{
 "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": "fowler-flap",
 "name": "Fowler flap",
 "kind": "standard",
 "category": "Aircraft design",
 "group": "Wing features",
 "year": null,
 "question": "What makes a Fowler flap different?",
 "tags": [
  "vehicle design",
  "wing features",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "fowler flap",
  "fowler flaps",
  "fowler flap rc",
  "sliding flap",
  "extending flap",
  "fowler flap mechanism",
  "fowler vs slotted flap",
  "track flap"
 ],
 "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/fowler-flap/",
 "sheet_txt": "https://xemstudio.com/objects/fowler-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 Fowler flap slides aft on tracks before drooping, increasing both wing area and camber; early extension adds lift with little drag, late extension adds drag with little lift (FAA PHAK ch.6).",
   "Its section CLmax increment is 1.3 x c'/c, where c' is the extended chord; double-slotted Fowler reaches 1.6 x c'/c and triple-slotted 1.9 x c'/c (Arnedo, Franchini data).",
   "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",
     "1.3 c'/c",
     "Arnedo (Franchini)"
    ],
    [
     "Double slotted Fowler",
     "1.6 c'/c",
     "Arnedo"
    ],
    [
     "Triple slotted Fowler",
     "1.9 c'/c",
     "Arnedo"
    ],
    [
     "Typical CLmax/cos(sweep), Fowler flap",
     "2.0-2.2 takeoff (15 deg) / 2.5-2.9 landing (40 deg)",
     "Arnedo"
    ],
    [
     "Reference build",
     "chord 100, 30% flap, 40 deg",
     "illustrative"
    ]
   ]
  }
 },
 "sheet_text": "Fowler flap — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/fowler-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 Fowler flap slides aft on tracks before drooping, increasing both wing area and camber; early extension adds lift with little drag, late extension adds drag with little lift (FAA PHAK ch.6).\n- Its section CLmax increment is 1.3 x c'/c, where c' is the extended chord; double-slotted Fowler reaches 1.6 x c'/c and triple-slotted 1.9 x c'/c (Arnedo, Franchini data).\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  1.3 c'/c  Arnedo (Franchini)\nDouble slotted Fowler  1.6 c'/c  Arnedo\nTriple slotted Fowler  1.9 c'/c  Arnedo\nTypical CLmax/cos(sweep), Fowler flap  2.0-2.2 takeoff (15 deg) / 2.5-2.9 landing (40 deg)  Arnedo\nReference build  chord 100, 30% flap, 40 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/fowler-flap/index.json\nAPI: https://xemstudio.com/api/geometry?object=fowler-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",
  "split-flap",
  "slotted-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 do airliners use Fowler flaps?",
   "a": "They add area and camber, giving the highest CLmax of common flaps (Arnedo)."
  }
 ],
 "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": "fowler-flap-wing-segment",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/fowler-flap/fowler-flap-wing-segment.step",
   "stl": "https://xemstudio.com/files/hardware/fowler-flap/fowler-flap-wing-segment.stl",
   "note": "fowler flap: wing segment 100 mm chord × 300 mm, 30 % chord surface deflected 40°"
  }
 ],
 "markdown": "https://xemstudio.com/objects/fowler-flap/index.md"
}