Ground effect: height/span ratio and induced-drag reduction — dimension sheet
Source: 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/)
Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
Catalog version: 2026-10-20

Sizes: see table below
- 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.

parameter  value or range  source
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

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

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/ground-effect-height-span-ratio/index.json
API: https://xemstudio.com/api/geometry?object=ground-effect-height-span-ratio