What is it and what does it do? 
Is there a definition somewhere?
I can’t seem to find any info on it…
Mark
I received a reply from Rob_L and collective compensation is in fact H_Col_Yaw in advanced params list.
Has to do with collective pre-comp for keeping the tail rotor compensated for the amount of thrust applied by the main blades…
Huh… who’d a thought…
Many thanks Rob 