Two Kakadu rangers and their pilot have been "very lucky" to survive a helicopter crash while culling feral animals in the Northern Territory.
The surgeon who treated the men said it was a miracle they survived the crash when the chopper "dropped like a stone from 80 metres" in Kakadu National Park on Tuesday.
"I think this is a horrible accident and given the severity of it, it is a miracle the three men are alive," Darwin Hospital trauma surgeon Angelika Na told reporters.
Two of the men were trapped for four hours, while the third freed himself from the wreckage, radioed for help and set off an emergency beacon.
An Air Force helicopter found the crash location in Kakadu's south and directed a CareFlight rescue helicopter to the scene.
The men were winched out and flown to Royal Darwin Hospital with serious injuries.
The pilot, who suffered the worst injuries, was then taken to Melbourne for further specialist treatment.
Rangers Fred Hunter, 47, and Ian Conroy, 49, suffered chest and spinal injuries.
Mr Hunter's brother-in-law Andy Ralph posted on Facebook: "Ian, Fred and Pilot Andy ... were VERY lucky to get out of this alive".
"Fred said the Chopper dropped like a stone from 80m and went straight in ... Pilot (Fred said very experienced and competent) couldn't do a thing.
"Looks like Fred has fractures in his back, a few gouges out of him, but can wriggle his toes so Docs hoping no long term damage."
The rangers were culling feral buffaloes and pigs from the air in the helicopter owned by Darwin company Jayrow.
Kakadu's operators Parks Australia grounded all helicopters in the park while it reviews what went wrong, while the Australian Transport Safety Bureau is also likely to investigate.
"It is not at all clear at this stage what caused the crash, details are very sketchy, we are still going through the processes but it looks like it went down very quickly," Parks Australia director James Findlay said.
CareFlight pilot Jamie Humphries landed his rescue helicopter on a nearby ridge, allowing a doctor and nurse Paul Campbell to winch themselves to the crash site.
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