Trans RINA, Vol 152, Part B2, Intl J Small Craft Tech, 2010 Jul-Dec
However, it is instructive to elaborate on some of the issues considered by the group.
The proposal by China [12] for standard formulae of wave height/speed limitation curves did not attract any support and so was discarded. Based largely on [11], an initial draft
of the guidelines was prepared for
consideration by the group. It provided for the operating limitations, drawing on the parent provisions of the amended 2000 HSC Code, to take into account:
• Maximum distance from place of refuge • Available resources
rescue and operational support
• Physical operational environment (wind force, minimum air temperature, visibility and depth of water)
• Sea state limitations – significant wave height • Trials demonstrating compliance in relation to operating limitations
• Navigational matters • Display of operating limitations.
Much of the resulting text was uncontentious and remained virtually unamended through to finalisation of the guidelines. However, a number of issues were the subject of vigorous discussion and some are likely to remain “on the boil” even beyond the finalisation of the guidelines. These are outlined below.
2.1 EVACUATION CONSIDERATIONS
As part of the operational philosophy of high-speed craft is to evacuate into survival craft in the event of significant emergency, it has been a prime concern since AMSA’s first involvement with high-speed craft under its jurisdiction that these craft should not operate in sea conditions where safe evacuation demonstrated.
has not been This was of particular concern in early
high-speed craft where passengers were required to climb down the side of the craft and into a life-raft without the benefit of a marine evacuation system (MES).
During the development of the Guidelines, a leading Australian liferaft and MES manufacturer submitted to AMSA that the
requirement of the life-saving test
procedures [13] for heavy-weather sea trials of MES (Figure 4) in seas of significant wave-height of 3.0 m should not restrict craft on which the MES is fitted to operations up to that sea state.
The submission was
along the lines that, although the MES could no doubt be safely used in worse conditions, the personal safety hazards associated with more severe sea conditions would negate any safety benefits of further testing those conditions. On this basis, the satisfactory completion of MES type approval should not restrict the craft using those MES to the sea conditions in which they were tested.
Figure 4. Marine Evacuation System (MES)
Understandably in light of the Sleipner tragedy [14], Norway was not happy with accepting evacuation arrangements involving evacuation directly into the survival craft without the use of MES. Accordingly, a clause was inserted into the guidelines providing the Administration in such cases with the right to require satisfactory evacuation trials in weather and
sea
conditions up to the worst intended conditions stipulated on the Permit to Operate.
2.2 EXTRAPOLATION OF SEA TRIAL RESULTS
Prior to the 2006 amendments, the HSC Code placed no restriction on the extent to which linear extrapolation could be applied to sea trial results when setting operational limitations. An amendment to paragraph 3.2 of Annex 9 of the Code
reduced this permissible extrapolation to 150% of the trial sea conditions.
In this regard it should be noted that weather and sea conditions closely approximating the worst intended conditions may not be readily available for a high-speed craft builder to prove the safe operations of his product. Nor is it practicable to require a craft that is to enter commercial service to be tested in full scale to the worst intended conditions, where the safety of the craft (eg. in relation to bow diving of a catamaran or skirt tuck-in of a hovercraft when manoeuvring) may be marginal. On the other hand, technological developments since the 1994 HSC Code was adopted are such that non-linear seakeeping calculations can be conducted using software that is freely available from commercial sources.
However, for the two years that the guidelines were under development by the correspondence group, the United Kingdom insisted that they were unhappy with accepting any substantial extrapolation, but could if necessary accept a small extrapolation.
This position
As other Administrations took a similar view to this manufacturer, AMSA agreed to accept this outcome and change its policy approach accordingly.
This removed
one factor from those that may define operational limitations.
©2010: The Royal Institution of Naval Architects
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