A report into the Rescue 116 tragedy has found databases didn't detect the island which the crew crashed into.
Four members of the Irish Coast Guard lost their lives in the tragedy off the Mayo coast in March 2017.
Captain Dara Fitzpatrick, Captain Mark Duffy, winch operator Paul Ormsby and winchman Ciaran Smith died in the crash.
This report contains harrowing details of the final moments of Rescue 116 where the winchman can be heard announcing come right now, come right, COME RIGHT.
The investigation has found the helicopter was flying at 200 feet in poor weather just before 1am and were unaware that a 282 foot obstacle- namely Blackrock island - was on the flightpath.
It says contributory causes to the crash was that neither their databases nor imagery indicated the presence of Black Rock.
The bodies of Dara Fitzpatrick and Mark Duffy were recovered but the bodies of Paul Ormsby and Ciaran Smith remain lost at sea.