OK456 "...the NG VNAV system when the coded E/D is not at an RWXX waypoint and..."
Quotes FCOM:
- An E/D point must be defined in order to accomplish a path descent. It may be defined manually or by the selection of an arrival procedure.
- If a path (VNAV PTH) descent is active when a vertical angle leg becomes active, the path mode will remain active, but VNAV will follow the vertical angle rather than the idle thrust descent path.
- For an approach without a runway waypoint on the RTE LEGS page, the VNAV path is calculated to the MDA or a calculated altitude at the missed approach point. The calculated altitude may be below the MDA to ensure a flight path angle and normal threshold crossing height.
And most importantly this NOTE:
It is the flight crew’s responsibility not to descend below the MDA until adequate visual contact is achieved.
Thus we do not need necessarily a RWXX point, but an angle coded and a E/D point or RWXX point