Single accident but perhaps some lessons for future
As one who lives in Manhattan and can see the heli and small fixed wing traffic fly the Hudson VFR corridor, I must say in my opinion we here in NYC have been lucky until today. There is a lot of sightseeing tour traffic with heli tours being offered by many operators: NY Tours, All New York Tours, New York City Tours, US Helicopter, Liberty Helicopters, New York Helicopter, Viatour; are but some of the listings.
If the tour heli lifted off of the 30th street heliport and moved to the westside of the river and headed south while climbing, then the piper also headed south on the suggested west side of the river flying below the max altitude may not have seen him climbing from below his cowling until too late. Some witnesses say the piper banked at the last minute, a left?, exposing his right wing to the blades of the climbing chopper? Early speculation, but points out the weakness of voluntary radio position reports while in the corridor as VFR may not have been sufficient in this set of circumstances, as piper pilot may never have seen heli below and was approaching the climbing heli from above and behind at a greater speed.
I suggest three possibilities: required radio position w/ alt and speed reports at waypoints, required freq monitoring with check in to corridor, and, precise and set tour heli routes well designed with no corners to be cut; for discussion. Harbor traffic has required radio contact and they are going 10-20 knots not 140 knots.