Bad judgement! The faster smaller Airplane was in a decending left bank and couldnt see through the floor or his plane and ran into the larger Airplane.
Just a Guess afer seeing the two smaller planes ahead of the Crash. Probably a formation flight split up to land and spacing wasnt there with the B17.
I come from a family of pilots,
but I've gotta say I always thought that the visibility out the front of most aircraft just sucks! The instrument panel is too high and/ or the engine cowling blocks too much of your view.
This may have been a necessary evil for single engine aircraft with a big engine (especially a radial engine ) mounted at the nose, but for other types of aircraft it's a design defect.