Originally Posted by SpanWise
Once airborne both Vis/RVR and ceiling are limiting.
Unless chart specifically states "Ceiling required" (Jeppesen), there is no need to have the required ceiling when starting approach or pasing OM (or equivalent point) - you do need required RVR/visibility to continue approach though - see EU OPS Appendix 1 to OPS 1.430 (new).
OPS 1.405
Commencement and continuation of approach
(a) The commander or the pilot to whom conduct of the flight has been delegated may commence an instrument approach
regardless of the reported RVR/Visibility but the approach shall not be continued beyond the outer marker, or equivalent
position, if the reported RVR/visibility is less than the applicable minima (see OPS 1.192).
....
(c) If, after passing the outer marker or equivalent position in accordance with (a) above, the reported RVR/visibility falls
below the applicable minimum, the approach may be continued to DA/H or MDA/H.
To keep it simple: one can make an NDB approach to MDH/MAPt with 9999 OVC001, but one can't shoot an ILS Cat I with 0200 SKC.