It is commonly agreed, that the game default values for AI bomber crew accuracy was extremely low, so bad in fact, that it was impossible to even "accidentally" hit the target due to the way the drift and speed errors worked, it wasn't a case of hit or miss, it was a case of miss by alot or miss by a little. By default values, it would take about 10 missions of missing targets before the bombardier crews would have enough experience to hit the target. But by that time, you would almost get fired by command for such bad performance.
You can fix this several ways, one way is to "manually" correct the bomber on the bomb run, due to the experience factor for human players, i think the calculation was x5 exp if a human is at the controls, rather than a default 2x for the AI.
The easiest way, and most effective, is to alter the RiversandRoads.DB file (B-17 Flying Fortress\Resources\Databases) and change the bombardier minimum drift error from 5 to 2. Then adjust the speed error from 30 to 10. Any lower and the game AI will never miss. Making this adjustment means the bombing run is so much more realistic, it is still possible to miss completely, but no way near as often as it is by default.
Hope this helps, have fun over the German skies!
