An investigation into the Irish Coast Guard helicopter R116 crash that claimed four lives has identified “systemic safety issues”.

It found that the aircraft was manoeuvring at 200ft and nine nautical miles from the intended landing point, at night and in poor weather conditions, unaware that a 282ft obstacle was on the flight path.

There were “serious and important weaknesses” with the operator’s safety management systems (SMS) in relation to navigation and the reporting of safety issues, “such that certain risks that could have been mitigated were not”, its report said.

Rescue 116 crashed off Co Mayo at 12.46am on March 14 2017 with four crew on board after it struck Blackrock Island, 12 miles off the coast.

Captain Dara Fitzpatrick, the commander of the flight, was pulled from the sea in the hours after the crash and never regained consciousness, while the body of Captain Mark Duffy, the co-pilot, was taken from the cockpit 12 days later by Navy divers.

The bodies of winchmen Paul Ormsby and Ciaran Smith were never recovered despite weeks of intensive seabed, surface and shore searches.

The investigation report found that concerns had been raised over the navigation system – the Enhanced Ground Proximity Warning System (EGPWS) – four years before the crash.

Emails from 2013 highlighted that the lighthouse at Blackrock was not listed in the obstacle database.

The crew “probably believed” that the route taken, by design, “provided adequate terrain separation from obstacles”, the report said.

The conditions on the night in question meant it was not possible for the crew “to accurately assess horizontal visibility”.

“There were serious and important weaknesses with aspects of the operator’s SMS, including in relation to safety reporting, safety meetings, its safety database Sqid (Safety and Quality Integrated Database) and the management of FMS (flight management system) route guide, such that certain risks that could have been mitigated were not,” it added.

The report by the Air Accident Investigation Unit (AAIU), published on Friday, has made 42 safety recommendations in light of the findings, which the Department of Transport said it “fully accepts”.

Transport Minister Eamon Ryan said: “This was a tragic accident that claimed the lives of four individuals who were dedicated to saving the lives of others.

“I would like to again convey my condolences to the families and loved ones of the R116’s crew at this time.

“The completion of the investigation and the publication of the report is a key step in ensuring that such accidents are prevented in the future.”

The report also called on CHC Ireland, the company which provided the helicopters to the Irish Coast Guard, to review its guidance, operating and training procedures in respect of its EGPWS navigating system, and to ensure crews “are aware of the limitations”.

The body of Captain Mark Duffy is accompanied by a guard of honour as it is driven along the seafront at Blacksod, Co Mayo (Chris Radburn/PA)In addition, questions were raised over whether the rescue mission was necessary under official protocols.

The National Search and Rescue (SAR) Framework states that such missions are for people “who are, or are believed to be, in imminent danger of loss of life”.

Reports showed that the fisherman at the centre of the rescue was in danger of losing a thumb, but did not appear to be at risk of bleeding out.

In a statement, the family of Ms Fitzpatrick said aspects of the report were “utterly harrowing”.

The statement, posted by her sister Niamh, said she and the other crew members had been “badly let down” by CHC Ireland because they had not been provided “with the safe operating procedures that they were entitled to expect”.

It added: “There is a weighty responsibility on the operator of the SAR service to minimise the risk to the crew by designing-out risk and providing the crew with safe procedures on which they rely.

“Unfortunately this was not done on this occasion. CHC provided the crew with a low-level approach chart that started right above a fatal hazard.

“That hazard was not adequately highlighted on charts and the charts had no vertical profile to provide crew with safe crossing heights.

“There were many other failings by the operator that contributed to this accident.

“These include not training the crew on all the specific approaches on simulators and in the aircraft, and ensuring that before they were tasked to fly into different landing sites they had prescribed recent experience.

“We hope that the AAIU Final Report and the Review Board Report will ensure that those responsible for this operation, both directly and at a supervisory level, urgently implement the necessary changes and that in future they pay attention to the feedback that they get from the crew as to any inadequacies and hazards in the operation, so that such an accident will never happen again, that no one else will needlessly lose their lives, and that no other families will have to endure the devastating loss that we endure with the untimely death of our beautiful Dara.”

In a statement, CHC Ireland said it is committed to implementing the appropriate safety recommendations in the report.

CHC general operations manager Rob Tatted said: “I would firstly like to express our deepest sympathy to the family and friends of our lost colleagues; Ciaran, Dara, Mark and Paul.

“The accident and loss of the crew was a terrible tragedy.

“Their colleagues in Search and Rescue bravely continue to serve the people of Ireland on behalf of the Irish Coast Guard as they have done for over 20 years.

“Their unwavering commitment to the role that they perform is admirable.

“Our crews continue to fly hundreds of search and rescue missions every year, saving many lives.

“Our team is justifiably proud of our global safety record and everyone in CHC Ireland is committed to the safe delivery of our service.

“We continue to honour the memories of Ciaran, Dara, Mark and Paul. They will never be forgotten.”