7 ms·

"Longer path" has no bearing on reality. A flat plate can generate plenty of lift even with both sides the same. It's also hard to define "path," as the air sta

by nether 10y ago

"Longer path" has no bearing on reality. A flat plate can generate plenty of lift even with both sides the same. It's also hard to define "path," as the air starts convecting well ahead of the wing in subsonic flow.

hexane360 10y ago
Additionally, the paths don't meet up/join at the trailing edge of the wing. There's no reason air above and below needs to separate and meet up into the same flow.
xelxebar 10y ago
While you're on point about flat wings, in wind tunnel tests on profiled wings, you do in fact see a velocity difference between top flowing and bottom flowing streams. It's not enough of a difference, however, to cause coincident streams on the leading edge to line back up at the trailing edge.
teapot01 10y ago
NASA has even published on this issue https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html
ajross 10y ago
Flat plates generate lift even in near vacuum conditions where the whole idea of Bernoulli flow is inapplicable, even.
simion314 10y ago
If I remember right the "longer path" thing was in Encarta, there was a guy that used Encarta to prove to me that the theory is right and I believed it m it made sense I am wrong and not the encyclopedia.
cyberferret 10y ago
Sorry, but I don't subscribe to the 'flat plate' theory. There is a reason that almost every commercial (and most military) aircraft have leading edge slats to generate lift at lower speeds (by making the top of the wing more convex and the bottom of the wing more concave). If pure 'flat plate' theory was valid, then all those aircraft speeding down the runway with the leading edge of their wings canted downwards 20 or so degrees would result in the airplanes simply being pushed towards the ground and never lifting off... And Boeing, Airbus et al would build planes with flat slab wings mounted at a 45 degree angle to the airflow, because that would give the maximum lift by the 'flat plate' theory, wouldn't it? Not that I disbelieve that a flat slab cannot generate lift - but that it is probably a very inefficient way to generate lift compared to the standard aerofoil shape. [0] - https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Boeing_727-2S7_Advanced_Champion_LAX.jpg/1200px-Boeing_727-2S7_Advanced_Champion_LAX.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Bo... [1] - https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg
- dorfsmay 10y ago
  The shape of the wing makes a huge difference, so a plate or a piece of wood wouldn't make a good wing, but it is still able to fly. Proof? Inverted flight on low power aircraft and gliders.
  - cyberferret 10y ago
    And as I have mentioned elsewhere on here - I have flown inverted a few times, and to do so take a tremendous amount of forward pressure on the control stick to even try and attempt to hold altitude while inverted, in order to counteract the wings natural (slight) positive AoA and the tendency for the wing to move towards it upper surface. In fact, most of the aircraft I have flown would not be able to sustain inverted flight at all. The fact that full aerobatic and military jets do, is because they (as I explained earlier) usually don't have that curved 'fish' shape cross section, but are usually symmetrically shaped on the top and bottom of the wing. To whit, I've had the fortune to fly an old DH Tiger Moth biplane - on that little baby, when you approach the stalling point, you can actually see the the canvas on top of the bottom wing bulge and contort with pressure differential, and you can hear the sucking sounds as the airflow struggles to 'stick' to the wing. There is a little movement on the bottom surface of the top wing too, but not as pronounced. I'd be interested to see in this thread, who here has actually studied aeronautical engineering, or flown actual aircraft, and who is relying on YT videos or a pure theoretical approach to come up with these theories? Also interestingly, I believe most of the textbooks I used at flight school were filled with data from NASA and other US military branches with regards to flight dynamics etc., and here on this thread we see articles from NASA (albeit aimed at K-12 audience rather than trainee pilots) basically disproving their earlier academic research.
    - jonsen 10y ago
      > I have flown inverted a few times, and to do so take a tremendous amount of forward pressure on the control stick to even try and attempt to hold altitude while inverted, in order to counteract the wings natural (slight) positive AoA and the tendency for the wing to move towards it upper surface. I don't think that is right. The tail wing has a different angle of attack than the main wing. On the order of one degree I think. This is so to give a self stabilizing effekt. When flying upside down you have to compensate heavily to avoid what would be a destabilizing effect.
stereo 10y ago
Yes, it’s hard to visualise for some people, but it’s the same reason why a small sailboat can turn with a flat rudder.

by nether 10y ago

hexane360 10y ago

Additionally, the paths don't meet up/join at the trailing edge of the wing. There's no reason air above and below needs to separate and meet up into the same flow.

xelxebar 10y ago

While you're on point about flat wings, in wind tunnel tests on profiled wings, you do in fact see a velocity difference between top flowing and bottom flowing streams. It's not enough of a difference, however, to cause coincident streams on the leading edge to line back up at the trailing edge.

teapot01 10y ago

NASA has even published on this issue https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html

ajross 10y ago

Flat plates generate lift even in near vacuum conditions where the whole idea of Bernoulli flow is inapplicable, even.

simion314 10y ago

If I remember right the "longer path" thing was in Encarta, there was a guy that used Encarta to prove to me that the theory is right and I believed it m it made sense I am wrong and not the encyclopedia.

cyberferret 10y ago

Sorry, but I don't subscribe to the 'flat plate' theory. There is a reason that almost every commercial (and most military) aircraft have leading edge slats to generate lift at lower speeds (by making the top of the wing more convex and the bottom of the wing more concave). If pure 'flat plate' theory was valid, then all those aircraft speeding down the runway with the leading edge of their wings canted downwards 20 or so degrees would result in the airplanes simply being pushed towards the ground and never lifting off... And Boeing, Airbus et al would build planes with flat slab wings mounted at a 45 degree angle to the airflow, because that would give the maximum lift by the 'flat plate' theory, wouldn't it? Not that I disbelieve that a flat slab cannot generate lift - but that it is probably a very inefficient way to generate lift compared to the standard aerofoil shape. [0] - https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Boeing_727-2S7_Advanced_Champion_LAX.jpg/1200px-Boeing_727-2S7_Advanced_Champion_LAX.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Bo... [1] - https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg https://www.metabunk.org/sk/20141127-081301-jrgr5.jpg

dorfsmay 10y ago
The shape of the wing makes a huge difference, so a plate or a piece of wood wouldn't make a good wing, but it is still able to fly. Proof? Inverted flight on low power aircraft and gliders.
- cyberferret 10y ago
  And as I have mentioned elsewhere on here - I have flown inverted a few times, and to do so take a tremendous amount of forward pressure on the control stick to even try and attempt to hold altitude while inverted, in order to counteract the wings natural (slight) positive AoA and the tendency for the wing to move towards it upper surface. In fact, most of the aircraft I have flown would not be able to sustain inverted flight at all. The fact that full aerobatic and military jets do, is because they (as I explained earlier) usually don't have that curved 'fish' shape cross section, but are usually symmetrically shaped on the top and bottom of the wing. To whit, I've had the fortune to fly an old DH Tiger Moth biplane - on that little baby, when you approach the stalling point, you can actually see the the canvas on top of the bottom wing bulge and contort with pressure differential, and you can hear the sucking sounds as the airflow struggles to 'stick' to the wing. There is a little movement on the bottom surface of the top wing too, but not as pronounced. I'd be interested to see in this thread, who here has actually studied aeronautical engineering, or flown actual aircraft, and who is relying on YT videos or a pure theoretical approach to come up with these theories? Also interestingly, I believe most of the textbooks I used at flight school were filled with data from NASA and other US military branches with regards to flight dynamics etc., and here on this thread we see articles from NASA (albeit aimed at K-12 audience rather than trainee pilots) basically disproving their earlier academic research.
  - jonsen 10y ago
    > I have flown inverted a few times, and to do so take a tremendous amount of forward pressure on the control stick to even try and attempt to hold altitude while inverted, in order to counteract the wings natural (slight) positive AoA and the tendency for the wing to move towards it upper surface. I don't think that is right. The tail wing has a different angle of attack than the main wing. On the order of one degree I think. This is so to give a self stabilizing effekt. When flying upside down you have to compensate heavily to avoid what would be a destabilizing effect.

stereo 10y ago

Yes, it’s hard to visualise for some people, but it’s the same reason why a small sailboat can turn with a flat rudder.