It’s the secrecy that particularly upsets David Naggs. After all, Defence didn’t lose a precious son. He did.

And yet, Naggs has found frustratingly few answers as to why his son Alex died, along with three other army aviators, on July 28 last year off Lindeman Island in Queensland.

Defence wouldn’t even tell David where in the Whitsundays Alex’s helicopter had crashed. He wanted to at least know the nearest beach so he could visit.

Others knew, such as the first responders to Defence’s late-night call for search and rescue assistance.

And by chance, when David made his own trip to the Whitsundays with 60 Minutes to see the area for himself, he took a boat owned by a company whose staff were first on the scene that disastrous night.

Alex Naggs’ MRH-90 Taipan helicopter plummeted at high speed into choppy seas with the exact co-ordinates -20.40863, 148.94173. To David, these are 15 grim digits.

“It’ll always be where I lost him, to remember him,” David told 60 Minutes. “It’s a beautiful part of the world. But gee, it’s still a lonely, cold place to die, isn’t it?”

Captain Danniel Lyon, Lieutenant Max Nugent, Warrant Officer Phil Laycock and Corporal Alex Naggs died instantly that night.

Never-before-seen photos taken about three hours after the crash showed their Taipan, with the call sign Bushman 83, splintered on impact.

A ripped section of the aircraft’s undercarriage still attached to the Taipan’s orange automatic flotation system is evidence of a high-speed catastrophe. A few other pieces of lightweight composite could be seen bobbing in the sea, but little else.

Most of the fuselage, along with the crew, had sunk 40 metres below the surface.

“I’m told they found minimum remains. I gave a DNA sample and they had something like the size of a 20¢ piece that responded to my DNA, that’s it,” David said.

“The funeral was with an empty casket … walking around with an empty box was, was something. You know, they treated it with reverence and all that, and I’m thinking, ‘But there’s nothing in there, guys, and there never will be.’”

The doomed helicopter, Bushman 83, had been flying in formation with three other army Taipans at the time of the crash.

They had been stationed at Proserpine awaiting the call to pick up special forces soldiers on Lindeman Island, as part of the Talisman Sabre war games exercise with the US and other international forces.

The call from Lindeman came at 10pm and the Taipans took off soon after.

The weather was far from ideal. The flight path was adjusted as the Taipans flew across the Whitsunday Passage in what’s called a heavy left formation, the lead aircraft flanked by one aircraft to its right and two to its left, all staggered to allow maximum visibility.

But it was hard to see anything that night. Low cloud obscured the moon and the horizon was barely visible.

Adding to the danger, the Taipans were flying at low altitude – just 61 metres from the surface of the water.

“If all of those conditions were present, that would be probably about as tough as it gets,” said Tim Leonard, a former squadron commander who spent 32 years in the navy and another 10 years as a Defence contractor, mostly flying helicopters including the Taipan.

As the Taipans approached Lindeman, they began a series of left-hand turns to wait for final confirmation for the pick-up.

Bushman 83, flying second to the rear, was seen to climb suddenly, before pitching nose-down towards the water.

The mission commander in the helicopter at the rear of the formation radioed, “83, pull up, pull up, pull up” but to no avail.

Bushman 83 pummelled into the ocean.

David Naggs has been told it all happened in a shockingly quick time – as few as three to four seconds.

He was told that when Bushman 83 pitched into the sky, it reached an altitude of 356 feet – information he presumes came from the black box which was retrieved 10 days after the crash.

Defence has also revealed something else from the black box.

“It’s a statement of record and fact from the data that was gathered from the voice and flight data recorder that at the point of the accident, the engines were functioning normally – that’s a fact,” Chief of Army Lieutenant-General Simon Stuart told a parliamentary committee in February.

So if the engines were operating normally, what could cause a Taipan to suddenly pitch up and then plummet nose-down in defiance of the mission commander’s demands to correct course?

Suspicion has fallen on a hi-tech helmet that the Taipan pilots were using that night.

The TopOwl has been used by militaries around the world for the best part of two decades. It comprises a helmet-mounted sight display that provides critical information about the aircraft, including altitude, height above ground, pitch and roll (attitude), ground speed, vertical speed and whether the aircraft is climbing or descending.

The latest software upgrade for the TopOwl, HMSD V5.10, was found to carry significant risks, according to an experienced test pilot with the Army Aviation Test and Evaluation Section (AATES).

He found that when the aircraft was in a turn, the displayed angle of bank washed out if he looked to the left or right; a 30-degree angle of bank would, for example, be represented as 23 to 25 degrees if the pilot turned his head 90 to 120 degrees either side.

In the test pilot’s own words, the “ambiguous aircraft attitude” represented an “unacceptable risk to flight safety”.

Even more alarmingly, the test pilot found the new software could result in “controlled flight into terrain”, making it a “substantial risk of multiple deaths”.

Greens senator David Shoebridge, who has been investigating the safety of the Taipans ever since one ditched in Jervis Bay four months before the Lindeman Island incident, said he was deeply concerned about the AATES report from June 2019.

“This is the kind of report that should ground the fleet. ‘Substantial risk of multiple deaths’; if that doesn’t ground the fleet, what does?” Shoebridge said.

But Army Aviation safety experts found other serious problems with the latest version of the TopOwl.

The image intensifier – two tubes on either side of the TopOwl helmet that assist night vision – was found to degrade when looking to the side, according to an AATES report in April 2020.

And the forward-looking infrared system was reported in July 2020 as being unsafe as a “primary means of detecting and avoiding obstacles”, with “failure during terrain flight” assessed as “catastrophic” and “probable”.

Tim Leonard, the former Taipan pilot, said earlier versions of the helmet-mounted sight display had a key difference to the V5.10 update that troubled army test pilots.

In earlier versions, the aircraft’s attitude – that is, the pitch and roll – could only be seen in the display when the pilot was looking forward and not when they looked to the left or right.

“There have been various studies to say that presenting attitude information off-axis in a helmet-mounted display significantly increases the chances of spatial disorientation,” Leonard said.

“I believe the original anchoring of attitude was probably the correct methodology. It’s hard enough as it is with this symbology without introducing more problems.”

After receiving the AATES reports, Defence conducted its own testing, a so-called “operational evaluation” over 12 hours, on and off ships in both day and night sorties.

But 60 Minutes has been told these tests were conducted in relatively benign conditions.

“So basically Defence tested this equipment on a sunny day and on a moonlit night, never down low and never in the situations where pilots most need them,” Shoebridge said.

“The reason they did that was because even the people Defence found to do the testing said ‘well, there’s no way you’re going to take this below 500 feet where I can’t see the horizon and we’re at risk, because it’s too bloody risky’.”

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Defence doesn’t dispute the findings of the test pilot but says a number of mitigation measures were put in place after conducting its own tests.

Pilots were given extra training on using the TopOwl and the flight manual was updated to prohibit reliance on infrared night vision for navigation.

They were also told that when using the helmet-mounted sight display, pilots should only look forward when assessing the attitude or orientation of their aircraft, rather than to the side.

Shoebridge said this was an absurd workaround, especially when pilots were expected to make split-second decisions in tricky environments.

“The idea that you’d say to the pilot, ‘Well just ignore what’s happening on your heads-up display and refer to the primary instrument when they’re in conflict’ … it doesn’t take an expert to tell you that that’s a major problem,” Shoebridge said.

Leonard said pilots were always taught to rely on their instruments at times of disorientation.

“It becomes life-savingly critical in many cases to get onto the instruments and believe what they say,” he said.

“And that’s what they always talk about: if you become disorientated, don’t trust your own body, believe what the instruments are telling you.”

Defence insiders have told 60 Minutes there was a tension between those overseeing safety and those who wanted to keep aircraft flying. This tension, they say, results in an operational bias where matters of safety risk running second.

Two days after the Lindeman Island crash, the Royal New Zealand Air Force had its own version of the Taipan back in the air.

A New Zealand Defence Force spokesman said the force’s fleet of NH90 aircraft had not experienced any serious problems since going into service. The Royal New Zealand Air Force does not use the TopOwl helmet system.

Six weeks after the crash, the Taipan’s manufacturer, NH Industries, wrote to its European and Middle East customers assuring them that initial analysis of the voice and flight data recorder “has not identified any information … relating to a failure, malfunction (or) defect to the NH90 type design”.

David Shoebridge said bluntly: “This tells you there’s nothing inherently wrong with the Taipan helicopter. The issue here is all the mod cons that the Australian Defence Force whacked on it, all of these things that they kept getting reports about saying this is unsafe.”

Leonard said the Taipan had been unfairly targeted by detractors in Defence who would have preferred Black Hawks in the first place.

“There was a lingering dissatisfaction with that decision and people were not keen on the MRH-90 Taipan being introduced into Army Aviation,” he said.

“Now, subsequent to my time, I believe that those who operated the aircraft and those who flew it and those who maintained it came to love the aircraft because it is a very good aircraft.

“It is a magnificent aircraft. It is a Lamborghini compared to a Holden.”

But if the cause of the Taipan crash on July 28 was pilot disorientation caused by compelling albeit inaccurate or ambiguous information, it’s nothing short of a scandal, given the warnings issued by Defence’s own safety experts.

For David Naggs, there’s a simple equation.

“You’ve got a report that says, ‘You do this, you’re gonna end up with dead people’. They do it, they’ve got dead people.”

Shoebridge said Defence didn’t adequately deal with the risks identified by the test pilots.

“Instead they literally went opinion shopping to try and find an alternative opinion to allow them to continue to fly it,” he said.

Defence Minister Richard Marles rejects this claim but says the Inspector-General Australian Defence Force inquiry into the crash would likely consider the tension between operational requirements and safety concerns.

“It is important that we have systems in place which maintain safety and obviously maintain capability,” Marles told 60 Minutes.

“If there are tensions there, we learn and develop appropriate balances and mechanisms for balancing those tensions going forward.”

Marles has vowed to get to the truth.

“Clearly something went terribly wrong,” he said. “It is fundamentally important for the family’s concern, for the Defence Force and for the nation that we actually understand what did happen here.”

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Naggs said his son would never walk through the door again.

“Why? How? You’ve got all these people, very capable people looking after these aircraft, very capable people flying them … How the hell did this happen without a shot being fired?”

Thales, the manufacturer of the TopOwl, provided a statement on Friday, which said: “As this is an ongoing investigation, it would be inappropriate to comment at this time.”

If you are a current or former ADF member, or a relative, and need counselling or support, contact the Defence All-Hours Support Line on 1800 628 036 or Open Arms on 1800 011 046.

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