The co-pilot of a Coast Guard helicopter which crashed off the coast of Ireland said "we're gone" seconds before the impact, investigators have revealed.
Extracts from the cockpit voice recorder including the minutes immediately before the crash have been released by Ireland's Air Accident Investigation Unit (AAIU) along with a preliminary report into the accident.
The helicopter went down off Blackrock island, around eight miles off the coast of Co Mayo, on 14 March with the loss of all four crew.
Officials have revealed that one of the winchmen onboard the Rescue 116 helicopter alerted the pilots to an island as they returned to shore to refuel.
But the Sikorsky S-92's internal warning system did not include Blackrock, an Atlantic outcrop with a working lighthouse, in its database.
The AAIU report revealed the aircraft's Radio Altimeter gave a call of "altitude, altitude" 26 seconds before the helicopter struck the island.
Cockpit recordings show Captain Dara Fitzpatrick said there was "just a small little island" below the helicopter.
Ten seconds later one of the winchmen - thought to have been using a high definition and infrared camera - told pilots he could see an island directly ahead and urged Captain Fitzpatrick to "come right".
She confirmed the advice and the winchman replied: "20 degrees right yeah."
The black box flight recorder shows the helicopter changed heading, but the winchman then interjects with increasing urgency and calls: "Come right now come right come right."
Co-pilot Captain Mark Duffy then swears twice and his words "we're gone" were the last to be recorded.
Winchmen Paul Ormsby and Ciaran Smith have yet to be found.
The report said the cockpit voice recorder showed no reference by the crew to the presence of a lighthouse or terrain at Blackrock, during their briefing for the approach.
It also stated that the helicopter's Honeywell Enhanced Ground Proximity Warning System, EGPWS, which alerts pilots to imminent danger from terrain and obstacles, does not include either feature.
The manufacturer told the AAIU that it had looked at two alternative sources for terrain data and, while they mark Blackrock, the company said that the actual altitude of the island is "considerably higher".
The AAIU called for CHC Ireland, which operates the Irish Coast Guard search and rescue helicopters, to review and re-evaluate all route guides used in their aircraft.
Investigators said the helicopter was travelling at about 75 knots prior to the crash and pitched up rapidly in the seconds before it hit the western end of Blackrock and "departed from controlled flight".