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AssigneeCrouzet - A French "Societe Anonyme"
InventorsJacques Mandle, Jean-Claude Goudon
Estimating the term…
The air speed is determined by solving the equation ##EQU1## in which P.sub.z is the pitch of the antitorque device, .gamma..sub.z, the vertical acceleration of the helicopter, k.sub.1 -k.sub.10, parameters depending on the type of helicopter, p.sub.x,y, the longitudinal or transverse cyclic pitch, p.sub.o the collective pitch of the main rotor, .theta..sub.x,y the angle of bank of the helicopter about the transverse or longitudinal axis of the helicopter. The system for determining the air speed may also include a conventional anemometer for hybridization with the computed speed. The parameters k.sub.1 -k.sub.10 are determined by self-calibration and by assuring that the variations of the ground speed and of the air speed are the same from one flight configuration to another one of a pair of flight configurations, among a series of pairs, for which the sensiting parameters of the helicopter are measured in the earth's reference by means of an airborne ground speed reference.
A method for determining the air speed of a helicopter having a main lift rotor and an antitorque device, with a longitudinal axis OX, a transverse axis OY and an axis of the hub of the rotor OZ, a swash plate being provided for varying the longitudinal cyclic pitch Px, the transverse cyclic pitch Py and the collective pitch Po of the main rotor, in which method the two components Vx and Vy of said speed are measured along the axes OX and OY, respectively, as a function of the difference between the cyclic pitch (Px, Py) along the axis considered (OX, OY) and the angle of bank (.theta.x, .theta.y) of the helicopter about the other axis (OY, OX), wherein Vx and Vy are determined by solving the equations:
A method for calibrating a system for determining the air speed V of a helicopter of the linear form ##EQU30## the x.sub.i being n variables, representative of different sensitization parameters of the helicopter, to which the n multiplying coefficients a.sub.i are applied respectively, in which method the n coefficients a.sub.i are determined by solving a system of N linear equations with n unknowns of the form ##EQU31## N being the number of main flight configurations of the helicopter in which said sensitizing parameters of the helicopter are measured in the reference frame of the helicopter and the values of said N variables x.sub.i are calculated, in which calibration method the true attitude and heading of the helicopter are determined, each main flight configuration is split into a pair of elementary configurations closely related to each other so as to assume that the wind is the same in these two elementary configurations and, for each pair of elementary configurations, the ground speed of the helicopter is measured, in the two elementary configurations, whose variations are assimilated with those of its air speed, as well as the sensitizing parameters of the helicopter, which are transposed from the reference frame of the helicopter into the earth's reference frame and the equation, obtained by substracting the equations relative to the two elementary configurations one from the other, in the left and right hand sides of the equations, is considered (or taken) as the equation of the system of N equations to be solved.
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