With my basic understanding of aerodynamics the canards are forward of the center of mass thus there alpha should be positive if you want to generate lift. Evey video I see the forward canards put themselves at the same angle as the aft elevators, so to my understanding with there negative alpha they should generate downforce. But due too the amazing maneuverability of the SU-33 they seem to be generating lift so how do they do it?
In: Physics
There’s two different but related things going on.
1) The angle of attack (alpha) is relative to the *local* wind. The wing, as the largest lifting surface, has a big influence on the local flow direction around both the canards and tail, so even if the canards look like they’re at negative angle relative to the wing/body, they may be at positive alpha relative to the local airflow, hence develop lift. You can see this phenomenon really clearly if you look at the engine mounting angle on rear-engine jets like the MD-80, or the rain deflectors over the doors on large commercial jets. Those are all parallel to the local airflow.
2) The SU-33 canards are very small relative to the wing and tail, so they’re not there for stability, and they are relatively low aspect ratio so they don’t generate lift very efficiently. What they do do is throw an enormous energetic vortex, which helps prevent the wing immediately behind from stalling at high angle of attack. This is a similar function to the small fin you see on the nacelle of many commercial jets, or the leading edge extensions on the F/A-18…they help the wing function at higher alpha, enhancing lift and manueuverability.
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