A PROBLEM with the fuel system of the helicopter that crashed into the Clutha Vaults pub in Glasgow was discovered four months before the tragedy, an inquiry has heard.

Ten were killed when the Eurocopter EC135 police helicopter crashed through the roof of the bar in November, 2013.

The inquiry has previously heard that five low fuel warnings came on in the cockpit, yet the helicopter continued with missions to the east of Glasgow.

In October 2015 a report from the Air Accident Investigations Branch revealed pilot error and found fuel pumps were turned off.

The inquiry had also previously heard that Eurocopter Deutschland, run by Airbus, had been alerted to issues with water contaminating the fuel supply of its EC135 in 2003, 10 years before the crash and that 680 fuel sensors had been returned in the six years leading up to the fatal crash because of reported “misreadings” on aircraft caution advisory displays.

READ MORE: Clutha tragedy could have been prevented, expert says

The inquiry was shown a technical log for the ill-fated Police Scotland G-SPAO that revealed that four months before the crash, fuel content indicators were seen as "inaccurate".

It showed that a fuel sensor in the main tank had been replaced.

Bryan Meredith, 58, a quality assurance engineer with then helicopter operators Bond Air Services, told the hearings: "I would think the defect was correctly sorted out.

READ MORE: Clutha FAI: Expert says a helicopter modification could have prevented the tragedy

He further said that they identified five non-conformances with the the Clutha crash helicopter in an aircraft audit that ended in May, 2013, five months before the crash.

But none of them related to the aircraft's fuel system or fuel sensors.

An airworthiness audit completed in August, 2013, noted "anomalies" which a report said were "adequately addressed by the staff concerned".

Mr Meredith confirmed that he carried out a "physical survey" and records review, which looks at any repairs carried out for the airworthiness audit.

He agreed there was nothing that required him to check the fuel system or sensors in the fuel system of the aircraft during the airworthiness audit, but that he would talk to engineers to check for any issues they were aware of.

Asked if he would talk to the engineers about any issues with the fuel system or sensors, he said: "Not that I can remember."

The inquiry was shown issues with the fuel system of another EC135 found in Glasgow on July 1, 2013, four months before the crash.

A log revealed that it was suspected that a supply tank was indicating full irrespective of fuel contents.

After further examination, it was discovered the fuel supply was registering as having 47kg even when when a red warning light was on. The problem was fixed.

Sean Smith for the Crown asked: "Are these the kind of reports you were seeing at the time in the summer of 2013.

Mr Meredith said: "Possibly." When asked if faulty fuel guages were likely to cause danger that should result in a mandatory report that would be notified to the Civil Aviation Authority, Mr Meredith said: "Not always, no".

Mr Smith asked if it was likely these apparent issues with fuel indication issues would be the subject of a mandatory report that would be notified to the Civil Aviation Authority.

Mr Meredith said: "It would have been seen as a possible problem if we had.  We had a couple of occurrances.

"They were being actioned in accordance with the maintenance manual at the time so it was being done."

Asked by Shelagh McCall QC counsel for Lucy Thomas, financee of the helicopter pilot David Traill, if he would take any action in relation to fuel indication issues, Mr Meredith said: "I would probably speak to someone and ask what was being done, or anything like that."

Asked who he would speak to he said: "Someone in the engineering department." He said he would take it to management if nothing was being done.

An AAIB special report found both engines “flamed out”.

One of the fuel tanks was empty, while a second contained 0.4 litres. A third contained 75 litres, but transfer pumps to take this fuel to the other two engine tanks were switched off.

The probe also found fuel transfer pumps were turned off and a controlled landing was not achieved for “unknown reasons”.

And it recommended all police helicopters be equipped with black box flight recording equipment.

Pilot David Traill, 51; PC Tony Collins, 43; and PC Kirsty Nelis, 36, died along with seven customers who were in the bar, Gary Arthur, 48; Joe Cusker, 59; Colin Gibson, 33; Robert Jenkins, 61; John McGarrigle, 58; Samuel McGhee, 56; and Mark O'Prey, 44.

The inquiry before Principal Sheriff Craig Turnbull at Hampden Park continues.