 The mount on the quarterdeck was later removed as it was unusable in heavy seas.They were equipped with two triple-barrelled Limbo Mark 10 anti-submarine mortars.The "Blackwood"-class ships had the same sonar suite as the larger s where the Limbo mortars were controlled by three sonars, the Type 174 search set, Type 162 target-classification set and the Type 170 'pencil beam' targeting set to determine the bearing and depth of the target.