Ottawa returned to Canada in June 1941 and was assigned to the RCN's Newfoundland Escort Force which covered convoys in the Mid-Atlantic. She was transferred to Escort Group C4 in May 1942. In early September, the ship's captain refused to allow her director-control tower and rangefinder to be removed in exchange for a Type 271 target indication radar. On 14 September, while escorting Convoy ON 127 east of St. John's, Newfoundland, Ottawa was torpedoed by U-91. Ten minutes later, unable to manoeuvre, she was hit by a second torpedo. She sank ten minutes later; 114 crewmen lost their lives, including the commanding officer, while nearby vessels rescued 69 survivors.Douglas, pp. 515, 522, 524
