said no faults were confirmed that could have accounted for the situation.
In the months prior to the Delta Air incident, investigators at the AAIB
made significant progress in their probe into the Heathrow crash.
says the crew transmitted a "brief" mayday call before the helicopter, G-REDL, operated by Bond Offshore, lost contact with air traffic control.
said before the closure there had been several separate areas of the runway that had a temporary ungrooved base course asphalt surface while resurfacing work went on.
Disorientation, misjudgment or other factors may have led to this deviation but the cause of the accident was not positively determined, the AAIB
The incidents occurred in wet weather between November 2006 and January 2007, with three incidents investigated by the AAIB
taking place on 29 December 2006 and one on 3 January 2007.
The spokesman added: "The AAIB
will often make recommendations if there is mechanical failure involved."
Following a detailed review of the G-forces, the AAIB
has decided not to re-open its investigation into the accident near Shoreham Airport on 22 August 2015.
said the aircraft manufacturer has taken measures to rectify the landing gear problem.
report said the European Union Aviation Safety Agency classified the event as "not unsafe".
Pilots with this licence "must have a bona fide purpose for making the flight", according to the AAIB
. It added that rules stated: "The flight must not be made for the purpose of merely transporting the passenger."
The Air Accidents Investigation Branch (AAIB
) said: 'Following extensive visual examination of the accident site using the remotely operated vehicle (ROV), it was decided to attempt recovery operations.