dangers of petrol vapour caused an explosion in A5, which killed her commander and several others, and led to the move to adopt diesel engines which used heavy oil with a higher flash point. A13 was fitted with an experimental diesel engine for trials at sea. During these trials, the B and C Class vessels continued to be fitted with the same sixteen cylinder Wolseley petrol engine as in A5 to A12, but now made by Vickers and called the Vickers engine. In C19 to C38 the number of cylinders was reduced to twelve. Following the trials in A13, diesels were adopted for the D Class, and the use of petrol engines in new designs came to an end.
The A, B and C Classes, although intended for coastal defensive work, proved that the submarine was here to stay and with greater range could have an even more important role to play.
