Actually, the type of aircraft that protected the channel shipping was fighters. Coastal Command used bomber or scout type planes to patrol for U-boats. They would be useless for protecting channel shipping as the Stukas, Heinkels and Junkers would be escorted by ME-109's and would have made mincemeat of any Hudsons or Sunderlands sent to protect shipping.
The great tragedy of the Battle of the Atlantic was that only about 200 aircraft earlier in the war could have won the battle much sooner. Bomber Harris jealously hoarded any planes capable of bombing Germany for his zealous pursuit of strategic bombing. A handful of planes like the VLR Liberator were instrumental in turning the tide against the U-boats. Bomber Command was a vast waste of aerial resources compared to how much materiel and life was lost to U-boats due to lack of patrol planes.
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