How to Read NACA 4-Digit Airfoil Designations: NACA 2412 Explained

What the four digits mean

A NACA 4-digit name is a compact drawing instruction from the 1930s that is still the right first language for airfoil geometry. Read NACA 2412 as three numbers, not as a serial code:

NACA 0012 has m = 0 and p unused: it is symmetric and 12% thick. NACA 4415 is 4% camber at 40% chord and 15% thick. The family tells you the design intent before you open a coordinate file. It does not tell you the Reynolds number, and it does not promise a modern low-drag section.

How the shape is built

The thickness distribution, measured as a half-thickness about the camber line, follows a fixed polynomial. With x as fraction of chord and t as thickness fraction:

yt = 5 t (0.2969 √x − 0.1260 x − 0.3516 x² + 0.2843 x³ − 0.1015 x⁴)

The last coefficient in the original NACA equation leaves a very small trailing-edge thickness. Replacing 0.1015 with 0.1036 closes the trailing edge. Say which one you generated. A “closed” 2412 and a classic 2412 are not bit-identical, and a sloppy trailing edge upsets a panel code.

The camber line for a 4-digit section is two parabolas that meet at the crest p:

• Ahead of the crest, yc = (m / p²) (2 p x − x²)
• Behind the crest, yc = (m / (1−p)²) ((1 − 2p) + 2 p x − x²)

The thickness is laid perpendicular to that line, not as a simple vertical stack on y = 0, except for the symmetric case where the two pictures coincide. Upper and lower coordinates follow from the local slope of the camber line. That is the whole construction. Four digits, one thickness law, one camber law.

What 2412 is good at teaching

NACA 2412 is a gentle, fully documented section. At moderate Reynolds number it has a usable lift slope, a soft-ish stall compared with a thin section, and a modest nose-down moment. It is a fair wing section for light aircraft and for coursework. It is not automatically the right UAV section at Re = 100,000, and it is not a transonic section. Use it to learn the name, then compare it at your Reynolds number with a section drawn for that Reynolds number.

What the four digits do not say

• NACA 5-digit names (23012 and cousins) move the camber and were drawn for a higher design lift with the crest further forward. The digits are not read the same way.
• NACA 6-series names (65-210, 63-412) encode a target pressure distribution and a laminar bucket, not a simple camber percentage.
• Supercritical and modern UAV sections often have no NACA number at all. The coordinates are the definition.

If a file is labelled 2412, check the thickness and the camber you actually imported. A renamed coordinate set is a common way to lie to yourself. Generate the family in HENFOIL, or import a DAT you trust, and let the geometry report state thickness and camber before you analyse it.

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Where this sits in the series

In simple words: what this page is for

The four digits are maximum camber, where that camber sits, and thickness. NACA 2412 is 2% camber at 40% chord and 12% thick.

This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. How to Read NACA 4-Digit Airfoil Designations: NACA 2412 Explained helps you keep a clean trail from shape to polar to choice.

Why the topic matters

Engineers lose time when a title sounds clear but the page only sketches the idea. This article expands How to Read NACA 4-Digit Airfoil Designations: NACA 2412 Explained so you can answer three questions without jargon: what is the idea, when do you use it, and how do you check it in a HENDOI product.

Read the sections above for the core definitions. Use the steps below to move from reading into a real project trail you can share with a teammate.

How to apply this in HENDOI

In practice: create a HENDOI account or log in, open HENFOIL, bring a section in (create, import DAT, or digitize), pass the geometry gate, climb the analysis ladder only as far as the decision needs, then compare and archive. Every calculated number should keep its method label.

When the section choice is ready for the aircraft, continue in HENSYNTH for mission, compliance and trades. Same account. Same plans.

What this page will not claim: a teaching polar or geometry note is not a flight-Re certificate. HENFOIL labels methods so you know what you bought. Tunnel data and professional judgement still sit outside any single software run.

Checklist before you leave this page

• Can you state the idea of How to Read NACA 4-Digit Airfoil Designations: NACA 2412 Explained in one sentence?
• Do you know which product owns the next action — HENFOIL or HENSYNTH?
• Will every number you keep carry a method label or a stored-run source?
• If you are new here, have you opened Register or Login?

Related reading on this site

• Airfoil Parameterization Methods: NACA Equations, CST and Spline-Based Geometry
• How to Compare NACA 0012, NACA 2412 and NACA 4412 Airfoil Profiles
• NACA 0015 vs NACA 0018: Comparing Symmetric Airfoil Profiles
• NACA 23012 Airfoil: Design Features, Lift Characteristics and Applications
• All HENDOI blog articles
• HENFOIL product page
• HENSYNTH product page
• Pricing — Student, Professional & Team
• FAQ
• Login · Register now

• Previous: Symmetric vs cambered airfoils
• Next: How angle of attack affects lift, drag and stall
• Index: all HENFOIL airfoil lessons

These pages teach the ideas. They are not wind-tunnel data and not a certification analysis. When a number matters, compute it at a stated Reynolds number, Mach number and transition setting, and keep the method label on the result. In HENFOIL that production polar is a VIC polar — see the analysis ladder and the polar field guide.