Comcare had presented the Commonwealth Director of Public Prosecutions with briefs of evidence to pursue the Australian Defence Force over its poor fatigue management of personnel and for its deployment of a troubled hi-tech helmet used by pilots.

But the families of Captain Danniel Lyon, Lieutenant Max Nugent, Warrant Officer Phil Laycock and Corporal Alex Naggs were informed yesterday that the CDPP would not launch a prosecution, believing there is insufficient likelihood of success.

This is despite an independent inquiry into the July 28, 2023 crash of the Taipan helicopter hearing shocking evidence that test pilots had warned that the TopOwl helmet-mounted sight display used by aircrews were a lethal risk due to ambiguous readings projected into the pilot’s visor.

The Taipan had been flying in close formation with three other Taipans in low light, poor weather and in a left-hand turn when it smashed into the sea off Hamilton Island in the Whitsundays about 10.30pm.

Dan Nugent, the father of Lieutenant Nugent and an inspector in the NSW Police, said he was dismayed by the CDPP’s decision, saying the inquiry had heard compelling and ample evidence of poor fatigue management and concern about the safety of the TopOwl helmet.

“They were fatigued to a level that would have affected their ability to fly that helicopter,” Nugent said.

“How can we have confidence in any government entity, let alone our Defence Force, that if they’re not prepared or Comcare is not given the ability after recommending charges or a brief of evidence against Defence, for them not to contest that, for the public to be able to hear it in open court domain?

“It’s just disgraceful when their own documents say that fatigue was a contributing factor in the accident.”

The families are also angry that the decision not to prosecute Defence came just five days before the two-year statute of limitation expiry to the potential legal proceedings.

Nugent said he had been disturbed to hear evidence about TopOwl being a “substantial risk of multiple deaths” had been effectively ignored by Defence.

“These sorts of things just lead to a culture of risk normalisation,” he said.

Major Ian Wilson, a test pilot, told the inquiry that he had warned his superiors that they would be liable for “industrial manslaughter” if they allowed TopOwl to be used by pilots.

Despite this stark warning, TopOwl version 5.0 was put into service when Army Aviation conducted its own tests in benign conditions, finding it safe to deploy.

The Defence Flight Safety Bureau in May found that “unrecognised spatial disorientation” by at least one of the pilots that night caused the crash and that it was “very unlikely” that the TopOwl contributed to the disorientation.

“Max has said to me that he liked using TopOwl in daylight hours. He didn’t like using it at nighttime, because the visual acuity of the night vision system wasn’t as good as traditional night vision, yet they fly predominantly at nighttime,” Nugent said.

So where was the assessment? Where was the assessment of that?

“If the experts are saying – and I take Major Ian Wilson as an expert – he is the test pilot from their own test organisation says, ‘Don’t do this, this will potentially cause a crash’, and you continue to do that, then surely that’s liability, right there.”

Greens Senator David Shoebridge said the victims’ families have been failed.

“We know that the TopOwl system was not up to scratch, we know that it exposed people to extreme danger,” Shoebridge said.

“We know that fatigue was an issue in play, and we, in fact, know that training was an issue in play. When you put all that together, how do you get an explanation to the families that makes sense, that there won’t be a prosecution, that nobody will be held to account. I don’t understand.”

The ADF said the 2023 Taipan accident was subject to three ongoing investigations and inquiries, and that Defence had “not been formally notified that any of these investigations have concluded”.

“Defence is unreservedly committed to supporting the conduct of thorough and independent investigations to determine what happened and to identify actions to be taken to prevent aviation accidents and incidents,” the ADF said in a statement.