wrote:

From the model airplane world here is a product that controls both
pitch and roll.

http://www.futaba-rc.com/radioaccys/futm0999.html

It operates by optically referencing the horizon. So your day VFR
application would be a coincident limitation.

I don't know how current autopilots mechanically couple to the flight
controls but there are very large hobby servos that could probaby be
powerful enough to nudge the controls back and forth in response the
the control unit.

The servos you describe would be strong enough in a small aircraft since
autopilots I have worked on don't move the primary control surfaces
directly. They move trim tabs.

You could either just use their sensor and build your own controller or
attempt to use their controller.

BTW- The vibrating piezo gyros used for RC helecopters have some slow
drift so you can't use them directly but they do have a lot of promise
still for a stabization system. In the hobby application they act more
as dampers than absolute references as the horizon would be for the
earlier mentioned method. So the hobby gyro could counteract bumps but
the steady state error would have to be maintaned by the pilot.

There are pizeo gyros out there that are less drifty. If you have the
money go look at Crossbow. Their systems are interesting. Among other
things they make AHRS and INS modules.

Dan, U.S. Air Force, retired