Exploding wind turbine


This is something that will cause a few heart palpitations at UMM — we’ve begun this big push towards being a green university, exploring alternative energy and conservation, and we are very proud of our campus wind turbine, with plans to build more. This story of a wind turbine that lost a rotor and exploded in a storm is a wee bit unsettling.

However, I’ve never seen our turbine blades move that fast, even in the high winds we sometimes get around here, so I suspect we must be working with a newer and I hope better design here, unlike the ten-year old turbine in the video.

Oh, and our turbine is off campus, and if it did blow like this one, at worst it might kill a few cows.

(via Page 3.14)

Comments

  1. Bo Dixen Pedersen says

    That was actually in a storm in Denmark a few days ago and now they are contemplating safeguards.

    First time something like that actually made the head news, but maybe because of the footage, but it must be a pretty rare thing anyway considering how much energy we derive from wind power and therefore the number of windturbines compared to our small nation size (even though we want a lot more).

    However offshore really big wind turbines seems to be the future, but people with property near those shores obviously thinks it destroys the view and property value.

  2. student_b says

    AFAIK (and I’m too lazy to source it) that particular turbine had a defect in it’s mechanism which should prevent the blades from spinning that fast. Either the brakes or the mechanism to put it sideways to the wind.

    Also it looks like (based on the fact that there are two different videos of it) that it was known in advance that something will happen, ie. the defect was known.

    Still, looks pretty cool. :)

    Btw. for safety. There are about 35’000 wind turbines in that region and it’s the first time I’ve heard about something like this happening. So I would think they’re pretty safe.

  3. BlueIndependent says

    Ya, never seen one cruising like that. Hard to tell but it looks like one of the blades his the column, and the rest was physics after that. The crop of the video makes this turbine seem small, but then you see the cars next to the remaining base at the end, and then the scope of what occurred becomes real. I would have thought they’d have some type of fan speed protection in place in the turbine itself.

  4. The Backpacker says

    Michelle: Not resently, I am just going on anicdote. People taste like chicken, cow tastes better than chicked thus cow tastes better than people.

  5. says

    Wow, that shattering was rather shocking.

    However offshore really big wind turbines seems to be the future, but people with property near those shores obviously thinks it destroys the view and property value.

    Welcome to MA.

  6. Ollie says

    Those things are often designed to operate such that the tips of the blades are traveling at near the speed of sound. Pretty amazing stuff.

  7. True Bob says

    Wind turbines are supposed to control the pitch of the blades. The idea is to keep the prop’s axle rotating at a constant speed. With high winds, the blades should have been feathered, i.e. aligned with the wind. While this is kind of an odd example, it illustrates the concept nicely:

    http://www.kiwiprops.co.nz/

  8. Matt H says

    The Hwy 580 corridor through the Altamont Pass from the SF Bay Area to the Central Valley is lined with various turbines, many of which have been idled due to concerns about their effects on birds. Still, they’re amazing to watch – they generate a fair amount of power, and the different forms (some are experimental, like vertical turbines) provide food for thought.

  9. Matt J says

    The brakes on this turbine failed, it shouldn’t have been going that fast. There were actually 2 technicians inside it when the brakes failed. They got out in a hurry (leaving their van behind).

  10. Nentuaby says

    TheBackpacker @ #8:

    Actually, people are one of the few things that don’t taste like chicken… We, evidently, taste like pork. (Hence the “long pig” euphemism, I suppose.) It seems like a strange thing to have data on, but aside from the rare interviews with cannibals there seems to be some data backing it as objectively true. For instance, an operator who puts his hand into the beam of a system which optically identifies food by its chemical properties will generally be diagnosed as some type of pig product:

    http://archive.southcoasttoday.com/daily/09-06/09-03-06/03business.htm

  11. says

    TheBackpacker @ #8, Nentuaby @ #15:

    My brother will tell anyone who’ll listen (and also those who won’t listen) that human flesh tastes like pork. He was torching some steel at his summer job and some slag flew up and burned his arm. He sucked the wound and it tasted like pork.

    Then he got hungry.

  12. silence says

    Big storms do destroy turbines. I recall seeing a whole field full of shattered turbines at the south end of the big island of Hawaii.

  13. True Bob says

    After looking some more…

    Tip speed ratio is the ration of tip speed to oncoming wind speed. Optimal for high efficiency wind turbines is around 6 or 7. So you’re talking 100kt winds to get around M1. This kind of wind speed would subject the tower to very high structural loads, as the tower supports the prop. They look to spin under about 20 rpm.

    Also, I was mistaken about wind turbines (I blame society). My recollection was outdated. Modern turbines allow for varying rotational speeds.

  14. Ginger Yellow says

    “However offshore really big wind turbines seems to be the future, but people with property near those shores obviously thinks it destroys the view and property value.”

    I’d be happy to snap up one of those properties at a low, low price. I think wind farms look majestic.

  15. says

    A guy I work with knows quite a bit about wind turbines (he used to work for that department of the power company, and currently only works part time at my work, as he’s spending the rest of his time developing a new wind turbine design). Anyway, his guess was that the turbine in the video was about 150 ft. diameter, and that those typically spin less than 50 rpm. I forget exactly what speed he told me, I just remember it being slow enough that you should be able to watch the blades. Even running through a back of the envelope calculation on my own, on a sea level standard day, a tip speed of Mach 1 for a 150′ diameter corresponds to 142 rpm – not all that fast.

    Anyway, Matt J already pointed out that the brake failed on that turbine, explaining how it got to spinning out of control. My coworker also speculates that the collective pitch control might have failed, too. (He told me that the 3 ways these turbines typically control rpm is 1) pitch, 2) current – even adding variable resistors that can turn a lot of energy into heat to handle gusts when it’s too much for the generator, and 3) the mechanical brake to stop it from overspeeding. He also added that some designs can even turn the whole thing parallel to the wind, but I’m not sure if this one could.)

  16. says

    #20: Seconded. Wind turbines are far and away more attractive than coal, natural gas, or nuclear plants, especially when you factor in emissions. And yet you rarely (if ever) hear about coal plant proposals being turned down due to aesthetics.

    Oh, irony.

  17. Richard Eis says

    Exploding wind turbine or exploding nuclear plant…hmmm I know what i would prefer.

    Anyway, i think they are cool, i don’t see what people are fussing about the view. I’d watch them things spinning all day over staring at two cows on a hill.

  18. True Bob says

    142 rpm – not all that fast

    Only three times the target speed. Wait, that is fast – for a wind turbine.

  19. Jim Thomerson says

    I see wind turbine blades traveling down the highway on extended 18-wheelers. They are huge. I understand they are of composite construction: balsa wood, fiberglass, and carbon fiber. Demand for balsa for wind turbine blades is being blamed for a shortage of balsa for its intended purpose–building model airplanes.

  20. True Bob says

    Coal? Sickening. Now they get coal by cutting mountain tops off mand dumping them in valleys. Where’s your aesthetics now? Oh, right, it’s only poor coal miners that live there. Gotta preserve those beach front vistas for the rich. eyeroll

  21. says

    Ben wrote: “And yet you rarely (if ever) hear about coal plant proposals being turned down due to aesthetics.”

    Furthermore, I’m willing to bet that if a coastal city got rid of its factories and power plants along the waterline and installed offshore wind turbines instead, the shore property would increase in value tremendously.

  22. Robert Thille says

    But what about all the students out in the field, tipping cows? On the other hand, as an aid to selection, I think it would be marvelous…if you’re too stupid to move away from a turbine like that in a big storm, you’re too stupid to breed.

  23. sita says

    According to what i’ve heard, a lot of people object to the noise of wind turbines as much or more than the appearance.

  24. B. Dewhirst says

    Bladeout is a failure mode for jet engines as well, and yet we still fly.

    These are manageable engineering difficulties.

  25. Bill Dauphin says

    Yeah well cows are people too. Just a dumber and tastier type of people.

    The mind reels wondering how you might have come to know that people are less tasty than cows!

  26. says

    True Bob, here’s what I meant when I said that 142 rpm wasn’t all that fast. Since I don’t know exactly how fast wind turbines spin, I was trying to put an upper limit on it. My coworker told me yesterday, but he’s not in today. I just remember it being slow enough that you could see the blade turning, without it looking like a blur. I know for a fact that wind turbine blades are designed to operate with tip speeds below the speed of sound, so I was just throwing that out as an upper limit. The wind turbine in that video was spinning a lot faster than it should have been.

  27. silence says

    Ben: Coal plants are usually located where poor people are. Wind turbines are often located where rich people are. That makes all the difference when it comes to aesthetics.

  28. True Bob says

    Gotcha, FB. A car engine is way slow at 142 rpm, an old fashioned windmill is slow at 142, but modern wind turbines are way fast at 142 rpm.
    Totally agree that was spinning way too fast – out of control, even. Personally, I, like a few others above, like watching them. They look graceful and strangely pretty. Well, to me.

  29. Bill Dauphin says

    Hmmm… obviously I should’ve read through the whole thread before snapping off a reply. Sorry ’bout that.

  30. Torbjörn Larsson, OM says

    Oh, I feel so vindicated. During an environmental course years ago I mentioned a drawback with wind turbines – they use up a lot of area. I estimated that safety distances should be 100 – 200 m. Dunno how I came up with the number, but the other course members locked decidedly skeptical. Maybe it was the presentation.

    And now I read that typical safety distances are 150 m. And IIRC in one late destruction (Denmark ?) large bits traveled ~ 100 m by kinetic energy and small stuff 500 m by the wind.

    Not a laughing matter, but – I got the last laugh!

  31. Torbjörn Larsson, OM says

    Oh, I feel so vindicated. During an environmental course years ago I mentioned a drawback with wind turbines – they use up a lot of area. I estimated that safety distances should be 100 – 200 m. Dunno how I came up with the number, but the other course members locked decidedly skeptical. Maybe it was the presentation.

    And now I read that typical safety distances are 150 m. And IIRC in one late destruction (Denmark ?) large bits traveled ~ 100 m by kinetic energy and small stuff 500 m by the wind.

    Not a laughing matter, but – I got the last laugh!

  32. RamblinDude says

    As cool as wind turbine technology is, I’m guessing it will be obsolete in a few decades due to the amazing designs being invented for power generation from other natural sources. Like the wave power generator Pelamis P-750 machines. And when the highly efficient and cheap solar cell comes along, power farms won’t be noisy at all. Or maybe I’m completely wrong and we’ll see windmills all over the place. Hell, I don’t know.

    (Hey, all you invertors out there, get on with it, will you? We’re supposed to have flying cars by now!)

  33. Chris says

    As #6 student_b pointed out the Denmarkese, the Denmarkites, er uh, the Danish knew the turbine was going to fail. They don’t put cameras on every single windmill. Those types of turbines have brakes and other safeguards which failed. I suppose the question is what is the failure rate of this particular type of breakdown?

    Vertical axis wind turbines aren’t as efficient but they can tolerate a higher wind speed and don’t need to adjust for direction. They can also operate at lower windspeeds but they aren’t as effective for generating electricity at the lower speeds.

  34. True Bob says

    Dude, I thought I was the only one lamenting that. Where’s my flying car, dammit?

    Note, I now work for FAA. We’d be dying in droves if we really had flying cars. “Big sky, small airplane” goes only so far. And would Merkans put up with a driving test harder than for ground cars? ‘Nuff said.

  35. RamblinDude says

    Note, I now work for FAA. We’d be dying in droves if we really had flying cars.

    No, computers will do most of the driving, at least over populated areas, and we’ll just be passengers. You’ll get ten years in jail for overriding the system and driving yourself.

    Crap.

  36. Jim Harrison says

    All technologies have drawbacks. The main problem with wind power is not how dangerous it is, but how much it would have to grow to make a meaningful contribution to the energy problem. In 2006, for example, wind was the source of less that .3% of U.S. energy production. This contribution can be scaled up, of course; but energy demand will also grow.

    The answer to the question of what new sources of power are needed isn’t coal, natural gas, hydro, wind, biofuels, geothermal, or nuclear. It’s all of the above plus a significant degree of energy conservation.

  37. Ichthyic says

    I’d watch them things spinning all day over staring at two cows on a hill.

    there’s quite a bit of debate on that issue where I’m holed up currently (Palm Springs, CA).

    I took some pictures during a sunset last year… you can judge for yourself, I suppose:

    http://flickr.com/photos/83147904@N00/

    60-80kt winds in that particular area are not uncommon, as the winds get funneled between the gaps in the mountains.

    as to any windmills having catastrophic failure like the one in the vid… there are about 4-5 thousand of them here at last count, and I don’t recall hearing of any similar failures since around 1991 (well, at least my folks never heard of any).

    they typically auto-shutdown in bad wind situations, are able to be angle wrt wind direction, and also have brakes.

    they DO make a bit of noise though, if you are within say 100 meters.

    …and yes, the newer models are HUGE. the ones featured in the photos are around 50 meters tall (the blades are about 25m).

  38. October Mermaid says

    If you look really closely a split second before it explodes, you can see a Bond villain being thrown into the turbine.

  39. Gary Bohn says

    Re: #47

    Yes Ducks are intelligently designed* too.

    *According to at least one egnorant quack.

  40. KC says

    #21 has it. The big turbines have a number of mechanisms that are supposed to prevent this from happening – it looks more like someone had a serious series of mechanical breakdowns. And the fact that people were around with a camera to record this means they knew it was screwy in advance.

    I’ve been reading into winding my own stator for my own fun and profit, and fairly fool-proof safety mechanisms are (at least apparently) easy to put in. It makes me wonder about what went so wrong with that one.

  41. Ichthyic says

    And the fact that people were around with a camera to record this means they knew it was screwy in advance.

    out here we have a rather large problem with people stealing the copper wire out of the windmills, which of course destroys the generator.

    it wouldn’t be that hard to disable the automatic brake system if one is going to gut the thing for copper anyway.

    And the fact that people were around with a camera to record this means they knew it was screwy in advance.

    indeed, you might be on to something here.

  42. Forrest Prince says

    Matt at #14: a source for your info (“…[two] technicians inside…”) would be nice. If it is contained in the story as linked in PZ’s post I wouldn’t be able to confirm it myself as I don’t read German.

    However, it does seem likely that the failure was known to be imminent and emergency precautions initiated. It is highly unlikely the video would have been taken otherwise — you could sure burn up a lot of video time waiting for a turbine operating under normal conditions to fail. But a wind turbine spinning that fast is not going to last very long, that’s for sure. So it is even more likely that the systems to keep it safe from high wind conditions (brakes, prop feathering) also failed.

    My take on this story: this does not tell us that wind turbines are dangerous. This tells us that there are limitations to energy production via wind power, that any human invention is subject to human error, that system failure can be known in advance and its effects mitigated. As others have said, I’ll take the catastrophic failure of a wind turbine over that of a nuclear power plant any time.

    No cows were injured in the writing of this comment.

  43. Crudely Wrott says

    @ #10, MAJeff:

    I am moved to ask why, given their future distaste of windmills on the far horizon, these same complainers are not raising hell about the wires strung from poles just a few feet from their windows!

    One would think that a distaste for the imposition of windmills on the horizon would indicate a distaste for wires just outside the door . . . The level of imposition being so much higher and much more immediate and all. Would not the hatred of far windmills be merely the echo of hatred for wires on stumps? Considering that wires on stumps are everywhere and windmills on the horizon are visible to but a few? Oh, the questions.

    Would one not wonder why?

  44. True Bob says

    Ichthyic, I think you’d want the brake engaged quite solidly while you’re swiping copper. Or maybe that’s what you meant. Safety first: no moving parts while scavenging.

  45. O-dot-O says

    Am I the only person who thinks that the first segment of that video is fake? Or at best a well-intentioned animation that simulates what it probably looked like when it self-destructed? There is a qualitative difference between the footage of the spinning and disintegrating device, and the footage of the results. The vantage points are different yet the same windblown branches appears in the foreground…

  46. BaldApe says

    student_b said:
    “Also it looks like (based on the fact that there are two different videos of it) that it was known in advance that something will happen, ie. the defect was known.” (#6)

    I wondered about that.

    And RamblinDude #41 said (of flying cars):
    “No, computers will do most of the driving, at least over populated areas, and we’ll just be passengers. You’ll get ten years in jail for overriding the system and driving yourself.”

    Reminds me of a joke- guy is on a plane, hears a recording saying “Welcome to the first fully automated transcontinental flight. There is no human crew on board, but do not worry; everything has been checked and double checked. Nothing can possibly go wrong (click) go wrong (click) go wrong…..”

  47. says

    Many years ago, I met the Scottish musician Phil Cunningham (of Silly Wizard and Relativity) who wrote a tune called “The Man Who Shot the Windmill” and he told me the story. When he wrote the song, Phil lived on the Isle of Skye and the man in question was a neighbor who built a wind turbine to power his home. He hadn’t figured on the strength of the Atlantic gales. During one bad storm, the brakes failed on the turbine, so the owner had to get the coast guard to come and shoot the thing.

  48. corydalus says

    If you stop the video at 15 seconds and then step through it (by clicking on/off very fast; it’d be nice if there was an actual frame by frame advance feature) you will see that one of the blades disintegrated. Maybe it hit a flying branch or bird, or maybe it just came apart under the g-forces of the spin.

    Then it gets confusing; the broken blade seems “ghosted”…hard to describe. You have to step through it. It might be a second blade coming apart near the still-blade-shaped debris cloud of the first.

    After that a blade slices through the tower. I speculate that the loss of pressure on the one or two now missing blades caused it to tilt downwind.

    The whole key sequence is only about one second long.

    Very impressive indeed. Any chance that this was a deliberate test to destruction, since the cameras were ready?

  49. Carolyn says

    Aw, man, the one time PZ posts about something in my field, I’m eating out and miss the discussion. :(

    (Dinner was good, though.)

  50. Venger says

    I’ve heard the just below the speed of sound claim as well, but only in regards to big turbines. Like say the one Ontario Power Generation has at the Pickering Nuclear Generation Station east of Toronto. It is one of the largest wind turbines in North America, the tower is 78 meters (255.9 ft) high and a blade at top dead center brings the total height to 117 meters (383.8 ft). The system is designed to run at a fixed rotation of 15.7 rpm, and automatically shuts down if wind speeds reach 90kph.

    Pickering Wind GS

  51. Azkyroth says

    (Hey, all you invertors out there, get on with it, will you? We’re supposed to have flying cars by now!)

    The main problem isn’t so much the flying cars as it is the flying traffic lanes. And flying not having a lethal drop below you when (not if) the engine fails.

  52. demallien says

    (Hey, all you invertors out there, get on with it, will you? We’re supposed to have flying cars by now!)

    They’ve been busy with Facebook and D&D 4.0…

  53. maxi says

    One of my favourite drives in going north on the M6 throught the Lake/Peak District. You drive through a valley and then on your right a whole field of wind turbines comes into view. Such stately things, all turning slowly in time with each other.

    Like Ginger Yellow, I would gladly pay money for a house with a view of a field full of wind turbines.

  54. andyo says

    In a more aquatic light, there is research into how the design of humpback whale fins may yield more efficient blades.

    http://www.whalepower.com/drupal/

    Posted by: shifty | February 28, 2008 4:45 PM

    Sorry shifty, but I can’t tell if that’s a serious site or a spoof one (I’m leaning towards serious, but you never know). Is there any independent info on that? If the site is serious, it’s pretty, um, shifty. It has most of the signs of snake-oil companies, like making sure your “experts” always have “Dr.” preceding their names (though never actually saying what kind of doctor); extraordinary claims (without so much as even ordinary evidence); always referring to “studies” and “the science”, but no real information is given, just marketing speak for the most part.

    Also, “Dr. Frank E. Fish” sounds like a character from a bad copy of a Pixar movie (I am looking at you, Dreamworks!), but if that’s his real name, I’m sure he’s already heard all the jokes. The fact that a quick google of “Whale Power” doesn’t yield anything of substance or anything from a scientifically credible publication (correct me if I’m wrong) is also suspicious. Oh, and what’s with comparing “Dr. Frank E. Fish”‘s* “major” discovery with the likes of Newton’s and Archimedes’s? Talk about extraordinary claims!

    * Hey, grammar nazis, is the “‘s” supposed to be inside, or outside the quotes here? I’m only asking ’cause I’m one myself.

  55. Jim Battle says

    I used to work with a guy who helped put up the first generation wind farm up near livermore, california, back in the 80s. On any failure they’d do a full “autopsy” to help them drive improvements for the next batch of turbines they were putting up. There was a lot of empirical tuning going on, apparently. Anyway, for yuks they kept track of the furthest distance a blade had been thrown. Whenever the record was broken, it caused great excitement.

    Brooks, are you still out there?

  56. David Marjanović, OM says

    Matt at #14: a source for your info (“…[two] technicians inside…”) would be nice. If it is contained in the story as linked in PZ’s post I wouldn’t be able to confirm it myself as I don’t read German.

    It isn’t mentioned at all in the scienceblogs.de story.

  57. David Marjanović, OM says

    Matt at #14: a source for your info (“…[two] technicians inside…”) would be nice. If it is contained in the story as linked in PZ’s post I wouldn’t be able to confirm it myself as I don’t read German.

    It isn’t mentioned at all in the scienceblogs.de story.

  58. says

    Re: We’re supposed to have flying cars by now!

    I’ve actually written about that twice on my blog, Where’s My Flying Car? and When Will There Be an Aircraft in Every Garage?. Basically, I just don’t see it as being practical in my life time. A vehicle that acts only as an aircraft (i.e. can’t drive on the road) just isn’t going to be a financial option for many families. If you want something that you can fly and drive, you have to make a whole lot of compromises that significantly reduce its utility. Air isn’t very dense, so you have to push a whole lot of it down if if you want it to hold you up. The most efficient way to do that is big wings or rotors, but those don’t fit very well on highways. Once you start adding the folding mechanisms, you start driving up weight and complexity. Or, you can go with very small rotors (like the Moller Skycar), but then your efficiency drops way off, and it gets noisier (not a small concern for urban operations). So, flying cars are technically possible (just google “Pitcairn AC-35” or “Larry Neal Super Sky Cycle”), it’s just that the compromises have kept them from becoming successful. And you still have to consider maintenance requirements, or trying to get to your relatives during a thunderstorm.

    One more note – I work for one of the companies featured in that 60 Minutes link. We’re not trying to develop a flying car, so much as an efficient, high speed VTOL aircraft. There’d still be plenty of applications for that, without getting into Jetsons scenarios.

  59. Stephen Wells says

    As far as I know, the amount of power you can extract from the wind is essentially a function of the area of your wind farm; larger turbines produce more power, but must be spaced much further apart, and those factors cancel out.

  60. noncarborundum says

    Hey, grammar nazis, is the “‘s” supposed to be inside, or outside the quotes here? I’m only asking ’cause I’m one myself.

    I’d vote for inside, myself, but it’s not a clear-cut case. The “‘s” inflection has become separable from its noun to the point that it can be stuck on a word it doesn’t really belong to, as in a phrase such as “the King of England’s throne”. Back in Old English times, this would have been expressed as “ðæs cyninges Englalondes heahsetl”, with a possessive marker on the word for “king” (“cyning” + “-es”), but now the possessive belongs to the whole phrase “King of England”.

  61. Stephen Wells says

    noncarborundum, since you have some OE knowledge, could you clear up a point for me? I thought that the English ‘s possessive comes from an OE -es ending, but you sometimes see it explained as a contraction of “his”, which seems less plausible to me… what would you say?

  62. andyo says

    Ha! I only got to the second sentence, but I got the gist of it, thanks. The rest is way too much for me; English is only my second language. What I’ve found is that in English there are no strict rules, are there? People go by its use in “respectable” literature and other stuff like that, and the Oxford dictionary is not the ultimate law-giver.

    In Spanish, we have the Real Academia (“Royal Academy of the Spanish Language”) which, for better or worse, is supposed to be the authority. Some writers and people in-the-know don’t like it, but I think the majority just accepts it. I personally am OK with it, since having strict rules makes it more fun to play with them. You can gauge a writer’s style, for instance, in the way he or she jumps around and bends the rules without breaking them. It’s a little like music, and there are quite several Stravinskys. On the other hand, it’s easy to get carried away with the style, and offer no substance, I guess.

  63. noncarborundum says

    . . . you sometimes see it explained as a contraction of “his”, which seems less plausible to me… what would you say?

    The more parsimonious explanation is that the -es genitive singular ending (used in the masculine and neuter “strong” declension) became generalized to all nouns. To hold that the possessive ending came from “his”, you have to assume that the original genitive ending (which would have given “-s” regularly) was lost and then replaced by “his”, which was then similarly generalized. This is certainly not impossible, but it seems to me unlikely.

    It’s conceivable that there might have been a period when the old genitive ending was, through some process of hypercorrection, misconstrued as an unstressed pronunciation of “his” and so spelled, but this would be a folk etymology, not a true account of the ending’s origin.

    All that said, I should point out that IANAHL (I am not a historical linguist), and the above is mostly speculation on my part.

  64. MLE says

    From stepping through the video frame by frame, it is apparent that one blade fails at the tip without striking the pillar, but just as it swings passes past its low point (centrifugal force + gravity = max load). The same blade reaches the top of it swing a few frames later, by which time it appears to have split roughly in half, the failure propogating seemingly along the blade’s leading and training edges. Another couple of frames later, the blade has swung another 30 degrees or so, and the split reaches the hub. all three blades appear to detach, just before the blade ahead of the failing blade passes the pillar. This second blade impacts the pillar; the remains of all three blades are thrown away roughly simultaneously.

  65. wow says

    yikes, nature needs to fix that “design” with a few more properly placed magical mutations…then all will be well.