Originally Posted by
kindupnorth
As spoken about before, 2 miles before the IAF it will drop into approach logic, or selection of flap will do it aswell. I know its gone into approach logic when the FMA shows vnav pth, if you hit speed intervent it remains in path. Its more obvious if your in vnav speed at the time and see the change
Be careful with that statement.
VNAV does not remain in PATH because of the approach logic, it stays in PATH when flaps are expected to be selected (when VNAV commands calculated time to flap extension). With flaps selected and using SPD INTV the VNAV logic remains in PATH.
Originally Posted by
JT8D-17
Thanks for all the reply's so far.
It's a complete mystery. Last night we switched from VNAV SPD to VNAV PTH at 7.4NM from some random waypoint that I made myself as we were on vectors!
Same as per above