Originally Posted by
PEI_3721
Slope is that required, normally ground referenced; e.g.ILS GP is three deg.
Path is that being flown (or required) by the aircraft; aircraft referenced; e.g. flightpath is 4 deg, descending.
But PAPI = path indicator, whereas previously VASI = slope indicator !!!
Why the 'legal' tag ? Actions may be legal, but not necessarily safe.
This is the explanation that made sense to me, but I have not flown a precision approach in decades. My limited knowledge base was acquired "long ago and far away".
Cheers,
Grog