During the spring of 1949, a total of 59 flights ^Yere made on 42 

 different days from 28 February to 15 June inclusive. The duration 

 of these flights totalled 4G3.95 hours distributed chronologically as 

 shown in figure 1. The individual flights varied in duration from 0.3 

 hours to 11.4 hours. The flights averaged 7.86 hours per flight for 

 PBIG aircraft and 7.90 hours for the three flights made by PBY5A 

 aircraft which were used to take advantage of good flying weather in 

 May and June to enable the aircraft to search more area in a given 

 day. The maximum interval between flights was 7 days, occurring 

 between 23 March and 30 March. The remaining intervals between 

 flights are summarized below : 



Interval in days Frequency 



1 12 



2 10 



3 9 



4 5 



5 1 



6 2 



On the basis of an estimated average ground speed of 150 knots 

 for PBIG aircraft and 100 knots for PBY5A aircraft, it is estimated 

 that the aircraft flew a distance of about 08,000 miles during the 

 1949 season. As search courses are usually laid out parallel and 

 25 miles apart, it is estimated that the area searched Avas about 

 1,700,000 square miles. Since coverage is never 100 percent complete, 

 it is estimated that the total area visually covered w\as approximately 

 a million square miles. 



In good observing weather, the ability of a PBIG to search a 

 given area in a minimum of time is incomparably greater than that 

 of a slow-moving surface vessel. During poor aerial observing 

 weather, however, the surface vessel can do the job which becomes 

 impossible for the aircraft. Thus aircraft and surface craft supple- 

 ment each other and, in a normal year, together result in a more 

 efficient patrol than if operations were limited to one or the other. 

 Since the costs of operating aircraft are less than the costs of oper- 

 ating surface craft, by the judicious use of the two types of craft the 

 over-all cost of an efficient j^atrol can be kept down to about the same 

 figure as the cost of a less efficient completely surface patrol through 

 taking advantage of the seasonal fluctuations in aerial observing 

 weather. Thus by making use of aircraft alone during the first part 

 of the season, when good observing weather occurs with sufficient 

 frequency to permit following the progress of the ice by aerial obser- 

 vation and delaying the use of surface craft until midseason when 

 aerial observing conditions normally deteriorate in the critical areas, 

 the over-all cost is kept at about that required for an all-surface 



