RESTRICTED 



from the icebreaker, the influence of the icebreaker would hardly be 

 noticed. The vessel would therefore either stop or be stuck in the ice. 



Piloting a ship in convoy at reduced distances requires a certain 

 amount of experience on the i)art of both the icebreaker's company 

 and the personnel of the other vessels. It often happens that in heavy 

 ice, there are obstacles which the icebreaker cannot overcome on the 

 run. She may suddenly stop and give the signal "Full Astern" to 

 the following ships. In order to avoid collision, the ships must go 

 astern immediately. Wlien moving in such close formation, the thick- 

 ness of the ice ahead must be carefully observed by the icebreaker 

 so that probable fluctuations in speed can be anticipated, and the 

 necessary warning passed to the ships astern in plenty of time. The 

 danger resulting from a sudden stop on the part of the icebreaker 

 is obvious. The importance of maintaining the correct distance appli- 

 cable to the ice conditions is therefore clear. This distance should 

 never be greater than 3 to 3i/^ ship lengths, and is usually a matter 

 of only a few yards. To assist the conning officer in keeping the ship 

 in position, it is advisable to establish a "stadimeter watch"' who can 

 furnish readings as frequently as may be required. The spacing must 

 be changed with the varying condition of the ice, and great stress 

 must be laid on accurate station keeping. "Wlien navigating in ice, 

 disregard of these rules can result in very serious consequences. 



By virtue both of his experience and of his position in the convoy, 

 which enable him to assess as well as sample the ice conditions ahead, 

 the captain of the leading icebreaker must estimate the correct dis- 

 tances apart to be maintained by the ships. He must signal any 

 changes required due to altered ice conditions, etc. It is absolutely 

 necessary that the officers of the piloted ships should be thoroughly 

 acquainted with all the signals used for convoying in ice. It should 

 never be necessary for the icebreaker to repeat a signal due to slowness 

 of execution. 



COURSE AND SPEED OF CONVOY 



Before entering the ice, captains of the icebreakers and masters of 

 the piloted ships must clearly visualize the conditions of the ice in 

 the various sectors along the prospective route, consulting (if possible) 

 ice charts based on air reconnaissance observations and statistics of 

 winds and currents in these sectors. The track to be maintained is 

 decided upon by the operating staff or captain of the leading ice- 

 breaker, as the case may be, after a careful study of the ice charts 

 and the synoptic forecasts, as well as the coastal topography, depths 

 along the route, areas of permanent ice pressure, etc. The longest 



RESTRICTED 91 



