The Super Puma plunged into the sea off the Aberdeenshire coast while returning from the BP Miller platform on April 1 2009.
A fatal accident inquiry into the crash is being held before a sheriff in Aberdeen.
John Constable, 50, a trainer of helicopter pilots, and Andrew Miller, who had previously flown the helicopter involved, have both given evidence.
Their evidence has centred around the workings of some of a helicopter and procedures pilots would be familiar with. Mr Constable was head of training for helicopter operator Bond at the time of the crash. He told the inquiry it was an eight-week process to give a pilot who already has a commercial licence the additional knowledge to enable them to fly Super Pumas.
Helicopters also have various colour-coded warning lights, the witness told the hearing, with red being reserved for events which require immediate action.
He added that he had never had such a thing as a "gearbox chip warning light" in a Super Puma helicopter in his experience.
Mr Miller, 47, who flew the helicopter in question on its last completed journey, yesterday told the inquiry there were some "minor" problems but nothing to explain the catastrophic crash.
Several features of the oil system in a helicopter gearbox were also explained. He said he would be concerned if pressure in the system dropped below 3.7, on a scale of zero to seven.
A report has found the aircraft suffered a failure of its main rotor gearbox. The inquiry continues.