When it comes to operating commercial drones, there are some challenges that every operator needs to address: gaining official permission to fly, knowing where you can safely operate, staying on top of the weather… a professional dronist is rarely bored. But one issue, globally at least, is rarely discussed: the very real problem of birds of prey attacking unmanned aircraft in flight.
To explore this subject further, Waypoint met up with two senseFly operators: Troy Fardell, the director of RPAS Australia and Andrew Chapman, the NSW director of Australian UAV. Based in Australia—home to the aggressive wedge-tailed eagle—these mapping pros know a thing or two about working near winged invaders. In this exclusive discussion they discuss how birds attack, how to go about avoiding them, plus they highlight one specific incident that speaks volumes about the eBee’s durability.
Drone strikes by birds are surprisingly common and occur in many parts of the world; not only in Australia but also parts of Africa, select US states, parts of Europe and in Latin America. The culprits are typically serious—and seriously large—birds of prey.
Down in Oz for example, wedge-tailed eagles are one of the most common UAV attackers. “They are magnificent birds, much larger than even the American bald eagles,” says Australian UAV’s Andrew Chapman. “Here in Australia, we usually see an eagle on one job in four when flying in rural areas, and our drone is aggressively attacked perhaps one job in six or eight.”
Our drone is aggressively attacked perhaps one job in six or eight
Troy Fardell of RPAS Australia claims this attack ratio can be even higher: “I would guess that 40% of the time I have to perform at least one eagle avoidance,” he says. “They are always there.”
Fardell and Chapman have identified several factors that seem to increase the likelihood of an attack. “As an operator you need to be alert every flight, all year round. But the chances increase whenever there is anything that makes it easy for these birds to fly and eat, such as lots of thermal air currents and docile food,” Fardell says.
Fardell also avoids flying near chicken farms, as these locations increase the chances of an attack. “I look for these locations when planning in the office,” he explains. “I’ll use Google Earth and look for long sheds in the area, especially the free range type. Not far from my town there are dozens of these farms and I’ve counted over a dozen wedgies circling above them.”
Fardell says that when he hovered his quadcopter above one of these farms, he instantly knew these were sites to avoid. “I could see from the quad’s video feed that a predictable, ‘docile’ eBee would be like a lamb to the slaughter—just like the hundreds of chickens in the paddocks.
Although certain months do host more attacks, Chapman notes, there remains no single period when an Australian operator’s drones are completely safe in the sky. “The eagles have a pretty broad breeding season, from April to September, which is when they are most aggressive. But you’ll note that we aren’t in that period of the year now [Fardell and Chapman spoke with Waypoint in February]. They still attack us all the time; they’re just more aggressive and tenacious in the breeding season.”
“The birds are basically everywhere in Australia with the exception of the cities,” he adds, “however, we have even been attacked right on the fringes of Sydney. The bird experts will tell you that’s unlikely, but it happens. The birds seem to come from tens of kilometres away when they spot us in the air.”
“We heard from someone who was attacked while flying a bright red turbine helicopter. If the brightest coloured and noisiest thing in the sky doesn’t scare them off, that should tell you something!”
Not only that, but eagles are not exactly nervous observers. “These birds are at the top of the food chain, they’ve never had a natural predator. People ask why we don’t paint the drones a certain colour, or have them make a noise, but we’ve consulted the bird experts and there’s nothing you can do like that—they simply aren’t afraid of anything. They even attack manned aircraft. We heard from someone who was attacked while flying a bright red turbine helicopter. If the brightest coloured and noisiest thing in the sky doesn’t scare them off, that should tell you something!”
So what does a bird of prey attacking a drone actually look like? How does the attack work? Chapman and Fardell say, firstly, they come out of nowhere.
“Like a Frenchman in a wingsuit they are on top of your eBee”
“A bird can be on your radar kilometres away, or what appears to be 1,000 feet high, but you look down at your eMotion screen for five seconds and—bang!— like a Frenchman in a wingsuit they are on top of your eBee,” Fardell says. “They have an incredible glide path speed. They can easily cover one or two kilometres in the time it takes the eBee to turn a waypoint and take its first photo.”
Eagles often work together in groups too, Fardell adds. “When they are active I generally see three or more working together, six at the most.” That gels with Chapman’s experience. “It is not uncommon that there are large groups of eagles. I’ve personally had nine in the air at one time,” he says.
“I’ve personally had nine [eagles] in the air at one time”
Fardell has identified two distinct methods of attack. “The first is to attack from behind at an oblique angle. I think they want to go in for the kill but they are curious, so they follow the drone for a while before speeding up. These attacks are reasonably easy to get away from if a bird is hunting alone, although that’s rare. Once you climb they cruise away and use thermals to get back to normal attack height. That’s the second type of attack: top down.”
Fardell says these aerial dives are by far the most serious threat. The eagles dive head first, but then in the last three metres or so of their dives they rotate in the air to lead instead with their talons. “Effectively, they are out of control,” he claims. “I have never seen the head involved in the attack. Their MO is to puncture, strangle, rip open the ‘packaging’ of their target and then try to eat it.”
“We’re talking wings folded and diving down at 150 kilometres an hour,” says Chapman. “I had a heart rate monitor on during one of these attacks and my HR topped out at 135 bpm—who needs exercise?”
“I had a heart rate monitor on during one of these attacks and my HR topped out at 135 bpm—who needs exercise?”
What thickens the plot further is that wedge-tail eagles are, surprisingly considering their size, quite the covert operators. “Even at six and a half kilograms, and with a two and a half metre wingspan, they can hide in the sky. Hunting and surprising is what they do best,” Chapman explains. “They also learn really fast. Once, I had our eBee RTK three hundred metres out, heading straight at me, on the last run of the day. And I was being hyper-vigilant, knowing that eagles would be around, so I had my stylus hovering over eMotion’s Fast Climb button while staring at the aircraft. But even then, there’s no relaxing. Even though I was staring straight at the drone, I didn’t see the eagle until it opened its wings in the last final grab for the plane. Thankfully, button pressed, the drone went vertical and my day ended well.”
One of RPAS Australia’s most recent attacks took place at Hanson Heidelberg Cement, in Kulnura, New South Wales.
“Our eBee was cruising at around 100 metres above ground level at the time of the attack, capturing images on its standard flight path,” Fardell recalls. “What appeared to have happened, from my vantage point a few hundred metres away, was that the bird was in its committed dive and no longer able to manoeuvre, throwing its talons out as I engaged the rapid climb function—so the eBee went up as the bird went down. Its talons seem to have simply collided with the end of the wing, rather than the eagle clutching it. This would explain why both the winglet and three inches of the aileron appear to have snapped off, not been torn off. I think it was a collision.”
“There was no discernible impact on the drone’s ability to fly. Sure, it was wobbling after it was hit, but it carried on climbing”
What surprised Fardell, even with his extensive experience, was that the eBee itself didn’t go down. “There was no discernible impact on the drone’s ability to fly. Sure, it was wobbled for a moment after it was hit, but it carried on climbing—at no point did it go down with the wedgie. There are some talon ‘picks’ in the body but these were purely glancing shots and not deep. In fact, they could have been from one of the other two birds having a go too!”
View the results of the attack on RPAS Australia’s eBee:
How to avoid an attack
With aerial threats so prevalent, Fardell and Chapman’s teams have developed a range of avoidance tactics, mostly centred around the bird-avoidance functions built into senseFly’s eMotion ground station software.
“I will literally point to the eagle’s position while watching the eBee”
“I will literally point to the eagle’s position while watching the eBee; having my arm out like this keeps me vigilant,” begins Fardell. “My right hand, meanwhile, hovers over eMotion’s Fast Climb button.”
This climbing function is key to avoiding attacks, Chapman confirms. “In eMotion’s early days, before this feature was added, we experienced bird damage much more frequently. After we took delivery of two of the first eBees in Australia we were the first to really push for the ‘fast climb’ function, so our thanks go to senseFly for listening to our concerns and adding this.”
Fardell has also decorated his drone, adding mirror finish decals to make it easier to identify at a distance.
“With my blinged-up eBee, I can see it up to 1.2 kilometres out, under suitable conditions,” he explains. As for the eagles, they’re less troublesome to identify. “I can see the wedgies more easily since they are more than three times bigger than the drone! There have even been moments when I couldn’t see the eBee, but due to the ‘flight mode’ of the wedgie, I knew it was time to climb.”
“… knowing when to climb is all about the timing”
In the case of several birds being in play, Fardell says a good tactic is to bring the drone a little closer to home.
“I bring the fight closer so I can judge separation better, because knowing when to climb is all about the timing!” Just not too close. “I made this mistake once. I brought the game home, right above the drone’s landing point—bad move! Now you have some well-rested eagles circling inside your home point but, since you’re having this dog fight near the end of a mission, your battery level might be low, and you can’t keep just aborting your landing each time an eagle upsets your final approach. So keep the fights outside of your home.”
Once the battle has been brought closer, it’s all about tiring out the predator. “The goal is to make the big birdy buggered!” Fardell states. “Tiring them out is actually easy if it’s just one bird, but if you have three, then they each take turns and get a rest before their next attack. I generally find they each have three attempts in them before they need a hot cup of thermal rest.”
You just need to learn how to get out of the blocks fast, pace yourself and know your enemy
Chapman sums up his advice thus: “It comes down to one factor: you need to keep a very, very close eye on the aircraft and be ready to initiate evasive manoeuvres at just the right moment. Too early and the eagle will adjust its course to climb up and meet you. Too late is, well… too late. There’s not much you can do to avoid being attacked, it’s about what you do when it happens.”
In Australia, Fardell concludes, “Everything wants to kill you and your eBee. This drone is unmatched at what it does and that’s making our clients really happy, but it’s a lover, not a fighter (although it’s also a pretty good runner). You just need to learn how to get out of the blocks fast, pace yourself and know your enemy.”
Top Bird Avoidance tips
- Pimp your drone—to see it better from afar
- Tire out the attacker—create your flight plan with enough battery time remaining for several plunges and climbs
- Use a VuFine HDMI monocular—to retain visual line of sight while viewing your ground station’s screen
- Buy the eBee’s optional radio tracker
- Bring the attack closer to improve your view—but not all the way home!
Are you a drone operator with experience of bird attacks? Share your story in the comments below…