7 ms·

This raises the very important question: is the fear of drones hitting planes completely overblown?

timthelion 11y ago
Given that the plane didn't have any trouble landing, and they hit birds all the time, I think that this might show that it's fine to hit a drone so long as it isn't sucked into the engine ;)
jpollock 11y ago
A canada goose can weigh from 7-14 lbs, ducks are much smaller (3.5lbs). We test planes against bird strike. However, birds don't have screws and batteries. Even with that, they bring down planes (AWE1549) There is a reason why airports are very, very careful about the vehicles that drive onto runways - FOD (foreign object damage) is a very real thing with very severe consequences when a plane is on approach and take-off.
- nkurz 11y ago
  However, birds don't have screws and batteries. This often gets mentioned (and is obviously true) but I'm doubtful (but not certain) that it makes that much difference. Things we think about as "soft" can be remarkably hard at high velocity. At 120 mph terminal velocity, water and concrete are similarly fatal: the incompressibility matters more than the hardness. This isn't to say that drone strikes are not an issue, only that I don't think they are significantly more of an issue than bird strikes. And birds can do a lot of damage at several hundred miles per hour. When you are hit by one, whether it's filled with bones or metal probably isn't the biggest concern.
  - molecule 11y ago
    > Things we think about as "soft" can be remarkably hard at high velocity. At 120 mph terminal velocity, water and concrete are similarly fatal: the incompressibility matters more than the hardness. And yet planes fly through clouds and rain at several hundred mph without issue, though the same wouldn't be said about flying through concrete... The issue here is relative hardness. Bone is relatively soft to titanium turbine blades, whereas screws and titanium turbine blades are in the same ballpark of hardness, so are catastrophic when they meet when spinning @ several thousand rpm...
    - deleted 11y ago
      [deleted]
  - jpollock 11y ago
    I don't have any experimental data, but my mental models pull up: 1) chucking a chicken bone into an insinkerator vs a penny. 2) a hunk of wood vs a hunk of wood with a nail through a wood chipper.
    - nkurz 11y ago
      Good examples, although I wonder if the relatively low speed makes a difference. The closest comparable that I can find is this: http://www.discovery.com/tv-shows/mythbusters/videos/chicken-gun-minimyth/ http://www.discovery.com/tv-shows/mythbusters/videos/chicken... They shoot a frozen versus thawed chicken out of an air cannon, and conclude that the impact force is identical for both. I'm pretty sure that adding some metal bits inside both chickens wouldn't make much difference. Density would make a big difference though. A basketball and a 1.75" lead ball have about the same mass, but the lead ball is going to do much more damage. But not because it's harder, but because it's dense and cohesive. I'd guess that a drone of comparable weight to a goose is going to have a greater impact area, even though some of the internal bits are much harder, and I'd guess this is going to be more important for the level of damage. Here's an article that supports that view that mass is the main factor: http://spectrum.ieee.org/automaton/robotics/drones/what-might-happen-if-airliner-hit-small-drone http://spectrum.ieee.org/automaton/robotics/drones/what-migh... Here's more discussion (which I haven't read yet, and which may well contradict my instinct): http://aviation.stackexchange.com/questions/26223/would-a-drone-strike-be-more-dangerous-than-a-bird-strike http://aviation.stackexchange.com/questions/26223/would-a-dr...
  - SideburnsOfDoom 11y ago
    > I'm doubtful (but not certain) that it makes that much difference. Things we think about as "soft" can be remarkably hard at high velocity ... I don't think they are significantly more of an issue than bird strikes. Unlike birds, batteries by definition have a lot of stored chemical energy in them (1). in fact we want to put as much energy in as little weight as possible. Violent disassembly by jet engine is not going to be a good combination with that. 1) https://www.google.com/search?q=hoverboard+catches+fire https://www.google.com/search?q=hoverboard+catches+fire https://www.google.com/search?q=laptop+catches+fire https://www.google.com/search?q=laptop+catches+fire https://www.google.com/search?q=phone+catches+fire https://www.google.com/search?q=phone+catches+fire
    - jsolson 11y ago
      A GE90 jet engine like those used in a Boeing 777 can have a power output up to 75 MW. Let's take a fairly beefy phone battery -- 2500 mAh at 3.7 volts. Converting those units into something more useful we get 9.25 Wh. If we assume the entire chemical energy of the battery is converted into heat instantaneously, that's 33.3 KJ or .04% of the energy output of the engine per second. It's possible that such a release could cause a catastrophic failure, but I have a hard time convincing myself that the battery poses a real risk.
      - seanp2k2 11y ago
        I think the concern is more about the resultant chemical reaction of lithium: https://m.youtube.com/watch?v=gisdMQbtJqk https://m.youtube.com/watch?v=gisdMQbtJqk than the total power of the pack. Also, larger hobby aircraft (e.g. A 700-size heli) will be using battery packs on the order of 2x packs of 6 cells ("6s" aka 6 3.7v cells in series @4000-5000+ mah), so it's more like ~200-300Wh. Again though, doesn't matter, because even something like a 3s pack @2200mah can make quite a scary fire. This is why there are barrels of salt water at RC flying fields. An overheating lipo goes in the tank before it melts everything with hell fire. Lipo fires are also why you can't take "hoverboards" on airplanes and why Amazon recalled them all: http://fusion.net/story/250086/airplane-hoverboard-ban-list/ http://fusion.net/story/250086/airplane-hoverboard-ban-list/ http://www.theverge.com/2016/1/21/10806816/amazon-hoverboards-refunds http://www.theverge.com/2016/1/21/10806816/amazon-hoverboard... Not sure how this is affected by being struck with a blade rotating at tens of thousands of RPMs at hundreds of miles per hour, but my point is that lipos are nasty beyond just their specific energy density :)
mc32 11y ago
Depends on the size and mass of the drone(s) and where they impact the plane (fuselage, window, turbines, etc.)
youngtaff 11y ago
Really hard to tell as we don't know enough about the incident. We don't know how large the drone was or what part of the aircraft it hit, for example what happens if one of the larger commercial drones gets ingested into the engine. If you want to an example of what even a bird can do to a plane see this picture - http://i.dailymail.co.uk/i/pix/2016/03/13/12/3226FEF600000578-3490044-image-m-21_1457871270219.jpg http://i.dailymail.co.uk/i/pix/2016/03/13/12/3226FEF60000057...
- smoyer 11y ago
  Many plane's "noses" are non-metallic so that the front-facing radar can be placed at the front of the aircraft. The ones I've seen are often fiberglass and are pretty weak. Breaking the plastic has very little impact on the ability of the aircraft to fly (compared to sucking a bird into an engine for instance). The USAir flight that ended up in the Hudson river was disabled by striking a flock of Canadian geese (https://en.wikipedia.org/wiki/Chesley_Sullenberger https://en.wikipedia.org/wiki/Chesley_Sullenberger)
  - x1798DE 11y ago
    I never noticed that that guy's name is "Chesley". I wonder how often he gets people thinking that's a typo for "Chelsey" or something of that nature.
  - sokoloff 11y ago
    There are a few good shots of the Delta BOS->SLC flight that made an emergency landing in Denver after encountering a hailstorm en route: http://www.dailymail.co.uk/news/article-3193043/Captain-s-cool-ice-call-tower-say-windshield-smashed-hail-needs-make-emergency-landing-baseball-sized-hail-cracked-windshield-damaged-nose.html http://www.dailymail.co.uk/news/article-3193043/Captain-s-co...
    - smoyer 11y ago
      Wow! ... I'm assuming the pilot had no radar and (almost?) no visibility. The glide path antennas and receivers must have been intact but I'm not sure I'd have the nerve to trust a blind, hands-off landing in a damaged aircraft!
robert_tweed 11y ago
I suppose intent matters too. A drone hitting a plane by mistake is apparently not unlike a bird strike, but how do you tell if a given drone has an explosive payload and is being aimed intentionally at an engine intake? It's only a matter of time. It makes sense to keep drones out of airport flightpaths. More sense than most of the post-911 security theatre, at least.
- NinjaViking 11y ago
  And do you think that somebody who packs his drone with C4 and aims it at passenger aircraft is going to care if he is violating a flightpath? Forbidden is not the same as impossible.
  - Avshalom 11y ago
    Right but 'it is illegal to put a drone in this airspace' gives us permission to shoot down anything in a flight path before impact, including the ones with C4.
    - arjie 11y ago
      What weapons does one use to shoot down a toy drone? You can't miss because on the other side, there are people, and if it hits, it shouldn't lead to dangerous parts all over the runway.
      - Avshalom 11y ago
        I think right now the idea is generally a bigger faster one with a net.
        arjie 11y ago
        That's a clever one. More importantly, it makes for an amusing picture.
        11y ago
melling 11y ago
Depends on how much C4 is attached to it. Seriously, you're talking about hundreds of lives and a few hundred million dollars of equipment. Why do you want to take the one in a million chance?
7952 11y ago
Surely aviation safety is based on trying to eliminate or mitigate low probability threats. It may be irrational to worry about drone hits for a single flight, but across all flights everywhere it could contribute to a crash. This is well understood in areas like radio transmission where you need a licence to use frequencies. It would be nice if everyone could transmit at high power on any frequency, but we don't have the systems to deal with that safely so their has to be enforced regulation.
- nkurz 11y ago
  Surely aviation safety is based on trying to eliminate or mitigate low probability threats. Yes, this is part of the equation, but you also need to balance your efforts based on the "risk landscape". Spending effort in one place generally means that less effort is spent elsewhere. I think it's a direct parallel to optimizing code: measure first, then optimize. Making your inner loop 10% faster will make a difference, while speeding up your logging won't. Or vice versa, if you have no single inner loop and your logging is abysmally slow: measure first! If it turns out that drones have 1000x the per impact likelihood of causing a fatality than impact with a birds, but that you are 100000x more likely to hit a bird than a drone, then are you better off spending your efforts on reducing the risk of drone impacts or bird impacts? Or (seemingly perversely) is it better just to tolerate both risks as they are if measurements suggest greater return by concentrating your efforts on improving airport security (or mental health checks for pilots, or testing English proficiency, or even traffic safety on the way to the airport). In this case, my guess would be that adding regulations to reduce the risk of accidental drone strikes by aircraft will have negligible returns, that common sense "don't fly near airport runways" is sufficient, and that there is lower hanging fruit that makes more sense to concentrate on. Normal Accidents by Charles Perrow is an excellent book if you are interested in this topic: https://en.wikipedia.org/wiki/Normal_Accidents https://en.wikipedia.org/wiki/Normal_Accidents
  - nmrm2 11y ago
    It's really not clear to me that there's a trade-off between bird impact prevention and drone prevention (or anything else you mention) for two reasons. First, effort allocation isn't really a compelling explanation -- most of the world just doesn't work in those types of zero-sum terms. Drones are sexy; just because government or industry is willing to fund research and development on safe drone-airplane regulations now doesn't mean it's willing to allocate those same resources to something else. Second, even when resource allocation is strictly zero-sum, the sorts of calculations you suggest are mostly a matter of qualitative speculation about the future. Which means you're mostly just going through a number crunching process that "confirms" your prior beliefs. > that common sense "don't fly near airport runways" is sufficient I think the major challenge that incidents like this one demonstrate is that it might no longer be sufficient to assume pilots have common sense.
bradleyjg 11y ago
Even if the fear of bringing down a plane and killing everyone on board is overblown, what about doing thousands of dollars worth of damage and delaying a whole bunch of people in their travel plans? And what's tradeoff to this risk? A bunch of hobbiests who want no regulation of thier hobby? Who's going to compensate the airlines and the delayed passengers?
- dwild 11y ago
  Have you read the article? There's regulations, what he was doing was illegal and as the article say, can be punished with up to 5 years in prison. You can add as much regulation as you want, it won't change that it can be done the same way it already been done.
  - bradleyjg 11y ago
    You can have mandatory registration. That seems to work pretty well for guns in the UK.
benhue 11y ago
From the sounds of it they just don't know and need to fund some research. "And pilots have also called for the DoT to fund tests into what would happen if a drone got sucked into an engine or crashed into a plane's windscreen." "Last month, the British Airline Pilots Association noted that while the threat of bird strikes had been well researched there was little data about how much damage a drone could cause a plane." I wonder if any other organisations have conducted any rigorous testing?
- JoeAltmaier 11y ago
  A British Airways spokesman said: "Our aircraft landed safely, was fully examined by our engineers and it was cleared to operate its next flight."
InclinedPlane 11y ago
A large drone hitting the engine of a jumbojet during takeoff or landing would be very bad news. Not only would it cost maybe millions of dollars of damage it might down the plane.

Given that the plane didn't have any trouble landing, and they hit birds all the time, I think that this might show that it's fine to hit a drone so long as it isn't sucked into the engine ;)

jpollock 11y ago

A canada goose can weigh from 7-14 lbs, ducks are much smaller (3.5lbs). We test planes against bird strike. However, birds don't have screws and batteries. Even with that, they bring down planes (AWE1549) There is a reason why airports are very, very careful about the vehicles that drive onto runways - FOD (foreign object damage) is a very real thing with very severe consequences when a plane is on approach and take-off.

nkurz 11y ago
However, birds don't have screws and batteries. This often gets mentioned (and is obviously true) but I'm doubtful (but not certain) that it makes that much difference. Things we think about as "soft" can be remarkably hard at high velocity. At 120 mph terminal velocity, water and concrete are similarly fatal: the incompressibility matters more than the hardness. This isn't to say that drone strikes are not an issue, only that I don't think they are significantly more of an issue than bird strikes. And birds can do a lot of damage at several hundred miles per hour. When you are hit by one, whether it's filled with bones or metal probably isn't the biggest concern.
- molecule 11y ago
  > Things we think about as "soft" can be remarkably hard at high velocity. At 120 mph terminal velocity, water and concrete are similarly fatal: the incompressibility matters more than the hardness. And yet planes fly through clouds and rain at several hundred mph without issue, though the same wouldn't be said about flying through concrete... The issue here is relative hardness. Bone is relatively soft to titanium turbine blades, whereas screws and titanium turbine blades are in the same ballpark of hardness, so are catastrophic when they meet when spinning @ several thousand rpm...
  - deleted 11y ago
    [deleted]
- jpollock 11y ago
  I don't have any experimental data, but my mental models pull up: 1) chucking a chicken bone into an insinkerator vs a penny. 2) a hunk of wood vs a hunk of wood with a nail through a wood chipper.
  - nkurz 11y ago
    Good examples, although I wonder if the relatively low speed makes a difference. The closest comparable that I can find is this: http://www.discovery.com/tv-shows/mythbusters/videos/chicken-gun-minimyth/ http://www.discovery.com/tv-shows/mythbusters/videos/chicken... They shoot a frozen versus thawed chicken out of an air cannon, and conclude that the impact force is identical for both. I'm pretty sure that adding some metal bits inside both chickens wouldn't make much difference. Density would make a big difference though. A basketball and a 1.75" lead ball have about the same mass, but the lead ball is going to do much more damage. But not because it's harder, but because it's dense and cohesive. I'd guess that a drone of comparable weight to a goose is going to have a greater impact area, even though some of the internal bits are much harder, and I'd guess this is going to be more important for the level of damage. Here's an article that supports that view that mass is the main factor: http://spectrum.ieee.org/automaton/robotics/drones/what-might-happen-if-airliner-hit-small-drone http://spectrum.ieee.org/automaton/robotics/drones/what-migh... Here's more discussion (which I haven't read yet, and which may well contradict my instinct): http://aviation.stackexchange.com/questions/26223/would-a-drone-strike-be-more-dangerous-than-a-bird-strike http://aviation.stackexchange.com/questions/26223/would-a-dr...
- SideburnsOfDoom 11y ago
  > I'm doubtful (but not certain) that it makes that much difference. Things we think about as "soft" can be remarkably hard at high velocity ... I don't think they are significantly more of an issue than bird strikes. Unlike birds, batteries by definition have a lot of stored chemical energy in them (1). in fact we want to put as much energy in as little weight as possible. Violent disassembly by jet engine is not going to be a good combination with that. 1) https://www.google.com/search?q=hoverboard+catches+fire https://www.google.com/search?q=hoverboard+catches+fire https://www.google.com/search?q=laptop+catches+fire https://www.google.com/search?q=laptop+catches+fire https://www.google.com/search?q=phone+catches+fire https://www.google.com/search?q=phone+catches+fire
  - jsolson 11y ago
    A GE90 jet engine like those used in a Boeing 777 can have a power output up to 75 MW. Let's take a fairly beefy phone battery -- 2500 mAh at 3.7 volts. Converting those units into something more useful we get 9.25 Wh. If we assume the entire chemical energy of the battery is converted into heat instantaneously, that's 33.3 KJ or .04% of the energy output of the engine per second. It's possible that such a release could cause a catastrophic failure, but I have a hard time convincing myself that the battery poses a real risk.
    - seanp2k2 11y ago
      I think the concern is more about the resultant chemical reaction of lithium: https://m.youtube.com/watch?v=gisdMQbtJqk https://m.youtube.com/watch?v=gisdMQbtJqk than the total power of the pack. Also, larger hobby aircraft (e.g. A 700-size heli) will be using battery packs on the order of 2x packs of 6 cells ("6s" aka 6 3.7v cells in series @4000-5000+ mah), so it's more like ~200-300Wh. Again though, doesn't matter, because even something like a 3s pack @2200mah can make quite a scary fire. This is why there are barrels of salt water at RC flying fields. An overheating lipo goes in the tank before it melts everything with hell fire. Lipo fires are also why you can't take "hoverboards" on airplanes and why Amazon recalled them all: http://fusion.net/story/250086/airplane-hoverboard-ban-list/ http://fusion.net/story/250086/airplane-hoverboard-ban-list/ http://www.theverge.com/2016/1/21/10806816/amazon-hoverboards-refunds http://www.theverge.com/2016/1/21/10806816/amazon-hoverboard... Not sure how this is affected by being struck with a blade rotating at tens of thousands of RPMs at hundreds of miles per hour, but my point is that lipos are nasty beyond just their specific energy density :)

mc32 11y ago

Depends on the size and mass of the drone(s) and where they impact the plane (fuselage, window, turbines, etc.)

youngtaff 11y ago

Really hard to tell as we don't know enough about the incident. We don't know how large the drone was or what part of the aircraft it hit, for example what happens if one of the larger commercial drones gets ingested into the engine. If you want to an example of what even a bird can do to a plane see this picture - http://i.dailymail.co.uk/i/pix/2016/03/13/12/3226FEF600000578-3490044-image-m-21_1457871270219.jpg http://i.dailymail.co.uk/i/pix/2016/03/13/12/3226FEF60000057...

smoyer 11y ago
Many plane's "noses" are non-metallic so that the front-facing radar can be placed at the front of the aircraft. The ones I've seen are often fiberglass and are pretty weak. Breaking the plastic has very little impact on the ability of the aircraft to fly (compared to sucking a bird into an engine for instance). The USAir flight that ended up in the Hudson river was disabled by striking a flock of Canadian geese (https://en.wikipedia.org/wiki/Chesley_Sullenberger https://en.wikipedia.org/wiki/Chesley_Sullenberger)
- x1798DE 11y ago
  I never noticed that that guy's name is "Chesley". I wonder how often he gets people thinking that's a typo for "Chelsey" or something of that nature.
- sokoloff 11y ago
  There are a few good shots of the Delta BOS->SLC flight that made an emergency landing in Denver after encountering a hailstorm en route: http://www.dailymail.co.uk/news/article-3193043/Captain-s-cool-ice-call-tower-say-windshield-smashed-hail-needs-make-emergency-landing-baseball-sized-hail-cracked-windshield-damaged-nose.html http://www.dailymail.co.uk/news/article-3193043/Captain-s-co...
  - smoyer 11y ago
    Wow! ... I'm assuming the pilot had no radar and (almost?) no visibility. The glide path antennas and receivers must have been intact but I'm not sure I'd have the nerve to trust a blind, hands-off landing in a damaged aircraft!

robert_tweed 11y ago

I suppose intent matters too. A drone hitting a plane by mistake is apparently not unlike a bird strike, but how do you tell if a given drone has an explosive payload and is being aimed intentionally at an engine intake? It's only a matter of time. It makes sense to keep drones out of airport flightpaths. More sense than most of the post-911 security theatre, at least.

NinjaViking 11y ago
And do you think that somebody who packs his drone with C4 and aims it at passenger aircraft is going to care if he is violating a flightpath? Forbidden is not the same as impossible.
- Avshalom 11y ago
  Right but 'it is illegal to put a drone in this airspace' gives us permission to shoot down anything in a flight path before impact, including the ones with C4.
  - arjie 11y ago
    What weapons does one use to shoot down a toy drone? You can't miss because on the other side, there are people, and if it hits, it shouldn't lead to dangerous parts all over the runway.
    - Avshalom 11y ago
      I think right now the idea is generally a bigger faster one with a net.
      - arjie 11y ago
        That's a clever one. More importantly, it makes for an amusing picture.
        11y ago

melling 11y ago

Depends on how much C4 is attached to it. Seriously, you're talking about hundreds of lives and a few hundred million dollars of equipment. Why do you want to take the one in a million chance?

7952 11y ago

Surely aviation safety is based on trying to eliminate or mitigate low probability threats. It may be irrational to worry about drone hits for a single flight, but across all flights everywhere it could contribute to a crash. This is well understood in areas like radio transmission where you need a licence to use frequencies. It would be nice if everyone could transmit at high power on any frequency, but we don't have the systems to deal with that safely so their has to be enforced regulation.

nkurz 11y ago
Surely aviation safety is based on trying to eliminate or mitigate low probability threats. Yes, this is part of the equation, but you also need to balance your efforts based on the "risk landscape". Spending effort in one place generally means that less effort is spent elsewhere. I think it's a direct parallel to optimizing code: measure first, then optimize. Making your inner loop 10% faster will make a difference, while speeding up your logging won't. Or vice versa, if you have no single inner loop and your logging is abysmally slow: measure first! If it turns out that drones have 1000x the per impact likelihood of causing a fatality than impact with a birds, but that you are 100000x more likely to hit a bird than a drone, then are you better off spending your efforts on reducing the risk of drone impacts or bird impacts? Or (seemingly perversely) is it better just to tolerate both risks as they are if measurements suggest greater return by concentrating your efforts on improving airport security (or mental health checks for pilots, or testing English proficiency, or even traffic safety on the way to the airport). In this case, my guess would be that adding regulations to reduce the risk of accidental drone strikes by aircraft will have negligible returns, that common sense "don't fly near airport runways" is sufficient, and that there is lower hanging fruit that makes more sense to concentrate on. Normal Accidents by Charles Perrow is an excellent book if you are interested in this topic: https://en.wikipedia.org/wiki/Normal_Accidents https://en.wikipedia.org/wiki/Normal_Accidents
- nmrm2 11y ago
  It's really not clear to me that there's a trade-off between bird impact prevention and drone prevention (or anything else you mention) for two reasons. First, effort allocation isn't really a compelling explanation -- most of the world just doesn't work in those types of zero-sum terms. Drones are sexy; just because government or industry is willing to fund research and development on safe drone-airplane regulations now doesn't mean it's willing to allocate those same resources to something else. Second, even when resource allocation is strictly zero-sum, the sorts of calculations you suggest are mostly a matter of qualitative speculation about the future. Which means you're mostly just going through a number crunching process that "confirms" your prior beliefs. > that common sense "don't fly near airport runways" is sufficient I think the major challenge that incidents like this one demonstrate is that it might no longer be sufficient to assume pilots have common sense.

bradleyjg 11y ago

Even if the fear of bringing down a plane and killing everyone on board is overblown, what about doing thousands of dollars worth of damage and delaying a whole bunch of people in their travel plans? And what's tradeoff to this risk? A bunch of hobbiests who want no regulation of thier hobby? Who's going to compensate the airlines and the delayed passengers?

dwild 11y ago
Have you read the article? There's regulations, what he was doing was illegal and as the article say, can be punished with up to 5 years in prison. You can add as much regulation as you want, it won't change that it can be done the same way it already been done.
- bradleyjg 11y ago
  You can have mandatory registration. That seems to work pretty well for guns in the UK.

benhue 11y ago

From the sounds of it they just don't know and need to fund some research. "And pilots have also called for the DoT to fund tests into what would happen if a drone got sucked into an engine or crashed into a plane's windscreen." "Last month, the British Airline Pilots Association noted that while the threat of bird strikes had been well researched there was little data about how much damage a drone could cause a plane." I wonder if any other organisations have conducted any rigorous testing?

JoeAltmaier 11y ago
A British Airways spokesman said: "Our aircraft landed safely, was fully examined by our engineers and it was cleared to operate its next flight."

InclinedPlane 11y ago

A large drone hitting the engine of a jumbojet during takeoff or landing would be very bad news. Not only would it cost maybe millions of dollars of damage it might down the plane.