Create airfoil fields: NACA, analytic and CST — what each digit means

Create vs import vs digitize

Create generates ordinates from known families and analytic maps — computed in-process, so you know where the points came from. Import brings Selig/Lednicer DAT. Digitize recovers a drawing. All three still pass the same geometry quality gate before serious polars.

Named research catalog cards stay metadata until licensed attested ingest. HENFOIL does not invent UIUC ordinates.

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Kind (generator)

Pick the family first. The UI shows a one-line note for each kind before you generate.

Result of Generate. Coordinates, display metrics, optional generator report with limitations, notes and decision-gate language. Read the limitations — especially on 6-series thickness approximations.

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NACA 4-digit fields (M, P, T)

Example. 2412 → M=2, P=4, T=12. Result. Exact 4-digit ordinates at the requested point count n.

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NACA modified 4-digit — I and Tloc

Why. Decouple nose radius and thickness station from the classic 4-digit thickness law. Result. Modified thickness distribution with the same camber digits.

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NACA 5-digit — design CL, P, reflex

Why. 5-digit mean lines target a design lift; reflex softens pitching moment. Result. Exact 5-digit mean line + thickness as defined by the generator.

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NACA 6 / 6A — family, Cli, mean a

Honesty. After generate, read the limitation note: thickness may follow the 4-digit quartic construction; the family digit does not always change thickness the way a tabulated card would. 6A uses an aft-recovery fade — an engineering approximation, not a tabulated 6A card.

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Joukowski / Kármán–Trefftz

Result. Exact conformal-map coordinates — cusped TE for Joukowski; finite TE angle for KT.

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Biconvex / wedge / diamond — xmax

xmax. Ridge or max-thickness station. Purpose. Simple supersonic section definitions. Do not use these as default subsonic wing sections without understanding the physics gap.

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CST

Purpose. Start from default Kulfan coefficients; refine in Designer or optimize in CST parameter space. Result. A CST-parameterized section ready for fit/edit — not a “mystery” spline.

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Point count n

Purpose. How many ordinate points to generate (e.g. 121). Why. Too few → coarse LE; extremely dense → heavier analysis with little gain. Cosine clustering is typically applied by the generator where appropriate. Result. Resampled closed section suitable for the geometry gate.

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What you should do after Generate

1. Read limitations / generator report
2. Save / select the airfoil in the workspace
3. Run Geometry quality gate
4. Optional: download the airfoil report package (PDF + images + data)
5. Only then climb the analysis ladder to VIC

Expected deliverables

• Coordinates you can export (DAT / package)
• Thickness, camber, LE radius metrics
• Honest generator provenance
• A section ready for the same gate as import and digitize

Create is fast. Honesty is the quality gate and the method ID on every later polar.

In simple words: what this page is for

Kind, M/P/T, 5-digit design CL, 6-series family, Joukowski μ, CST — purpose of every Create field and the coordinates and reports you get.

This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. Create airfoil fields: NACA, analytic and CST — what each digit means 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 Create airfoil fields: NACA, analytic and CST — what each digit means 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 Create airfoil fields: NACA, analytic and CST — what each digit means 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 selection with a documented why-#1
• The HENFOIL analysis ladder: when to escalate
• Digitize field-by-field: every control, why fill it, what you get
• Import and digitize airfoils into HENFOIL
• All HENDOI blog articles
• HENFOIL product page
• HENSYNTH product page
• Pricing — Student, Professional & Team
• FAQ
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