THE families of all 16 men killed on board a Super Puma which crashed into the North Sea have spoken of their frustration at the length of time it took for an inquiry to be held.

The AS332-L2 helicopter suffered a catastrophic gearbox failure on April 1, 2009, and fell from the sky. Two crew and 14 oil workers were on their way home from the BP Miller ­platform.

The Air Accident Investigation Branch launched a probe to establish what caused the disaster and published a report on its findings in November 2011.

Last year the Crown Office ruled no criminal proceedings would be taken due to insufficient evidence. A fatal accident inquiry finally got under way in Aberdeen at the start of last month.

Tom Marshall, the lawyer ­representing the families, yesterday criticised the time it had taken for the inquiry to be held. He said: "The near five-year delay has been prejudicial to the inquiry. This delay is entirely unacceptable."

Mr Marshall told the inquiry the recollection of witnesses giving evidence at the Super Puma inquiry had been impaired because of the delay. He said the families also only had four months to prepare for the inquiry, which made it "unneccesarily difficult".

Mr Marshall pointed out a fatal ­accident inquiry into the Lockerbie Pan Am Flight 103 bombing was held before the third anniversary of the disaster.

Depute fiscal Geoff Main told the inquiry the Air Accident Investigation Branch investigation took precedence over everything else. He said police and the prosecution service then liaised with the AAIB and considered whether criminal action would be taken.

After the hearing yesterday, Audrey Wood, who lost her son Stuart, 27, in the tragedy, spoke on behalf of the families.

Mrs Wood, of Newmachar, Aberdeenshire, said: "This has been the most horrific, traumatic five years of strung out emotional upsets for all 16 families and friends. It has been a perpetual rollercoaster of which we could not get off. Of course, the length of time this case has taken to get to court has prolonged the grieving process.

"We do hope we can find some peace in years to come. It's been a tough six weeks but we needed to hear the evidence and the lead up to the tragic event. We can only hope accountability and responsibility will be addressed, and await the sheriff's determination."

Final submissions from lawyers for all parties were submitted to Sheriff Derek Pyle yesterday.

The inquiry had heard proper procedures were not carried out when problems with the Super Puma were discovered on March 25, 2009, a few days before the crash.

However, Eurocopter lawyer Murdo MacLeod, QC, said in his submissions there were "no reasonable precautions" that could have been taken by the firm to stop the fatalities happening. He said the firm wished to pay tribute to all the men who died and express its sympathy to their families.

Sheriff Pyle's determination is expected to become available in about four weeks.