Dive angle is one of the larger variables in the dive bombing problem. It and release G are responsible for most misses.
Here is the manual dive bombing situation...
The pilot selects a specific weapon. Each weapon has its own unique ballistics, but in the case of free fall 'dumb' bombs, those ballistics are all pretty much the same.
Then he selects a desired release speed, dive angle, and altitude.
Once in the dive, his first problem is getting the airplane aimed at the correct spot. For a bomb delivery, this is NOT the target...it is a point on the ground past the target.
With his nose on this point (and held there), the pilot now accelerates to his desired release speed and then adjusts the throttle to hold that speed.
As he is doing this, he checks his dive angle. He knows that dive angle errors will have to be compensated for by adjusting his release altitude.
Now, back to our Ju-88 example.
The pilot rolls into his dive. He aims his nose past the target at the estimated 'aim off' distance. He stabilizes himself on this aim point.
As he accelerates in the dive, he checks his dive line on the side of the canopy. If he is on the proper dive angle, the line will parallel the horizon. If not, he will see that he is either shallower or steeper than his planned dive angle.
He now figures an altitude compensation for any error in his dive angle. If steep, he will release the bomb above the planned altitude...if shallow, he will fly through his planned release altitude and release at a lower altitude.
How much above or below? These values can be 'canned' and memorized..such as in 'two degrees steep, pickle 500' high'.
In this manner, the WW2 pilot can plan a specific dive angle and release altitude. He then used cockpit references to measure his dive angle and made corrections on his release altitude to 'work the bomb in'.
Andy