When pressing the VNAV button on the AFCS panel in AW139, AW169, and AW189 helicopters, it shows "VNAV is not installed" or "function unavailable."
Why is VNAV not engaged on these helicopters?
If NAV SOURCE is set to FMS, pressing the APP button activates a VGP approach. If NAV SOURCE is set to ILS, pressing the APP button activates an ILS approach.
When and how does the AFCS use the VPATH mode of VNAV submode?
