From: USA Me-FL-DC-Guam-WS-NE-IL-?
In my IJ game against the allied AI, I've lost 2 subs to 500-lb. bombs off the west coast. In deep water, too. I have a better grasp of detection level mechanics and such now...
This came up in another thread recently. Usually, ASW aircraft aren't very effective at actually damaging subs. Where they succeed is in raising the DL. I see that ops report message all the time, but I figure that maybe only 1 in 50 actually represents a successful attack. Especially from Catalinas...though that could just be a result of their longer range. I believe the IJN subs that I lost to ASW aircraft were to SBDs.
If you actually manage to hit a sub with a 500-lb. bomb, it's hurting. Noticed that from the above losses as well as several port strikes in various games - one decent bomb hit typically results in boom/glug-glug.
I've lost a small handful of subs to Allied ASW air attack-Catalinas. 500 lb. bombs did the trick.
It's difficult in the game as it was IRL to get a sub kill with an aerial bomb. From Clay Blair's Hitler's U-Boat War (Volume 1): a 500lb. bomb needed to land within about 10-15 feet of a surfaced submarine to cause lethal damage. Very difficult to do IRL.
So, OP, I'd assume that 75% of the "sub is reported HIT" messages are FOW. 25% are probably real. Most 500lb. (or 250kg bomb) "hits" (probably near misses IRL) will cause some pain requiring repair of the submarine. Rarely will you get an outright kill.
In order to increase the likelihood of a hit (or damaging near miss), trained bomber or patrol crews with an ASW rating of 70+ are advisable. Airframe weapon used is important too. A 500lb (or 250kg) bomb will do more damage than a 100kg (or 250lb) bomb, as you might imagine. Thus, select the best balance of airframe, range, ASW skill, altitude (<2000ft.) and co-ordination with other forces (ASW H/K groups, naval search, mines, etc.) for best effect.
Andre , in fairness, Blair was discussing type VII and type IX U-boats. EXTREMELY tough boats. Much deeper diving then USN or IJN boats , and I'd bet tighter seems too. I was always taught that a depth charge within 30 feet would probably be a kill. And btw , depth charge is a misnomer. Any bomb fitted with a hydrostatic charge is a depth charge. (I recall discussing with a couple of ordancemen the possibility of fitting a 2000 pound mine with such a fuse. They winced and said "Yeah that'll leave a mark.")
If I recall, not only will machine gun and air cannon mess up a sub, the RAF was real big on using Mosquitos with rockets as sub killers in the Bay of Biscay. And on that subject , I recommend "Submarines and Slide Rules", a real egg head study on ASW in the Bay (Some of you math geeks will drool over the studies, me? They gave me a migraine.:()
I'd think the Moose will confirm that Shock is what kills subs , and opening the seems (and causing high pressure leaks) and not so much a direct hit.
My point is that I suspect the strength and condition of the boat has more to do with the kill of a sub then the size of the bomb or if it penetrates the hull. In that regard , aspect might be more important than explosion. A smaller bomb near the shaft seems or the torpedo seams might do more damage then one amidships. But I defer to the Moose. He's the subject matter expert.
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