{
 "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": "power-augmented-ram-par",
 "name": "Power-augmented ram (PAR)",
 "kind": "standard",
 "category": "Aircraft design",
 "group": "Ground-effect design",
 "year": null,
 "question": "What is power-augmented ram (PAR) take-off?",
 "tags": [
  "vehicle design",
  "ground-effect design",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "power augmented ram",
  "par wig",
  "par thrust",
  "ekranoplan takeoff",
  "blown wing ground effect",
  "par engines ekranoplan",
  "wig takeoff hump",
  "air cushion takeoff wig",
  "power augmented ram 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/power-augmented-ram-par/",
 "sheet_txt": "https://xemstudio.com/objects/power-augmented-ram-par/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": [
   "PAR aims engine exhaust under the wing so it is trapped by endplates and a deflected flap, forming an air cushion that lifts the craft off the water before it reaches flying speed; near the ground lift comes mainly from that cushion (NASA TM-78793).",
   "In NASA tests, flap deflection beyond about 20 deg dropped the flap trailing edge below the endplates and lost the cushion; trapped efflux cut forward thrust to about two-thirds of fan thrust (NASA TM-78793).",
   "Soviet craft used dedicated PAR engines: Orlyonok had two 10 t PAR engines plus a 16 t cruise turboprop; Kaien-2 reached take-off CLmax 1.9 at 15 deg pitch-up, about four times cruise (Rozhdestvensky).",
   "Used on: Orlyonok, KM (Caspian Sea Monster), Loon, Kaien-2.",
   "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": [
    [
     "NASA model wing",
     "1 m chord x 2 m span (AR 2), Clark-Y 12%",
     "NASA TM-78793"
    ],
    [
     "Fan position",
     "about 0.76 chord ahead of LE (4 exit diameters)",
     "NASA TM-78793"
    ],
    [
     "Flap limit for cushion trapping",
     "~20 deg (flap TE meets endplate bottom)",
     "NASA TM-78793"
    ],
    [
     "CL with 19 deg nacelle, 10 deg flap, CT 1.6",
     "~3.5 at ~20 deg AoA",
     "NASA TM-78793"
    ],
    [
     "Forward thrust with trapped efflux",
     "~2/3 of fan thrust",
     "NASA TM-78793"
    ],
    [
     "Test heights",
     "0.08-0.50 spans",
     "NASA TM-78793"
    ],
    [
     "Kaien-2 take-off CLmax",
     "1.9 at 15 deg",
     "Rozhdestvensky 2006"
    ],
    [
     "Reference build",
     "span 400, chord 200 (1:5 of NASA model), endplates 30",
     "computed"
    ]
   ]
  }
 },
 "sheet_text": "Power-augmented ram (PAR) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/power-augmented-ram-par/  (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- PAR aims engine exhaust under the wing so it is trapped by endplates and a deflected flap, forming an air cushion that lifts the craft off the water before it reaches flying speed; near the ground lift comes mainly from that cushion (NASA TM-78793).\n- In NASA tests, flap deflection beyond about 20 deg dropped the flap trailing edge below the endplates and lost the cushion; trapped efflux cut forward thrust to about two-thirds of fan thrust (NASA TM-78793).\n- Soviet craft used dedicated PAR engines: Orlyonok had two 10 t PAR engines plus a 16 t cruise turboprop; Kaien-2 reached take-off CLmax 1.9 at 15 deg pitch-up, about four times cruise (Rozhdestvensky).\n- Used on: Orlyonok, KM (Caspian Sea Monster), Loon, Kaien-2.\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\nNASA model wing  1 m chord x 2 m span (AR 2), Clark-Y 12%  NASA TM-78793\nFan position  about 0.76 chord ahead of LE (4 exit diameters)  NASA TM-78793\nFlap limit for cushion trapping  ~20 deg (flap TE meets endplate bottom)  NASA TM-78793\nCL with 19 deg nacelle, 10 deg flap, CT 1.6  ~3.5 at ~20 deg AoA  NASA TM-78793\nForward thrust with trapped efflux  ~2/3 of fan thrust  NASA TM-78793\nTest heights  0.08-0.50 spans  NASA TM-78793\nKaien-2 take-off CLmax  1.9 at 15 deg  Rozhdestvensky 2006\nReference build  span 400, chord 200 (1:5 of NASA model), endplates 30  computed\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- NASA Langley / DTNSRDC (Thomas, Paulson & Margason): Powered Low-Aspect-Ratio Wing in Ground Effect (WIG) Aerodynamic Characteristics, NASA TM-78793 (1979) — web — Publisher's page; dimensions are facts — https://ntrs.nasa.gov/api/citations/19790022970/downloads/19790022970.pdf\n- Progress in Aerospace Sciences (K.V. Rozhdestvensky, 2006): Wing-in-ground effect vehicles (review) — web — Publisher's page; dimensions are facts — https://www.hassanhameed.com/wp-content/uploads/2016/01/wingingroundeffectvehicles-130120003005-phpapp01.pdf\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/power-augmented-ram-par/index.json\nAPI: https://xemstudio.com/api/geometry?object=power-augmented-ram-par\n",
 "sources": [
  {
   "publisher": "NASA Langley / DTNSRDC (Thomas, Paulson & Margason)",
   "title": "Powered Low-Aspect-Ratio Wing in Ground Effect (WIG) Aerodynamic Characteristics, NASA TM-78793 (1979)",
   "url": "https://ntrs.nasa.gov/api/citations/19790022970/downloads/19790022970.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Progress in Aerospace Sciences (K.V. Rozhdestvensky, 2006)",
   "title": "Wing-in-ground effect vehicles (review)",
   "url": "https://www.hassanhameed.com/wp-content/uploads/2016/01/wingingroundeffectvehicles-130120003005-phpapp01.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
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  "tolerance_mm": null
 },
 "related": [
  "ground-effect-height-span-ratio",
  "ground-effect-height-chord-ratio",
  "lippisch-reverse-delta-wig",
  "ekranoplan-wing-tail-layout",
  "tandem-wig-configuration",
  "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": "How much flap for PAR?",
   "a": "About 20 deg in NASA's tests; more lets the flap drop below the endplates and spill the cushion (TM-78793)."
  }
 ],
 "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": "power-augmented-ram-par-wing",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/power-augmented-ram-par/power-augmented-ram-par-wing.step",
   "stl": "https://xemstudio.com/files/hardware/power-augmented-ram-par/power-augmented-ram-par-wing.stl",
   "note": "power augmented ram: span 400, chord 200 mm, anhedral 0°, endplates 30 mm (scale to your craft)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/power-augmented-ram-par/index.md"
}