Most of the time it is a spur of the moment reaction when a surge of adrenaline sparks deep, hidden instincts.

They call it the flight or fight response – a split-second reaction to a confrontation with danger.

For Sergeant David Key it was always more calculated. For on most days of his working life he knew he might have to risk his to save someone else's.

There is nothing in law that says a police officer must risk death to do the job and that is why bravery medals are awarded for going above and beyond the call of duty.

If a gunman starts firing cops are entitled to hide rather than become targets. So it is a source of wonder how often the fight, rather than the flight, response kicks in.

But Key's career was not about taking on gunmen – it was way more dangerous than that.

By the time Key came to policing he already had an intimate knowledge of danger, having served in the army from 1973 until 1984, working as a Leopard tank commander. He left the army on a Friday to join the police academy on the Monday. He expected to work in general duties but after four years moved to the Air Wing.

Since 1988 his main job has been to dangle from a bucking helicopter at the end of a wire no thicker than a drinking straw to rescue those who have run out of options.

In about 800 rescue missions he has been on the end of the thin metal wire about 400 times and the winch operator in about the same number of operations.

And always there has been one rule: Nothing justifies endangering the aircraft. If things go bad the officer on the end of the line is expendable and will be cut free.

He has been the last chance for yachties, boaties, lost bushwalkers, snowboarders, skiers, and surf fishermen trapped by rising tides.

Some have been grateful while others allowed their anxiety to get the better of them with bushwalkers grabbing him by the legs as he descended and those caught in water trying to use him as a floating stepladder, clambering to try to climb the rescue cord.

He has a dry message for those drawn towards water-based recreations: "Learn how to swim." He is amazed how many of his aqua-rescues involve non-swimmers.

He says a good rescuer needs to be a good actor. "No matter what you feel you can't show it. You keep smiling and talking and don't show any fear," he says.

The life and death career that will end when he retires in a few days took him from the middle of mountainous seas in the 1998 Sydney to Hobart Yacht Race to the inferno that was the 2009 Black Saturday Bush Fires.

During those February 7 fires the police helicopter was reporting to ground units when they received a call of four people caught in Kinglake West surrounded by exploding bush.

As he sat on the edge of the helicopter about to be wedged into the cauldron, he thought there was next to no chance of saving those below but knew they had to try. The burning hot air he gasped into his lungs was high-altitude thin as the fire drew the oxygen to feed the flames.

Below were Juliet Moore and three friends. They were in Coombs Road, where 11 people would perish in fires that would take 173 lives.

Somehow Key made it to the ground and placed Moore and her dog, Poncho, in the harness. However the fire was sucking the air from the helicopter's blades putting it in danger.

"I knew if they tried to winch us up I could bring the aircraft down."

As per the drill he was cut loose to save the helicopter even though the odds were he would die with the others.

Key stood there with four people, three horses, a dog and a bushfire of apocalyptic proportions bearing down.

He marshalled his team into three cars, one pulling a double horse float, with Poncho in with Moore and the last horse led by the reins out the window of the leading vehicle.

With trees crashing, winds roaring like jet engines and fire heading up the hill it was impossible to see a way out from the ground but this group still had eyes in the sky.

Leading Senior Constable Bryan Norman and Pilot Constable Warrick Young saw a sliver of a chance directing the team through down a track to the road before the front closed in again.

"It was a real team effort," says Key.

Moore says the first thing Key gave them was a belief they would survive. "Dave was amazing, he remained so calm.

"He risked his life just to come down from the helicopter. We have stayed friends ever since. To some extent he is my hero and he is just a nice, normal bloke as well."

Epic Sydney to Hobart rescue with waves six storeys high

It was the day after Boxing Day 1998 when the crew of the ageing police Dauphin twin-engined Air 491 received a call of multiple emergency beacons in Bass Strait.

Five yachts in the Sydney to Hobart yacht race had sent mayday messages with two reported sinking.

As they flew to Mallacoota the strength of the winds became apparent. The helicopter had a top speed of 240km/h but the gauge showed 420km/h.

As a tailwind it was an aid but when they had to fly back to land it proved to be potentially deadly.

Seattle resident John Campbell was no deep-water novice. He crewed in two previous Sydney to Hobarts but both times the yachts retired through gear failure.

This time he was on board the heavy-weather specialist Kingurra when it was swamped by a giant wave and rolled before righting itself.

Campbell was knocked out and washed away. Attached by a lifeline but temporarily lifeless he slipped out of his harness. By the time he regained his senses he had swept away dressed in a T-shirt, blue long johns with no life jacket.

But for a moment the winds that could kill him were on his side. The 120-kilometre trip that should have taken Air 491 30 minutes from shore took just 10.

When Key was winched into the near freezing water, he was hit by 25-metre waves (the size of a six-storey building) whipped by the 160km/h winds.

This wasn't a rolling swell but angry, irrational waves that came from any direction – powerful enough to crush an ocean-going yacht let alone a policeman hanging from a thread.

The helicopter above dragged him along the surface of three waves the size of small hills – because the remaining crew, pilot Darryl Jones and winch operator, Barry Barclay, could see their target in the water.

They tried to hover about 30 metres above Campbell but rogue waves meant they had to power up to stop being swallowed by the giant seas that peaked just two metres under the craft.

Key was blown off course and carrying 15 kilos of rescue gear, had no chance of swimming to Campbell. "When I hit the water I just kept going down," he says.

Instead they dragged him like a fishing lure 100 metres to Campbell who was just minutes from death.

"I just saw this bloodless face. I grabbed him and he was like an eel to touch, he was that cold," Key recalls.

Once harnessed they were winched up – that is until it stopped just a metre from the craft. Finally they were dragged in to safety – or that's what they thought.

But the wind that blew them there in record time now blocked their escape.

The 160km/h headwind meant the helicopter was moving at a mere 40km/h and was swallowing one litre of fuel every 10 seconds.

They were 32 kilometres from shore when the five-minute fuel alarm activated and the crew prepared to ditch.

"I thought we would be going for another swim," says Key.

Barclay and Key tied themselves to Campbell, freed the life raft and opened the rear door then tensed for the jump order.

At a height of 50 metres Jones waited for a wave peak to minimise the drop. He would then bring the helicopter down 50 metres away to protect the others from shrapnel when the rotors smashed on impact.

Just as the three-minute fuel warning sounded the wind died as the helicopter fell under the protection of the shore cliffs.

Nursing the craft Jones landed the Air 491 on the sand with the tanks virtually empty.

Rather than count their blessings Key and the crew were back in action and the next day rescued four sailors from the Midnight Special – the last plucked from the sea as the yacht sunk.

In later years Key went to visit Campbell in Seattle.

"He named his daughter Victoria and had three goldfish named Dave, Darryl and Barry after us."

Having turned 60 Dave will retire next week as the longest serving member of the Air Wing.

And how will the former thrill seeker fill his days? He intends to help his wife Vicki (a former police officer) help ex-cops suffering depression and stress.

He is also planning a cruise on the Queen Mary – a maritime vessel where the greatest adrenaline rush will come from a vigorous game of deck quoits and his biggest plunge will be on the roulette table.