In the initial stages of the 8th USAAF strategic bombing campaign every B-17 was Norden-bombsight-equipped.
The Americans quickly realized that European skies are frequently cloudy, therefore the potential precision of the sight was often superfluous. Proper use of the sight also needed careful and time-consuming training, so the 'toggler' system was devised.
Lead aircraft in formations would have a trained Norden bombardier ; when he released, the following aircraft would 'toggle' and release their bombs at the same time.
So much for precision bombing...but that's another thread !
