6 ms·

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

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.
- samlittlewood 10y ago
  As an aside, modern aerobatic aircraft are often rigged 0,0,0 (wing incidence, tail incidence, dihedral), so level flight will need equal elevator deflection in the appropriate direction. Less efficient - but makes for symmetrical performance.
- Zak 10y ago
  The horizontal stabilizer of most aircraft has a negative angle of attack and produces downforce, not lift in straight and level flight. This allows the center of gravity to be forward of the wing's center of lift by moving the overall center of lift forward. The result is a tendency to pitch down if airspeed decreases without other control inputs, countering the reduced airspeed. Flying inverted in a relatively stable aircraft requires a lot of forward pressure because for the inverted aircraft's wing to have a positive angle of attack, the horizontal stabilizer has an even larger positive angle of attack. The pilot must counter this with the elevator to establish a stable ratio of lift to downforce.
votingprawn 10y ago
> I'd be interested to see in this thread, who here has actually studied aeronautical engineering I studied Aerospace Engineering (PhD in Aerodynamics), and I stay out of internet conversations over "how" lift is generated. For me it is one of those topics that is just not worth debating. It seems that people get _really_ attached to their personally preferred theory of lift.
- cyberferret 10y ago
  Agreed. That is what I have noticed in this thread. Who knew aerodynamics could be as polarising as politics or religion? :P I've contributed all that I wanted to say here, and am happy to bow out now and let the conversation take its course.
  - votingprawn 10y ago
    Its a somewhat common joke in our office that if you ask 3 researchers "What is lift?" you'll get 5 answers (and probably a bit of an argument). I think "It's complicated" and "Why do you need to know?" are often the only appropriate answers, as context is important. I've read some "aerodynamics for pilots" type books that from a research point of view I considered to be, to some degree, wrong. But ultimately they were _right_ in that they taught the pilot exactly what they needed to know. In a way it reminds me of electricity. I know enough to design and make simple circuitry, but I know electrical engineers and physicists that could run rings around me at both the circuit design level and the "That's not how electricity works, you idiot!" level.
- mtreis86 10y ago
  Flight is a complex system, there are multiple variables effecting it. And yet half the responses here are regurgitated from grade school without references. http://www.afahc.ro/ro/afases/2014/forte/prisacariu.pdf http://www.afahc.ro/ro/afases/2014/forte/prisacariu.pdf
- dhimes 10y ago
  Can you point to a source for those of us who want to know the right answer (like, sailors)?
dorfsmay 10y ago
> The fact that full aerobatic and military jets do, is because they usually don't have that curved 'fish' shape cross section, but are usually symmetrically shaped on the top and bottom of the wing. Fair enough, it is symmetrical, but still has a lot of shape to it - only time I've been inverted was in a grob 103, and was a passenger for that part of the flight, here's the cross section of it's little sister which is also fully aerobatic: https://en.wikipedia.org/wiki/File:Grob_G_102_Standard_Astir_III_N17999_20040514.jpg https://en.wikipedia.org/wiki/File:Grob_G_102_Standard_Astir... My point in the gp post was that since one can fly inverted, the shape of the wing is not the only fact. I think you and I are saying the same thing.

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.

samlittlewood 10y ago
As an aside, modern aerobatic aircraft are often rigged 0,0,0 (wing incidence, tail incidence, dihedral), so level flight will need equal elevator deflection in the appropriate direction. Less efficient - but makes for symmetrical performance.
Zak 10y ago
The horizontal stabilizer of most aircraft has a negative angle of attack and produces downforce, not lift in straight and level flight. This allows the center of gravity to be forward of the wing's center of lift by moving the overall center of lift forward. The result is a tendency to pitch down if airspeed decreases without other control inputs, countering the reduced airspeed. Flying inverted in a relatively stable aircraft requires a lot of forward pressure because for the inverted aircraft's wing to have a positive angle of attack, the horizontal stabilizer has an even larger positive angle of attack. The pilot must counter this with the elevator to establish a stable ratio of lift to downforce.

votingprawn 10y ago

> I'd be interested to see in this thread, who here has actually studied aeronautical engineering I studied Aerospace Engineering (PhD in Aerodynamics), and I stay out of internet conversations over "how" lift is generated. For me it is one of those topics that is just not worth debating. It seems that people get _really_ attached to their personally preferred theory of lift.

cyberferret 10y ago
Agreed. That is what I have noticed in this thread. Who knew aerodynamics could be as polarising as politics or religion? :P I've contributed all that I wanted to say here, and am happy to bow out now and let the conversation take its course.
- votingprawn 10y ago
  Its a somewhat common joke in our office that if you ask 3 researchers "What is lift?" you'll get 5 answers (and probably a bit of an argument). I think "It's complicated" and "Why do you need to know?" are often the only appropriate answers, as context is important. I've read some "aerodynamics for pilots" type books that from a research point of view I considered to be, to some degree, wrong. But ultimately they were _right_ in that they taught the pilot exactly what they needed to know. In a way it reminds me of electricity. I know enough to design and make simple circuitry, but I know electrical engineers and physicists that could run rings around me at both the circuit design level and the "That's not how electricity works, you idiot!" level.
mtreis86 10y ago
Flight is a complex system, there are multiple variables effecting it. And yet half the responses here are regurgitated from grade school without references. http://www.afahc.ro/ro/afases/2014/forte/prisacariu.pdf http://www.afahc.ro/ro/afases/2014/forte/prisacariu.pdf
dhimes 10y ago
Can you point to a source for those of us who want to know the right answer (like, sailors)?

dorfsmay 10y ago

> The fact that full aerobatic and military jets do, is because they usually don't have that curved 'fish' shape cross section, but are usually symmetrically shaped on the top and bottom of the wing. Fair enough, it is symmetrical, but still has a lot of shape to it - only time I've been inverted was in a grob 103, and was a passenger for that part of the flight, here's the cross section of it's little sister which is also fully aerobatic: https://en.wikipedia.org/wiki/File:Grob_G_102_Standard_Astir_III_N17999_20040514.jpg https://en.wikipedia.org/wiki/File:Grob_G_102_Standard_Astir... My point in the gp post was that since one can fly inverted, the shape of the wing is not the only fact. I think you and I are saying the same thing.