{
 "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": "ground-effect-height-span-ratio",
 "name": "Ground effect: height/span ratio and induced-drag reduction",
 "kind": "standard",
 "category": "Aircraft design",
 "group": "Ground-effect design",
 "year": null,
 "question": "How close to the ground does a wing need to be for ground effect?",
 "tags": [
  "vehicle design",
  "ground-effect design",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "ground effect",
  "ground effect height",
  "ground effect induced drag",
  "wing in ground effect height",
  "ground effect wingspan rule",
  "wieselsberger ground effect",
  "ground effect percentage",
  "how high is ground effect",
  "h/b ground effect",
  "ground effect rc"
 ],
 "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/ground-effect-height-span-ratio/",
 "sheet_txt": "https://xemstudio.com/objects/ground-effect-height-span-ratio/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": [
   "Near the ground the wingtip vortices and downwash are suppressed, cutting induced drag. At constant CL the reduction is about 1.4% at one span height, 23.5% at a quarter span and 47.6% at a tenth of a span (FAA-handbook values as reproduced by The Wise Pilot).",
   "NASA's tests of low-AR wings found Wieselsberger's h/b theory agreed with experiment for h/b of about 0.03-0.25, but underestimated the benefit below 0.03; the percentage gain in L/D at a given height is the same regardless of aspect ratio (NASA TN D-926).",
   "Lift-curve slope also rises near the ground while lift at 0 deg stays nearly constant; at h/c = 1 the wings were essentially out of ground influence (NASA TN D-926).",
   "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": [
    [
     "Induced drag reduction, h = 1 span",
     "about 1.4%",
     "The Wise Pilot (FAA values)"
    ],
    [
     "Induced drag reduction, h = 1/4 span",
     "about 23.5%",
     "The Wise Pilot (FAA values)"
    ],
    [
     "Induced drag reduction, h = 1/10 span",
     "about 47.6%",
     "The Wise Pilot (FAA values)"
    ],
    [
     "Wieselsberger theory valid range (tests)",
     "h/b ~0.03-0.25",
     "NASA TN D-926"
    ],
    [
     "Out of ground influence (chord basis)",
     "h/c = 1",
     "NASA TN D-926"
    ],
    [
     "Reference build",
     "span 600, chord 300 (AR 2) endplated",
     "computed"
    ]
   ]
  }
 },
 "sheet_text": "Ground effect: height/span ratio and induced-drag reduction — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/ground-effect-height-span-ratio/  (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- Near the ground the wingtip vortices and downwash are suppressed, cutting induced drag. At constant CL the reduction is about 1.4% at one span height, 23.5% at a quarter span and 47.6% at a tenth of a span (FAA-handbook values as reproduced by The Wise Pilot).\n- NASA's tests of low-AR wings found Wieselsberger's h/b theory agreed with experiment for h/b of about 0.03-0.25, but underestimated the benefit below 0.03; the percentage gain in L/D at a given height is the same regardless of aspect ratio (NASA TN D-926).\n- Lift-curve slope also rises near the ground while lift at 0 deg stays nearly constant; at h/c = 1 the wings were essentially out of ground influence (NASA TN D-926).\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\nInduced drag reduction, h = 1 span  about 1.4%  The Wise Pilot (FAA values)\nInduced drag reduction, h = 1/4 span  about 23.5%  The Wise Pilot (FAA values)\nInduced drag reduction, h = 1/10 span  about 47.6%  The Wise Pilot (FAA values)\nWieselsberger theory valid range (tests)  h/b ~0.03-0.25  NASA TN D-926\nOut of ground influence (chord basis)  h/c = 1  NASA TN D-926\nReference build  span 600, chord 300 (AR 2) endplated  computed\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- The Wise Pilot (pilot training page; values match FAA PHAK ground-effect figure): Ground Effect — web — Publisher's page; dimensions are facts — https://thewisepilot.com/?p=66220\n- NASA Langley (Fink & Lastinger): Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground, NASA TN D-926 (1961) — web — Publisher's page; dimensions are facts — https://ntrs.nasa.gov/api/citations/19980231058/downloads/19980231058.pdf\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/ground-effect-height-span-ratio/index.json\nAPI: https://xemstudio.com/api/geometry?object=ground-effect-height-span-ratio\n",
 "sources": [
  {
   "publisher": "The Wise Pilot (pilot training page; values match FAA PHAK ground-effect figure)",
   "title": "Ground Effect",
   "url": "https://thewisepilot.com/?p=66220",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NASA Langley (Fink & Lastinger)",
   "title": "Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground, NASA TN D-926 (1961)",
   "url": "https://ntrs.nasa.gov/api/citations/19980231058/downloads/19980231058.pdf",
   "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": [
  "ground-effect-height-chord-ratio",
  "lippisch-reverse-delta-wig",
  "ekranoplan-wing-tail-layout",
  "tandem-wig-configuration",
  "power-augmented-ram-par",
  "wig-endplates"
 ],
 "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": "When does ground effect start?",
   "a": "It is small (about 1.4% induced-drag cut) at one span and strong (47.6%) at a tenth span (FAA values via The Wise Pilot)."
  }
 ],
 "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": "ground-effect-height-span-ratio-wing",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/ground-effect-height-span-ratio/ground-effect-height-span-ratio-wing.step",
   "stl": "https://xemstudio.com/files/hardware/ground-effect-height-span-ratio/ground-effect-height-span-ratio-wing.stl",
   "note": "endplated wing: span 600, chord 300 mm, anhedral 0°, endplates 30 mm (scale to your craft)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/ground-effect-height-span-ratio/index.md"
}