Major equipment on one of the two significantly overdue ferries has been run successfully at the Ferguson Marine yard in Port Glasgow.
An emergency diesel generator has been run on MV Glen Sannox, with systems said to have performed as expected.
The vessel is one of two duel fuel ferries being built at the yard in order to serve the Clyde and Hebrides.
However, construction of the ferries has been plagued by setbacks since first being ordered in 2015.
They were due to enter service in 2018 but are now four years late and estimated to cost at least £240m.
The ferries have also been at the centre of a political storm, with the yard having been taken over by the Scottish Government in 2019.
In March, Audit Scotland concluded there had been a “multitude of failings” in the delivery of the two vessels and that there were “significant operational failures” still needing to be resolved.
On Monday, it was announced that the emergency diesel generator, the first piece of major equipment to be run on the Glen Sannox, was switched on successfully.
After it was running, commissioning engineers performed a test to demonstrate that the alarm and emergency shutdown functions were operating normally.
It was witnessed by the vessel owner, Caledonian Maritime Assets Limited (CMAL) and assessors from Lloyd’s Register, the classification society.
The engine will run periodically to ensure no changes in its condition, while further commissioning work continues on the vessel.
David Tydeman, chief executive at FMPG (Ferguson Marine Port Glasgow), said: “We’ve started the first bit of rotating machinery. This is a very reassuring milestone.
“Our commissioning team has been doing a lot of maintenance work on all major equipment, supported by manufacturers, to prevent detrimental conditions during commissioning.”