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Slotted flap

How does a slotted flap work? · Standard part · basis: Design rules and figures from the cited sources; example geometry by Xem Studio

Also called: single slotted flap, double slotted flap, slotted flap rc, slotted flap how it works, flap gap, slotted vs plain flap, high lift flap

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

sizes
5 in table

Notes

  • A slotted flap opens a gap between wing and flap so high-pressure air from below energises the flap's upper surface; it raises the lift coefficient significantly more than plain or split flaps and is the most popular type today (FAA PHAK ch.6).
  • Its section CLmax increment is about 1.3 vs 0.9 for a plain flap (Arnedo, Franchini data); large aircraft use double or triple slots (FAA).
  • 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.

Slotted flap size chart

parametervalue or rangesource
Section delta-CLmax1.3Arnedo (Franchini)
Wing delta-CLmax0.92 x dCl x (Sflapped/S) x cos(sweep)Arnedo
Typical CLmax/cos(sweep), slotted flap1.5-1.7 takeoff (20 deg) / 1.8-2.2 landing (40 deg)Arnedo
Typical CLmax/cos(sweep), double slotted1.7-1.95 takeoff (20 deg) / 2.3-2.7 landing (50 deg)Arnedo
Reference buildchord 100, 25% flap, 40 degArnedo landing setting

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

FAAPilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Ch. 6 Flight ControlswebPublisher'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)webPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

slotted-flap-wing-segmentslotted flap: wing segment 100 mm chord × 300 mm, 25 % chord surface deflected 40°STEP · STL
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Plain text: sheet.txt · JSON: /api/geometry?object=slotted-flap

Slotted flap, isometric render of a generated part
Render of slotted-flap-wing-segment from the free STEP; not to scale.

Fits with

Plain flap, isometric render of a generated part
Plain flap6 sizes★ 1 file
Split flap, isometric render of a generated part
Split flap3 sizes★ 1 file
Fowler flap, isometric render of a generated part
Fowler flap5 sizes★ 1 file
Leading-edge slat and fixed slot, isometric render of a generated part
Leading-edge slat and fixed slot5 sizes★ 1 file
Gurney flap, isometric render of a generated part
Gurney flap5 sizes★ 1 file
Leading-edge cuff (drooped leading edge), isometric render of a generated part
Leading-edge cuff (drooped leading edge)4 sizes★ 1 file

Questions

Does the slot matter?

Yes; the gap flow lets the flap deflect further without separating, giving about 1.3 vs 0.9 dCLmax (Arnedo).