Talk about luck!
Started a new career in 1944 with SH3Cmdr and 11th Flotte just so I could try the XXI for once (never used it before... and I've owned the game since day one!).
Well, I was travelling west and kept getting these 'radar detected!'. I ignored them and continued to sail on the surface, making sure my AA guns were manned.
Well, lo and behold, a shat-ton of DDs show up. I'm like, great.
So, I look through my UZO to check bearings and - SHIPS AHOY!!!
Illustrious Fleet Carrier, bearing 347 degrees!
I immediately go to periscope depth, ahead full (they already saw me so I didn't care), set all 6 for impact det (using all Type III Electrics), closed to 3700+m and ripped them all off in rapid succession.
Damned if all 6 didn't hit and detonate.
Turns out I only needed about 3 of them as she erupted in spectacular fashion.
Ironically, I got away quite easily...