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Compared to your regular asymmetric cambered airfoil, How much does lift do supercritical airfoils produce?

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    $\begingroup$ Supercritical aerofoils and 'regular' aerofoils have characteristics that suit them to different applications. The lift produced depends on airspeed, angle of attack and other factors. You can't say that a supercritical aerofoil produces n times the lift of a regular aerofoil without being specific about the conditions. $\endgroup$ – CatchAsCatchCan Oct 25 at 23:43
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Supercritical airfoils produce comparably more lift than conventional cambered airfoils but less than optimised high-lift airfoils. This is because

  • they have blunter noses which work over a wider angle of attack range,
  • the blunt nose also allows to use effective slats or Krüger flaps,
  • they have plenty of camber in the aft section of the airfoil and
  • the high rear loading allows for thin, highly cambered flaps.

From history.nasa.gov:

In the course of developing the wings for these flight programs, it was learned that the supercritical airfoils had excellent high lift characteristics because of their large leading-edge radii. This important benefit tended to offset the fact that their subcritical profile drag is higher than for comparable 6-series sections.

However, the forward part contributes relatively little to lift because it has negative camber. Also, the rear loading causes a high pitching moment.

In the supercritical speed region their upper side produces more suction since local speeds can reach up to Mach 1.3 while conventional airfoils must struggle to keep speeds subsonic. Part of that advantage is used up by making the airfoil thicker so suction on the lower side is also higher than on conventional airfoils, but an advantage remains. More recent airfoils add some more lift at the nose by designing a slow speed rise on the lower side while the upper side accelerates the local flow more quickly. Their main lift, however, comes from the thin, highly cambered aft section.

When R. Whitcomb researched supercritical airfoils, he noticed their high subsonic lift and modified the general shape by adding more forward camber into the GA(W)-1 and -2 (General Aviation Whitcomb) airfoils which became popular choices for modern GA aircraft due to their high lift and benign stall characteristics (witness 93 hits on Dave Lednicer's incomplete guide to airfoil usage, among them the Piper PA-38, the Glasair and the Edgley Optica).

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  • $\begingroup$ @RobertDiGiovanni Modern super-critical airfoil can be thin and have large stall AOA (at least in non-icing, contamination-free condition). $\endgroup$ – JZYL Oct 27 at 1:24
  • $\begingroup$ Peter Kampf, appreciate your continued refinements. Perhaps the question would be better phrased as "which wing produces more lift at a given speed" as this has become an incredibly relevant subject for newer airliner wings and could lead to improved procedures for when to apply slats and flaps. $\endgroup$ – Robert DiGiovanni Oct 27 at 13:02
  • $\begingroup$ The larger leading edge seems to universally improve higher AOA characteristics, particularly Clift/Cdrag vs Alpha, where many of the sharper leading edge designs begin to fall off at around 5 degrees! Looking at even some of the early Gottingen thick airfoils, amazing that their lift to drag was very favorable (So to save drag use a smaller Gottingen). $\endgroup$ – Robert DiGiovanni Oct 27 at 13:06
  • $\begingroup$ "...while conventional airfoils must struggle to keep speeds subsonic" Must they? They should, primarily for the sake of lower drag, but strictly speaking the OP didn't ask about drag ;) Given the same conditions (which we must assume for fair comparison), local speeds (or rather, peaks) will be higher on the conventional airfoil, and the question is (indirectly) how that will affect lift. I don't think it's clear from the paragraph; some may even conclude that speeds are lower... $\endgroup$ – Zeus Oct 27 at 23:55
  • $\begingroup$ @Zeus this is why the Reynolds number formula may need a Mach factor built in. At lower Mach, "conventional" airfoils benefit from accelerated airflow (circulation) over the top, but, as aircraft speeds increased, began to encounter the shockwave "barrier". Without taking Mach into account, at lower airspeeds, "supercritical" lift to drag performance (especially while maneuvering and actively changing AOA) is rather poor, particularly with sharper leading edges. I am hoping this leads to better "when do we fully retract slats and flaps" SOPs. $\endgroup$ – Robert DiGiovanni Oct 28 at 2:21

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