A SERIES of freak incidents led to a helicopter crash in which 11 people died, accident investigators said yesterday.

Three of those who died when the Sikorsky S-76A ditched into the North Sea 30 miles off Cromer, Norfolk, in July 2002 came from North Yorkshire and the North-East.

Yesterday, an Air Accident Investigation Branch (AAIB) report said there was nothing that anyone on board could have done to avoid the crash.

The incidents took place when the helicopter's main rotor blades separated as it prepared to land.

Investigators traced the problem to a small manufacturing fault dating from 1981, which caused a weak spot.

But the report revealed there was no danger until years later, when the blade was struck by lightning.

Repairs were made, routine inspections carried out and there was no visible damage so the helicopter returned to service.

Witnesses recalled hearing a "single or double muffled bang or boom" as the structural failure destroyed the helicopter, the AAIB said.

No one could have known the routine ten-minute flight was doomed and there was nothing the pilots could have done to prevent the tragedy.

Everyone on board, including the pilot, Captain Mark Wake, who was brought up at Newton-on-Derwent, near York, died.

Also on board were Douglas Learwood, of Marton, Teesside, and Stuart Coggon, of Middlesbrough.

Recommendations to tighten up safety have included frequent checks to the leading-edge erosion covers of main rotor blades.