Bill is based at the trust's Hamilton base, on Waikato Hospital grounds, with three full-time pilots - Grant Bremner (base manager/chief pilot), Loren Haisley and Dan Harcourt -- and another crewman, Simon Burrows.
The pilots will do 24-48 hours on call. That's fewer hours than the crewman because the pilots need to be as fresh as possible at the controls. They don't necessarily have to be at the base - they live just a 6-8 minute drive from base so if the pager goes off they're there in a flash.
"The crewmen do 96 hours on, 24 hours off, 72 hours on, 48 hours off," says Bill. "Ideally we're here most of the time and that's because of what our job entails; there are a lot of equipment, helicopter and personnel checks. We're not tied to the base but during the day we make it a habit to be available from here."
At the beginning of his shift, around 7am, Bill will go through the aircraft, checking the condition and type of fuel, checking latches and that doors open and close properly, that there's no damage to the external areas of the aircraft or the blades, stabilisers or tail. He'll go through all the medical equipment on board.
"We do that on a daily basis. Yesterday it could all be okay. Overnight the battery could have gone flat."
Then they check their equipment they take to jobs - bags full of wetsuits, flippers and masks for water rescues; helmets; harnesses.
"We're always making sure it's well maintained. People put these harnesses on and dangle them from a cable so we want to make sure it's in good condition and not damaged or exposed to the elements. We do that weekly, three-monthly and on a six-monthly basis we send it away to certified height lifting and testing equipment people."
Once the checks are done and if the pager hasn't gone off, there's often admin or emails to deal with.
"I have a lot of correspondence with the other bases, training, setting up training, setting up scenarios. We'll get days when the pager doesn't go off, but it's seldom we're sitting around doing nothing."
Occasionally if it's really quiet Bill might have a chance to head to the gym, although he's alert to needing to race back to base if the pager goes off.
"There are no set hours you have to do. You just have to be available for 96 hours. Simon, who lives in Hamilton, he just goes home.
"I live in Tauranga and I come over here for my shifts and live in the accommodation upstairs. I can go up there, turn the TV on. You're on call and ready to go but there's no expectation to be doing something all the time."
During the day, the guys have a response time of 10 minutes, from the time the pager goes off to the time they're airborne.
"That varies from 3-4 minutes to 10 minutes," says Bill. "We could be waiting for a [St John] medic off the road... they could be tied up at a job or they might have to drive from one side of town to the other to get here."
While they have a pool of St John Ambulance medics at their disposal, there are also HEMS doctors - helicopter emergency medical service doctors.
"It depends on the job we're going to... a road crash or someone hurt on a farm or an assault... we have different levels of qualification we can take. Ninety per cent of it is done with the paramedics. If they're tied up on another job we have access to the doctors that we can bring in."
If the job they're going to requires the winch, the crewman will attach that. If not, it stays off so they aren't wasting valuable fuel with the weight and drag from the winch.
Bill says sometimes the initial information that's been relayed from those on the scene via the ambulance service isn't quite accurate. The adrenalin is often pumping and they're focused on helping those injured; details can be exaggerated or hazy.
"But the gaps are generally filled in for us en route," says Bill.
"We've been called because it's potentially really bad, or the access in is difficult, so we're not just going out for a Sunday drive. But sometimes it's not always as bad as the information received."
When the pager goes off, the helicopter is pulled out of the hangar on its trailer system.
"We'll either wait for an ambulance crew to get here or we'll get airborne with our doctor on board and go to the job. We don't spend a lot of time on the ground talking about that job. We get airborne and start heading to the general location. They'll give us directions... say you're heading to SH1 at Cambridge. It's one big road, we don't know exactly where we're going but we know we're heading towards Cambridge. As we are doing starts and pre-take off, the ambulance service is picking up more and more information. They'll end up with a cross street, look on their map and give us a GPS location. We'll punch that into our avionics or GPS system and pretty much fly to that.
"We will get information from people on the ground... say, there's a big red barn next to five trees... land next to the house. We'll take that information but we won't necessarily land near there. We make that final decision. It's wind and weather dependent, how many people are down there, what obstacles are down there - power lines, for example. The 70-80km/h winds the helicopter creates can blow a lot of debris in all directions. We'll do a couple of circuits above what we're looking at."
Once they've got "skids on the ground", the helicopter attracts people like bees to honey. That's when Bill will get out and make sure no one is approaching the aircraft until he says it's safe to do so.
"This thing here - your stabiliser and your tail rotor - is head height. The exhaust is pumping out 700-odd-degrees." The last thing they need is for anyone to get too close to a spinning tail rotor or blasting heat.
"We'll get our medics and our doctor out to go to the scene to start their assessment while we shut down the machine. We may not need to shut down. The people on the scene might already have the patient ready to go, we load them on board and off we go."
As the job is progressing the crew is constantly making decisions, reassessing what needs to happen.
"We might have two or three patients and we figure out if one needs to go now and one can wait. We can transport two patients if we need to. Ideally the sickest goes on the stretcher. We have a backboard under the seats we can pull out and lie that across the seats as a stretcher."
No two jobs the helicopter goes to are the same. Retrievals from smaller hospital bases - Tokoroa, Te Kuiti, Taumarunui, New Plymouth, Whakatane, Tauranga, Rotorua - to Waikato, one of the country's largest tertiary hospitals, are common.
They help with searches... lost trampers, bodies in the river. And they attend countless accidents on the region's roads.
"You're exposed to what a lot of people wouldn't be able to look at or deal with but experience as an on-road paramedic... it's like any job, you get to the point where you deal with it at the time. Sometimes there are things that can affect you no matter how long or how short a time you've been in the job. You don't focus on it at the time. Afterwards we still have debriefs."
There isn't one job that stands out as being the worst for Bill but seeing kids injured gets to him. "It's their innocence," says Bill, who has four sons ranging from two to 19. "They haven't created this and they do get pretty banged up. And you almost have to be careful not to be making judgements on people because still today there are people who will carry their [baby]on their knee while they're travelling along. You will not hold onto a child in your arms in a crash.
"You have to put that aside. Everyone gets treated the same....the drunk driver that's crashed into the family...there's no discrepancy between the two. The person that's the sickest gets the treatment. There are times afterwards you stop and reflect and ask yourself why. But it will go on.
"You lose some people and for a variety of reasons and ages. It's not as hard to lose and 85 year old person in a medical event as opposed to a 16 year old in a car accident who's been hit by someone who's done something stupid."
As with other professions, there's black humour. A coping mechanism for the horrors they witness most days.
But Bill's 19 years on the road as a paramedic has served him well. He's used to the sights, sounds and smells that go hand in hand with chaos and carnage.
He started jumping on board the rescue helicopter as a road paramedic.
In time, it became apparent there was a need for more specialised skills on the helicopter - a winch operator, someone who could use night vision goggles, someone to train others who may be on board missions such as police, search and rescue personnel, the AOS.
"The role was developed initially in Auckland and it's come down to other operators such as us. I was looking for a bit of change in career so Philips Search and Rescue funded my training for all of my certificates to get me to a point where I could transition from an on-road paramedic to a crew chief, crew operator on the helicopter. It's taken close to six years to get to this point."
Just as a pilot couldn't just jump into any of the helicopters and fly them, nor can crewmen.
"The BK117, the Bell222, the Squirrel, the others we have at other bases...they're all helicopters, but they're all slightly different specifications so you need different ratings. In aviation it's about getting those hours up.
"I have a trainer either from Auckland or the Hawkes Bay that will put me through scenarios every three months. Because of the specialist work we do you have to be 100 per cent at what you do. There's no give or take."
As PSRT's chief trainer, Bill trains crewmen and other personnel at other bases around the North Island. His skills are so highly regarded that he's sought after around the world for his training abilities. He has training gigs lined up in South Africa, China and Canada. He also crews on helicopters that fight bush fires in Australia.
The work is intense. It can be draining. So why does Bill do it? His response comes in the form of a rescue story.
"We had five ladies - trampers - from Auckland. They'd come down the other side of Te Kuiti and gone on a tramp. There were 15 of them in the party, five of them decided they wanted to go elsewhere. They got lost, activated their emergency locator beacon and we got sent out. We find them there. It's dark, it's in a confined area. We land then we fly them back to their rendezvous point uninjured.
"There was nothing wrong with them, they were just lost. There's a bit of banter going on and I'm always asking for a cake, bring something in, do a bit of baking. These five ladies turned up one Sunday morning with this massive spread. It's quite humbling. For them it was a huge deal. For us it was one of the least taxing missions. But they were just over the moon.
"They come back and can't thank you enough. And that makes you stop and think that you don't want to become too clinical. The people that you're dealing with ... they're someone's daughter, son, brother, wife. I get huge job satisfaction from that."
Given the intensity of the role at times, crew could be forgiven for getting burnt out and leaving the industry.
But Bill says the opposite is mostly true.
"There are a couple of medics - Barry Watkins and Bruce Kerr in Auckland. Bruce has just turned 70 and he's still doing it. And Barry, he's just basically retired because his body's not what it used to be. I think he's late 60s."
Those bases that operate with a volunteer crew sometimes find the task taxing.
"We try to work it so there are four per base and they have one week on and three weeks off. But some of them find being away from family difficult... getting called away at dinner time.
"When I was doing it, if we were going out we'd always take two cars so I could dash away if I had to.
"There are a couple of guys in Taupo who've been volunteers for 18 years. Two guys in Tauranga have just made the 18 month mark and decided they can't keep doing it. But I don't know of any one who can't do the job because of what they're exposed to.
"In this role here you've already got that experience behind you. You won't have anyone working on a helicopter with less than five or 10 years experience as a senior medic on-road."
Bill says there are some medics who want to get on to the helicopters because it's seen as "a bit of a glory job". The work he and fellow rescue helicopter crews do is immortalised on the television show Rescue 1, but Bill is quick to play down the glorification.
"We'll fly into a scene and there have been ambulances on the road and four or five patients and vehicles smashed 200 metres across the road and they've been going flat out. We land and people go 'oh the helicopter's here'. We load them in the back, we fly off, ya know... we don't even get dirty.
"People call us heroes of the sky and angels.. stuff like that. For me, I love my job so it doesn't matter to me if someone thinks I'm an angel or an idiot. I'm there to do the job and I want to make a difference. As is everyone involved in the emergency services to different extents."
While horrific road accidents will make the news, other missions that Bill crews on do not.
"There was a little one who came to the open day with his mum, a little cardiac baby. We transported him. To her it was the worst day of her life. She's given birth to this little boy, he was premature and his heart wasn't working properly and she had to hand him over to us - complete strangers.
"We pop him into this incubator in a big steel box and then in the helicopter and take off. You don't read about those jobs but that mother's gone through just as much grief and worry. And then they bring these kids back in and the kids are incredible to talk to...the adversity they've been through. You go 'my life is pretty easy really... I struggled to get to the gym today and this poor young fella has just started to walk'. You think I have had an affect on that life.
"They come through with huge smiles on their faces. They know they're alive because they've beaten the odds."
And it's seeing the smiles on the faces of people Bill's helped rescue that will ensure he doesn't throw the towel in anytime time soon. Infact, it might just be that he follows in Bruce Kerr's shoes and he'll still be doing the job when he's 70.