I am experiencing a problem that seems like a glitch but could easily be 'pilot error'. Let's suppose I'm in Peter Hager's (beautifully modelled and deliciously complex) A380, at SPEED, CRZ ALT, and NAV, tracking the flight plan perfectly. Now, for whatever reason (following a tutorial prompt in fact) I 'pull' the heading knob (clicking right on it), to enter HDG mode, the change registering in the FMA. I immediately (about 1 second later) push the knob back in by clicking just above it. The FMA still registers HDG, and the aircraft 'refuses' to go back to NAV mode, leaving me to effect all lateral nav manually. What am I doing wrong? Why won't the aircraft reenter NAV mode? Peter has patiently explained that while HDG is always available, not so NAV, and that if the aircraft's course is divergent, NAV won't arm, or activate. That makes perfect sense, but how can course be divergent after only a second or so, and no course parameter has been changed other than switching from NAV to HDG? I would be very grateful for any enlightenment. I hate to pester Peter any further - he has been very kind and prompt. I'm a newbie at chiming in on the forum. Please let me know if I'm out in some way in protocol.