Yep...that's all sorted now :yep:

When I cross the Bay after May 1943 many times I get attacked less than 10 minutes after I surface, and I run at 1024X. I have almost fully depleted my batteries many times before being able to break into the Atlantic.

It also has to do with visibility.

Aircraft will not always spot you even at 1x TC.

Really, the Bay is no picnic after Spring 1942 although you can sometimes clear the Bay with no interference then.

Put it down to 'the fog of war' matey :up: :arrgh!:

The AI technic is quite simple actualy.
Saw it like time jump on a time line...
At t0, your object (a plane in this context) as some property such as position, bearing, speed, etc... at t1, the AI is gonna compute what your object have done in the interval of time between t0 and t1 and what are his properties at t1 they he will triger event if his new properties answer some equation as for exemple being in a specific radius of your own ship. Thing is, AI have to compute the properties for every object in the game and pause a while (few millisecond to few second... for a sub sim, probably in second) between each computing to not take ALL the CPU resources.
In SHIII world, AI has a lot of object which need to have their properties refreshed. As a computer game developper myself, I guess it s not computing for every object each turn but have a dynamic cycle according to the range between the object and your sub. Which mean, the closer the object is, the more often is properties are refreshed.
Still for your plane you gonna have some real life time between two refreshes of properties. If you use a high time compression, the plane properties and your own sub properties are going to change so much that they gonna jump over each other. Just like closing your eyes, moving 30km, hopening your eyes. As the plane do the same, when you crossed each other you both have your eyes closed. And when you'll open them again, you'll missed each other.

Think is, the interval between each computing is dinamicaly linked to the time compression you use. At such point that if you use high time compression, the interval of time can be null in the code. But not in term of CPU time :). Because the game and you computer as other stuff to do than refresh object properties, you will always have a interval of time you can't decrease and logicaly, it s linked to the performances of your computer.
In SHIII you can actualy use the FPS counter to get a good idea I think. FPS are the refresh rate of what you re seeing. It s not linked to the AI computing, but if your FPS droped under 10 it s because your CPU is overused, then you can guess that the AI computing rate is also droping big time for the same reason and that you have more chance to miss stuff.

Hope it helps to understand the mechanic and sorry for my poor english.