The fiancee of the pilot blamed for killing 10 people in the Clutha helicopter crash has criticised the findings of the fatal accident inquiry and claimed the sheriff downplayed evidence showing the manufacturer and aircraft were at fault.

Dr Lucy Thomas, who was engaged to marry David Traill, the pilot, said there was clear evidence about the helicopter’s record of faults and errors in its maintenance manuals that meant Traill was not to blame.

After the fatal accident inquiry (FAI), Traill was blamed by the sheriff principal Craig Turnbull for failing to transfer more fuel into its supply tanks after fuel warning lights came on in the Eurocopter EC135. He said Traill “consciously took a risk. [That] decision had fatal consequences”.

The helicopter, which was carrying two police officers, crash-landed on the roof of the Clutha bar in Glasgow at 10.20pm on Friday 29 November 2013, before falling through the roof, killing its occupants and seven customers in the bar.

Thomas, from Lochwinnoch in Renfrewshire, said Turnbull was wrong. She said the sheriff had failed to take proper account of the helicopter’s history of faults with its caution advisory display, of “erroneous or spurious fuel indications” and problems such as fuel tank contamination.

“I find it distressing and incomprehensible that given months, not moments, to consider the facts, the sheriff principal has come to this conclusion,” she said.

“Instead, the sheriff principal has opted to sully the distinguished reputation of a pilot with an exemplary record who was renowned for his sense of responsibility and his regard for the safety of his crew.”

Traill’s decision to keep flying despite seeing the fuel warning flights was a key issue for the inquiry. Turnbull ruled the pilot should have had ample fuel for the journey back to base, and should have followed the warning lights by shifting fuel to the supply tanks.

Turnbull decided it was “more likely than not that the quantities of fuel displayed on the fuel quantity indication system of [the helicopter] contradicted the low fuel warnings, in a manner that persuaded Captain Traill that it was safe to continue flying”.

Thomas said his findings insulted the intelligence of those who knew about the aircraft’s history. She said the model’s maintenance manual had wrongly said a flameout time between engines would be about three to four minutes.

In fact, the correct time was more than one minute but, because of the design of the fuel tanks, Traill had only 32 seconds before flameout. In a statement, she said of the victims: “This has devastated the lives of all who surround them and impacted on so many more.”

A spokeswoman for the Judicial Office for Scotland said: “The sheriff principal carefully considered all the evidence put before the inquiry before making his determination which fully sets out the reasons for his decisions.”

A spokesman for Airbus, which makes the Eurocopter, would not comment on her criticisms and reissued the statement it issued after Turnbull’s ruling last week.

The firm said it had cooperated with all the investigations into the crash and had taken note of the findings of the FAI and the previous investigation by the Air Accidents Investigation Branch.

“All of us at the company remain deeply saddened by this tragic accident and the heavy loss of life. We would like to express once again our deepest sympathies to the families, friends and colleagues of those who lost their lives,” he said.

“The safety of our fleet remains our number one priority and we are committed to doing everything possible to ensure the safe operation of our helicopters by the thousands of operators whose crews and passengers rely on them every day all around the world.”