Originally Posted by
Broadlands
1. Performance calculations are completed. The quotes LDA is measured from the threshold, not the PAPIs.
Yes. But the figures for LDR (landing distance required) in the aircraft manuals are calculated for a screen height of 50ft above the threshold which will result in a touchdown 1000ft down the runway i.e. right next to the PAPI. So both LDA and LDR take into account that the first 1000ft / 300m of the runway are "wasted". Which is not really true because that "waste" of runway is factored into the obstacle clearance. Therefore in my eyes (and in those of my flying school superiors and those of every examiner I have ever flown with) it is a mistake to fly below a PAPI when one exists on the landing runway - independently of the flying conditions.