An air accident investigator has lamented a lack of evidence available from a police helicopter which crashed on to the roof of a pub, killing 10 people.

Peter Wivell, a senior inspector at the Air Accidents Investigation Branch (AAIB), told a fatal accident inquiry it is “frustrating for everyone” that some questions cannot be answered because of the available evidence.

Pilot David Traill, two crew members and seven customers in the Clutha bar in Glasgow were killed when the aircraft crashed on to the roof of the building on November 29, 2013.

The inquiry heard the helicopter did not have a flight recorder fitted.

Mr Wivell reiterated calls made by the AAIB for more aircraft, both old and new, to be fitted with wider recording equipment.

The recommendations would allow future investigations access to flight information, data on board and visual displays.

Replying to a question from Sean Smith QC, for the Crown, Mr Wivell said there “was a lack of evidence to answer off”, adding: “There are questions we can’t answer, which is frustrating for everyone.”

Mr Wivell added: “If we had had a picture of the display panels, we would be much better positioned to understand events.

“Helicopters are not required to have audio or image recordings, therefore my understanding is there is a push to get some data on these recorded flights.”

Clutha crash scene
Ten people were killed in the tragedy in November 2013 (Andrew Milligan/PA)

Donald Findlay QC, representing the family of Robert Jenkins who was one of the victims in the pub, said: “Friends and family will be concerned by the comments you made earlier about a lack of information.

“Is that a correct statement?”

Mr Wivell replied: “Yes.”

Mr Findlay also made reference to the A380 plane – which began its first service from Glasgow on Tuesday evening – and if it would be fitted with similar equipment.

The investigator replied it would have flight and data recorders but could not say about a visual recorder.

When asked by Mr Findlay if visual recorders are something of the future, Mr Wivell replied they are “becoming the present” but also said they had been “historically resisted”.

Mr Wivell was also shown an animation depicting the general sequence of events leading up to the crash.

Roddy Dunlop QC, for Airbus, iterated it was not a comprehensive reconstruction but was based on available data and subsequent assumptions.

It showed a pre-flight checklist for the twin-engine helicopter, one of 1,350 which had been delivered after first coming into service in 1996, before detailing its movements the night of November 29.

The aircraft took off at 8.44pm heading to the Oatlands area of Glasgow, before moving on to Dalkeith near Edinburgh where it remained for three minutes.

Clutha bar
The Clutha reopened in July 2015, decorated in murals (PA)

At 9.49pm it is suggested fuel stopped being supplied, with no explanation as to why both pumps came to be in the switched off position.

Ten minutes later the pilot contacted air traffic control (ATC) in Glasgow, with the warning lights calculated by experts to have come on before Bothwell, South Lanarkshire.

Five low-fuel level warnings would have been acknowledged by the pilot, who again contacted ATC when over Bargeddie with no issues reported.

At 10.21pm the right engine flamed out, followed by the left engine approximately 32 seconds later.

Mr Dunlop highlighted the fact the main and tail rotors were not turning at the moment of impact and asked Mr Wivell’s view on the consistency of the video to the report and his findings.

He replied “I have found it consistent”, barring caveats had with the video not showing Caution and Advisory Display (CAD), which is among the recommendations.

More than 100 people were at the Clutha Vaults pub when the helicopter, returning to its base on the banks of the River Clyde, crashed through the roof.

The inquiry, before Sheriff Craig Turnbull, continues at Hampden Park on Thursday.