When the first two equations are substituted in the third, the following expression is obtained for the location of the neutral point
For the fixed-wing UAV the location of the neutral point is
m. The negative sign means that the point is aft of the nose. For a static margin of 10% the centre of gravity location must be
m. The table below lists the stability derivatives for the fixed-wing UAV evaluated for the center of gravity at
The deflections of the ailerons
follow positive conventions. Port aileron down is positive, elevator down is positive, rudder to port is positive. The value for
per radian. The negative sign indicates that for a positive increase of the angle of attack there is a negative (nose-down) pitching moment. This shows that the fixed-wing UAV is statically stable in pitch. The signs of the
also show that the fixed-wing UAV is statically stable in roll and yaw. The derivatives of the fixed-wing UAV with respect to the rolling, pitching, and yawing were obtained following the approach in the wing-tail configuration example. The figures below show pitch and roll forced oscillations with an amplitude of 5 deg and frequency of 2.5 Hz. The respective derivatives are listed in the table above.