Sheriff Principal Derek Pyle said he believed several failures by Bond Offshore Helicopters to properly deal with metal particles found in the engine during routine checks could have led to the crash.
Any prosecution would be expected to be carried out under the Health and Safety Act.
But lawyers acting for some families believe it is enough to show there was a possibility that the inaction of the operators was a major factor for there to be a case to answer.
The Crown Office, however, defended its decision not to prosecute, insisting there was not enough evidence to justify a criminal investigation against Bond Offshore Helicopters for repeated breaches of health and safety rules.
Audrey Wood, whose son Stuart was one of those killed, said: "How they arrived at that decision will haunt us, as not only did we hear of multiple breaches of health and safety, but the decision was also made without all the evidence being present, as vital witness statements had not been given.
"We, the families, feel let down by the system. We just wanted answers. We will never have closure, this will go on and on for us."
The Crown Office said the Sheriff Principal had made clear that a "reasonable doubt" remained over the technical cause of the crash.
For a criminal prosecution to proceed, the cause would have to be beyond reasonable doubt.