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Airfoil Selection for Tailplanes: Stability, Control and Trim Considerations
HENDOI · 26 October 2026
A tailplane usually wants a symmetric section, because it must lift both ways. Its Reynolds number is not the wing’s, and its stall is a control failure, not just a drag item.
The tail is not a small wing
A conventional tail in cruise often carries a download, to trim a nose-down wing moment and to sit in a stable layout. In a maneuver or a flap change it may carry an upload. The section therefore lives on both sides of zero lift. A cambered wing section, efficient at one positive CL, is the wrong default. A symmetric section — NACA 0012 and thinner cousins are the usual language — has the same behavior inverted, a zero-lift angle near zero, and a quarter-chord moment near zero. Camber on a tail is a deliberate choice for a one-sided job, not a leftover from the wing.
What to size the section for
| Requirement | What to check |
|---|---|
| Trim download and maneuver upload | CL available on both sides at the tail’s Reynolds number, with margin before the tail stalls. |
| Elevator as a flap | The lift increment per degree of elevator, and the deflection where the hinge line separates. A stalled elevator is a lost pitch control. |
| Hinge moment | Stick force or actuator size. Aerodynamic balance reduces it. It also changes the control feel and the flutter picture, so it is not free. |
| Thickness | Enough for the spar, the hinge and the mass balance. Extra thickness is drag and a lower tail critical Mach if you are fast. |
| Reynolds number | Tail chord is smaller than wing chord, and the tail sits in a slowed, messy wing wake. Analyse the tail at its own Re, not at the wing polar you already like. |
Stall of the tail is a different emergency
A wing stall you can plan for with twist and a gentle section. A tail stall removes the moment that was stabilizing or controlling the airplane. The tail section should still be lifting, in the correct direction, at the angle and elevator deflection of the recovery and of the flapped approach. Check both signs. A section that stalls abruptly at a modest negative angle will arrive as a pitch-up or a heavy nose at the moment the pilot needs the tail most. Symmetric does not mean “stalls late.” It means the two sides match. You still have to read CLmax at the tail Reynolds number, clean and with the elevator gap you will actually build.
Where this sits in the series
In simple words: what this page is for
A tailplane usually wants a symmetric section, because it must lift both ways. Its Reynolds number is not the wing’s, and its stall is a control failure, not just a drag item.
This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. Airfoil Selection for Tailplanes: Stability, Control and Trim Considerations 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 Airfoil Selection for Tailplanes: Stability, Control and Trim Considerations 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 Airfoil Selection for Tailplanes: Stability, Control and Trim Considerations 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
- How Adverse Pressure Gradients Affect Airfoil Boundary Layer Separation
- What Is the Aerodynamic Center of an Airfoil? Location, Meaning and Applications
- What Is Airfoil Aerodynamic Efficiency Across a Range of Flight Conditions?
- All HENDOI blog articles
- HENFOIL product page
- HENSYNTH product page
- Pricing — Student, Professional & Team
- FAQ
- Login · Register now
- Previous: Pitching moment and longitudinal stability
- Next: Flap deflection: lift, drag and moment
- 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.
Both products live
Use this lesson in the HENDOI workspace
This page sits in Stability and integration. HENFOIL and HENSYNTH are both live on one account. These articles are screening lessons — not certification reports.
Live · section
HENFOIL
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.
To Know MoreLive · aircraft
HENSYNTH
After the section is chosen, set geometry and mission requirements, run screening, read compliance, synthesize candidates and download or mail the report.
To Know MoreAerospace industry collaboration
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