You might be thinking of Royal Navy Swordfish attacking the Bismarck. While it's possible that the low speed of the swordfish were throwing off the Bismarck's firing solution, post war examination of the Bismarck's plans show that its AA guns were on non-stabalized platforms and were not centrally controlled or radar directed.

In other words, the Brits painted themselves as the plucky underdogs using their wits to turn the slow speed of their planes into an advantage but it's also very possible that the Bismarck's AA suite was just that shit and couldn't hit slow flying targets.