proceedings in September 2013 against AgustaWestland over safety concerns relating to oil leaks and rotor blade issues, as well as problems with the aircraft's communication and navigation systems. Investigation The Air Accidents Investigation Branch (AAIB) opened an investigation into the accident. AgustaWestland assisted the AAIB in their enquiries. The aircraft's data recorders were recovered from the wreckage on 15 March 2014. A Special Bulletin published by the AAIB on 4 April revealed that there had been no mechanical failure with the helicopter and that it had not contacted any object between taking off and the crash site. The final report into the accident was originally scheduled to be published around March 2015. It was published on 8 October 2015. The investigation found that there was no mechanical failure with the aircraft. The crew were found not to have used checklists when operating the helicopter. The cause of the accident was pilot error, with spatial disorientation due to somatogravic illusion a major factor. An inquest into the deaths of the four victims was opened on 20 March at Norwich Coroner's Court. After hearing that all four people died from head and chest injuries sustained in the accident, the inquest was adjourned until 24 July. The inquests concluded in January 2016, with verdicts of accidental death being returned against all four victims. During the inquest, the Coroner demanded that the AAIB release to her the recordings from the Cockpit Voice Recorder, imposing two fines of £100 each on the Chief Inspector of Accidents at the AAIB. The matter was referred to the High Court, where it was stated that only the High Court had the power to demand such disclosure of evidence. The fines were overturned. References External links Aviation accidents and incidents in 2014 Aviation accidents and incidents in Norfolk Accidents and incidents involving the AgustaWestland AW139 2014 disasters in the United Kingdom 2014 in England 2010s in Norfolk South Norfolk Aviation accidents and incidents involving fog March 2014 events in the United Kingdom