Originally Posted by
Maisk Rotum
The descending helicopter would have had the departing one on the left and below it, thus obscured. The departing one likely would have been able to see the other one on his right and above, but with no 'relative motion' likely would not have been picked up in his peripheral vision.
Post#33 suggests these helicopters were set up to fly from the left side so the incoming helicopter would have had a clear view of the helipad.