no problem mutt !
i found a pic where we are on the return leg from tunis which may help a little what LNAV stands for, what it does and what not, and what is illuminated on the autopilot when active.
the cheyenne III turboprop you see is not equipped with an fms, but with a GNS530 and an autopilot fully capable of flying lnav .
so...
you see on the autopilot panel upper left the following : flight director engaged, autpilot engaged, altitude hold ( the ap just captured alt hold from alt arm since we are in the moment of the pic just at top of climb in fl280- the vario even shows a slight climb rate and the aircraft is levelling off) AND nav coupled . simultany you see a fix on the gns display we are cleared to and the aircraft flying to it. the important thing on the display of the gns is the green "GPS" light bottom left on the display screen.
so : nav on the autopilot , gps mode on gns and a activated waypoint. on bigger aircraft the difference would be that the main position source is INS not gps and you insert the wypoint to a seperate fms- but the final situation is pretty the same.
i could now turn the heading knob where i want or tune in a vor i want- the autopilot will at this setup just follow the wapoint activated on the display. you see actually a vor tuned in ( you see it on the gns display , as well its DME on the dme gauge below the horizon-TUC vor, a course to the vor which is different to the course the autopilot holds- the autopilot is like said in lnav not interested in the vor or whatever radial to it.
thats the mighty lnav gents.
when i would want to fly to the tuned in vor i have two options ( beyond heading mode)
1) inserting the tuc vor as a waypoint and activating it. then on at the above written setup the ap would turn towards it.
2)kick off gps mode , tune the vor freq , center the HSI needle and let nav on autopilot. then the autopilot seeks for following a "real" tranmitted radial to the vor- in the first method the autopilot reckons the vor just as a waypoint and is completely uninterested in a radial or even tuning in the vor freq.
its improtant to say that when you really fly an radial from or to a vor you are
not fly lnav but vor navigation.
this aircraft splits lnav and vor navigation in the setup of the gns ( like mentioned- for lnav the green "gps" light must lit !) , some aircrafts have two buttons on the autopilot : nav and lnav. with the one you seek a really tuned vor , with the other you fly an computed waypoint - inserted in the gns or an fms.
you see just one wypoint inserted, not the whole plan. well... the only reason is that we pilots are lazy and inserting 50 or more waypoints on this route ( flight DTTA-EDDC) just to see that atc directs you to something other and you inserted waypoints are pretty useless is a work what we save when smooth at level and everything is fine. in dense areas you of course insert more points and select a departure route. and we of course have the flight plan with all waypoints on hand.
thats how it looks in real life, i hope i could help a little.
best regards !
ps.: i was also to lazy to paint out the callsign, its not that secret for what company i am working
- but nevertheless -psssst
