The jets could be used if high speed dash was required, for example, (I'm assuming), to get to a target before it submerged. But, as stated above, it came at quite a cost in fuel. I understand (from bar talk) that, in the event of a failure of one of the radials at high weights, the jets served a double purpose - providing much need extra thrust, but just as importantly, shedding weight by expending all that unwanted fuel. Very, very quickly.