How to Compare Airfoils Using Multi-Condition Performance Maps

A map is a polar with a second axis

A polar is CL, CD and CM against angle at one Re and one Mach. A mission is a region: a band of CL, more than one Re, sometimes more than one Mach. A performance map plots one output over two of those inputs. Typical and useful maps:

• CD as contours over CL and Re, at fixed Mach and transition.
• L/D as contours over the same plane, so the ridge of best efficiency is visible as Re changes.
• CD against Mach at several CL values, which is the drag-rise map.
• CLmax against Re, a line rather than a carpet, because stall is a boundary.

Two airfoils are compared by overlaying their contours or by subtracting them. A region where the difference changes sign is a region where the winner changes. That is the fact a single-point matrix can miss if you only scored the design CL.

How to build one without smoothing away the physics

1. Choose the axes from the mission, and choose the ranges so the corners are conditions you might actually fly. An enormous map of impossible corners invites interpolation across a stall.
2. Compute a grid of polars. Do not compute five points and spline a carpet through a laminar bucket and a stalled corner as if both were the same surface.
3. Mark unconverged cells and leave them blank. A contour line through a failed point is a drawing.
4. Hold transition policy fixed on one map, and make a second map for the tripped case. The difference map is the roughness sensitivity.
5. Use the same colour scale and the same CL definition for every section you overlay.

How to read a comparison

A map is still a set of section polars. It becomes a wing comparison only after each station has its own Re and its own local CL. The next lessons take that step.

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Where this sits in the series

In simple words: what this page is for

A performance map shows a coefficient over two operating axes, such as lift coefficient and Reynolds number. Comparing sections on one polar hides the axis where they actually differ.

This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. How to Compare Airfoils Using Multi-Condition Performance Maps 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 Compare Airfoils Using Multi-Condition Performance Maps 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 Compare Airfoils Using Multi-Condition Performance Maps 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

• Multi-Objective Airfoil Optimization: Balancing Lift, Drag and Pitching Moment
• Multi-Point Airfoil Optimization: Balancing Cruise, Climb and Low-Speed Performance
• All HENDOI blog articles
• HENFOIL product page
• HENSYNTH product page
• Pricing — Student, Professional & Team
• FAQ
• Login · Register now

• Previous: Airfoil coordinates into CAD sketches
• Next: Airfoil selection for high-lift aircraft
• 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.