Two other men did not need hospital treatment.
The Hughes MD600N helicopter was undertaking a commercial survey operation in the area, when at 8.50am, Rescue Coordination Centre NZ received an alert from the ELT distress beacon on board, providing a location at Oturua Stream.
RCCNZ Search and Rescue Mission Coordinator Dave Wilson said another helicopter from the same company was initially sent to provide a fast, initial response to determine the situation, with the Greenlea Rescue Helicopter from Taupo arriving on scene soon after to provide medical care.
Greenlea Rescue Helicopter pilot Nat Every said they were the first helicopter on the scene by about 40 minutes.
The Transport Accident Investigation Commission sent three investigators to the crash site and has opened an inquiry.
The chief investigator of accidents, Captain Tim Burfoot, said the helicopter was extensively damaged in the crash.