{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "split-flap",
 "name": "Split flap",
 "kind": "standard",
 "category": "Aircraft design",
 "group": "Wing features",
 "year": null,
 "question": "What is a split flap?",
 "tags": [
  "vehicle design",
  "wing features",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "split flap",
  "split flaps",
  "split flap rc",
  "lower surface flap",
  "intrados flap",
  "split flap vs plain flap",
  "dive flap",
  "landing flap drag"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/split-flap/",
 "sheet_txt": "https://xemstudio.com/objects/split-flap/sheet.txt",
 "sheet": {
  "basis": "Design rules and figures from the cited sources; example geometry by Xem Studio",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A split flap hinges down from the lower surface only, leaving the upper surface in place; it gives slightly more lift than a plain flap but high drag, and fully extended it adds high drag with little extra lift (FAA PHAK ch.6).",
   "That drag is useful for steep approaches. Arnedo groups the plain and 'intrados' (lower-surface) flap together at a section CLmax increment of about 0.9.",
   "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."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Section delta-CLmax (intrados flap)",
     "0.9",
     "Arnedo (Franchini)"
    ],
    [
     "Lift vs plain flap",
     "slightly greater",
     "FAA PHAK ch.6"
    ],
    [
     "Reference build",
     "chord 100, 25% lower-surface flap, 45 deg",
     "illustrative"
    ]
   ]
  }
 },
 "sheet_text": "Split flap — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/split-flap/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Design rules and figures from the cited sources; example geometry by Xem Studio\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A split flap hinges down from the lower surface only, leaving the upper surface in place; it gives slightly more lift than a plain flap but high drag, and fully extended it adds high drag with little extra lift (FAA PHAK ch.6).\n- That drag is useful for steep approaches. Arnedo groups the plain and 'intrados' (lower-surface) flap together at a section CLmax increment of about 0.9.\n- 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.\n\nparameter  value or range  source\nSection delta-CLmax (intrados flap)  0.9  Arnedo (Franchini)\nLift vs plain flap  slightly greater  FAA PHAK ch.6\nReference build  chord 100, 25% lower-surface flap, 45 deg  illustrative\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- FAA: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Ch. 6 Flight Controls — web — Publisher's page; dimensions are facts — https://www.faa.gov/sites/faa.gov/files/08_phak_ch6.pdf\n- LibreTexts (Arnedo, Fundamentals of Aerospace Engineering; data from Franchini et al.): 3.4.3 Increase in CLmax (high-lift devices) — web — Publisher's page; dimensions are facts — 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\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/split-flap/index.json\nAPI: https://xemstudio.com/api/geometry?object=split-flap\n",
 "sources": [
  {
   "publisher": "FAA",
   "title": "Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Ch. 6 Flight Controls",
   "url": "https://www.faa.gov/sites/faa.gov/files/08_phak_ch6.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "LibreTexts (Arnedo, Fundamentals of Aerospace Engineering; data from Franchini et al.)",
   "title": "3.4.3 Increase in CLmax (high-lift devices)",
   "url": "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",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "plain-flap",
  "slotted-flap",
  "fowler-flap",
  "leading-edge-slat-slot",
  "gurney-flap",
  "leading-edge-cuff"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "Why use a split flap on a model?",
   "a": "It is easy to add and gives high drag with a lift gain for steep landings (FAA PHAK ch.6)."
  }
 ],
 "files_license": {
  "name": "Xem Studio Design License",
  "holder": "Xem Studio",
  "url": "https://xemstudio.com/license/",
  "note": "Xem Studio's own design: free to use, print, modify and sell things made from it; not to be republished or redistributed as files."
 },
 "offers": [
  {
   "file": "split-flap-wing-segment",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/split-flap/split-flap-wing-segment.step",
   "stl": "https://xemstudio.com/files/hardware/split-flap/split-flap-wing-segment.stl",
   "note": "split flap: wing segment 100 mm chord × 300 mm, 25 % chord surface deflected 45°"
  }
 ],
 "markdown": "https://xemstudio.com/objects/split-flap/index.md"
}