Helicopter pilot Peter Maloney saw a warning light and within seconds knew the aircraft was going down.
"I did observe a turbine warning light then heard an audible warning and declared a mayday," Mr Maloney said yesterday soon after he was rescued from the Waitemata Harbour by the navy and Auckland Westpac Rescue Helicopter staff.
He and crew member Nina Heatley had been taking the prototype carbon fibre helicopter along the East Coast Bays over the water when the aircraft suddenly lost power. A second chopper from Mr Maloney's company Composite Helicopters was flying nearby filming it.
"It would appear we had engine failure. We will need to do a full investigation with the CAA [Civil Aviation Authority] to determine the exact cause."
He turned the aircraft on to its side as it hit the water near North Head. The impact could be seen from the Westpac chopper base at Mechanics Bay, where rescuers scrambled into action.