Could this be Australia's Bermuda Triangle?

On a cool August morning in 1987, two air force pilots set out on a routine flight down the east coast of Australia.

Dennis Hume, then 30 years old, was behind the controls, flying a bright orange Aermacchi jet with his colleague Brendan Heslin seated behind him.

The pair had left the Royal Australian Air Force (RAAF) base at Amberley, west of Brisbane in Queensland, on a low-level flying exercise headed for Victoria.

For the first 45 minutes of the flight, everything had gone smoothly, but that changed when they reached the notorious Barrington Tops National Park on the NSW Mid North Coast.

"I noticed that the engine's RPM was winding down, which was a bit alarming," Dennis Hume said.

Within seconds of reaching the Barringtons, Mr Hume's jet was engulfed by cloud and the engine failed.

Mr Hume tried to restart the engine but it didn't respond, likely as ice had clogged the engine's intake.

"That's when I ordered the ejection," he said.

Mr Hume and Mr Heslin successfully ejected.

They became two of only four people to survive a plane crash in the Barrington Tops region.

Since 1945, nine planes have crashed in or around the Barringtons, claiming the lives of 30 people and earning the area the nickname the "Devil's Triangle".

"It's been regarded as like Australia's Bermuda Triangle to a certain extent,"

Mr Hume said.

Disappearing planes and a string of fatal crashes

The first recorded plane crash in the Barrington Tops National Park was 81 years ago, when an RAAF Mosquito fighter-bomber, flying in poor weather conditions, crashed into a mountain, killing both men on board.

It took nine months before the wreckage was located on an almost 5,000-foot (1,500 metres) mountain peak, which was later dubbed "Aeroplane Hill" after the tragedy.

Since then, eight other planes have crashed in or around the area, with bad weather conditions a contributing factor in almost all of them.

Arguably the most notable of these crashes was in August of 1981, when a Cessna 210 light plane registered VH-MDX disappeared over the national park after encountering cloud and severe turbulence.

It remains the only civilian plane to crash over mainland Australia with no trace ever found.

Other crashes in the region include:

• September 2, 1948: A Douglas DC-3 passenger aircraft travelling from Brisbane to Sydney crashed north-west of the Barrington region after encountering a storm, killing all 13 people on board.
• September 14, 1954: A Lockheed Hudson newspaper delivery aircraft ploughed into a mountain side in the Barrington Tops National Park during heavy rain and mist, killing the three men on board.
• September 25, 1967: An RAAF Mirage III-O jet fighter crashed over the Barrington Tops following an engine flame-out; the pilot safely ejected.
• April 3, 1973: Another RAAF Mirage III-O jet fighter suffered severe engine vibrations and crashed 8 kilometres from Gloucester, killing the pilot.
• March 31, 1975: A Piper Cherokee light aircraft flying from Cessnock to Armidale encountered extensive low cloud, the pilot becoming disorientated before crashing, resulting in two passenger fatalities and serious injuries to the pilot.
• November 11, 1982: A Piper Cherokee Warrior light aircraft flew into cloud while en route to Taree from Scone. It crashed at Billabong Park in Gloucester, killing all four men on board, including the father of former prime minister Malcolm Turnbull.

What's to blame?

Some liken the area to the Bermuda Triangle, blaming the string of plane crashes over the decades on mysterious aviation phenomena or a disrupted magnetic field.

But pilots familiar with the region say the reality is far less mysterious.

Phil Unicomb runs a flight school in the Hunter Valley and says the Barrington Tops, with mountains reaching to 5,200 feet, make it prone to poor and rapidly changing weather.

"Because of the height of the hills, westerly winds in particular come through and you can get a lot of mechanical turbulence from that," Mr Unicomb said.

"It's the air being swirled like waves in the ocean … it can rough the air up and give you a rough ride."

Some call this "mountain wave turbulence", which can rapidly lift or drop aircraft hundreds of feet in seconds.

Another risk of the area is severe icing, where supercooled water droplets freeze onto planes, affecting engine function and adding hundreds of kilos of weight.

Mr Unicomb said another danger was the lack of places to make an emergency landing, with the Barrington Tops region spanning 125,000 hectares of mountainous terrain.

He said for all these reasons, he tells his students to avoid the area "like the plague".

"It's so dense and the trees so tall, that you could find yourself going down through the canopy of trees and it'd be very, very difficult to find you."

Like trying to find a needle in a haystack

For the few, like Mr Hume, who have survived a plane crash in the region, that was only the first challenge: the next was being found.

After ejecting from his plane, Mr Hume's parachute caught in the tree canopy and he found himself clinging to a branch 12 metres above the ground as snow began to fall.

The force of the ejection had fractured three vertebrae in Mr Hume's back and cracked his teeth, leaving him seriously injured as he waited to be rescued.

"I was in a fair bit of pain … and I was cold. Very cold,"

he said.

As an RAAF pilot, Mr Hume was wearing a "dingy pack" that held several emergency survival items, including a radio beacon.

"I'm just thinking about survival," he said.

About 45 minutes later, another RAAF aircraft searching for him passed overhead and detected his radio's distress signal.

"A Hornet [aircraft] can't get you out of a tree, but they know where you are … so that was of enormous relief to me," Mr Hume said.

It took another four hours before rescuers on the ground reached him.

Despite what he endured, Mr Hume said he considered himself lucky.

"I [wasn't far from] Devil's Hole lookout and there's a cliff there which is also very heavily vegetated," he said.

"I've been back several times, and I often think if I was in a tree down there, I'd still be there.

"It'd be almost impossible to rescue you."

It took seven years to find the remains of Mr Hume's jet.

This is the daunting landscape that greets searchers for the still-missing plane VH-MDX.

Despite disappearing 45 years ago, dedicated searchers for the plane and missing passengers remain hopeful that the Barringtons will one day give up the secret of VH-MDX.

Follow Expanse: Disappearing in the Devil's Triangle on ABC listen to catch every episode.