Tony Collins tells the BBC about his magazine's report

All 29 people on board the helicopter died, including some of Northern Ireland's most senior police and intelligence experts.

The aircraft was flying to Inverness from Ulster when it crashed in thick mist.

An RAF board of inquiry ruled the pilots - Flight Lieutenants Jonathan Tapper and Richard Cook - were to blame but the conclusion has been strongly contested by their families and some politicians.

The BBC's Emma Simpson: The magazine says the technical investigation was flawed

Based on the limited evidence, the inquiry said the wrong rate of climb was the most likely cause. It decided that although technical malfunction was unlikely, it could not be positively disproved.

Now, Computer Weekly reports that the helicopter's engine control software may have been the cause of the crash.

'Car pedal'

The magazine's Executive Editor, Tony Collins, said with the benefit of hindsight new evidence had come to light which was not available to crash investigators.

Flt Lt Tapper is said to have expressed concerns about the speed at which the Chinook's "full authority digital engine control" was being put into service.

The pilots were said to have chosen the wrong climb rate

Mr Collins likened the software to a car's accelerator pedal.

"If the engines receive a signal from the software telling them to accelerate when the pilots don't want to, the only way they can bring down the speed is to go into cloud in a way which they don't want to," he said.

"That has not been generally understood. It has been thought that if the software fails, it would fail in a predictable manner."

Mr Collins said he did not think the inquiry had been deliberately misled but it was clear that crash investigators have difficulties when examining computer software after an accident.

"Gross negligence can only be brought if there's no doubt whatsoever as to the cause of the crash," he told the BBC.

Verdict 'unsafe'

"In this case, there are too many uncertainties and the evidence that we have highlighted proves that the evidence on which the verdict was based is inconclusive.

"We are saying that the verdict of gross negligence is manifestly and demonstrably unsafe."

Computer Weekly also questions whether the aircraft should even have been allowed to fly as it believes evidence from America should have alerted the army to the potential software problems.

Other theories which were rejected at the time of the inquiry included interference from laptop computers, mobile phones, submarine communications and the possibility of a passenger bursting into the cockpit.

Menzies Campbell: Call for inquiry review

Questions also arose about whether the crew members were running out of flying time and were going flat out to stay within their designated hours.

After a four-week fatal accident inquiry in 1996, a sheriff recommended the immediate installation of cockpit voice and accident data recorders.

He said he was not satisfied that the cause of the accident was the pilots' choice of an inappropriate rate of climb.

Liberal Democrat defence spokesman, Menzies Campbell said the inquiry's findings should be reviewed.

He said: "I have long been convinced that there is an injustice here.

"The RAF's own regulations at the time required that every other cause had to be eliminated before deceased pilots could be found to be negligent.