I've just noticed recently that NAV hold is not working properly on any of my aircraft with the autopilot engaged. I can align within say 10-20 degrees of the selected radial, engage NAV hold and the aircraft starts to turn slowly towards the radial then misses it and continues for about 25 degrees the other side. It then turns back at a bank angle of 5 degrees and then flies past it again. And so on ...... Any ideas? I'm baffled:( AndyB

Have you set the NAV/GPS switch to NAV? R-

Yes, NAV/GPS set to NAV. I've looked at all the obvious causes. Starting to wonder if any addons could cause problems like this.AndyB