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Airfoil Selection for Human-Powered Aircraft: Maximizing Lift-to-Drag Ratio
HENDOI · 26 October 2026
A human can produce a few hundred watts for a long effort. The airplane only closes if airplane L/D is very high, which means a large aspect ratio and a section whose profile drag is small at low speed.
The power ceiling is the specification
A pilot can sustain on the order of a few hundred watts. At the speed of a human-powered airplane, that power buys only a small drag. Airplane L/D has to be very large, historically well above ordinary sailplanes, which is why the span is enormous and the weight is extreme. The section’s job is to keep profile drag from spending the budget that aspect ratio just created. A mediocre section on a superb planform can still miss the flight. A brilliant section on a heavy structure misses it too, because weight raises induced drag.
Speed is low. Even with a chord of a metre, Reynolds number can sit around a few hundred thousand. This is not a high-Re sailplane section transplanted onto a lighter fuselage. Bubbles, trips from tape and wire bracing, and a precious leading-edge radius all matter. Analyse at that Re.
Section requirements
| Need | Why |
|---|---|
| High section L/D across the cruise CL | Profile drag is a large share of a drag budget that is already tiny. The airplane L/D is still lower than the section L/D once induced drag remains. |
| Low pitching moment | The tail is small and the pilot cannot afford trim drag. Reflex or a very mild moment is part of the section score. |
| Enough depth to build a spar that does not weigh the induced drag back | Thickness is structural. The lightest section is the one that minimizes airplane drag, not the one with the lowest clean CD on a fixed weight. |
| A surface you can keep smooth | Film coverings, tape and bracing wires are trips. A tripped polar is a required case, not a sensitivity. |
| A propeller section at its own Re | The propulsor is also an airfoil problem, at low Re and at a section speed that changes along the blade. The wing polar does not design the propeller. |
Maximize airplane L/D, with the section polar as the profile-drag lookup and the span as the induced-drag lever. A section L/D quoted by itself will overstate the airplane, and on this class of aircraft the overstatement is the difference between flying and not flying.
Where this sits in the series
In simple words: what this page is for
A human can produce a few hundred watts for a long effort. The airplane only closes if airplane L/D is very high, which means a large aspect ratio and a section whose profile drag is small at low speed.
This lesson exists because section decisions fail when geometry, method labels and selection reasons are scattered. Airfoil Selection for Human-Powered Aircraft: Maximizing Lift-to-Drag Ratio 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 Human-Powered Aircraft: Maximizing Lift-to-Drag Ratio 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 Human-Powered Aircraft: Maximizing Lift-to-Drag Ratio 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: Airfoils for solar-powered UAVs
- Next: Wind turbine airfoils along the span
- 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 Specialized applications. 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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