Originally Posted by
Manicured garden
* you are flying on heading 300 degrees,
* airport has 1 runway, 09-27 rwy, and 09 in use.
* airport is at your north (360 degrees), 10 NM ahead of you
* on ND, magenta line is straight from RWY09 (direct intercept)
You will NOT see ARM ever, LNAV will be annunciated when criteria are met.
In this case, the angle between 090 inbound course and flown course of 300 is 150 degrees, thus it does not meet 90 degree intercept angle requirement.
If my above reading of your situation is incorrect, maybe a picture of your situation may be useful