knots it is practically impossible to determine whether or not the 

 target speed is less than say 2 knots. In periods of reduced visibility, 

 it is usually possible to identify radar targets by visual sighting. 

 However, when an area is completely blanketed by fog, safe flying 

 practices prohibit visual identification of radar targets. The risk of 

 collision with a pinnacled berg at low altitudes is real. Flights were 

 sent out whenever terminal conditions, flying weather, and weather 

 in observing areas gave promise of successful aerial reconnaissance. 



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DISTRIBUTION OF PLANE HOURS, 1949 



Figure 1. 



-Distribution and duration of aerial reconnaissance flights during tlie 

 1949 season. 



