Advanced aerodynamics
What Is Airfoil Stall? Comparing Leading-Edge and Trailing-Edge Stall
HENDOI · 27 October 2026
Stall is the lift break after separation wins. Trailing-edge stall arrives gradually. Leading-edge stall arrives as a burst. Thin-airfoil stall is a long bubble. They are not the same event.
Stall is a separation pattern with a name
An airfoil stalls when increasing angle of attack no longer increases lift in a useful way, because separated flow has taken over the suction that was producing that lift. The angle and the shape of the break depend on how the separation grows. The classical classification, associated with McCullough and Gault’s work at low speed, splits ordinary stalls into three patterns. Real Reynolds numbers blur the boundaries. The names are still the right vocabulary.
The three patterns
| Pattern | Where it starts | Lift curve | Often seen on |
|---|---|---|---|
| Trailing-edge stall | Separation begins at the trailing edge and creeps forward as α rises. | A rounded top. The slope falls before CL max. Comparatively gentle, with warning in the forces. | Thicker sections, roughly the mid-teens of percent chord and above, with a generous nose, at moderate and high Re. |
| Leading-edge stall | A short laminar bubble near the nose bursts, or the nose separates abruptly, and the suction collapses. | A sharp peak and a fast drop. Less aerodynamic warning. | Moderate thickness, often quoted around 9–15%, when the nose is sharp enough and Re is high enough for a short bubble. |
| Thin-airfoil stall | A laminar bubble forms at the leading edge and lengthens along the upper surface as α rises. | A kink, then a long rounded plateau rather than a single cliff. Moment and drag have already degraded. | Thin sections, often under about 9%, and many low-Re sections even when they are thicker on paper. |
Those thickness bands are historical guidance, not gates. Reynolds number, camber, nose radius and roughness move a section from one column to another. A 12% section at Re = 105 can behave like a thin-airfoil stall. The same coordinates at Re = 6×106 can show a trailing-edge or a leading-edge break. This is another reason a borrowed CL max is not your CL max.
What you can see in a polar
- A gradually falling slope and a soft maximum suggest trailing-edge stall, if the method is capable of showing trailing-edge separation at all.
- A sharp CL peak followed by a drop suggests a leading-edge event. Many viscous panel codes smear this or miss the burst. Do not certify a gentle stall from a method that cannot represent one.
- A lift curve that bends early and then limps upward is a hint of a long bubble. Look at the skin-friction or the shape of Cp. A flat pressure region under a bubble is the signature.
Why the type changes the airplane
A wing is a row of sections at different Re, different local α (twist, taper, fuselage) and different contamination. The stall type of the root section and the tip section together decide whether the wing stalls root-first, which is what you want for aileron authority, or tip-first, which is how an airplane drops a wing. Choosing a section with a gentle two-dimensional stall does not guarantee a gentle wing. It is the input to that design, together with twist and planform. Quote the section stall as a section result, then design the wing so the spanwise stall order is the one you can live with.
Where this sits in the series
In simple words: what this page is for
Stall is the lift break after separation wins. Trailing-edge stall arrives gradually. Leading-edge stall arrives as a burst. Thin-airfoil stall is a long bubble. They are not the same event.
This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. What Is Airfoil Stall? Comparing Leading-Edge and Trailing-Edge Stall 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 What Is Airfoil Stall? Comparing Leading-Edge and Trailing-Edge Stall 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 What Is Airfoil Stall? Comparing Leading-Edge and Trailing-Edge Stall 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
- Active Flow Control on Airfoils: Suction, Blowing and Synthetic Jets
- What Is the Aerodynamic Center of an Airfoil? Location, Meaning and Applications
- How to Identify Numerical Convergence Problems in Airfoil Analysis
- How to Build an Airfoil Analysis Database with Consistent Simulation Conditions
- All HENDOI blog articles
- HENFOIL product page
- HENSYNTH product page
- Pricing — Student, Professional & Team
- FAQ
- Login · Register now
- Previous: Laminar vs turbulent flow over an airfoil
- Next: Roughness, insects and erosion
- 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.
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Use this lesson in the HENDOI workspace
This page sits in Advanced aerodynamics. HENFOIL and HENSYNTH are both live on one account. These articles are screening lessons — not certification reports.
Live · section
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Turn this lesson into a section you can draw, check, analyse and compare. Run the polar at the Reynolds number of the vehicle. The method name stays on the result.
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HENSYNTH
After the section is chosen, set geometry and mission requirements, run screening, read compliance, synthesize candidates and download or mail the report.
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