Dimless computes the dimensionless rotational velocities pb/2V, qc/V, and rb/2V. Of course, the computation itself is trivial if the elements of the state vector x are known, but since these variables may be needed more than once it is still useful to compute them in a separate block.
Dimless is contained in the subsystem Aerodynamics Group (Beaver) of the Beaver model. Other blocks in that subsystem are: Aeromod (Beaver) and FMdims.
x = [V alpha beta p q r psi theta phi xe ye H]' (states) V : airspeed [m/s] {alpha: angle of attack [rad] } {beta : sideslip angle [rad] } p : roll rate [rad/s] q : pitch rate [rad/s] r : yaw rate [rad/s] {psi : yaw angle [rad] } {theta: pitch angle [rad] } {phi : roll angle [rad] } {xe : x-coordinate in Earth-fixed reference frame [m] } {ye : y-coordinate '' '' '' '' [m] } {H : altitude above sea-level [m] }
The state variables which are not actually needed by Dimless have been displayed between curly braces.
ydl = [pb/2V qc/V rb/2V]' (dimensionless rotational velocities). pb/2V: dimensionless roll-rate (b = wing span) qc/V : dimensionless pitch-rate (c = cbar = mean aerodynamic chord) rb/2V: dimensionless yaw-rate (b = wing span)