3D Robotics

3689635554?profile=originalA very good piece in IEEE Spectrum reports on the research on the risks small/med bird strikes in aviation. Short conclusion: it rarely causes a fatal accident -- indeed, there may be no record of one with standard aircraft.

Last December, a group of investors called the UAS America Fund petitioned the Federal Aviation Administration to create a set of rules that would govern “micro unmanned aircraft.” The basic idea is that these microdrones—defined as being 3 pounds (1.4 kilograms) and under—pose much less of a hazard than many of the model aircraft now flying in the United States, which can weigh as much as 55 pounds (25 kilograms). So it makes no sense to regulate all “small unmanned aircraft systems,” as the FAA likes to call them, the same way, which might well be what the U.S. government has in store.

While the rules the investment group has drafted make for an interesting read, what I found particularly eye-opening was an attached report from Exponent, a failure-analysis consultancy. That report tries to quantify the threat such microdrones—a category that includes popular models like the DJI Phantom and 3DR Iris—would pose to full-scale aircraft using data the FAA has collected on collisions with birds.

Bird strikes, as these incidents are called, have plagued aviation since its inception. And that’s not surprising. There are a lot of birds—10 billion in the United States, according to Exponent—and some of them get quite large. You only have to think back to the dramatic goose-caused ditching of US Airways Flight 1549 in the Hudson River in 2009 to realize that birds are more than a theoretical threat.

Fortunately, the aviation industry and regulators have found ways to reduce these natural hazards. For example, airports use a type of grass that geese don’t particularly like to eat. And aircraft are subject to various regulations about how robust they have to be in the face of something like a goose flying into the blades of a jet turbine.

That’s not to say that the aviation industry has this problem licked. By no means. Bird strikes are a very real threat to aviators and their passengers. But as Exponent’s report aptly shows, the severity of the danger scales with the size of the bird, which only makes sense.

US Airways Flight 1549, for example, suffered crippling damage to its engines on takeoff after it ran into a flock of Canadian geese, which can weigh as much as 18 pounds (8 kilograms). And there are plenty of other examples of other large birds—pelicans, vultures, cranes, and so forth—creating similar havoc in the air, sometimes with tragic results.

But Exponent’s examination of the FAA’s wildlife-strike database reveals something interesting. The smaller classes of birds documented there (those the size of sparrows or gulls) rarely cause aviation fatalities. Indeed, the FAA’s database, which records incidents back to 1990, lists only three fatal accidents attributed to small or medium-size birds, according to the Exponent report. And a deeper examination of those three accidents casts considerable doubt on whether a collision with smallish birds really caused two of the three.

The earliest of these three fatal accidents took place in 1994. According to the ensuing report of the National Transportation Safety Board, the helicopter involved crashed not because of an actual collision with one or more birds, but because the pilot took aggressive evasive actions to avoid a flock of birds and inadvertently overstressed his aircraft. The rotor then struck the tail boom, and the helicopter dropped out of the sky.

The second of the three fatal incidents took place in 1998. Here it was a fixed-wing aircraft involved. Two people flying in the plane died. Thankfully, the plane killed no one on the ground, despite crashing into the roof of New Jersey condo. The type of bird responsible for this tragedy remains unknown. Actually, investigators are not at all sure there really was a bird involved.

The evidence for some sort of avian component to this accident consists of one witness’s report that she saw a large number of birds flying in the area. There was some enigmatic damage to a portion of the plane’s horizontal stabilizer, but no bird feathers, blood, or remains were found on the plane. Swabbing by ornithologists called in to examine the wreckage failed to turn up bird DNA. And after reviewing the relevant photos, the Air Force’s Bird/Wildlife Aircraft Strike Hazard Team, like the ornithologists, demurred in attributing the damage to a bird strike.

This leaves only one more fatal accident in the FAA database that has been ascribed to a small or medium-size bird. This one, the crash of a helicopter ferrying oil-field workers to offshore platforms in the Gulf of Mexico, took place in 2009. Two pilots and six of the seven passengers died.

Although there was no obvious evidence of a bird strike on initial inspection of the wreckage, swabs sent to the Smithsonian Institution’s feather-identification lab turned up DNA from a female red-tailed hawk. Such birds generally weigh a kilogram or perhaps slightly more (say, 2 to 3 pounds), so it’s surprising at least to me that a collision with something this small would be enough to take down a helicopter. The National Transportation Safety Boards summary of this accident hints at a complicating factor, however: a windshield that might not have been up to par.

You see, the company running this helicopter-ferry service had had issues with the stock glass windshields on its helicopters delaminating, so they replaced them with aftermarket acrylic windshields, which according to the NTSB report hadn’t been tested for their resistance to bird strikes. And an identical acrylic windshield installed in a different helicopter allowed a colliding gull to pass right through it three years earlier. But that incident hadn’t caused this obviously fragile windshield design to be removed from service generally.

So some bird strikes can be darn dangerous. But despite that fact, and despite the enormous numbers of these creatures zooming around the sky, only very rarely do collisions with smaller varieties of birds kill people. Less serious accidents aren’t, however, uncommon.

According to the Exponent study, the FAA’s database has a total of 150,000 entries, and out of those, there are 13,906 reports that note damage from small or medium birds. And there are 227 incidents noted that had non-fatal injuries. Of course, we have no idea how many inconsequential bird strikes go unreported. So it’s hard to judge odds of a bird strike being significant from these numbers.

What’s more, if you only consider small- and medium-size bird strikes that occurred in places where microdrones would be likely allowed (below 400 feet altitude and more than 5 miles from an airport), the results don’t look at all alarming: the Exponent report says there have been zero fatalities and at most a handful of accidents with injuries.

This is all to say that drones of about a kilogram or so in mass would likely pose little danger, so long as people flew them away from where full-size aircraft are allowed to fly. (In the United States, piloted aircraft are supposed to fly above either 500 feet or 1000 feet above ground level, depending on how densely the area is populated.)

So why not let drones of a size that pose comparatively little danger fly without imposing onerous restrictions on them? Any flub-ups that bring a full-sized aircraft and a microdrone to the same area and altitude are bound to be no more worrisome than the situation equivalently sized birds have long put aviators in. And we’ve somehow put up with that.

 

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  • How anyone could believe a goose caused the damage shown in the pictures is beyond me.  An armor plated goose shot out of a cannon maybe.

    If you read the NTSB report both planes were equipped with collision avoidance systems - and they still hit each other.

    A couple witnesses on the ground said they saw it happen quite clearly.  The report doesn't state it, but I expect they HEARD the two planes quite clearly which is why they saw it.  At least one pilot didn't see anything until the last second even though he was getting a collision alert.  What the other pilot saw we don't know because he's dead. 

    This does show where the sense and avoid problem is.  All pilots really know this, but some don't want to admit it.  Visual sense and avoid from the cockpit is the weak safety link in aviation today.  Someone flying his model aircraft near the ground has much, much better situational awareness.

  • Michael Clapp

    LiPo for RC usage NOT have hardness of the metal.
    It does not contain any large solid hard metal components.

     

    In your argument you are constantly MIXED different cases and differen objects.

    Your opinions are very subjective and emotional.

    The result of the collision is very dependent on the combination of all the factors - speed , construction element, mass and consistency of object.
    A propos
    https://www.youtube.com/watch?v=lp7uLTNiGrQ
    https://www.youtube.com/watch?v=_jfXX7qppbc

    =)

  • Michael, I am hardly a fearless (or careless) drone pilot, and care deeply about this.  As a motorcycle rider, I know how it feels when others drive without care.

    However, as I said, the risk lies somewhere between what manned aviators fear and what this IEEE report states.

    IMO, if we can keep drones below 400 feet and away from airports, the risk to manned aviation is very small. Certainly less than the pilots operating below 400 feet far away from airports are already putting themselves in, *by their choice*.

  • Rob,

    I grabbed the first image I saw of many. The crow was very real and spend any time on an pilot's forum and you'll see plenty of birdstrike examples or just google it for images. I can dig further and find every example if you like but I'm not sure it will convince anyone here that it's an issue that shouldn't be dismissed by some fearless drone pilot flying from the safety of the ground. Go fly in your own plane and see how you feel about surprises in the air.

  • While I agree the risks are likely overstated, it's unscientific to assume that the only determining factor in a collision is mass (i.e. a 3 pound bird poses the same risks as a 3 pound drone).  The fracture toughness of metal components and LiPo batteries, compared to organic materials, changes the impact mechanics, and poses a significantly greater risk to turbine blades and windshields (for example).

    Agree 100% Guy!

    I think the truth about the risk posed by drones lies somewhere between here, and there.  More dangerous than birds, pound for pound, but less dangerous than all the other things going on in manned aviation already.   We need to find out where it really is.  Model aircraft have been flying to 100 years, and there still hasn't been a mid-air collision.  I think if commercial and recreational flying can simply be restricted to below 400ft and away from airports, we'll be fine.

  • Technicus I realize your typing skills are texting challenged but apparently your reading skills are as well. There are no web pictures of the crow hit because it was in early 2000 in a Metroliner out of Concord (CCR). It was 24K to fix then. Probably more now. Just google aircraft bird strikes and you'll see quite a few.

  • Does just getting hurt count or does somebody have to get killed? A friend hit a crow taking off out of Concord and the repair was $24K. There are numerous instances of hawks going through the Plexiglas windshields of airplanes and the fragments injuring pilots. Hit a goose (agreeably a heavier bird) with a light plane and it can be a big problem.

    http://www.vansairforce.com/community/showthread.php?p=220186

    My guess is the plane was a total. Just because drones haven't been around that long so the exposure has been shorter. 

    Michael, please read the thread before linking it.  You just perpetuated the myth about bird strike damage.  I guess this one has been circulating for a while already.  Just the 3rd post down corrects the facts.  The damage to the Beech Baron was caused by a Cessna, not a goose!

    This is what's wrong with the internet.  This is why we can't have nice things. ;)

    (Just teasing, in case it's not clear.  But seriously, I wish people would fact check more before reposting.)

    Bird strike photograph - Page 2 - VAF Forums
    Bird strike photograph Close Calls / Lessons Learned
  • Michael Clapp
    "Single crow twelve inches from the right wing root about 300 ft off the ground on takeoff. You're going 80 mph or faster with limited lower forward visibility due to the climb and things you have to pay attention to. You don't even see it most of the time and if you do it's barely before it hits."


    Big CROWD very goоd visible.

    If u talk bout photo u linked - its NOT allowed get such damage from crow on 80mph. U  make unreal fantasy.

    Autor described goose - weight more 5-10 times bigger
    "This is a Beech Baron that was traveling at 185 knots when it hit a goose."
    But damage area too big for any type of birds, except ostrich,
    And finally, from comments


    "Phil that damage was not done by a goose but a similar beast, Cessna 180K.
    Avweb news: http://www.avweb.com/eletter/archive...ll.html#186939
    NTSB factual: http://ntsb.gov/ntsb/GenPDF.asp?id=LAX04FA095A&rpt=fa

    lol. =)

  • Do something stupid with a paper plane and u stay alive and healthy. Because paperplane or small drone NOT aircraft. =)

  • Do something stupid with a manned aircraft and the results can be brutal and final for you. Do something stupid with a drone and chances are somebody else pays the price. There are a lot more barriers to entry as well. Especially with the DJ swarm that landed at Christmas for anyone with a credit card.

    To be a threat to others the UAV by nature has to be operating some distance away from the operator. Unless it's through FPV I can't even tell front from back at 100 ft. At 400 ft. your see and avoid is non-existent without FPV. And it's really not that easy to spot other things flying while you're flying anyway. The average lay person has no chance and even if your eyes are trained it's difficult. Listen to ATC around an airport on a nice day and you'll hear a lot of call outs and lot of "Looking" from pilots trying to figure out where other full-sized aircraft are.

    The FAA's Congressional mandate isn't encourage aviation. It's aviation safety and it came into being after several major accidents in the 50's. It's been a long time since they encouraged aviation and while it would be nice they are always going to fall back on safety. I'm not saying I disagree that they are hopelessly slow at coming up with reasonable standards but it's an entirely new arena for them and they are poorly equipped to deal with the public. They don't even really like general aviation for the most part.

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