This decision soon began to affect NEF's capability to operate. In October, Royal Canadian Navy vessels were averaging 28 out of every 31 days at sea. Both US and British concerns over the force's effectiveness became apparent that month. To ease the strain in mid-October, every ocean-going escort of the Royal Canadian Navy was deployed to the NEF. The area of sea which became known as the "Black Pit" coincided with the gap between land-based air cover. This area, coupled with the slow speed of SC convoys became so dangerous to the convoy system that in November, convoy SC 52 returned to Canada after it was intercepted by U-boat packs shortly after beginning its trans-Atlantic voyage. In mid-November the NEF gained respite as the Germans abandoned the North Atlantic and re-directed their efforts elsewhere.