8
$\begingroup$

Why are supercritical airfoils not used in GA aircraft? The 787 is assumed to use a supercritical airfoil, so why don't GA aircraft use them?

My guess is that they're harder to manufacture, and a lot of GA aircraft today are older. (Not sure though)

(I'm mainly referring to smaller propeller planes when I say GA)

$\endgroup$

3 Answers 3

16
$\begingroup$

Because supercritical airfoils are designed for the transonic regime of flight speeds, which GA aircraft do not operate in. Many other considerations, such as flutter, limit GA aircraft speeds even in a dive. For GA aircraft, engines, airframe, and yes, even wings, are designed to only operate in a far slower speed range than a 787.

Summary: supercritical = fast and GA = slow, so supercritical ≠ GA.

$\endgroup$
4
  • $\begingroup$ oh okay, but don't supercritical airfoils still reduce drag at lower speeds? $\endgroup$
    – Wyatt
    Mar 13 at 0:03
  • 10
    $\begingroup$ If they do, it is because they sometimes achieve some extent of laminar flow -- however, at low speed, you're better off using a laminar flow airfoil if that is what you want. $\endgroup$ Mar 13 at 0:47
  • 2
    $\begingroup$ Supercritical airfoils are like swept wings in that they are used to avoid the effect of compressibility, which creates problems not present at lower speeds and which imposes an additional constraint on design choices. When one says that they reduce drag, that is compared to a wing optimized for lower speed being used at a speed where compressibility is a problem, not that they reduce drag in all circumstances. Not only does this give no reason to think they are better in other cases, the fact that they are a response to an additional constraint suggests that they are likely to be worse. $\endgroup$
    – sdenham
    Mar 14 at 13:22
  • $\begingroup$ re: sdenham's good comment, this "likely to be worse" is even likelier when considering that "worse" may be due to other factors such as manufacturability (e.g., developable surface that can be formed from sheet material) and resulting structural mass (e.g., skin thickness needed to maintain desired profile despite surface concavity) in addition to strictly aerodynamic performance of the resulting surface. Even ease of analysis, ease of modification, or response to bug and ice accumulation can be considerations that affect the "best" result in the real world. $\endgroup$
    – p8l
    Mar 18 at 22:12
10
$\begingroup$

Actually, Whitcomb's GA airfoils were based on experience gained with supercritical airfoils. They share the large leading edge radius and the strong rear loading with them.

Other than that, suppressing shocks is not needed when flying at speeds where air is almost incompressible.

$\endgroup$
6
$\begingroup$

The Piper Tomahawk, Beech BE.77 and the Dornier Do228 all used the GAW-1 airfoil, which is shaped like the higher speed supercritical airfoils. The certified OMF Symphony SA160 (formerly kit built GlaStar) uses the similar GAW-2. Features in this usage are the thick airfoil section making for a lighter structure, rounded leading edge which allows high cl at high angles of attack and a wide drag bucket for efficiency. The experimental X57 Maxwell also uses this airfoil.

$\endgroup$
1
  • 1
    $\begingroup$ Well, the GA(W) airfoils have markedly more camber at mid-chord. They are no longer suitable for transsonic flight. $\endgroup$ Mar 13 at 14:03

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .