and ceases. Thus a large component of left is lost. You drop. You still have some lift, but it is not sufficient to keep you airborne. Jim http://www.unconventional-wisdom.org |
#2
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Jimbob,
He is describing the traditional airfoil theory which is correct. Uhm, no. -- Thomas Borchert (EDDH) |
#3
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He is describing the traditional airfoil theory which is correct. Uhm, no. Oh uhm, YES! |
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On Fri, 09 Sep 2005 13:57:30 +0000, Jimbob wrote:
[snip] There is another mode that is related to the force of the air impacting on the bottom of the wing at high AOA producing lift as well. Think of your control surfaces. Your rudder control surface is symmetric, yet it produces horizontial components of force. IIRC, the Jeppesen books cover high AOA effects as well. Isn't this the theory behind lifting bodies (aka, Space Shuttle) and why many low wing planes tend to generate some minor amount of lift across the fuslage area, in between the root coords? [snip] |
#5
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Jimbob wrote:
On Fri, 09 Sep 2005 14:29:18 +0200, Thomas Borchert wrote: Wings generally tend to have a curved suface. The upper surface has a greater arc or curvature than the lower surface. As the air flows across the surfaces of the wing, the upper surface air is forced to move faster than the lower surface air thus causing a pressure difference between the two surfaces. Forced by what? And how does your "theory" explain inverted flight? I don't buy Forced by limiting the space through which the fluid must flow. Think of your garden hose. If you put your thumb over the end and constrict the space the water flows faster through the opening. As the speed increases the pressure decreases, air moves from high pressure to low pressure and the wing of the airplane is in the way of this movement so it is lifted up with the high pressure air. This also explains wing tip vortices and why for a given configuration a higher aspect ratio wing will produce more lift than a lower aspect ration wing. Inverted flight and equal camber wings use AOA to create the air pressure differential. Margy BTW, this has been beaten to death in countless aviation newsgroup discussions. I once thought like you, because I was taught that way. It's still a bad theory. I suggest googling. Keywords might be: lift, flight, Bernoulli, Newton. He is describing the traditional airfoil theory which is correct. It is the most efficient method as it produces lift with minimal drag. That's what most people are taught. There is another mode that is related to the force of the air impacting on the bottom of the wing at high AOA producing lift as well. Think of your control surfaces. Your rudder control surface is symmetric, yet it produces horizontial components of force. IIRC, the Jeppesen books cover high AOA effects as well. Inverted flight is accomplished by the second of the two effects. They have to fly at a higher AOA relative to normal flight to compensate for the airfoil effect. Some aerobatic planes have symmetric airfoils for this reason. As AOA increases, the deflection takes more of a role. At stall, the deflection is suffcient for the airfoil effect to be interfered with and ceases. Thus a large component of left is lost. You drop. You still have some lift, but it is not sufficient to keep you airborne. Jim http://www.unconventional-wisdom.org |
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Forced by limiting the space through which the fluid must flow. Think
of your garden hose. If you put your thumb over the end and constrict the space the water flows faster through the opening. As the speed increases the pressure decreases, air moves from high pressure to low pressure and the wing of the airplane is in the way of this movement so it is lifted up with the high pressure air. This also explains wing tip vortices and why for a given configuration a higher aspect ratio wing will produce more lift than a lower aspect ration wing. PV=nRT |
#7
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("Margy" wrote)
[snip] Forced by limiting the space through which the fluid must flow. Think of your garden hose. If you put your thumb over the end and constrict the space the water flows faster through the opening. As the speed increases the pressure decreases, air moves from high pressure to low pressure and the wing of the airplane is in the way of this movement so it is lifted up with the high pressure air. Garden hose + thumb: "As the speed increases the pressure decreases..." part throws me. As the flow increase? C'mon over here and explain it again please. Yes, yes. Of course I'll keep the hose kinked --- almost in range. hehehe Montblack |
#8
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Gone Flyin'. -----==0==----- wrote: It's also worth noting that VNE decreases with altitude. Actually, it's not. the true airspeed at which VNE occurs is greater as altitude increases, but the calibrated aurspeed (VNE is defined as a calibrated airspeed) remains the same regardless of altitude. |
#9
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buttman wrote:
He said that lift is directly and soley related to AOA and AOA only. So if you are doing slow flight, you are producing more life than you are when you're cruising. So, if follows that if I stand my airplane on its tail, sitting on the ground with an airspeed of zero, it's producing the maximum amount of lift possible. |
#10
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Thats what I told him. This guy is an amazing instructor. He's an MEI
and a CFII with a ton of CFI and CFII singoffs. I was just wondering if we were thinking of two different concepts. My definition of lift being different than his... |
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