An unseasonal shift of tracks was recommended on 18 April 1966 and 

 Trans-Atlantic Lane Eoutes C and D were maintained in effect. On 28 

 April 1966, the rather exceptional 1966 International Ice Patrol Season 

 was terminated. Detailed monthly ice conditions appear in a latter 

 section. 



AERIAL ICE RECONNAISSANCE 



Thirteen ice observation flij^lits were made, using two Lockheed 

 Hercules (HC-130B) aircraft, by the U.S. Coast Guard Air Station, 

 Argentia, Newfoundland, during the ice season. These flights averaged 

 1,100 miles in length and 5.1 hours long. The longest flight was 2,609 

 miles in length. In addition, seven preseason and four postseason ice 

 observation flights were conducted. 



The primary objective of the aerial ice reconnaissance was to guard 

 the southeastern, southern, and southwestern limits of the ice-encum- 

 bered area in the vicinity of the Grand Banks so that shipping might 

 be advised of the extent of the dangerous area. In addition, the aerial 

 ice reconnaissance had the purpose of maintaining detailed up-to-date 

 information on the ice situation in the Grand Banks region and north 

 for the benefit of mariners traversing the ice area. Ice reports from 

 shipping were of invaluable assistance in attaining these objectives. 



The flight plans were usually made up of a system of parallel lines 

 spaced at about 20 to 25 mile intervals, depending on visibility. The 

 spacing was predicated on the ability of readily sighting bergs at 15 

 miles, hence, it provided a margin of overlap on parallel tracks and 

 covered a sufficiently large search area. From past experience, it ap- 

 peared that this search pattern is quite efficient for the purposes of 

 detecting ice on days with good visibility. "Wlien poor visibility oc- 

 curred, such that 15-mile visual sightings of bergs was precluded, this 

 spacing ajjpeared to be the optimum for a radar search and permitted 

 sufficient reserve of flight hours to divert the aircraft from the pattern 

 in order to identify targets. A trained aerial ice obsen-er was assigned 

 to each ice reconnaissance flight. Loran-A was the primary positive 

 method of air navigation. An airborne doppler sensor system was used 

 to navigate all flight plans, corrected when possible, by Loran-A or 

 other available means. The use of doppler radar visual readout pres- 

 entations provided the ice observer continuous track and cross track 

 information greatly assisting, and increasing the accuracy, in position- 

 ing bergs. Maneuvers off the prescribed tracks, once extremely difficult 

 to plot, could now he plotted. Radar aided tlie observer in locating 

 ice, especially when visibility conditions were minimal. A passive 

 microwave radiometer, with the frequency selected for optimum ice 

 emissivity, was installed on one Ice Patrol aircraft. A full evaluation 

 could not be conducted due to continuing aerodynamic problems 

 caused by the location of the microwave antenna dome. 



