function xdot = xdot_TC06_uAC_RegSt(ts, x, u, param)

% Function to compute the state derivatives (i.e., RHS of state equations)
% Definition of model, flight data, initial values etc. 
% test_case = 6 -- Unstable aircraft, short period, OEM
% variables:       states  - w, q
%                  outputs - az, w, q
%                  inputs  - de
%
% LS/OEM RegStartup method for unstable aircraft - Short period model
% test_case=6 is similar to test_case=8. The changes are in the state and
% observation equations. Measured values of w and q are used as u(2) and u(3).

fak = 0.0;
u0  = 44.5695;

w   = x(1);
q   = x(2);

eta = u(1) + fak*w;
wm  = u(2);
qm  = u(3);

zw    = param(1);
zq    = param(2);
zeta  = param(3);
mw    = param(4);
mq    = param(5);
meta  = param(6);

xdot(1) = zw*wm + u0*q + zq*qm + zeta*eta;
xdot(2) = mw*wm +        mq*qm + meta*eta;
    
% xdot must be a column vector
xdot = xdot';

return
% end of function