After considering the responses to this thread, it was clear that, although most were aware of the presence of the circle on the helideck (soon to be also used on heliports), these markings were not in use throughout the world - even though they are essential elements of safety for offshore operations.
The continuing work on Annex 14 Part II (heliports) has resulted in amended Standards and Recommended Practices for helideck/heliports, one of which is the acceptance of helidecks of less than 1D for helicopters below 3,175kg (7,000lbs). There has also been acceptance that even with 1D (or larger) decks, accurate positioning is critical to safe operations (an incident in Norway where a pilot performed a spot turn, without maintaining positioning on the Touchdown and Positioning Markings (TD/PM) - i.e. the bum line, indicated that there was room for further reinforcement of the reasons for markings and accurate positioning.)
In view of that we took a commitment to produce a paper to explain the principles behind the markings, and explain why their use is important. That paper has now been produced and the Helideck Certification Agency (HCA) has kindly agreed to host the paper on their site. It can be found at:
http://www.helidecks.org/download%20...r%20V1%209.pdf
We welcome any comments on this paper and will amend it in accordance with those comments.
NB the revised Standard for helidecks of less than 1D can be found at Appendix C to this paper.
Jim