I understand, however the departing chopper is tracking directly away from its helipad more or less to impact. The arriving helo would have to be at the point of impact for the departing helo to be still in line with the helipad from his point of view. In that case, the climbing helo would be nose on. The geometry of the videos doesn't work for me. You extrapolate the dotted bearing lines in the above back and as per the diagrams, they don't go back to the same place.