 The Type IXA submarines were the first German submarines to have a double hull. This allowed for a greater chance of survival in the event of an attack and gave them better seaworthiness on the surface. The Type IXA submarines had a test depth of 230 metres (750 ft). The class had two MAN M 9 V 40 / 46 supercharged 9-cylinder diesel engines that produced 4,400 PS (4,300 shp; 3,200 kW) as well as two SSW 2 GU 345 / 34 double-acting electric motors that produced 1,000 PS (986 shp; 735 kW) and allowed them to travel at 18.2 knots (33.7 km / h; 20.9 mph) while surfaced and 7.7 knots (14.3 km / h; 8.9 mph) submerged. The Type IXA submarines had a range of 10,500 nmi (19,400 km; 12,100 mi) at 10 knots (19 km / h; 12 mph) while on the surface and up to 78 nmi (144 km; 90 mi) at 4 knots (7.4 km / h; 4.6 mph) while submerged. The fuel capacity was 154 tonnes (152 long tons). The maximum crew capacity was 56, though the number on board was usually around 45 – 48.
