I have an Allegro 2000 which is a glider-style plane with 36 ft wings, a long fuselage and relatively small vertical stab and rudder. (Drawing on my website http://www.aero-siam.com/page23.html )
The ailerons are fairly large and powerful and have a 3:1 differential. However, the differential is achieved by a triangular bellcrank. Small aileron movements typical of the autopilot input have no differential which only starts to take effect with the stick moved about half travel - at that point the bellcrank starts going over-center giving full differential.
I have tried all different combinations of the settings for the roll servo. The basic problem is that as the AP rolls out onto the correct heading, the plane yaws a few degrees the opposite way. So the AP is constantly hunting. At gentle settings, the AP just keeps rolling left and right. At more aggressive settings, it starts to get ugly.
I have tried flying the plane just with rudder inputs to simulate the AP attached to the rudders but the result is pretty much the same.
Is there anything in the settings that would resolve the problem? Currently, if the AP is banking to the left and rolls out on a north heading, it will yaw a few degrees to the right and the AP starts continually correcting, rolling and yawing around the required heading.
In contrast, in pitch, the AP works beautifully.
Thanks
The ailerons are fairly large and powerful and have a 3:1 differential. However, the differential is achieved by a triangular bellcrank. Small aileron movements typical of the autopilot input have no differential which only starts to take effect with the stick moved about half travel - at that point the bellcrank starts going over-center giving full differential.
I have tried all different combinations of the settings for the roll servo. The basic problem is that as the AP rolls out onto the correct heading, the plane yaws a few degrees the opposite way. So the AP is constantly hunting. At gentle settings, the AP just keeps rolling left and right. At more aggressive settings, it starts to get ugly.
I have tried flying the plane just with rudder inputs to simulate the AP attached to the rudders but the result is pretty much the same.
Is there anything in the settings that would resolve the problem? Currently, if the AP is banking to the left and rolls out on a north heading, it will yaw a few degrees to the right and the AP starts continually correcting, rolling and yawing around the required heading.
In contrast, in pitch, the AP works beautifully.
Thanks