A fresh review is under way into the fatal military helicopter crash that claimed three lives and left a serviceman with life-long injuries.
Almost a decade after the crash, Cabinet has approved funding for Michael Heron QC to carry out a "desktop review" of the inquiries made so far in response to ongoing anger and frustration from some of those affected by the 2010 accident.
Defence Minister Ron Mark said the review aimed to provide closure to those affected by the crash and fulfilled a pledge by NZ First to answer questions still outstanding after the crash.
The early morning accident came as a flight of Royal New Zealand Air Force helicopters made their way from Ohakea base in Manawatu to Wellington for a dawn flight as part of Anzac Day commemorations.
The flight became disoriented at Pukerua Bay north of Wellington, with one helicopter crashing into the hillside killing Flight Lieutenant Hayden Madsen, Flying Officer Dan Gregory and Corporal Ben Carson. Sole survivor Sergeant Stevin Iain Creeggan was left with life-long injuries from the crash.
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The official Court of Inquiry found a "can do" culture of "rule breaking" at 3 Squadron, the Iroquois helicopter wing.
Yet reporting by the Herald in 2012 and 2013 revealed the depth and extent of command breakdown, with recommendations from multiple safety inquiries not progressed and gaps throughout the Air Force's safety systems.
Further inquiries followed, introducing new systems for health and safety across the Air Force and the removal of a loophole that appeared to exempt the military from external inquiries in serious accidents.
For the Carson and Creeggan families, there was concern over accountability with the accident resulting in only failed military prosecutions of low and mid-level officers and a successful private prosecution of NZDF as an institution by Creeggan.
Mark told the families this month Cabinet had agreed to have a "desktop review" carried out into the inquiries that had been carried out so far.
The terms of reference for the review show Heron - a former Solicitor-General - would review documents held by NZDF, police, the State Services Commission and the Ministry of Business, Innovation and Employment. It included legal advice received and records from court martial proceedings.
The Carson family was concerned the Terms of Reference did not include the secret Air Accident Analysis report, which was evidence put forward to the military's Court of Inquiry by its top crash investigator.
The Herald has reported on the content of the report, which raised questions about safety across the Air Force and revealed that failures to make changes once put at risk an Air NZ passenger flight with more than 300 people on board after NZDF unlawfully transported a flammable chemical device on the plane.
Mark's office, and NZDF, have since confirmed the report will be made available to Heron.
Mark said the decision to hold the inquiry would be difficult for those who considered the tragedy closed. One family who had lost a son was strongly opposed to any further inquiry.
The review would seek to find whether there were questions unanswered from the crash.
"It's complex, it's emotional and it's difficult. It will be done in a way that gives closure to all the families."
Heron had been asked to identify any gaps that existed, and if there were, to recommend any further necessary steps.
Mark said a fresh inquiry would also be confronting for the Air Force and wider NZDF family, who were - in some cases - even closer to fellow military personnel than to their own families through the bonds of service.
"People under-estimate the impact a loss such as this has on that Air Force family. When these things are dug up again and again, I'm very conscious of the impact on the wider family."
Andrew Carson welcomed the review, which he and wife Pauline saw as NZ First leader Winston Peters meeting a promise previously made over the crash.
"We're absolutely thrilled. Pauline has put in a huge amount of work to get to this stage. The fact they're looking at it at all says it all."
Carson said he considered Heron also needed to see the Air Accident Analysis Report, which included details about command responsibility and safety failures not raised in other inquiries.
He said the areas the family hoped Heron would focus on included the handling of the court martial process, which didn't consider culpability at the higher levels of command until the three-year time period during which it was possible to lay charges had almost expired.
He also wanted a close examination of the Air Force's behaviour towards the families of those lost in the crash and whether some were treated differently than others.
"What I would like to see come out of it is somebody who was responsible being named for being responsible. They should be named and shamed and have it affect their future as it affected the family's future."
NZDF has always held the view the Air Accident Analysis Report cannot be made public because it was evidence put before its Court of Inquiry process, and like other submissions, was only for that purpose. By making it available to Heron, it will meet concerns those reviewing the accident and its response did not have all information available.
There has never been a full inquiry into the accident other than the military's own "lessons learned" inquiry, which was aimed at preventing future accidents rather than apportioning blame.
Chances to fully probe the crash bypassed police and health and safety officials before landing on the coroner, who opted to accept the NZDF's Court of Inquiry rather than conduct a fresh investigation.
Creeggan, who now lives in Australia, took the extraordinary step of taking a private prosecution against his own commanders while still serving in uniform. In 2014, NZDF pleaded guilty in the Wellington District Court to health and safety charges.
None of those flying that morning were qualified to do so in the circumstances, taking off when it was dark and flying on night vision equipment.
The Air Force conceded it had not provided a safe working environment for its personnel and offered an unreserved apology.