Dave's right, there is no way to avoid triple A since they are obviously unpredictable. All you can do is cross your fingers while you cross seven 20mm cannons firing away....or probably take them out first with your guns...
I agree with all above. It really is unpredictable, all you can do is "Jink" or change direction and altitude constantly, Its alot easier in a fighter than a bomber, but if you a bomber on the bomb run, its pretty much inpossible to jink your way through as you have to remain level till bomb drop. Only after that is when you can start jinking around (sounds kinky I know).
To be honest, if I'm in a fighter or a Ju87, I'll swing wide and let the AA pick someone else up...
As soon as it locks onto another friendly, I'll make my run and if I'm in the GA role, I'll note the position of the nearest AA battery and get on 'em as soon as possible and then get back out and away to repeat as often as nessecary.
If I'm in a bomber, I go in level steady, grit my teeth....
Reminds me of a F4F mission over Guadacanal. It was a patrol, right over Henderson Field. Found out staying straight and level in Triple A is a bad idea. I got the pleasure of seeing my pilot killed, and my wildcat spend a minute flying pilotless before my plane took a dirt nap.
As others have said, the praying and puckering may the only thing to try against the unrealistically uber aim of Il2 AAA unless you cripple it in the FMB setup. I have had some occasional success against ships and AAA by approaching at high speed at an angle to the AAA, only turning directly toward my target at the last minute. Usually the AAA has been tracking slightly behind me and has been shooting in spurts so if I'm lucky it doesn't settle in on me until I'm able to deliver the ordinance. I still often get plastered after my attack but my dead pilot can at least claim a ground kill. Ships and Wirbelwinds are just about impossible. If you use the full mission builder, the best bet is to reset their RoF and "wake up" to better simulate people with nornal vision and aim.
One of the helpful recent mods (in HSFX 4.1 I think) as a change to AAA AI that makes the gun crews run away from their guns if they are heavily strafed. You don't have to destroy the gun itself (which can be pretty hard). This seems realistic and means you can set wingmen/squad mates to attack AAA to help clear the way for the bombing runs.