CALMAC ferry services remain in a state of turmoil - as it emerged that one of its oldest vessels has been sidelined for nearly three months.

The 38-year-old MV Hebridean Isles, which has been hit with issues since Boxing Day, was removed from the CalMac firing line on February 16 with freight services providing vital supplies to Arran from Troon suspended.

At the time a fault within the control system of the MV Hebridean Isles led to it being removed from service with the freight service suspended.

Users were told by the Scottish Government-owned ferry operator that an "appropriately qualified engineer" was expected "as quickly as possible".

CalMac told users in a briefing that MV Catriona would be brought in to carry out two round trip sailings from Tarbert to Lochranza on Arran as a result in a move expected to last till Friday.

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The lifeline service to Brodick on Arran, one of the busiest on the west coast of Scotland, has remained a one-vessel service as MV Hebridean Isles has been unavailable for passengers and concentrating on providing freight services.

Concerns were previously been raised about disruption being felt across the network as the depleted ageing fleet was redeployed to try and cope with the loss of both 38-year-old MV Hebridean Isles and 30-year-old MV Caledonian Isles to passengers.

It has now emerged that MV Hebridean Isles has still not been able to make a return to service.

CalMac say that the vessel is holed up in Ayr with a pitch propeller issue.

It had been expected to support services to and from Islay with the MV Isle of Arran for an overhaul for two months from February 5 as part of the rejigging of the network through the state-owned service's programme to improve fleet sustainability through its overhaul programme.

The Herald:

But neither vessel was able to make it.

One ferry user official said: "The fleet should not have to be relying on ferries of the age of MV Hebridean Isles, it is as simple as that. The fact that it remains a vital cog in the CalMac wheel remains a concern and only urgent action on improved capacity in terms of new or second-hand vessels will come close to resolving this chaos."

The development came as CalMac announced changes to its vessel deployments across the Clyde and Hebrides routes, due to continued issues with the return of ferries to service and the delayed annual maintenance of the ageing fleet.

CalMac chief executive Robbie Drummond said: “We are aware of the significant effect this situation is having on customers and businesses.

“This is at the forefront of our mind as we continue to focus on resuming a normal service.

“We will be able to return to the usual summer timetable as soon as vessels return from annual maintenance.

“Berthing trials for MV Alfred have also been completed and we look forward to the much-needed resilience she will provide to the network.”

However, no date has yet been set for the continued use of a £1m-a-month 'emergency' ferry MV Alfred to try and ease the effect of the nation's ferry fiasco.

MV Alfred owners Pentland Ferries has said that issues found after berthing trials mean the vessel cannot yet enter service off the west coast.

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It emerged there are no bookings available to and from Orkney for over two weeks after MV Alfred's sister vessel ran aground on Orkney.

The Herald: MV Pentalina at the pier in St Margaret’s Hope, Orkney after running aground

Ministers confirmed there was a possibility that MV Alfred may return to Orkney - even though they say there is no contractual obligation.

While trials to test MV Alfred on certain west coast ports have been completed, CalMac has said there are "no details of a confirmed deployment yet".

And Pentland Ferries has now said that issues found after berthing trials mean the vessel cannot yet enter service.

The ferry company is now conducting a service of hydraulic systems.

"During this period of downtime CalMac are making minor amendments to the stern door to ready the vessel for service.  An update on when works will be complete, allowing the charter to recommence, will be issued on Monday," a spokesman said.

Questions over whether MV Alfred will be able to continue to support island services run by Scottish Government-owned CalMac off the west coast of Scotland after ministers chartered it for nine months at a cost of £9m have come after Pentland Ferries' sister vessel MV Pentalina ran aground at St Margaret's Hope in Orkney with 60 passengers on board at the weekend.

Smoke was detected in the engine room of the MV Pentalina on Saturday night before it became grounded near the village of St Margaret’s Hope on the island, leading to the evacuation of 60 passengers, including three children and an infant.