exactly proportional to the berg count, but every effort is being made 

 to keep the cost consistent with the danger to shipping. During 

 1952 only 14 bergs were estimated to have drifted past the 48th 

 parallel, and none past the 47th. From this figure, and by compar- 

 ison with average ice limits shown in The Ice Atlas of the Northern 

 Hemisphere, Hydrographic Office Publication No. 550, it can be seen 

 that 1952 was a very light ice year. Details of the ice movement 

 for each month of the year are given under Ice Conditions, 1952. 

 (See figs. 1 to 4.) 



AERIAL ICE OBSERVATION 



During 1952 the entire program of ice oljscrvation was carried out 

 with two PBlG (Bl7) aircraft, capable of flj^ing 1,500 miles on a 

 normal patrol. These planes were equipped with two loran indica- 

 tors, both manned at all times during flight by trauied operators 

 who acted as aides to the navigator. With positions being obtained 

 approximately every 3 minutes, it was possible to accurate^ fix the 

 location of every ice formation sighted. An experienced ice observer 

 was carried on each flight, and seated in a position to have unrestricted 

 visibility from beam to beam. A continuous radar watch was main- 

 tained, even during periods of good visibility, and as a further aid to 

 the observer, a remote radar oscilloscope was mounted for his use. 



To ensure that ice formations were not missed while searching under 

 normal conditions, the tracks followed by the aircraft were planned 

 to be parallel and 25 miles apart. With flights planned in this manner, 

 the average search was believed to cover effectively a sea surface 

 area of 30,000 to 35,000 square miles. Durmg 1952, ice conditions 

 were never severe enough to justify aerial searches during marginal 

 weather. On several occasions fog or low stratus developed during a 

 flight and forced completion of the search by radar alone. Wlien this 

 occurred, it was sometimes possible to identify radar targets by 

 passing over them at altitudes from 300 to 500 feet. 



Flight statistics for the season are given in the following table. 



