AERIAL ICE OBSERVATION 



During the 1954 ice season, 84 ice observation flights were made. 

 The average flight duration was 8.4 hours, and the average distance 

 flown was 1,190 miles per flight. Two PBlG (B-17)-type aircraft, 

 supplemented occasionally by UF-type aircraft, were utilized for these 

 flights. 



The ice observation flights were planned to locate the southeastern, 

 southern and southwestern berg limits and field ice limits in the Grand 

 Banks area and to scout upstream from those limits to determine tlie 

 positions of bergs and the extent, concentration, and geograpliical 

 distribution of field ice which endangered, potentially or actually, the 

 shipping lanes. The usual flight plan covering tlie area to be scouted 

 was a system of parallel lines spaced at 25-mile intervals. Because of 

 the high frequency of poor visibility conditions in the scouting areas, it 

 was necessar}' to keep well informed of weather conditions in order to 

 choose da3^s on which flights would be visually efl^ective for ice obser- 

 vation. The weather forecasting service provided by the United States 

 Fleet Weather Central at Argentia and the regular four hourly weather 

 reports made to Commander, International Ice Patrol, by ships in the 

 ice patrol area were of very great value in this connection. As 

 mentioned previously, allowance was made for the probable drift of 

 ice in planning ice observation flights to relocate that ice. 



Most of the ice observation flights covered such large areas that it 

 was unusual for visibility conditions to be good over the entire search 

 area, and where visibility was restricted a radar search was carried out. 

 There are, however, certain disadvantages to a radar search. First, 

 small bergs or growlers may escape detection. Second, to distinguish 

 between berg and nonberg radar targets it is necessary for the plane to 

 divert from her search plan to close the range within the limit of 

 visibility. A number of such diversions may use up so much plane 

 fuel that part of the search plan must be deleted. Third, if the 

 ceiling is too low, a radar target may not be identified at all.- Never- 

 theless, radar is a powerful aid to ice observation and has detected 

 many a berg which might not have been discovered by visual means 

 alone. It is also very useful in fixing the positions of bergs found 

 visually. 



A qualified observer was carried on each flight. He was responsible 

 for plotting all ice sighted and recording berg sizes and descriptions 

 and field ice concentrations. Berg descriptions, in written or sketched 

 form, were useful in identif3'ing bergs when they were relocated on 

 subsequent flights. The ice observer worked closely with the plane 

 navigator, who had at his disposal two automatic-tracking loran 

 receivers as well as the usual equipment for celestial and dead reckon- 

 ing navigation. 



2 Unsuccessful tests were conducted with an airborne radiation tliermomet er for tlie purpose of distinguish- 

 ing between berg and nonberg radar targets under conditions of poor visibility. 



