# Leading-edge slat and fixed slot

> How do slats and slots delay the stall?

- Category: Aircraft design › Wing features
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/leading-edge-slat-slot/ · JSON: https://xemstudio.com/api/geometry?object=leading-edge-slat-slot · Plain text: https://xemstudio.com/objects/leading-edge-slat-slot/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

- Fixed slots duct air to the upper surface to delay separation at high angle of attack; movable slats are leading-edge segments on tracks (FAA PHAK ch.6). Leading-edge flaps raise CLmax and reduce the nose-down moment of trailing-edge flaps (FAA).
- Section CLmax increments: fixed slot about 0.2, Krueger/drop flap about 0.3, slat about 0.4 x c'/c (Arnedo, Franchini data). Triple-slotted flaps with slats reach CLmax/cos(sweep) of 3.2-3.5 for landing (Arnedo).
- 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 |
|---|---|---|
| Fixed slot dCLmax | 0.2 | Arnedo (Franchini) |
| Krueger / drop flap dCLmax | 0.3 | Arnedo |
| Slat dCLmax | 0.4 c'/c | Arnedo |
| Triple slotted flap + slat, wing CLmax/cos | 2.4-2.7 takeoff / 3.2-3.5 landing | Arnedo |
| Reference build | chord 100, 15% slat, 20 deg | illustrative |

## Where the files are

- FAA: [Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Ch. 6 Flight Controls](https://www.faa.gov/sites/faa.gov/files/08_phak_ch6.pdf) — web — Publisher's page; dimensions are facts
- LibreTexts (Arnedo, Fundamentals of Aerospace Engineering; data from Franchini et al.): [3.4.3 Increase in CLmax (high-lift devices)](https://eng.libretexts.org/Bookshelves/Aerospace_Engineering/Fundamentals_of_Aerospace_Engineering_(Arnedo)/03%3A_Aerodynamics/3.04%3A_High-lift_devices/3.4.03%3A_Increase_in_CLmax) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/leading-edge-slat-slot/index.json · license: https://xemstudio.com/files/hardware/leading-edge-slat-slot/LICENSE.md

- leading-edge-slat-slot-wing-segment: [STEP](https://xemstudio.com/files/hardware/leading-edge-slat-slot/leading-edge-slat-slot-wing-segment.step) · [STL](https://xemstudio.com/files/hardware/leading-edge-slat-slot/leading-edge-slat-slot-wing-segment.stl) — Wing segment with a deployed leading-edge slat (gap and angle illustrative)

## Questions

**Slot or slat for a STOL RC plane?**

A fixed slot is simplest (dCLmax ~0.2); a slat extending the chord gives more (~0.4 c'/c) (Arnedo).

## Fits with

- [Plain flap](https://xemstudio.com/objects/plain-flap/)
- [Split flap](https://xemstudio.com/objects/split-flap/)
- [Slotted flap](https://xemstudio.com/objects/slotted-flap/)
- [Fowler flap](https://xemstudio.com/objects/fowler-flap/)
- [Gurney flap](https://xemstudio.com/objects/gurney-flap/)
- [Leading-edge cuff (drooped leading edge)](https://xemstudio.com/objects/leading-edge-cuff/)