bered by a few bergs and very light concentrations of sea ice on the 

 Grand Banks; track F, while in effect after 15 May, was clear of ice. 

 The Strait of Belle Isle route, Track G, was navigable with caution 

 by 12 June. An earliei* opening of this route was prevented by heavy 

 pack blocking the eastern approaches to the strait, although the strait 

 itself was essentially free of field ice by the last of May. Shipping 

 routes to ports in the Gulf of St. Lawrence and the St. Lawrence 

 River were clear by 16 April, except for occasional patches and 

 strings of sea ice. 



The ice threat to the shipping lanes in the Grand Banks area was 

 considered negligible by 10 July. Numerous bergs still existed inside 

 the 1,000 fathom curve off Newfoundland north of the 49th parallel, 

 but their set and drift and high melting rate eliminated them as 

 dangers to the shipping lanes in the Grand Banks area. Broadcast 

 of ice bulletins ceased and the International Ice Patrol office at 

 Argentia Avas closed on 15 July. However, at the request of Com- 

 mander, International Ice Patrol, the U. S. Coast Guard Air Detach- 

 ment at Argentia made several postseason aerial reconnaissances to 

 prevent the undetected drift of any stray berg into the shipping lanes. 



AERIAL ICE OBSERVATION 



The U. S. Coast Guard Air Detachment at Argentia utilized three 

 PBlG (B-17) type aircraft, supplemented occasionally by one UF 

 type aircraft, to carry out the aerial ice observation program for the 

 International Ice Patrol in 1955. During the season 60 flights were 

 made. The average length and duration of these flights were 942 

 miles and 7.0 hours, respectively. The longest flight was 1,585 miles 

 in length. The absence of ice on the east slope of the Grand Banks 

 and in the Flemish Cap area permitted the average flight length to be 

 shorter than normal. 



As in previous years, all the ice patrol aircraft were equipped with 

 loran receivers and radar, the former being the primary means for 

 navigating the aircraft and the latter for the detection of ice under 

 conditions of low visibility. Identification of radar targets was accom- 

 plished by closing the range until the target was sighted visually. 

 Because of low ceilings this was not always possible. The usual flight 

 plan covering the search area was a system of parallel lines spaced 

 at 25-mile intervals. Flights were normally made only on days when 

 the weather forecast promised success in visually searching a major 

 portion of the area to be scouted. 



