Steady flow and static stability of airfoils in extreme ground effect

SummarySteady flow over a thin airfoil-like body in close proximity to a plane ground surface is analysed on the basis of a one-dimensional, but non-linear, gap-region flow, matched to the outside via a trailing edge which may possess significant flap-like appendages. The resulting lift and moment predictions are used to estimate quasisteady stability derivatives in heave and pitch. The results are applied to longitudinal stability of tail-less uncambered airplanes, and to manoeuvring of ships near to a bank, indicating instability in both cases.