APPENDIX E
CVN 68 CLASS SHALLOW WATER NAVIGATION IMPROVEMENTS
Due to the deep draft of the CVN 68 Class aircraft carriers, port and shipyard access can be restricted, in
order to minimize the cost and environmental impacts of deep dredging, actual ship loading, tides, and favorable
weather conditions can be used. Utilizing these factors affects operational issues such as operating schedule and
contingencies as well as ship loading and speed. Actual transit situations will vary and will involve different
combinations of these factors. Current dredging plans will not provide unrestricted access to CVN 68 Class home
ports and shipyards. To reduce the risk of grounding, it is recommended that shallow water navigation aids be
improved.
The wave and motion determination process in shallow water is complex. Wave conditions are port
dependent; each port must be individually studied for an accurate assessment. The most extreme CVN motions are
generated from seal swells originating from storms hundreds of miles away; consequently, they are difficult to
detect. Waves and swells are predicted from the Fleet Numerical Oceanographic Center or observed by the crew.
Waves seen in or predicted for the open ocean may not be that which are experienced at any given port. Local land
and bottom effects and changes due to wind, tides, and currents are not included.
This plan improves onboard shallow water navigation aids by:
(a)
Providing a channel guidance system.
(b)
Providing real time channel condition measurement.
(c)
Improving ship's draft and attitude indication.
(d)
Providing a load management system.
These systems and other supporting systems would be integrated as appropriate to facilitate overall
functionality and minimize cost.
Channel Guidance System
NAVSEA has developed and tested an onboard CV Channel Guidance System (CVCGS). This system
aids in the determination of under keel clearances and the probability of grounding while operating in ports. It is a
PC computer program which calculates depth requirements based on data from the ship's force concerning load
and trim conditions. Environmental conditions are down loaded from Fleet Numerical or input from the ship's
navigator. Ship motions, under keel clearance, and probability of grounding predictions are then calculated for
channel transits. The CVCGS has been validated by ship model tests and full scale wave measurements. This
system will be sent to all CVs by the and of FY95.
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