Crab,
The merits of dynamic vs. benign helipad vertical takeoff procedures have been debated for decades. The Category A vertical procedure WAT curve is based primarily on the ability of the helicopter to transition from AEO vertical climb to OEI forward flight. The dynamic procedure produces optimal performance with respect to payload and/or ground clearance during OEI continued takeoff, but causes the helicopter to climb (balloon) higher (especially at light weight) following engine failure thereby increasing workload during the vertical rejected takeoff maneuver. The same arguments for and against the dynamic procedure have been made with respect to helideck vertical takeoff procedures. The dynamic procedure produces better payload and reduced dropdown with more generous deck-edge clearances during OEI continued takeoff, but produces higher balloon heights for the rejected takeoff. Bottom line, the dynamic procedure yields better payload performance and can be used as long as the rejected takeoff issues don’t become limiting.
HT