From a hangar full of bits:
1. the PAPI and the recommended instrumented approach angle may not be aligned
2. FAA PAPI angles sideways spread, ICAO and CAA are not necessarily the same
3. the nominal touchdown point is not suitable for land and hold short operations in most cases when using a PAPI
4. The ILS and PAPI, even if both 3.00 degrees are not necessarily aligned to the same point
5. Please remember ICAO Annex 14 Volume 1 statement about a requirement for a runway to be equipped with PAPI for all turbojet operations. If the runway does not have vertical light guidance, you should not be going there.
PM me if you need more
Cheers
Discount