Two parameters are needed: Eye-to-wheel height of aeroplane
in the approach configuration, and Flightcrew’s eye-to-aerial height. The usual Boeing/Airbus planning documents don't appear to give these (or at least I can't find them). Any ideas on a source would be gratefully received.
EDIT1 Let me answer my own question: Appendix 6 of Aerodrome Design Manual Part 4 gives the eye to wheel and eye to aerial heights of aeroplanes.
EDIT2 The PAPI manufacturer Siemens has produced this really first class manual on the PAPI, answering all the questions about siting, MEHT, harmonisation with ILS, worked examples (p19) and plenty of "tricks of the trade" for cross-checking each step. A must-have for father's day (groan - what a bad pun)
Siemens PAPI Manual
https://www.industry.siemens.com/adb...M02512E401.pdf