A SENIOR aviation operations executive warned manufacturers about a "lack of attention and priority" after raising concerns about the airworthiness of the type of helicopter that crashed into the Clutha Vaults pub in Glasgow six 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.

Emails previously shown to the inquiry revealed that David Price, who was at the time director of engineering with helicopter operators Bond Air Services, alerted Eurocopter Deutschland, run by Airbus, and France-based engine manufacturers Turbomeca that there were issues with water contaminating the fuel supply of the EC135 in 2003, 10 years before the crash.

READ MORE: Airbus 'put on hold' solution' to EC135 safety concerns on day of Clutha tragedy

Mr Price, who appeared at day 16 of the fatal accident inquiry was shown an email he sent Kelly Brookes of Eurocopter in June 2013, which revealed his concerns over the lack of action by Eurocopter and Turbomeca over his flight safety concerns.

He wrote that the issues had been ongoing for ten years and added that "we are extremely unhappy with the lack of attention and priority this subject has been given by ECD [Eurocopter Deutschland] and TM [Turbomeca] especially when you look at the internal corrosion that occurs with the HMU (hydro mechanical unit) and the possible consequences thereof".

"With this in mind I would be grateful if you could give us an estimated time scale that this will be resolved in that we can share with confidence with our local authority."

Asked whether it was an airworthiness safety issue he said: "Yes, potentially, yes."

Mr Price had said that he had raised his concerns to Eurocopter in 2003 but it was not until 2014, after the crash, that a 'final solution' air service bulletin was issued.

He had been concerned that the HMU (hydro mechanical unit) had been sucking water into the engine.

Ralf Nicolai, a 61-year-old sales promotion manager of Airbus, who Mr Price approached about the issue in 2003 had previously said that an investigation later found water contamination could also lead to fuel sensors giving an "over-reading" indicating the aircraft had more fuel than it did.

Mr Price, who is now the head of maintenance and engineering with the Babcock Aviation Group, indicated the water issues had not been totally eliminated even now.

Asked by Shelagh McCall QC, counsel for Lucy Thomas, the fiancée of the dead pilot David Traill if the water issues had been fixed, he said: "Well, with the concession that is now in place, it eliminates that, but fundamentally the root cause when we are talking about the root valve assembly and injectors, that has not been resolved.

"So in simple terms, yes, that is correct, there has been a lot of additional procedures put in place to mitigate the risk of water going in.

Asked if he was satisfied he knew all the ways water can enter the fuel system and they are all sufficiently mitigated for, he responded: "From our own [Babcock's] mitigation, is yes. The real question is that risk assessment doesn't lie with the operator, it lies with the type certificate holder and with all due respect, that is the question that should be presented to the type certificate holder."

The hearing was previously told that both water and compressor washing fluid could affect fuel gauge readings.

In cross-examination by Donald Findlay, representing the family of victim Robert Jenkins, Mr Price said they were aware that for "all aircraft" the issue of water in the fuel system might affect cockpit cautions and low fuel warnings.

Mr Findlay asked: "That being so, what was Bond doing about it?"

"We were monitoring it as laid down by the legislative requirements we work to," said Mr Price.

"But your aircraft were still flying as normal," added Mr Findlay.

"As was every other aircraft," said Mr Price.

"Be that as it may, your aircraft were still flying as normal," asked Mr Findlay.

"We are all working to the same regulatory requirements," added Mr Price.

Mr Findlay went on to ask why it was there had been no test of water in the fuel system after a compressor wash.

Mr Price said that they thought they had fixed a water problem when in 2003, Bond brought in their own design changes including putting a vent into a drain pipe to eliminate the possibility of fluid being sucked by the HMU.

The fatal accident inquiry into the Clutha helicopter crash has previously heard from Robert Vickery of the Air Accidents Investigation Branch that there was no evidence the aircraft's fuel had been contaminated. But he acknowledged that fuel contamination on such a small aircraft would be "barely detectable".

It also previously heard that the helicopter's pilot had received five low fuel warnings before the crash.

And as the aircraft did not have a flight recorder, it meant there was no data about when fuel warnings came on and the length of time they stayed on.

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 at Hampden Park before Principal Sheriff Craig Turnbull continues.

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