I recently read that C152 have two different airfoils on its wing. NACA 2412 at the wing root and NACA 0012 the wingtip. Why? And why are those particular airfoils (with their inherent aerodynamic properties) installed at the root and the other at the tip?


1 Answer 1


At the end you'll find the answer to the question plus a short question to verify if I've made myself clear ;-)

An airfoil can be basically described by 3 parameters:

  • the shape/curvature of its camber line;
  • the radius of its leading edge (the trailing edge is almost always pointy);
  • the distribution of the thickness upon the camber line.

Those 3 parameters are enough to define any airfoil of practical use (source Wikipedia):

 Airfoil nomenclature

Without any claim to thoroughness (that would cover an entire book) the following can be said:

  1. A rounder leading edge and higher thickness (>10% of the chord) give a smooth stall with a progressive loss of lift; pitching moment also changes smoothly approaching the stall region; thick airfoils have also a big volume that can be used for fuel and structure $\rightarrow$ good for the root of the wing or of a propeller.
  2. A thinner leading edge/thickness gives a more nervous stall with a higher pitching moment variation; anyway at high subsonic speeds a thinner airfoil possesses a lower drag than a thick one since it retards the formation of shock waves (which give rise to the boundary layer's detachment and stall); being thinner, it also weight less $\rightarrow$ good for the tip.
  3. At low subsonic speeds, a thickness of 12% is the sweet spot to have the highest L/D ratio.
  4. A pointy leading edge is necessary at supersonic speeds in order to avoid the formation of a detached (aka bow) shock which increases drag and temperature $\rightarrow$ virtually all the wings of supersonic fighters are built around a very thin, pointy airfoil; the loss in internal volume for fuel and structure is compensated for by the use of delta planform for the wing.
  5. Camber is mainly used to control/delay stall and limit pitching moment; a very pronounced camber (one that makes the airfoil look like an arc) is used when lift needs to be generated at very high AoA i.e. low speeds; this is typically the shape that a bird's wing possesses or that a wing assumes when its high-lift devices are deployed; in those cases a round, thick leading edge helps too, as already said; anyway a lot of camber doesn't work at high speeds since the boundary layer tends to detach and make the airfoil stall (the only exception being turbine/compressor blades); as a side effect, an airfoil with high camber generates also a high pitching moment which needs a lot of structure to be carried (to partially offset this, the camber can be built in such a way to go upward toward the trailing edge in a sort of "S" shaped pattern; in this way the good aerodynamic characteristics at high AoA are retained but without the increased torsional moment).
  6. In order to aerodynamically and structurally optimise the wing, the spanwise lift distribution should become lower and lower toward the wing tips.

All that being said, we can now better understand the airfoils choice on many airplanes. In particular for the C152 we have that:

  • Both the root and the tip have the same thickness of 12% $\rightarrow$ see point 1 and 3. Plus, having the same thickness, manufacturing might be simplified.
  • Being cambered, the airfoil at the root (NACA 2412) generates more lift and that, combined with the flaps, gives good stall and low speed characteristics; the higher pitching moment due to the camber is structurally not a problem being the airfoil thick (more space for the structure) and close to the fuselage (it doesn't have to travel along the whole wing) $\rightarrow$ see point 5.
  • At the same AoA, the uncambered airfoil at the tip (NACA 0012) delivers less lift than the cambered airfoil (NACA 2412) at the root $\rightarrow$ see point 6.

Let's see if I've made myself clear and why, for example, the B-52 used a NACA 63A219 for the root and a NACA 65A209 for the tip; or why the F-18 uses a NACA 65A005 for the root and a NACA 65A003 for the tip?

  • $\begingroup$ Thnk you for explanation, one more question: shouldn't a cambered airfoil be placed at the wing tip so that the wing root stalls first and ailerons remain functional as long as possible? $\endgroup$
    – Konrad
    Commented May 8 at 16:18
  • $\begingroup$ Yes right. I'm not sure but the C152 should have a couple of degrees twist so that the tip stalls after the root. $\endgroup$
    – sophit
    Commented May 8 at 17:06
  • $\begingroup$ It was silly of me to think I could answer this question with such a limited knowledge. Great answer. I'll stick to what I actually know in future :D $\endgroup$
    – Jamiec
    Commented May 9 at 8:01
  • 2
    $\begingroup$ @Jamiec: we are all here to learn from each other 🤗 $\endgroup$
    – sophit
    Commented May 9 at 8:59

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