I think the other skill that plays a part is "LowN" or low altitude navigation, in that you can't hit something that's out of sight. In my view, you need to patrol at low level (1K) so that your aircraft can drop to 100 feet in its attack (which is part of the 1K search profile). I think you are right that the bigger the bomb the more chance of success, but in truth success is stopping an attack and the gravy is sinking the sub... so a 50kg bomb can be just as effective as a 500kg bomb in relation to the latter. I quite often use P-40Es (P-40Bs do NOT have this capability) in the first few months of the war as ship killers (although I have not used them as sub killers, but it might be a good idea) as they carry a 500pd bomb and if trained (combat being the most effective trainer) can nail LOTS of ships, especially large slow targets such as xAKs or xAPs.....
LowN is Low Altitude Naval Attack, not Navigation.
IIRC Alfred has chimed in before on what skills count in ASW and I was surprised by the ones that don't count, just don't want to misquote what I can't remember exactly.
I don't think LowN counts as ASW takes its place. I don't recall if Alfred stated that Nav Search doesn't count either, being replaced by ASW.
Defense will certainly count for avoiding flak in low level attacks.
Hans is correct.
1. Air units tasked with the ASW mission, the only relevant skill employed by the pilots is ASW.
2. Air units tasked with the Naval Search mission, the only relevant skill employed by the pilots is Naval Search.
3. If you want to locate and prosecute an air attack on subs, you should be on the ASW mission. What players seem to forget is that a sub patrol Task Force IS a task force and therefore, as A task force, it may be spotted by Naval Search. But aircraft on naval search are not as efficient nor effective in finding or prosecuting an anti-sub attack than if they are on an ASW mission.
4. The size of the bomb is not really a useful metric. The first thing you have to do is actually achieve a hit, and that is dependent on pilot skill (see point 3 above re pilot ASW skill), not on size of bomb. The second thing is that a detected sub TF is much less likely to pose a threat and detection has absolutely no correlation to bomb size.
5. Fighters (and attack bombers) are not going to drop to 100' to attack a submarine. Fighters on a naval attack mission do not attack sub TFs; they cannot be assigned either a Naval Search or ASW mission which are the air missions which can interfere with a sub TF. It therefore follows the Low Naval pilot skill is not used.