function [ M ] = GangedSpring(alpha)  %Moment due to spring, PER WING PAIR.
global k_global;

%k_up = ((114-60)*4.5/10)*.0254*4.45/12;  %N-m/deg
%k_down = ((180-114)*4.5/30)*.0254*4.45/12;  %N-m/deg

%k_up = k_down;
%k_up = 1*k_up;
%k_down = .4*k_down;
k_up = k_global;  %N-m/deg
k_down = k_up;  %Symmetric spring

idx = find(alpha > 0);
M(idx) = -k_up*alpha(idx);
idx = find(alpha <= 0);
M(idx) = -k_down*alpha(idx);

M(idx) = M(idx)+.5;