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and 30 or 40 feet thick can be shoved aside as long as there is open 

 water for them to be pushed into. The deciding factor as to naviga- 

 tion in ice more than 6 to 8 feet thick is whether or not there are any 

 open water spaces for the broken ice to move into. 



In a seaway, the icebreakers, lacking keels, are extremely lively. 

 A 50° roll has been recorded off Nantucket Lightship. They are also 

 reported to be wet in a head sea, although by virtue of their sturdy 

 construction they can take a tremendous amount of punishment. 



OPERATING IN ICE 



The most expedient way to traverse ice is to find the open leads and 

 polynyas even if it entails actually going much greater distances than 

 intended. Too frequently ships that do not follow the above rule will 

 find themselves back-tracking and looking for these open leads after 

 having wasted many hours trying to bull their way through a short 

 cut. The best means of finding leads, open water, and areas of ice 

 that can be traversed is by use of the ship's helicopter. The H03S 

 type attached to the Edisto easily made reconnaissance flights up to 

 30 miles and with good visibility could pick out leads several miles 

 ahead of her farthermost position. Navigating solely from its own 

 observations, a ship can only proceed according to what it can actually 

 see for about 7 or 8 miles around. Even this information is uncertain 

 when the ice begins to get fairly heavy and thick because the appear- 

 ance of the ice is frequently deceiving. However, there are numerous 

 aids such as water sky, iceblink, and direction of prevailing wind that 

 may be used with a great deal of success. The following up of water 

 sky has proved quite helpful in navigating the ice fields ; heading to- 

 ward ice blink in an effect to short cut across the pack has almost 

 always proved inadvisable in that the longer route had to be taken 

 eventually anyway. 



Therefore, the first recommendation for successful ice field negotia- 

 tion is to use a helicopter to pick out the best patch to follow; in the 

 absence of available aircraft for this purpose, follow the water sky 

 and stay away from the iceblink. AVhen the visibility closes down so 

 that neither of the above methods can be used successfully, it is best 

 to stop and lie to until visibility improves again. This advice pre- 

 supposes, of course, that little or nothing is known of ice conditions 

 ahead and that local ice conditions offer a navigational handicap. 



Brash, slush, pancake, and new ice may tend to slow the ship but do 

 not prevent her from maintaining a course. All these types are navi- 

 gable by ordinary ships and are mentioned because they are quite 



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