in good or fair weather, the prevalence of fog in spring months 

 occasionally requires that a flight be made in marginal or poor 

 visibility where the aircraft must seek out its targets by radar 

 and then descend to near the surface to gain visual identification 

 of either ship or berg. 



During the 1958 season three PBIG (B-17) aircraft were uti- 

 lized for 30 ice observation flights. Aircraft statistics for the 

 season are given by the following table : 



Table 1.— Aerial Ice Observation Statistics for the 1958 Season 



1 Days on which possible to search visually at least 50% of scouting area with 25-mile spacing 

 between legs of flight plan. 



2 Ratio ( X 100) of area actually searched visually to area of search pattern. 



COMMUNICATIONS 



With the inauguration of Ice Patrol services on 14 March, the 

 International Ice Patrol Radio Station (NIK) commenced its 

 services of collecting and broadcasting of ice information. The 

 first of regularly scheduled advisories was at 0048 GMT on 15 

 March. Thereafter, broadcasts were made twice daily at 0048 

 and 1248 GMT on frequencies 155, 5320 and 8502 kilocycles. All 

 broadcasts were CW signal with an emission power of 2 kilowatts. 



A general call to ships on 500 kilocycles preceded each advisory 

 bulletin with instructions to shift to the broadcast frequencies. 

 A one-minute period of test signals transmitted on those frequencies 

 was sent to facilitate receiver tuning. Bulletins were transmitted 

 twice; once at 15 words per minute and repeated at 25 words 

 per minute. 



Each broadcast concluded with the request that all ships in the 

 patrol area report to NIK all ice sighted and sea temperatures and 

 weather conditions every 4 hours. The importance of such reports 

 cannot be overemphasized. A major portion of all ice information 

 collected by the Ice Patrol comes from ships, and the isotherm 

 charts (figs. 13-18) produced from ships' reports are an essential 

 instrument for analyzing and predicting iceberg drift and de- 

 terioration. Aerial observation flights are planned on the strength 

 of ships' weather reports and a general weather map is kept cur- 



