# Anhedral angle

> Why do some aircraft have drooping (anhedral) wings?

- Category: Aircraft design › Wing planforms
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/anhedral/ · JSON: https://xemstudio.com/api/geometry?object=anhedral · Plain text: https://xemstudio.com/objects/anhedral/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Anhedral (tips below root) reduces roll stability; it is used on swept and high-wing designs that already have too much stable dihedral effect, and on fighters for roll rate (ERAU; NASA Glenn).
- Jets like the Harrier, Jaguar and Alpha Jet combine high wings, sweep and anhedral to get a small stable net effect; on a straight-wing light airplane anhedral 'will almost undoubtedly' make it laterally unstable (Kitplanes).
- On ground-effect craft anhedral tips trap a high-pressure air tunnel; a reverse-delta study chose 15 deg anhedral (Frontiers 2022 review).
- Used on: C-5 Galaxy, Harrier, SEPECAT Jaguar, Alpha Jet, Wright 1903 Flyer.
- The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Wright 1903 Flyer | slight anhedral | NASA Glenn |
| WIG reverse-delta study | anhedral 8-45 deg tested; 15 deg selected | Frontiers 2022 review |
| Reference build | high swept wing, -3 deg | illustrative |

## Where the files are

- Embry-Riddle (Leishman), Introduction to Aerospace Flight Vehicles: [Wing Shapes and Nomenclature](https://eaglepubs.erau.edu/introductiontoaerospaceflightvehicles/chapter/wing-shapes-and-nomenclature/) — web — Publisher's page; dimensions are facts
- NASA Glenn Research Center: [Beginner's Guide to Aeronautics: Wing Geometry](https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/wing-geometry) — web — Publisher's page; dimensions are facts
- Kitplanes (B. Wainfan): [Wind Tunnel: Roll's role in lateral stability (2008)](https://www.kitplanes.com/wind-tunnel-135/) — web — Publisher's page; dimensions are facts
- Frontiers in Aerospace Engineering (2022): [Review of ground-effect experiments on rectangular, reverse-delta and delta wings](https://www.frontiersin.org/journals/aerospace-engineering/articles/10.3389/fpace.2022.975158/pdf) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/anhedral/index.json · license: https://xemstudio.com/files/hardware/anhedral/LICENSE.md

- anhedral-wing: [STEP](https://xemstudio.com/files/hardware/anhedral/anhedral-wing.step) · [STL](https://xemstudio.com/files/hardware/anhedral/anhedral-wing.stl) — swept planform: span 1000, root 250, tip 120 mm, LE sweep 30°, dihedral -3°, NACA 2412

## Questions

**Should a straight-wing RC plane have anhedral?**

No; it will almost certainly be laterally unstable (Kitplanes).

## Fits with

- [Rectangular (constant-chord) wing](https://xemstudio.com/objects/rectangular-wing/)
- [Tapered wing (taper ratio for minimum induced drag)](https://xemstudio.com/objects/tapered-wing/)
- [Elliptical wing](https://xemstudio.com/objects/elliptical-wing/)
- [Swept-back wing](https://xemstudio.com/objects/swept-wing/)
- [Forward-swept wing](https://xemstudio.com/objects/forward-swept-wing/)
- [Delta wing](https://xemstudio.com/objects/delta-wing/)