Garda divers are expected to search the area around Blackrock Island into which R116 crashed on March 14 with the loss of all four crew.
The bodies of pilots, Capt Dara Fitzpatrick and Capt Mark Duffy, were recovered. Despite exhaustive efforts, the bodies of winch operator Paul Ormsby and winchman Ciarán Smith have still not been found.
Favourable sea conditions should allow for a fresh survey of the area and a trawl of the seabed. Divers will be assisted by the Irish Lights vessel, Granuaile.
While the helicopter’s main fuselage has been recovered, one of its engines is still on the seabed. Smaller items of debris have been washed ashore in recent weeks, including a piece of a stretcher board. They have all been gathered and catalogued by gardaí at Belmullet, and air accident investigators have been notified.
Supt Tony Healy, who is leading the investigation, said the weekend searches are the latest stage in what is an ongoing inquiry.
The Dublin-based S-92 Sikorsky struck the western end of Blackrock Island as it was routing towards Blacksod lighthouse to refuel as part of a top-cover mission supporting the Sligo-based Coast Guard helicopter on a medevac off the west coast.
A preliminary report from the Air Accident Investigation Unit (AAIU) in April ruled out mechanical anomalies in R116, and flagged deficiencies in its enhanced ground positioning warning system.
The system, which should not be relied upon for navigation, did not have the coordinates for Blackrock Island, or the island terrain, programmed into its database.
The AAIU recommended an immediate review of the system across the Coast Guard helicopter fleet.
Prime Time reported on Thursday that Coast Guard pilots flagged concerns about deficiencies in the system in 2013, and it raised questions about the Irish Aviation Authority’s ( IAA) role in relation to terrain and obstacle data in the fleet’s databases.
The programme reported that Coast Guard pilots based at Dublin said the system fitted to the new S-92 aircraft was alerting them to phantom obstacles on the east coast. It also reported Skellig Michael off Kerry was inaccurately depicted on official IAA maps, with revised maps issued last month increasing its inaccurate map height from 174ft to its true height of 712ft.
The IAA rejected the issues raised by the programme. The AAIU says it cannot comment while its investigations are ongoing.