Originally Posted by
safetypee
BraceBrace " The PAPI's are perfectly safe to be used by any 777 "2 reds, 2 whites", whatever the body length, " This is debatable; requires the equivalent data for 777 as in #50, and context re PAPI - threshold distance i.e. rwy 22 and grass.
Straight from Boeing (who also state the a 2 bar VASI is unsafe)
"
When the airplane is on a normal 3° glide path, the pilot sees two white lights on the left and two red lights on the right. The PAPI may be safely used in relation to threshold crossing height, but may result in landing further down the runway. The PAPI is normally aligned to intersect the runway 1,000 to 1,500 feet beyond the threshold."
If you want more info, the numbers are in the FCTM.
The "blocks" are 1300-1500ft from the threshold and work perfectly as aiming points from a
visual approach. If you want to feel safe, you might use the "farther" edge, but you risk long landings, especially on a glider like the 777. I very very vaguely recall an approach where the approach plates indicate wide bodies have to consider "3 whites" on the PAPI's. But I suspect this is because people have been calculating the numbers on the ground and have found variations to the standard setup requiring the note.
If you want to argue, I suggest you contact the Boeing engineers. But I'm pretty sure they've already done the calculations you have been doing here.