Aircraft ground effect altimeter for autonomous landing control

A method for automatic aircraft landing control using ground effect to determine how close an aircraft is to the ground, comprising:

• (a) providing an electronic processor configured to communicate with a navigation unit on an aircraft, said aircraft configured with an electronic instrument cluster for takeoff and landing control, said aircraft selected from the group of aircraft consisting of fixed and rotary-winged air vehicles, said fixed wing air vehicles having a wingspan and said rotary-winged air vehicles having a rotary diameter;
• (b) receiving an aircraft model (M) from said navigation unit of said aircraft;
• (c) using said aircraft model (M) to compute aircraft modeled quantities, said aircraft modeled quantities including:
• aircraft accelerations ({umlaut over (x)},ÿ,{umlaut over (z)}), rotation velocities ({dot over (α)},{dot over (β)},{dot over (γ)}), and altitude (h) as a function of aircraft surface control settings (C), thrust settings (T), and hypothesized ground altitude (g) at time (t), wherein (m) denotes said aircraft modeled quantities, wherein Pm=[{umlaut over (x)},ÿ,{umlaut over (z)},{dot over (α)},{dot over (β)},{dot over (γ)},h]m=M(g,C,T,t), wherein, •Pm are state parameters corresponding to said aircraft modeled quantities;
• (d) initializing said time (t) at (t=0);
• (e) receiving an initial altitude (b) of said aircraft from a barometric altimeter on said aircraft, wherein initial aircraft velocities ({dot over (x)},{dot over (y)},ż) and initial aircraft orientations (α,β,γ) are from said navigation system;
• (f) initializing said aircraft model (M) as M(b,{dot over (x)},{dot over (y)},ż,α,β,γ);
• (g) receiving accelerations, rotation velocities, and altitude from the output of the accelerometers, gyros, and barometric altimeter valid for said time (t), where (α) denotes the actual measurements of said aircraft, wherein Pα=[{umlaut over (x)},ÿ,{umlaut over (z)},{dot over (α)},{dot over (β)},{dot over (γ)},h]α, wherein Pα are state parameters corresponding to said actual measurements of said aircraft;
• (h) receiving the surface control (C) and thrust (T) settings, at time (t), from said instrument cluster;
• (i) computing a best hypothesis for the ground altitude (g) with lowest error (e) searching over g in the range (g=h to h−l), where (l) is the length of said wingspan when said aircraft is a fixed wing air vehicle or said rotary diameter when said aircraft is a rotary-winged air vehicle, and denoting (gmin) as the error minimizing hypothesized ground altitude, wherein said lowest error (e) is defined by
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• (j) determining whether (e)<threshold and gmin<(l) and when it is determined that (e)<threshold and gmin<(l), reporting (gmin) as ground altitude.