Originally Posted by
TeeS
It's quite possible that I am talking bolloxs though
Tees, more than possible
The FAA produced a paper in 1991,
Helicopter Rejected Airspace Takeoff Airspace Requirements which seems to be addressing the problems of too-steep departure paths and a more flexible airspace system to allow for this. Prior to this report, the helicopter manufacturers were following the fixed wing criteria laid down by the FAA (IIRC).