The HV diagram defines the area in which a safe landing is not assured after sustaining an engine failure. Category A defines an operating doctrine which, if followed would guarantee either a safe takeoff of a safe land back after sustaining and engine failure. Included in the Cat A takeoff profile is the land back area and drop down altitude from a raised heliport. The FAA’s definition of Cat A is:
Category A, with respect to transport category rotorcraft, means multiengine rotorcraft designed with engine and system isolation features specified in Part 29 and utilizing scheduled takeoff and landing operations under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight in the event of engine failure.