medium berg. It was hoped that some method could be developed 

 so that bergs could be distinguished from fishing vessels ; however, 

 no such method has yet been found. Thus the ice patrol cutter or 

 plane must investigate every radar target in thick weather to deter- 

 mine its nature. 



As a result of the shipboard work conducted in 1945 and 1946 it 

 was concluded that the 10-cm. model tested was superior to the 

 3-cm. model for ice detection. Hand in hand with a radar's poten- 

 tial ability to detect ice must go its operation, maintenance, and 

 ability to withstand vibration. It was found that the 10-cm. radar 

 was easier to keep in operation at peak performance than was the 

 3-cm. radar. A much higher percentage of time in operation was 

 noted with the 10-cm. radar. This coupled with the reliability of 

 the 10-cm. radar in picking up echoes has led to the recommenda- 

 tion of the 10-cm. model radar tested as the primary search radar 

 for Coast Guard cutters engaged on ice patrol. 



Air-Borne Radar 



The experimental work with air-borne radar was carried out in 

 conjunction with routine flights for the purpose of ice scouting. 

 Two types of planes both equipped with 3-cm. radars have been 

 utilized in routine coverage of the critical ice areas over the Grand 

 Banks for the past two seasons. These planes were the PBY-5A 

 equipped with the AN/APS-3 radar gear and the PB4Y-1 equipped 

 with the AN/APS-15A radar gear. The radar was used during 

 the patrols when visual contact with the surface was either greatly 

 limited or impossible because of fog, haze or heavy low cloud for- 

 mations. Throughout a flight qualitative observations of the be- 

 havior of the radars on all ice targets were made and recorded. 

 The maximum range at which each target was detected was noted 

 so that the average detectible range for all type targets could be 

 found. All of the operational controls were fully utilized to deter- 

 mine the over-all value of air-borne radar for ice detection. 



The fact that both radars were of the 3-cm. band prohibited the 

 possibility of a frequency comparison as was done with the ship- 

 board experimentation program. However, it was felt that some 

 knowledge of the ability of air-borne radar to detect ice was gained. 

 These two radars had many different features which allowed an 

 over-all evaluation to be made. The AN/APS-3 radar has a "B" 

 type scope (range plotted vertically against bearing plotted hori- 

 zontally) with a constant scanning arc of 150° centered dead ahead. 

 The antenna can be tilted up or down to increase th- jff"ectiveness 

 of the beam pattern in a certain area. One disadvantage of the 

 "B" type presentation is the fact that the distortion of the image 

 on the scope makes the definite recognition of land masses difficult 

 to an operator without considerable experience both as to the radar 



186 



