A DELIGHTED engineer today revealed the progress being made during trials of a lifesaving underwater vessel.

Perry Slingsby Systems Limited (PSSL), in Kirkbymoorside, built NATO's "Rescue Submersible" - which has the capability to rescue 15 people at a time from submarines in distress - for the governments of the UK, Norway and France.

In a rescue operation, the submersible - which cost £30 million to build - would be flown by aircraft to the port nearest the submarine in trouble, after which it would be deployed on to a ship with lifting equipment.

The ship would then sail out to the area, where the submersible would submerge and dock on to the submarine's rescue hatch, from which it would retrieve the "rescueees".

The submersible was built to replace the vessel that was involved in the rescue efforts to save the crew of the Russian nuclear submarine, Kursk, which grounded on the sea bed in August 2000.

The 30-tonne, nine metre-long submersible was transported in October to Faslane naval base, at Clyde, in Scotland, where it has undergone trials.

The sub has been tested for its inclination, stability and manoeuvrability, and it has also been involved in simulated rescue missions.

PSSL's engineering manager, John Mortonson, said: "One of the first things you've got to do is prove the submersible is stable.

"We did that at Faslane, and the results were analysed and approved, and that allowed the submersible to come off the hook which was giving it stability before."

Mr Mortonson said that so far he was delighted with the progress the submersible had made in the trials.

"They've been excellent - very good," he said.

"I can't see any major problems with it going through the remainder of the trials.

"There are a number of issues still to address - which you would expect from a complex system - but they are not major."

He revealed it would undergo trials at sea in the new year.

This is not the first time PSSL has built a submersible - it started making them back in the 1970s. At that time, the vessel was designed for a commercial purpose - to undertake offshore pipe line surveys.