{
 "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": "plain-flap",
 "name": "Plain flap",
 "kind": "standard",
 "category": "Aircraft design",
 "group": "Wing features",
 "year": null,
 "question": "What is a plain flap and how much lift does it add?",
 "tags": [
  "vehicle design",
  "wing features",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "plain flap",
  "simple flap",
  "hinged flap",
  "plain flap rc",
  "plain flap lift increase",
  "flap types",
  "trailing edge flap",
  "camber flap",
  "plain flap vs split 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/plain-flap/",
 "sheet_txt": "https://xemstudio.com/objects/plain-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 plain flap is a hinged section of the trailing edge that increases camber and lift coefficient at a given angle of attack; it greatly increases drag and moves the centre of pressure aft, pitching the nose down (FAA PHAK ch.6).",
   "Its section CLmax increment is about 0.9 (Arnedo, data from Franchini et al.); on a NACA 0012, a 20% chord flap at 40 deg raises CLmax from just under 1.6 to 2.4 (Virginia Tech Appendix A, NACA data).",
   "Wing-level gain for plain flaps scales with flapped area ratio and cos^3 of quarter-chord sweep (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."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Section delta-CLmax",
     "0.9",
     "Arnedo (Franchini)"
    ],
    [
     "NACA 0012 + 20% chord flap at 40 deg",
     "CLmax ~1.6 -> 2.4 (Re 6e6)",
     "Virginia Tech Appendix A"
    ],
    [
     "NACA 0012 zero-lift angle with that flap",
     "about -12 deg",
     "Virginia Tech Appendix A"
    ],
    [
     "Wing delta-CLmax",
     "0.92 x dCl x (Sflapped/S) x cos^3(sweep)",
     "Arnedo"
    ],
    [
     "Typical CLmax/cos(sweep), plain flap",
     "1.4-1.6 takeoff (20 deg) / 1.7-2.0 landing (60 deg)",
     "Arnedo (Franchini)"
    ],
    [
     "Reference build",
     "chord 100, 25% flap, 300 span, 20 deg",
     "Sadraey/Arnedo-range example"
    ]
   ]
  }
 },
 "sheet_text": "Plain flap — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/plain-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 plain flap is a hinged section of the trailing edge that increases camber and lift coefficient at a given angle of attack; it greatly increases drag and moves the centre of pressure aft, pitching the nose down (FAA PHAK ch.6).\n- Its section CLmax increment is about 0.9 (Arnedo, data from Franchini et al.); on a NACA 0012, a 20% chord flap at 40 deg raises CLmax from just under 1.6 to 2.4 (Virginia Tech Appendix A, NACA data).\n- Wing-level gain for plain flaps scales with flapped area ratio and cos^3 of quarter-chord sweep (Arnedo).\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  0.9  Arnedo (Franchini)\nNACA 0012 + 20% chord flap at 40 deg  CLmax ~1.6 -> 2.4 (Re 6e6)  Virginia Tech Appendix A\nNACA 0012 zero-lift angle with that flap  about -12 deg  Virginia Tech Appendix A\nWing delta-CLmax  0.92 x dCl x (Sflapped/S) x cos^3(sweep)  Arnedo\nTypical CLmax/cos(sweep), plain flap  1.4-1.6 takeoff (20 deg) / 1.7-2.0 landing (60 deg)  Arnedo (Franchini)\nReference build  chord 100, 25% flap, 300 span, 20 deg  Sadraey/Arnedo-range example\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- Virginia Tech Pressbooks (data from Abbott & von Doenhoff, NACA): Appendix A: Airfoil Data — web — Publisher's page; dimensions are facts — https://pressbooks.lib.vt.edu/aerodynamics/?p=52\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/plain-flap/index.json\nAPI: https://xemstudio.com/api/geometry?object=plain-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
  },
  {
   "publisher": "Virginia Tech Pressbooks (data from Abbott & von Doenhoff, NACA)",
   "title": "Appendix A: Airfoil Data",
   "url": "https://pressbooks.lib.vt.edu/aerodynamics/?p=52",
   "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": [
  "split-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": "How far should a plain flap deflect?",
   "a": "Typical design points are 20 deg for takeoff and 60 deg for landing (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": "plain-flap-wing-segment",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/plain-flap/plain-flap-wing-segment.step",
   "stl": "https://xemstudio.com/files/hardware/plain-flap/plain-flap-wing-segment.stl",
   "note": "plain flap: wing segment 100 mm chord × 300 mm, 25 % chord surface deflected 20°"
  }
 ],
 "markdown": "https://xemstudio.com/objects/plain-flap/index.md"
}