A LOW fuel warning was modified out of the Airbus EC135 class of helicopters around the time of the Clutha Vaults crash, it has been claimed.

The allegation was made by Peter Gray, representing Babcock, which took over the helicopter operator Bond Air Services after the tragedy on November 29, 2013.

He has been questioning Christian Bernhardt, a safety investigator with Airbus, during the eleventh day of a fatal accident inquiry looking into whether lessons can be learnt over why the Eurocopter EC135 Police Scotland helicopter crashed through the Clutha roof.

Ten people were killed - including three helicopter crew - and 31 people were injured.

Mr Bernhardt agreed that with new generations of Airbus helicopnters there is a positive requirement on pilots to ensure fuel pump switches are kept all at all times.

In October 2015 a report from the Air Accident Investigations Branch revealed pilot error after both engines of the EC135 "flamed out".

It found fuel transfer pumps were turned off and a controlled landing was not achieved for "unknown reasons".

Mr Bernhardt said he was not aware the newer Airbus H160 and new generation EC135s which have the Helionic software has a light that turned red on the main tank display at any time when fuel is not being transferred from the main tank to the supply tank.

And he said such an alteration could not have been employed on the EC135s that were used at the time of the Clutha tragedy.

"It is a completely different computer and software. It's just two different things," he said.

Mr Gray then asked if he was aware that 15 years ago on the old type EC135s that when the level of fuel in the supply tanks dropped to a certain level, the background colour of blue turned to another colour.

"On the EC135, you say?," said Mr Bernhardt.

"Yes," replied Mr Gray, who had earlier Mr said the older generation of EC135s, did have a digital reading of the amount of fuel in each of the supply and main fuel tanks.

Mr Bernhardt added: "I am not aware of that. I have never heard this before. You say we had it and removed it?"

Mr Gray said: "Exactly what I was going to come to. And that was modified out. There was a modification to the Avionics software...  You are not aware?"

"I am not aware of that," said Mr Bernhardt.

 It comes a day after the court was told helicopter manufacturers Airbus knew about issues with the EC135 model's fuel readings a decade before the Clutha crash.

In 2003, Airbus had been made aware of issues with fuel readings in its EC135 helicopters and this was suspected to have been caused by water rusting the the hydro mechanical unit (HMU), part of the fuel system.

The inquiry previously heard from Air Accident Investigation Branch senior inspector Marcus Cook that five separate low fuel warnings would have gone off in the doomed helicopter which smashed into the Clutha bar, and some of the warnings would have been made intermittently.

The 2015 Air Accident Investigations Branch investigation said that Clutha pilot David Traill, 51, one of the ten that died, did not follow emergency protocol and flew on despite low fuel warnings, the investigation said.

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.

And the AAIB 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 continues.