The planning calculation allows perhaps three torpedo hits to write off a dreadnought, with only about one weapon in four functioning usefully. Removing eight ships therefore calls for roughly 25 to 30 hits. Because each aircraft carried one 18-inch torpedo, that requirement produced a force of about 100 to 120 aircraft. The aim was to remove a squadron from the wartime order of battle, even if some ships could later be salvaged.
Notable Point · 40:37-44:38
The torpedo arithmetic behind a 120-aircraft raid
Royal Navy planners could derive the 100-to-120-aircraft requirement from expected torpedo failures and the hits needed to write off a German battle squadron.