Power-augmented ram (PAR) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/power-augmented-ram-par/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
Catalog version: 2026-10-20

Sizes: see table below
- 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.

parameter  value or range  source
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

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- 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
- 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

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/power-augmented-ram-par/index.json
API: https://xemstudio.com/api/geometry?object=power-augmented-ram-par