Trespassing, petty theft, car crime – these data visualisations show what the Eagle helicopter gets up to, and where.

This story was first published on Stuff. 

You’re in bed when it begins: a low, indistinct bass murmur. The direction is uncertain, the location distant. But the murmur sharpens, crescendos, until it’s an overhead roar; a throbbing whop-whop-whop-whop-whop so cacophonous it seems the roof of the house might be sucked into the night.

The clangour drifts away, and then it’s back. Circling, fading and building, fading and building with each go-round. Finally, the spiral of noise dies away for the last time – for tonight, anyway.

Ask anyone in Auckland, and they’ll swear an oath that the police helicopter, known as Eagle, is above their house, all the time.

Flying just about the aviation floor of 1,000 feet for built-up areas, it is a literal eye in the sky, arrayed with gyro-stabilised binoculars, infra-red, night vision, and a battery of radio equipment to stay in contact with, and often direct, patrol cars on the ground.

Police consider it a vital piece of equipment. In the year to June 2022, it attended more than 7600 incidents, helping to locate an offender in two-thirds of cases.

With a top speed of nearly 300kmh, it can get from its base at Pikes Point on the Penrose foreshore to just about anywhere in Auckland in minutes. But the sound it makes in the process isn’t just annoying. Research has shown repeatedly that aviation noise – especially from low-flying aircraft at night – can disturb sleep and have serious health consequences that are magnified the longer and more frequently the noise persists.

The Eagle isn’t some shadowy, night-riding twin of Santa Claus – it can’t truly be everywhere, all at once. Stuff has collected and analysed four months of flight data to track where it goes and what it does.

Read more: A night aboard the most loathed aircraft in New Zealand

What the data shows

The Air Support Unit – to give the Eagle its proper name – has operated in Auckland since 1988, although it only became a round-the-clock operation in 2017. It was based at Mechanics Bay on the Waitematā waterfront for decades, before moving to its current base in 2019.

Police do not fly the helicopters themselves – the contract is held by Advanced Flight, which provides the civilian pilots and maintenance services. Each pilot is accompanied by two sworn ‘tactical officers’, who operate specialist equipment, communicate with police and other emergency services on the ground.

You won’t find the Eagle on standard aircraft tracking websites – most of these services block radar data for certain aircraft by request – but it’s possible to track all three aircraft that make up the Eagle fleet on ADS-B Exchange, a tracking website based on satellite navigation data.

Stuff collected flight data for the three Eagle helicopters between February and June. Over that period, the Eagle recorded an average of eight flight hours a day, including about three during ‘unsociable hours’, which Stuff has defined as anything between 9pm and 7am.

The data showed that the Eagle traversed nearly every part of Auckland (sometimes flying as far north as Northland or south to Waikato), but some areas emerged as clear hotspots.

The map below shows the flight tracks for the entire data set: the warmer the colour, the more frequently the Eagle was directly above. Red areas are places the helicopter visited most often.

The data has been smoothed to remove some “noise” – so single flight tracks, such as to west coast beaches to assist with rescues, tend not to show up.

Other than the base where the helicopter takes off and lands, there are two distinct high-flight areas, Ōtara and Manurewa, and some lesser hotspots scattered throughout west, central and south Auckland. The map also shows where the helicopter is not. The entire North Shore gets a mostly free pass, along with anything west of the Waitākere Ranges.

But the Eagle operates 24/7 and where it is depends very much on the time of day. The map below shows the difference in flight patterns between 3pm and 6pm, and 3am and 6am. You can zoom in to explore the maps.

But for some suburbs, especially those in the shaded box on this chart, the number of nights the Eagle was active in the area and how long it spent there on those nights were both high.

And when you group this data by deprivation level, it becomes clear that poorer neighbourhoods generally bear the brunt of Eagle helicopter activity, day and night.

Higher crime rates might account for some of the extra Eagle presence in these areas, but not all of it. Stuff matched crime volume to the time spent overhead in each suburb. In the wealthier half of neighbourhoods, there was a relatively strong pattern of flying minutes increasing as crime in the area increases.

In poorer neighbourhoods, the correlation was more tenuous. Not all of the most-visited areas have the highest crime levels and some poorer neighbourhoods with similar crime levels to wealthy ones were visited more frequently. Māngere (a decile 1 neighbourhood – one of the most deprived in the country) and Grey Lynn (decile 3) had similar crime volumes, but the Eagle spent more than twice as long above Māngere at night.

This pattern persists across the two groups: while the trend climbs at about the same rate (i.e., more crime, more Eagle presence), it starts from a higher base in poorer neighbourhoods. The grey-shaded areas show the 95% confidence levels for these trends, which only begin to overlap when the crime volume becomes extremely high.

Police repeatedly refused interview requests for this story. Asked about this apparent link between deprivation and how frequently the Eagle visits, Auckland City police district operations manager Vaughn Graham said (in a written response): “Eagle responds to a variety of critical incidents that require police attendance. It deploys where it’s needed.”

So what is it doing up there?

Late at night, somewhere in Takanini, a hatchback car has pulled up near a digger parked on a plot of undeveloped land. Through the infrared camera on board the Eagle, the heat of the car engine is a bright white glow. A small, luminescent figure emerges, trudging over to the digger clutching two square canisters.

If the helicopter hovering nearby is audible, the figure pays it no attention, focused on the task of lowering a hose into the digger’s diesel tank of the machinery and siphoning the contents.

The camera zooms out. Two other vehicles – patrol cars – are racing to the scene. The figure sees them and stumbles over clodded earth back to the hatchback only to be caught by an officer, pushed to the ground, and handcuffed.

“Comms, yeah, we got him in custody,” someone says over the radio. “No issues.”

A lot of the Eagle’s work appears to be chancing upon incidents like the diesel-siphoning. About 15% of incidents the Eagle assisted with were classed as either burglary and alarms, or suspicious activity and trespass.

Aviation expert and veteran helicopter crash inspector Tom McCready believes this sort of intervention is part of a vital service. “It’s an asset,” he says, “I’m surprised they don’t spend more time in other cities.”

“If there’s a police pursuit going on and the helicopter turns up overhead and ends that pursuit pretty quickly because you can track the car, that’s stopping some crazy going down the motorway at 160km an hour.”

The benefit doesn’t come cheaply. The three helicopters that make up the Air Support Unit’s fleet are Bell 429s, which chew through an estimated 290-340 litres of fuel an hour. At current prices for Jet A1 fuel, that would put the fuel costs for the last financial year at $2.8 million to $3.3m – about a quarter of the ASU’s $12.4m operating budget. Then there’s the carbon and carbon-equivalent emissions: between 2665 and 3156 tons – equivalent to a herd of up to 1100 dairy cows.

Noise annoys

But the Eagle’s cost can also be measured in decibels.

Official specifications for the Bell 429 give 88.9 decibels on take-off, 89.6 decibels when flying directly overhead, and 91.4 decibels landing. Those figures are measured from a distance of 150m (about 400 feet), so just under half the altitude the Eagle is usually flying at.

But there’s no doubt that it is still loud, even at 1000 feet or more. In 2020, a student in one of Wyatt Page’s undergraduate classes at Massey University, frustrated by the noise of the helicopter at night, decided to do some research. Over several months, she measured the volume of the Eagle helicopter when it flew over her neighbourhood, day and night. Directly overhead, the volume hit about 70dB. Further away, it peaked at about 55dB.

“Those levels are what you'd deem to be acceptable during daytime when you are awake,” says Page, an associate professor of acoustics and human health, “But they are not acceptable during the night.”

The World Health Organisation global community noise guidelines, issued in 1999, recommend that outdoor noise at night should not exceed an average of 45 decibels. The WHO updated its European guidelines in 2018, recommending that aircraft noise at night should not exceed an average of 40dB.

Research has shown that noise disturbance can have a huge impact on human health, especially through its effect on sleep. WHO and others have singled out aviation noise in particular. Whereas road noise tends to be a continuous, non-modulating sound, aircraft noise is “highly impulsive”, Page says. “[it’s] made worse with helicopters, because of their very nature – they come right overhead.”

David Welch, associate professor of audiology at the University of Auckland, says aircraft noise is also much harder to mitigate, because there’s little to block it from above. New Zealand’s notoriously flimsy housing doesn’t help. “The sound can go through them quite well. A corrugated iron roof won't really won't stop it very effectively.”

The links between noise, disturbed sleep, and the resulting health effects are rooted in our most ancient biology. Even during the deepest state of sleep, the primitive brain is listening to and processing sounds, Wyatt Page says, “with the aim of waking you up really, really quickly.”

Sudden, loud noises may not wake you up completely, but they do trip your fight-flight system, flooding the body with adrenaline and the stress hormone cortisol. “Your sleep becomes disturbed and fragmented,” Page says. “So what happens [is] ... you get certain people who will wake up feeling completely exhausted, they will feel frightened, and they don't know why.”

That stress can also be heightened if you are fully roused by a loud sound at night and then can’t get back to sleep – especially if the noise continues, Welch says. The reaction is cumulative: “It has this effect of making you feel annoyed, and it's a bit of a vicious cycle. So if you've been annoyed by it once, you're likely to be more annoyed next time.”

None of this is good for us. Lack of sleep and the associated stress has clear links with poorer mental, cardiovascular and metabolic health. “So something breaking your sleep on a regular basis is likely to have health impacts,” Welch says. “Things like body weight and diabetes.”

Society tends to underestimate the impact of noise, Welch says, and even what counts as ‘noise’.“If you're the person who's about to be murdered, the sound of the helicopter turning up wouldn't be noise at all, it would be an absolute delight. So I tend to prefer to think of sound as sound, and then noise if you don't want it. Where you draw the line between wanting and not wanting it is a tricky one.”

Both Welch and Page are concerned about the higher level of Eagle activity in more deprived neighbourhoods. “People living in poorer areas are probably more likely not to have double glazing, not to have air conditioning so have windows open if it's hot, all of that kind of thing – so they've got greater vulnerability to noise when they are exposed to it,” Welch says.

For Page, the concerns run even deeper: “Given that you've got a significant population density in there who are already adversely health-affected in terms of socio-economic factors, there's an argument to be weighted against [the benefits] of, is this really what you should be doing? Because you've just added a whole bunch of other stress elements in there that are likely to result in poor health outcomes for a group that's already got poor health outcomes.”

Who’s complaining – and who isn’t

Complaints about the Eagle helicopter are common, but they tend to be low-level grumblings among workmates, friends and on social media. The comments below, selected from a 2019 thread on the ‘Manurewa - Spread the News’ Facebook page, are typical of the breadth of online chatter.

Manurewa ward councillor Angela Dalton, who has lived in the area most of her life, takes comfort in hearing the Eagle overhead. “I lived alone in Weymouth and every time I heard Eagle I felt safe.” Operations requiring the helicopter to hover in place at length were “quite disruptive”, she says. “But what can you do? You’ve got to really trust that they’re using their best judgement on something like that.”

Ōtara ward councillor Alf Filipaina, a former police officer, has a theory about who is complaining about the helicopter – and it’s not people in his constituency. “The people that end up complaining the most are the ones in the affluent areas who don’t want to have any bloody noise when they sleep. They’ll say, ‘Oh, they disturbed my sleep’ – well, maybe it’s because they were trying to catch people to make sure you were sleeping safely.”

In the year to September, police received 227 complaints about the Eagle, of which 85 were from one complainant and 38 were from another. In his written response, police district operations manager Vaughn Graham said police “frequently” receive positive feedback about the helicopter.

“There is some noise generated while attending incidents which we acknowledge may cause some inconvenience to residents, particularly at night-time,” Graham said. “Where possible we take extra steps to minimise this inconvenience by flying neighbourly, where Eagle flies above the minimum height while moving between areas.”

The Eagle flies south

Auckland may be used to the sound of the Eagle, but what happens when you place it into a new community?

In early 2020, police got permission to trial use of the Eagle in Christchurch, sending one of the three helicopters south for five weeks. There, it found a fresh, and largely unreceptive, audience. RNZ reported that four weeks into the trial, there were nearly 40 official noise complaints laid, while city councillors reported fielding further, informal complaints from disgruntled residents.

The dataset for Christchurch is smaller, but features similar patterns to Auckland: a focus on generally low-deprivation neighbourhoods (Aranui, Bexley, Phillipstown, Linwood, Edgeware), though more well-heeled suburbs like Bryndwr and Waimairi Beach are not immune.

A hearts and minds campaign, which included delivering the ball at the start of a Crusaders match, failed to change public perception. At the end of the five weeks, the helicopter had attended 346 incidents, resulting in 210 arrests – but the trial did not become permanent.

Wellington also got a taste of the Eagle helicopter in early March this year, when it was dispatched to monitor the end days of the anti-mandate protests in the capital’s parliamentary precinct. Here, it had a specific purpose and so the pattern is very different from Auckland and Christchurch.

Broad use and acceptance of aerial surveillance should not make the Eagle helicopter immune to criticism, or change, Wyatt Page says.

He believes alternative technologies could fulfil some of the Eagle’s duties. “The surveillance side of it... I would have thought modern drones could do that just as effectively and with minimal noise generation,” he says. “And, when necessary, a helicopter comes in when you actually do need eyes and direct interaction.”

Is current drone technology up to the task, though? Central Otago-based company Landpro is one of several aerial surveying companies in New Zealand to introduce drones to its fleet in recent years. General manager and chief executive Jason Wills-Harvey says drones and other unmanned aerial vehicles (UAVs) are increasingly stable, can stay up longer than they used to, and are now capable of carrying multiple sensing instruments as miniaturisation makes everything smaller and lighter.

Wills-Harvey is not convinced, however, that drones could replace much of the work of a police helicopter. “We’re sensing. But what we’re not doing is pursuing.” Despite technological improvements, there is still a crucial difference between drones and manned aircraft, he says. “You are limited to an artificial view of the world, whereas there’s nothing that beats that live ability to make a decision on the spot or follow something.”

“As humans, we have a bit of an innate sense of what’s moving, what’s tracking… [With the drone camera] you miss some of those cues and those nuances.” He would never say never, though. “It’s definitely a ‘watch this space’ thing.”

Helicopter crash inspector Tom McCready doesn’t think the regulatory framework exists yet to operate drones for police purposes. “In helicopters and aeroplanes, we have all sorts of inspection criteria... But a lot of those drones don't.” That’s fine, he says, “until one flies apart over Auckland city and blades are coming through your house”.

Elsewhere, though, drones are being used to complement and even replace some policing work being carried out by helicopters. In 2015, Devon and Cornwall Police became the first police force in the UK to use drones in this way, monitoring public protests and large music, sporting and community events; and for missing person searches.

The drone team’s Sergeant Chris Linzey says the advantages include lower cost, lower noise impact, lower risk, and lower environmental impact. “Also, although drones have a limited flight time, as they are in close proximity to the ground crew, they can be quickly landed, have their batteries replaced, and be back in the air within just a few minutes.”

New Zealand police have, in fact, used drones – though not as a replacement for the Eagle. Most policing districts have a handful of small quad-copter drones, and a 2020 'proof of concept' report revealed that 121 drone flights were made over six months, mostly to survey and photograph car crashes, arsons, and other crimes.

The report concluded that for now, drones and other remote piloted aircraft systems (RPAS) were “not appropriate … for following high speed vehicles or tracking vehicle movements across multiple suburbs”. “In the medium term it is possible that larger fixed-wing RPAS may be able to undertake some of the tasks currently performed by Eagle, such as fleeing driver tracking.”

That was two years ago. When Stuff requested further information about any work to expand drone use, police provided only this brief response: “While police continues to explore the use of RPAS and the benefits this technology can bring to police, nothing that would specifically replace the tasks currently being carried out by the Air Support Unit is being considered at this time.”

For now, the Eagle rides.