Captain Dominic Lawlor was 37 and had flown the Penzance-St Mary's route over fifty times. Captain Neil Charleton was 30 and had flown it over a hundred times. Cabin attendant Robin Lander was 22. The 23 passengers had boarded for what was, for many, a holiday trip to one of England's most beloved island destinations. The named survivors were Howard Goddard, who was 12 years old that day, Ellen Hanslow, who was 15, and Lucille Langley-Williams and Megan Smith, both 60. The rest, 17 passengers and Robin Lander the cabin attendant, are not named in the public record of the disaster. Their families know who they were. Three of the dead, including Lander, were never recovered from the wreck.

The morning had been bad for visibility from the start. The earlier flight, Delta Alpha, had been delayed from 7:50 to 10:46 am before conditions cleared enough to depart under visual flight rules. Lawlor waited until he had confirmation that Delta Alpha had landed safely before taking off with Oscar November. Then came the moment that the investigation would identify as decisive. The crew of Oscar November believed they had received a verbal weather report from the Delta Alpha crew on the return leg, indicating visibility of half a mile at 300 feet. The Delta Alpha crew did not recall making such a transmission. Lawlor interpreted the message to mean the cloud base was at 300 feet and descended to 500 feet to assess the situation. Charleton interpreted it differently, believing 300 feet referred to the height the Delta Alpha crew had been observing from. The two pilots did not discuss the discrepancy. Then Oscar November, which both pilots believed was holding 250 feet, hit the sea three successive times.

Both sponsons were torn off in the impact, breaking the seal that should have let the helicopter float. Water flooded in through the broken floor. The fuselage rolled over and went down. None of the six survivors had managed to retrieve a life jacket. Both pilots were injured but they did what they could: they gathered the survivors together in the water and helped them stay afloat using passenger suitcases as flotation aids. Ellen Hanslow, 15 years old, spotted 12-year-old Howard Goddard struggling and swam to him. They were in the water for around an hour. A Royal Navy Wessex helicopter from RNAS Culdrose reached the area first but in the fog could not see them. Langley-Williams said afterward that the helicopter had been directly overhead at one point and could not find them. The St Mary's lifeboat, the Robert Edgar, located the crash site by the smell of aviation fuel on the water and pulled the six survivors from the sea. A Sea King followed, directed in by flares from the lifeboat.

Matt Lethbridge, the coxswain of the St Mary's lifeboat, was singled out for particular commendation by David Harris, the Member of Parliament for St Ives. The Accidents Investigation Branch investigator, D.A. Cooper, concluded the helicopter had been mechanically sound and that the cause was pilot error: an unintentional descent that was not noticed or corrected, in conditions where visual flight was simply unsuitable. The minimum guidelines for visual flight in the operating procedures themselves were listed as a contributory factor. Lawlor admitted at the coroner's inquest that his piloting undoubtedly did play a part. The AIB made eight recommendations, of which seven were adopted. The most consequential: by August 1985, audible ground proximity warning systems became mandatory on all UK passenger helicopters. Altimeters were moved nearer to the pilot's natural line of sight. Seat strength was improved (every twin seat in Oscar November had sheared off in the impact). Automatically deployed emergency beacons became standard. The disaster remained Britain's worst civilian helicopter accident until a Chinook crash off Sumburgh in 1986 killed 45. The Penzance-St Mary's helicopter service continued under British International Helicopters until 2012, and resumed under Penzance Helicopters in 2020. The route still exists. The safety systems that protect it were written in the lives of the people who did not come home on 16 July 1983.