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Boeing Dreamliner Safety Concerns Are Specious
Posted by
kdawson
on Thu Sep 20, 2007 10:06 AM
from the composite-journalism dept.
from the composite-journalism dept.
SoyChemist writes in to note his article at Wired Science on the uproar Dan Rather has stirred up with his claim that Boeing's new 787 Dreamliner aircraft may be unsafe. "Dozens of news agencies have jumped on the bandwagon. Most of them are reporting that the carbon fiber frame may not be as sturdy as aluminum. Few have bothered to question Rather's claims that the composite materials are brittle, more likely to shatter on impact, and prone to emit poisonous chemicals when ignited. While there is a lot of weight behind the argument that composite materials are not as well-studied as aircraft aluminum, the reasoning behind the flurry of recent articles may be faulty. The very title of Rather's story, Plastic Planes, indicates a lack of grounding in science. Perhaps the greatest concern should be how well the plane will hold up to water. Because they are vulnerable to slow and steady degradation by moisture, the new materials may not last as long as aluminum. Testing them for wear and tear will be more difficult too."
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I don't know (Score:4, Funny)
TV reporters are idiots. (Score:5, Insightful)
This kind of crap is infuriating for airline companies...It doesn't take much at all to kill a whole line of planes, just the vague reputation for being unsafe. A report like this, based on a flawed understanding of Carbon vs Aluminum where the "reporter" doesn't even grasp the real issue, could do real harm.
Re:TV reporters are idiots. (Score:5, Interesting)
Yup. Michael Crichton's "Airframe" was actually a pretty good read on this very subject. Well, it INVOLVED this sort of subject. Most people also don't understand that the airframe ain't the same as the engines, and ain't the same as the particular airline's choice about all sorts of other things (from avionics packages, to training programs/frequency, etc). But it shouldn't just be infuriating to airlines, it should be infuriating to ANYONE who manufactures anything, works for someone who does, likes buying from anyone who does, has some of their Mom's 401k invested in someone who does, likes the fact that we get tax revenue from someone who does, who would rather buy from Boeing than ship the cash consortium manufacturer, and more.
I'm way more worried about the corrosion of national critical thinking skills and basic science education (which allows this sort of stuff to be written and passively consumed) than I am about the prospects of water-based corrosion to a CF airframe 20 years from now. We can fix/replace an airframe, but we can't fix some teenager that's been trained to not think, and who finds the trouble of actually grokking issues like this to be unfashionable and too much work. That Dan Rather is pandering to that cultural flaw (while suing CBS for $70 million for getting busted having done it before!) isn't just embarassing, it's Actually Evil(tm). And not just for Boeing's upper management bonuses.
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Re:TV reporters are idiots. (Score:5, Insightful)
There are many classifications of materials that could be interpreted as "brittle." Brittle is much too general a term to be used in engineering, so you have to be suspicious of the news article.
You can measure tensile strength, which is a measure of how much something can bend until it break. There's another measurement where you find how much something can bend until it permanently deforms, so that it won't go back to its original state. Each of these could be called "flexibility" but that doesn't tell you the whole story.
Carbon fiber when it fails may fail explosively and shatter, while a soft metal would simply deform slowly when bent far enough. This could be called "brittleness" but it really has little to do with the actual engineering problem, since if you design the carbon fiber component to high enough tolerances, you're not worried about it breaking, since the force required to break it would be so huge you'd have other, much bigger problems besides the breaking of the part. (Like, how do we get the people out of the broken plane when Godzilla is about to eat it?)
It would be easy to criticize the engineering of the plane on the news, because nobody is going to sit there for three months to check everything out -- they'll watch the demo of a small piece of carbon fiber breaking and think, "Oh my god, that could be the wing of my plane!"
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Re:TV reporters are idiots. (Score:5, Informative)
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CF is anisotropic material (Score:5, Insightful)
The types of CF composite that degrade faster are the ones where the resin doesn't have a UV inhibitor in it. UV degrades the resin just like it does to any plastic but with proper protection that isn't a problem. Once this was understood companies developed UV inhibitors for the resins to make them resistant to UV degradation. And you can bet the farm on a $150+ million dollar plane being adequately protected. There is no reason to think that they won't last just as long as an aluminum plane. Never mind that the resin only carries a tiny fraction of the load, in the directions the fibers aren't laid up for. Meaning the resin is mainly there to keep the material from delaminating.
Though some may not know it, but as aluminum oxidizes over time it becomes aluminum oxide which is more brittle and prone to fracture. So you face the same problem with aluminum, but it is adequately protected and hasn't been a problem for the many many years that commercial aircraft have been flying. Just like fiberglass boats, adequately protected and maintained they last a long time.
But what do I know, I'm just an aerospace engineer with some composite materials training. I should leave the science to Dan Rather.
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Re:CF is anisotropic material (Score:5, Interesting)
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Trusting Dan Rather is like.... (Score:5, Interesting)
- Buying Madonna's book: Screwing for Virginity.
- Buying MS Vista for it's speed and congeniality.
Seriously folks, Dan Rather has about as much common sense as a Bugby.This is the guy that went on the airwaves with a "memo" supposedly typed in the 1970's, with proportional fonts and different-font sized superscripts! I would not trust someone like that to tell me it's raining.
Carbon-fiber composite construction has been around for going on forty years now. It's been accellerator tested in hot humid ovens and passed with darn good results. Boeing doesn't make junk. And airframes are warranted for tens of thousands of Hobbs clock hours, so the airlines are not at risk, they're voting with their checkbooks.
Ahh the wonders of politics. (Score:5, Insightful)
If you go "this is unsafe!" and you were wrong, you can go well my conserns were addressed and score a political victory.
If you go "this is safe!" and it is safe. Nothing really happends no creditability loss or gained.
If you go "this is safe!" and it was found unsafe. You get fired, invistagations, rumors you were in colution with with contrators....
So if you were trying to run or stay in office what will you demmand.
Government is a failure driven buisness it is what you do wrong that hurts you and if enough people above you were fired then you finally get promoted. So Screamming and yelling and making false accuasations and make the world seem like an unbarable place to live is the best thing you can do for your job.
Composites fail differently (Score:4, Insightful)
In the End CArbon fiber isn't better or worse than a metal plane. It's just different with different things that can go wrong.
F-16 is made of composites (Score:5, Insightful)
One concern the USAF had with the F-16 was that in the event of a crash, a cloud of electrically conductive carbon fibers would settle over the base, shorting out anything electrical. Judging by the F-16 we had burn on the taxiway at Hahn AB in 1985, that wasn't the case.
Chip H.
So is the GEnx (Score:5, Informative)
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If you ask me... (Score:4, Funny)
Shorter Testing Schedule? (Score:4, Informative)
What they don't mention is that, while the testing schedule is shorter in terms of calendar days, Boeing is logging just as many, if not more, flight hours with the 787 test aircraft as they have with earlier projects. The accelerated schedule is to meet their delivery deadline, but all the requisite tests are still being done.
Boeing knows that the health of the company for the next 10-20 years rests with this aircraft. Airbus, despite its problems with the A380, isn't going to cease being a fierce competitor. If Boeing screws this project up, and gets a lot of bad PR from an aircraft failure, they'll be lucky to survive. With so much at stake, I trust them to do their jobs right.
unsafe, huh? (Score:5, Interesting)
Death stats found here http://www.the-eggman.com/writings/death_stats.html [the-eggman.com].
Aircraft deaths do not even make the list. How can something that accounts for less then 0.1% of all accidental deaths be called "unsafe"?
Not as well studied? (Score:5, Interesting)
Carbon fibre, Aramid and glass fiber are the predominant construction materials in sailplanes. They all have a long, proven track record of reliability and endurance.
When a plane crashes, toxic fumes (emitted mostly by the material's matrix, usually epoxy raisin) will probably be the least of your problems.
Carbon fibre will burn to C02, because, as the name implies, it consists of carbon.
PS: I know what I'm talking about, because we build sailplane prototypes at the University of Darmstadt (the kind where you can actually sit in and fly).
oh how much misinformation (Score:5, Informative)
Carbon fiber is a VERY active area of research, and it is definitely true that more is known about aluminum than CF structures, but this is for the simple fact that aluminum is about 10x simpler to understand and model than CF. You are talking about a metal that is isotropic (material properties the same no matter what direction you measure them) versus two different polymers, bonded together. Composite mechanics are incredibly complex, but that doesn't mean we don't understand them enough to make them safe. It only means that we have to use larger safety margins in our designs. As research continues, you will not see airplanes get safer, only cheaper and lighter. Safety is driven by FAA regs, and performance that is driven by material knowledge.
In general, carbon fiber is stiffer and stronger than aluminum. This means that you can make the plane weigh less and flex more. Good, right? It also will have better fatigue properties than Aluminum, since it does not have to deal with crack propagation. Aluminum will fail catastrophically, while CF will go gradually. Chances are that you will detect a CF failure long before it becomes a safety problem, as long as you use those fancy infrared/X-ray/gamma ray inspection devices. For those concerned about "water fatigue", there are a number of industry standard tests to measure this degredation, and it is included with every roll of CF that you order. It's definitely not something they haven't thought of.
The FAA has some of the most stringent regulations of any government agency when it comes to airplanes. The chances of an unsafe product making it to market are very low, simply because of the maintenance required and number of test hours needed. If you remember scandals of the past, they all come from companies either cheating the regulations or the regs failing to be applied. Please don't get riled up unless one of these two things is happening.
Re:Typical Dan Rather (Score:5, Interesting)
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Re:Typical Dan Rather (Score:5, Insightful)
-jcr
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Re:Typical Dan Rather (Score:5, Informative)
Nope, it's about a guy who got canned for making racist remarks on the job, looking for some way to lash out at Boeing and get some revenge. Fuck him.
-jcr
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Re:Typical Dan Rather (Score:5, Insightful)
This isn't Shockley we're talking about, it's someone who was fired for cause, who didn't raise these issues before he was fired. If his former colleagues refuse to get on that plane, then I might give some credence to his claims, but until and unless that happens, I think he's full of shit.
-jcr
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Re:Typical Dan Rather (Score:4, Informative)
There' also the very plain fact that Boeing is rushing this plane to market with far less testing than was used for recent generations of more conventional passenger jets. That gives Boeing every incentive not to listen to doubts. Boeing is betting that this can finally allow them to pull decisively ahead of Airbus, who has caused Boeing serious hurt over the last decade. Maybe it can, in the short run. Orders are coming in. But what happens if there's a spectacular crash or three? Will Boeing take the reputation hit that, say, Ford took about the Pinto? Maybe not. The public expects there to be no survivors from jetliner crashes. On the other hand, the sheer number of people these things will carry means the first such crash will be the most fatal - not counting people in buildings crashed into - ever. There will be weeks of international media scrutiny.
Boeing, we should be relieved to know, has tested the fuselage by dropping a section of it
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Re:Typical Dan Rather (Score:5, Informative)
The 787 has not yet had wing tests conducted. The "touch over the cabin" part of your statement comes from the fact that many of the engineers at Boeing believe that to be possible; carbon fiber is so much more flexible than aluminum that it is, in theory, possible to bend the wings up over the fuselage until the two wingtips touch. Boeing will not perform the stress test to that extreme, however. Boeing will test the wings to the design maximum and then stop. They will not test to failure.
The reason for this is twofold: first, it doesn't matter after the design max. If the plane actually experienced design max stresses in flight, several other components (like the fuselage, or the vertical stabilizer) would fail first, so as long as the wing reaches that maximum without a problem, there's no need to test further. It doesn't matter how strong your wings are if your fuselage snaps in half first. Second, carbon fiber does not have a plastic strain region; it's all elastic strain before failure. That means that it will just continue to bend farther and farther without damage to the wing right up until failure (contrast with metal... when you bend far enough, it doesn't return to it's original shape anymore, but it has not yet failed). But, when it does finally fail, it doesn't snap, it shatters. That means clouds of hazardous carbon fiber dust and shards would be sent flying around in the factory. Not good.
The video on YouTube is of the 777 wing stress test conducted in the 90s. It was designed to reach 150% of max in-flight loading before snapping. It actually snapped at 154% (which is impressive
IAABE, but I don't work on the 787.
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Re:Typical Dan Rather (Score:5, Insightful)
The FAA has set some tests that must be completed by all aircraft manufacturers - and the tests have extremely simple, impossible to fake criteria. For example, the fully loaded plane must go at full throttle on the runway up to the no return line, and slam on the brakes. The plane must stop before the end of the runway, sit for 5 minutes (worst case overheating of the brakes), and then taxi to the terminal. The tires are expected to blow, and the brakes may catch on fire, but other than that no damage is allowed.
There are many tests like this. They have to pass them all. If you build a plane from glass and it passes these tests, it is just as safe as a solid steel one - it would just be a lot harder to design.
Materials do not give a plane safety. Engineering is what gives a plane safety.
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Aluminum (Score:5, Interesting)
Likewise the biggest single boon to aircraft safety was World War 2. There they had many plane designs (any given plane might have many different configurations) and they learned all sorts of fun things. Like for example that you had to not route all the electrical system through a single junction box (A washer got loose and shorted out a plane during turbulence that then crashed in SF bay). Or how you need to run both the main and backup fuel pumps up to full pressure during takeoff because if the mains fail then there is not enough time to spin up the backups to speed before the engines lose power. Or how you have to make the fuel pumps big enough to dump the tanks fast for an emergency landing. All of those discovered by "accident".
Some may recall the crash in NY where the composite tail ripped off when the pilot whipped the rudder too and fro in a non-standard maneuver.
THe good news is that the military uses composites and so they have had enough accidents to work things out for the commerical jets.
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