Part 29 helicopters have the HV Diagram in their limitations section; Part 27 helicopters do not.
Having the HV Diagram in the limitations section is a problem for Part 29 helicopters; the majority of them work in offshore operations where they are in the diagram during most take-off and landing profiles.
That is why both FAR 91 and JAR-OPS 3 alleviate from the effect of this limitation. FAR 91 for heliports constructed over water - in 91.9(d); and JAR-OPS in Appendix 1 to JAR-OPS 3.005(c).
It has been known for some time that having, what amounts to, an operational limitation in Part 29 is unnecessarily limiting. It was put in about the time that Category A become a compulsory requirement for Part 29 helicopters.
Jim