At 21.29 hours on 4 April 1942 the unescorted Alphacca (Master Reindert Johannes van der Laan) was hit aft of amidships by one G7a torpedo from U-505 after chasing her for more than seven hours about 154 miles south of Cape Palmas, Ivory Coast. When the ship began to settle by the stern, most crew members and all passengers abandoned ship in four lifeboats without sending a distress signal before she sank. 14 crew members were lost. The U-boat surfaced afterwards and approached the lifeboats to question the survivors. The Germans asked the usual questions about the name, nationality, cargo and route of the vessel, but also if they had enough supplies and water and were given the course and distance to Cape Palmas. Before the U-boat left they wished each other good luck and bon voyage. Initially the conversation had been in English but soon changed to German, a fact noted by Loewe in the war diary with the comment: Irony of fate, we fight against people who speak our language. The lifeboats then sailed towards the coast, but a fireman died of wounds the following day and was buried at sea. On 9 April, all four boats made landfall east of Cape Palmas. The survivors boarded HMS Hydrangea (K 39) (A/LtCdr J.E. Woolfenden, RNR) and FFL Commandant Drogou (K 195) after a week and were taken to Freetown, where five wounded men were admitted to a hospital on 18 April.

On 27 March 1942 an accident aboard Alphacca severely injured three engineers when they tried to repair the refrigerator. The chief engineer Jakob de Vries and the second engineer Pieter Willem Kooij both subsequently died of injuries and were buried at sea.