LTN is a different case. So are you saying, FFB, that perf is calculated from the intersection but they still backtrack a couple of hundred metres, do a 180°, and then depart? Why? Why not calculate full length and taxi an extra 20 seconds, do your 180° in the turning circle provided and then depart. Or leave your intersection performance but still use FULL length - LTN isn't the longest of runways (and very unforgiving if you go off the end of 26
).
The only reason possible is to save time (seconds) - so why back track at all if you've got valid perf from the intersection - what is the objective here
A4