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Boeing's New 787 Wings — Amazingly Flexible
An anonymous reader writes "Boeing is making the wings of its new 787 out of carbon fiber instead of metal. That means the wings are so strong and flexible that they could bend upward and touch above the fuselage — or come close. The company is expected to deliver the first 787 to All Nippon Airlines in May 2008. 'Boeing has completed static testing of a three-quarter wingbox, but engineers are still considering whether to limit testing of the full wing to a 150% load limit held for 3 sec. or to continue bending it to see when it breaks. 'There's a raging debate within the engineering team to see if we should break it or not,' says [787 General Manager Mike] Bair.'" They have come a long way in wing flexibility.
Airbus have been doing it for some time now. From The Telegraph
"The entire wing structure of the Airbus A 350 is made of carbon fibre and the same material will account for 50 per cent of the Boeing 787, which its manufacturers say will be the most fuel efficient and environmentally friendly aircraft in the air."
Breaking it isn't necessary for certification, but Bair says the wing is so strong and flexible that there's been talk that maybe it could be bend far enough for the wingtips to touch above the fuselage--or come quite close.
From the article:
No one's ever really tried that before, so testing is critical.
Since this seems like such a new concept (please correct me if I'm wrong; I don't follow plane technology too much), it would just seem prudent to try bending the wings until they break... how can they make accurate judgments and calculations without knowing exactly how much stress the wings can take before snapping?
You could, instead of downright trying to see how much it will take, try to get it up to 200% (or something, I'm not an aerospace engineer) and see for how long it can hold up to extremes like that. Might be more valuable data. Maybe someone more in the know can elaborate.
The 787 will be the envy of "tuner" kidz everywhere with it's carbon fiber wings.
If only one could find a 4ft diameter chrome exhaust tip...
Pull them back, let them go, and... BOEINNNNG!
Of course, having the wings be flexible is a good thing, but the real important part here is that they are made of carbon fiber. Carbon fiber is much less dense than metal, which reduces the weight of the plane. If the surface area of the wings is held constant, then fuel consumption can be reduced significantly, as the downward pull of gravity is shrunk as well.
Well shit, if they can bend that much, why not make the thing just flap its wings like a bird instead of using jet engines!!
I really don't see what the fuss is about.
This machine is not going to go appreciably faster or farther than the current crop.
It's frankly shocking how little civilian aviation has advanced in the last 30 years. In fact, it has regressed, with the retiring of the Concorde.
Why can't I fly from LA to New Zealand in less than 12 or so hours?
Don't Boeing, et. al. developed technology for the US Military? Could we not have some of that (which our tax dolalrs pay for, after all) to make our own traveling a little faster for us poor average non-military folk? It would be spent much better on that, IMHO.
The summary leaves out an important detail (to be fair, so does the blog entry) about why there is even a debate as to whether to test the wing to failure. When carbon fibre "breaks", it creates lots of carbon dust as well as small shards. The dust is quite toxic to humans and can contaminate equipment and the shards are very sharp, akin to glass. Bottom line, it would be very messy and would require hazmat like conditions to clean up.
Perhaps this is an inane question, but did Boeing redesign their aeroplane to accommodate the flex-wings? The craft will be lighter, they can utilize the increased flex to their advantage (refer to the McLaren front wing in their F1 cars) and such. I presume from the 787 name that it will remain a similar design to existing crafts, but research is probably under way...Let's hope for the best
Regardless, this should be a cheaper aircraft to operate. But are we going to be paying lesser for flights? I don't think so... But can they atleast put in smoking sections at airports or develop technology so that I do not have to remove my shoes everytime I want to smoke at a stopover?
Cheers!
Atheist: Buddhist in a Prius
All they need now are large hydraulic actuators then airplanes could flap their wings as they fly thru the air.
try { do() || do_not(); } catch (JediException err) { yoda(err); }
If any article screams out for a Slashdot poll, this one is it.
1. Chicken out and don't break 'em
2. See how far they go and post it to YouTube
3. Orinthop mode! Pull 'em back and let 'em flap!
4. Cowboy Neal
Learning HOW to think is more important than learning WHAT to think.
Airbus: Care for some metal wings?
Boeing Client: No, thank you, I take them flexible, like my women.
No, you are wrong. Boeing use good old US carbon fiber, while the Europeans use that low rent carbon fibre stuff. No comparison at all. Carbon fibre comes in litres and the fibre length is in metres, while carbon fiber comes in gallons (or perhaps liters) and fibers are measured in feet, (or perhaps meters). See how easy they are to distinguish?
Pining for the fjords
Does it really matter if, because of how they are bent, you lose lift?
...as long as they post a video of it on their website!
Insisting on "correct" English is like saying that there is only one, definitive recipe for chili.
...What happens in the case of violent turbulence with wings that can bend? If they're flexible enough to be wrapped around to touch above the fuselage, are they also flexible enough to warp or twist? The last thing I want to try is a barrel roll in a passenger jet...
Any plan which depends on a fundamental change in human behavior is doomed from the start.
Am I going to be the first person here to think these engineers sound like they're just having way too much fun with this?
Also I wonder what would break first, the wing, or the connection to the plane. I'm expecting the video to hit the internet in about a week.
If they don't break, ensure they break in some way! ;-)
Seriously though, that idea isn't useful only for entertainment and cool effects, it is useful to know the tipping point, what boundaries they're actually working with, and not just to see if it does or does not work. And as they so often tell there -- the only way to know for sure is to test it in the real world on a non-scale model!
Beware: In C++, your friends can see your privates!
A flying Ugly Stik
RS
Shoes for Industry. Shoes for the Dead.
"They have come a long way from even just a year ago."
The linked video may have been uploded about a year ago, but it cites as its source a PBS production from 1995. (Which, incidentally, is discussing an entirely different airplane, the 777.)
With reasonable men I will reason; with humane men I will plead; but to tyrants I will give no quarter. -- William Lloyd
I can't imagine that the debate is really among the engineers. Any engineer that I've known would want to break the wings, just because it would be fun, make a big mess and a loud noise. The debate must be between the engineers and some management element that wants to portray the wings as 'unbreakable'
I metamoderate, therefore I am
Anyone notice that the "year ago" was a video of "Boeing 777 Wing Ultimate Load Test"
Anyone notice that the date on the file is 1/14/1995?
The implication that this was a 787 wing in test a year ago - is in error....
Thin flexible wings date back to the Boeing B-47. Up until this plane appeared in 1947, planes tended to have thick rigid wing structures. Advances in aeronautics, fluid dynamics, and structure design enabled engineers to create thin flexible swept wings that offered lower drag at high speed without flutter or breakage. The wings of B-47 (and B-52) were so floppy, they needed outrigger wheels to keep the wings from dragging on the ground during landings and take-offs.
Two wrongs don't make a right, but three lefts do.
Slashdot needs an "Aerospace" or "Aeronautics" news category to compliment "Space." "Science" or "Hardware" don't fit all that well to stories about aicraft.
A bit of wisdom from a Retired Boeing exec who I forgot the name of.
The story was about one of the earlier Boeing's, they had stressed the wing to like 10 times any theoretical force that could be possibly placed on it during a rather publicized testing of its strength. They test folks were all about trying to break it.
During the process of doing this an exec asked them what they were doing. "Breaking the wing" they replied.
The exec said No, stop the testing.
Why? the testers asked.
Because the headline won't read ,
"Boeing wing breaks at 40 times the stress encountered during possible flight conditions",
Instead it will read
"New wing of new Boeing Jet Breaks".
Please note Its been awhile since I heard that story, but I think the point is pretty clear.
You mad
I want to see these suckers break. It should be almost as good as chucking birds through engines.
Not a typewriter
So if you don't break it, how do you know for sure when it will break? Sure there's simulation, but that's... simulation.
Deleted
"They have come a long way from even just a year ago."
Makes it sound like that test didn't go well. It did. The failure was at 154% Sounds great to me.
This would make one heck of a good video for Youtube would if it's done right. I would be very interested to watch the test accompanied by the 1812 overture with the wings snapping in a spectacular fashion just as the drums hit! Oh, and add two squirrels and a cat fighting to the video. And while you're at it add lightsabers and two chicks kissing. Now that would make a good video!
load "$",8,1
Airplane wings flex quite a bit more than you'd expect. Airliners.net has a great head-on shot of a 747 taking off that shows the wingtips flexed up higher than the fuselage. Kinda freaky looking.
When you have nothing left to burn you must set yourself on fire
They have come a long way from even just a year ago.
Or did I go through a time warp and suddenly it's January 14th, 1996 again?
Your hair look like poop, Bob! - Wanker.
The actual requirement from Title 14, Code of Federal Regulations, Part 25, Subpart C, paragraph 303 is where ultimate load definition comes from:
Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified
The three second requirement comes out of paragraph 305(b):
(b) The structure must be able to support ultimate loads without failure for at least 3 seconds. However, when proof of strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation induced by the loading. When analytical methods are used to show compliance with the ultimate load strength requirements, it must be shown that--
(1) The effects of deformation are not significant;
(2) The deformations involved are fully accounted for in the analysis; or
(3) The methods and assumptions used are sufficient to cover the effects of these deformations.
If our intrepid engineers manage to test to 200% for 3 second, then somebody is going to come along and say, "let's see if we can make the wings lighter"
Good thing or bad thing?....depends upon your point of view I guess.
As it turns out, validating airframe structures with respect to FAA airworthiness requirements is kinda what I do for a living.
A goal is a dream with a deadline
Problems on other carbon fibre structures.
Deleted
So, what you're saying about these wings is they are considering bowing them?
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Flexing when empty is one thing, but wouldn't it have a tendency to sag more when filled when fuel? I'm sure they've engineered something that's reliable, but the flexibility of them has to be hindered when they're completely filled.
"Please, shut up. Just when I think you can't say anything more stupid, you speak again." -Archie Bunker.
Airbus is a joke.
r ch/1204
http://www.compositesworld.com/hpc/issues/2006/Ma
I want to see the 787 do the Y-M-C-A :)
There are a few ways of handling that issue but, suffice to say, aero-elastic behaviour is a discipline in and of itself. I'll throw out a couple of possibilities knowing full well that there is no way I can go into much detail in this forum.
ONE OPTION: Use the layup to tailor the bending axis of the wing so that it will respond to a gust in a self-correcting fashion.
SOMETHING COMMONLY DONE TODAY: Hang the wing mounted engines in on pylons that put the engine CG ahead of the wing, this has a tendancy to stabilize it's aero-elastic response.
Just a couple of thoughts.
A goal is a dream with a deadline
I'm glad they can bend like crazy and all, but does that mean they will bend more during flight or that they can just take extra abuse should it arise? Speaking as someone terrified of flying, often close to pissing his pants whenever the wings wiggle, I just want to know if I should just pull the flap down and not look out the window at all anymore.
The engineers at Boeing are smart enough to design the wing for optimal performance under normal conditions. That includes whatever wing bending occurs under nominal conditions.
If the aircraft is experiencing extreme conditions which are bending the wing excessively, then you _want_ to lose lift, rather than stress the wing and airframe more. Kind of like how sailors change to smaller sails during storms.
"National Security is the chief cause of national insecurity." - Celine's First Law
Use carbon fiber stucco wings!
Now parge the wings.
--
"Outlook not so good." That magic 8-ball knows everything! I'll ask about Exchange Server next.
Ladies and Gentlemen, this is your captain speaking... If you take a look out the windows on the left side of the plane, you will notice our right wing....
The above comments are not guaranteed to make sense to anyone other than the author...
They don't need to know when it will break. They need to know that it won't break under the most extreme flight conditions, plus some safety factor. As an example, say the wing experiences 50% more load than normal during the worst storm. If they make sure it doesn't break at 150% added load, it's fine with me. (Granted, I'd still want this to be a real test, not simulation.)
With the recent advances in carbon fiber technology, EA thought it would be best to keep up with times. The new NFS game will now include a chance to pimp out your airplanes with neon, spinners, and of course, replacement carbon fiber parts.
Apparently the failure of the SUV racing mode wasn't sufficient, it's time to go bigger and badder!
[/sarcasm]
Personally, I'm curious as to how much flex they expect during a regular flight... wouldn't that affect the plane's potential lift force?
Patience is a virtue, but haste is my life.
The fact that the 787 is a "plastic airplane" will get a lot of play, and having wings that bend, potentially to the point that they will tough, is just the most obvious and mediagenic manifestation of that. But it is just the tip of the iceberg of the innovations.
1) Yes, it's almost completely carbon fiber. This means that the plane can (and is) lighter, so it will be more fuel efficient. Also, it's easy to make complex curved shapes, so the wings and fuselage are slightly more aerodynamic. Because carbon fiber structures are so strong, the windows can be larger, and the plane can be pressurized to a lower altitude (it will be pressurized to 6000' instead of the typical 8000' of today's fleet). There is no corrosion, and little worry about fatigue in composites.
2) The plane is not built in Seattle, although that's where the final assembly takes place. All of the building takes place in multiple facilities around the globe, each producing parts to Boeing's plans. These parts will "snap together" in the Everett plant. The first 787 is being assembled right now, and will roll out on 7/8/7 (just over a week from now.) Apparently the left wing was off by 2 thousands of an inch or so, the right wing was absolutely perfect. Boeing converted three 747's to be gigantic cargo transporters to move all the parts from around the world to Everett.
3) The plane has almost completely electric, without the high-pressure pneumatic systems that older planes had. In particular, the AC systems are electric. This will be somewhat more efficient, and safer.
4) The plan for certification of the plane is borderline insane. The final assembly started a couple of weeks ago, and the plane will be rolled out in a week, the first flight will be in a couple of months, and the first delivery will be in Q2 2008. This is a tiny fraction of the time this process required on previous airplanes -- maybe 1/4 the time of the 777 and even less than that of the latest Airbus. This would be remarkable, even if the plane wasn't revolutionary in every other way, too!
5) Aviation Week and Space Technology visited the final assembly line recently, and were surprised to find that it was almost an empty building. That's not because they weren't ready -- that's because there are almost no tools needed to assemble the plane. They snap together the pieces, install the landing gear, and roll it down the building on its gear installing the various subassemblies. Boeing intends to assemble a plane every three days once they get going, a remarkable and unprecedented schedule.
Anyway -- there are so many revolutions in this airplane that I would have thought it was a scam if it was any other company than Boeing. It remains to be seen if they can meet their goals, but so far things are going remarkably according to the plan they laid out a few years ago.
Thad
I love Mondays. On a Monday, anything is possible.
Wouldn't breaking such large carbon fiber structures put a lot of dangerous particles into the air?
I could see them NOT doing this due to the liability related to contamination of the air, machines, and potential need for a hazmat crew.
I am an aerospace engineer, however i am a propulsion engineer and not a structures guy. Ill try to add some light on the subject.
First off the requirement is a 1.5 saftey factor, ie 1.5 times greater load on the wings then they would encounter during operations. In the past, wings were always broken on new planes. Not only is this fun (engineers do like breaking things, its true), but it provides very useful data to validate your computer models and test methodology. Not often does an engineer get to shatter such an expensive and large article! Predicting before hand when a wing will snap can be very useful on future airplane designs to optimize the structural layout. Remember, any load past the 1.5 saftey factor just means you made the wing too strong, and thus it has extra weight!
Now a days, the structural FEMs (finite element models) and load definitions from CFD (Computational Fluid Dynamics) have become so good, that its not necessary to validate the tools. They have been validated before, and there is a high level of confidence. Someone mentioned above me that these wings were different since they are composite, but in fact commercial airplanes have had composites in the wings for a long time. The military has been making nearly all composite airplanes for even longer.
The A380 from Airbus ran into trouble a few years ago, as they designed the wing for 1.5 load factor, but on testing it only made it to 1.48. Hence they had to add extra weight and strengthen it. But being that they aimed for 1.5 and got to 1.48 shows you how accurate the tools have become.
There might also be a cost element in this decision. I believe Boeing could potentially use that model for some other purpose, whether it be passenger escape tests, wing fuel fire tests, wing fatigue tests, or maybe even just for a model to sit in a hanger somewhere and generate PR. Personally, im hoping to see a great video on YouTube of those wings splintering into pieces!
I find it hard to believe that anyone on the engineering team would not like to see it break it.
ccalam - acoustic versions of new songs.
One of the pioneers of composite materials is Burt Rutan of x-prize fame. He also built the Voyageur which was the first plane to fly around the world without stopping or re-fueling. One of his first planes was built to about ten times as strong as it had to be so that it could be as stiff as it had to be. I remember a picture of people standing shoulder to shoulder along the wing of one of his small airplanes (the VariEze maybe). I'm not sure I'd try that with the ole Cessna.
http://en.wikipedia.org/wiki/Burt_Rutan
That's the first thing I thought of.
This would be the "Headline contradicted by story" news category for the Farkers.
...a perfectly engineered wing would break at 150.000001% Anything stronger is over-engineered and represents an unnecessary weight penalty. (Other versions of the 777 video make this same point; the engineers were sweating the fact that the wing did NOT break at 151, 152 or 153) The reason for breaking the 787 wing is to prove that it is not over-engineered. The problem is the geometry of the carbon fiber wing flexion may allow the tips to flex and touch without representing meaningful aerodynamic loading. Once you've pulled the tips past vertical you've entered he realm of the hoop wing and exited the realm of meaningful testing and data.
If there's one in the Salt Lake City airport, I've never been able to find it.
There was one in Chicago though, last time I went through there, about 4 years ago.
Also, St. Louis has one, in the middle of the D gates.
In Seattle and SFO, now, you can't even smoke on the sidewalks out front anymore.
If the masses can keep you down, you're not the Ubermensch.
Sailplanes and their wings have been build from carbon fiber since the 1970s. While they do not carry as much load as the 787 will, sailplanes experience much higher G-forces; they are commonly rated upwards of 5g (10g for aerobatics-qualified planes).
. wmv
Check out http://www.dgflugzeugbau.de/bruchversuch-e.html for the spectacular destructive test of the DG-1000's wing. This two-seater sailplane has a 20m wing span, 750kg maximum weight, and the wing snapped only upwards of 12g.
Direct link to video file: http://www.dgflugzeugbau.de/Videos/bruchversuch-i
The same debate comes up in web programming projects. Some clients would rather you NOT find the breaking point of the code, even though it endangers their business to have possible serious flaws. What could possibly be the logic behind this? Does anyone in any industry think past short term profit?
In any proper production of the 1812 Overture, it wouldn't be drums, it would be cannons.
</PEDANTIC>
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
I don't care whether they test the wings or not. I just don't ever want to have to get on a plane and see the wings bend any more than aluminium wings. If I look out the window and see the wings actually flapping and flexing under force any more than I'd usually expect, which is little flexing at all, I'm going to be violently sick from at least two orifices.
Good grief, am I the only guy who was once a red-blooded American juvenile delinquent?
I can't believe that a bunch of self-proclaimed "engineers" would even debate how to proceed in this matter.
If there were any justice in the world, they would be forced to turn in their pocket protectors & their slide rules and slither home with their tails between their legs and their heads hung in shame.
Just had to say this.. My Dad designed some of the machines (and workspaces for using them) for the GeNX Engines from GE that will be powering this beautiful plane.
/GEAE Ex-IT drone myself.
More orders than they know what to do with.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order- Ed Howdershelt Via Tass
What kind of nerd engineers WOULDN'T want to break the wings to see what they could withstand? Dang it, don't let the suits win! You ain't paying for the test wings, fold them babies up! ;)
First off:
If something does go wrong, is the FAA culpable if it turns out the limit was too low?
In practice, the regulations are the product of generations of actual aviation experience and are driven by the industry itself. In fact, every proposed regulation or change to an existing regulation is subject to public review. In theory, any citizen is free to comment but, in practice, the aviation industry experts have far more clout. I have actually sat on such advisory committees and participated in the drafting of recommendation (not wings but, other critical structural elements)
So, in short, the FAA will not be culpable because they didn't dictate that limit, it evolved over time and experience. Also, bear in mind this is only the ultimate static load test - there are others, including a power spectral density analysis which evolved from the old "sharp-edged gust load".
I have rarely seen a safety factor of 1.5 for something that involves human life.
Okay....can't really speak to your personal experience, I'm mearly referencing the regulations themselves.
Then again, Tresca and Von Mises criterion may themselves differ by a factor of close to 2...
Where the Von-Mises criterion will plot as an ellipse set at 45 degrees, The Tresca criterion is a hexagon inscribed in that ellipse (Tresca's Hexagon) [Refernce Bruhn, Meyers & Chawla, et. al]. You'd be hard pressed to show any point where they differ by a factor of 2.
In short, I find that hard to believe but feel free to site a reference, I'd love to see it.
A goal is a dream with a deadline
Since they like breaking things anyway...
Imagine this:
Carbon fiber flexible wings able to change shape using cablesto tension the wings to a more economical shape for flying vs. Landing and Take-off.
It would be easy to accomplish an up ward "swept" wing if what they are talking about is real.
How much is your data worth? Back it up now.
"carbon brake discs are about to be banned from Formula-1 car races because many drivers are already ill."
Neither of the points addressed in that sentence are true. Since the guy who responded on a fucking blog is now a proven liar, why do you think anything else he says is reliable?
It's a BAD THING to have wings flexing. You lose aileron control effectiveness. You lose lift. The engines get off axis and lose intake efficiency. The flight envelope warps. The wings might be able to flex, but all the contained torque tubes, wiring ducts, landing gear, tanks, pipes, motors and valves have to be specially designed to tolerate the flexing.
This is just the PR geniuses at Boeing making a good thing out of a bad thing. Give them a raise. They've fooled almost everybody.
My materials engineering professor hated plastic. He pointed out that the properties of any metal, when tempered in a known process, were known and consistent throughout the material. And the manufacturing process for plastic generated chains of unknown and varying lengths. Therefore, the actual properties of any given plastic material, weren't completely known.
Why trade a perfectly known material for an imperfectly known material?
Then again, Tresca and Von Mises criterion may themselves differ by a factor of close to 2...
You wouldn't use Von-Mises criterion on a composite material, you'd probably go with Tsai-Hill, or possibly Tsai-Wu.
Cheers
A goal is a dream with a deadline
Participate or shut up.
Take a look here. There was a 1.5 inch difference in the diameter of the Section 41 (nose and cockpit) and the Section 43 (forward fuselage, where the forward entry door is). The parts are made in Wichita and Charleston, SC. They have managed to join them now, but the job was "challenging".
Now I am an engineer at an aircraft MRO. Once these things hit more than 15 years old, there are going to be a million problems with this fuselage. Carbon fibre is a very different beast to aluminium, or even fibreglass. For one, the carbon is a conductor of electricity, which can lead to galvanic corrosion (the circumferential frames are still aluminium, there are still metallic fasteners going through the skin to attach them). Also, repairs are going to be an absolute bitch.
Twice in the last month, we have had to fix large holes in the side of aircraft due to trucks driving into the side of them. These incidents happened at outstations (where there were no major repair facilities) and we had to send out a small team to assess and repair the damage. In both instances these were done by a repair engineer, inspector and a couple of sheet metal workers in a couple of days. They took a sheet of metal, an air compressor and a bucket of rivets.
Currently, composites are used on a number of components on almost all aircraft. Invariably they are removable components, like flight control surfaces, or fairings. In order to repair them, they are usually removed from the aircraft and repaired in a composites shop, where temperature and humidity can be controlled - preferably in an autoclave.
Now, how the hell is anyone going to remove a fuselage section to drag it into a shop?
In fact, there is a seperate "limit load" test that is performed at 100% and must show no detrimental permanent deformation. It is not unheard of that a structure will pass the ultimate load test yet fail the limit load test because of this criterion even though the limit load is smaller.
A goal is a dream with a deadline
Sincerely, every engineer who ever got a degree in aerospace.
Plus, uh, Beavis.
Just a quote from a poster to the orignial article's forum:
"> Wasn't that crash in Brooklyn a few months after 9/11 due to a carbon composite tailfin ripping off?
That was an Airbus plane... American products are genetically such superior that they need no testing at all! BTW, Boeing's reason for not testing is that fine carbon powder released by a tension breakage would contaminate and destroy expensive equipment and require hazmat cleaning procedures afterwards. Imagine if a B787 crashes real-life, what pollution would be there! Carbon fibre shards and powder are known dangerous to lungs, carbon brake discs are about to be banned from Formula-1 car races because many drivers are already ill. I think Boeing is doing an ugly thing purely for profit and fate will punih them."
'There's a raging debate within the engineering team to see if we should break it or not,' says [787 General Manager Mike] Bair.'
I can't believe there is really a debate about that!
Of course we need to see it break.
-- -- Warning. Do not stare directly at the sun.
The first time this was really driven home to me was in undergraduate school in '88. A classmate was working on a portable carbon-fiber bridge project for the Army. It had to support the weight of a main battle tank crossing it. In the full-scale test demo, the general overseeing the project commented that you'd get one and only one tank crew to cross the bridge. He felt that after the other tank crews saw how much the bridge flexed, there was no way they'd want to drive on it.
I did a rough calc, and for the wings to touch it looks like the strain in the wing skins would be ROM 3%. Now, MMPDS lists the strain to failure of 7075-T6 (the classic wing alloy) as 8 or 9%. But we know aluminum wings don't touch during ult tests, which is explained by the fact that the failure mode of airplane bits is almost never material yield.
As someone pointed out previously, graphite is less nonlinear than aluminum and tends to have smaller strains to failure, and also has all sorts of non-yield failure modes. I would have to think graphite wings of similar geometry would be less likely to deform further than aluminum ones, not more. Since it was the 787 program manager who speculated about the tips touching there must be some substance to the claim, and I suspect the wing is so flexible because it's thin and highly engineered to avoid flutter, not because it's graphite. That's just a guess though.
Wish I could explain what I'm working on right now. Lets just say it's for something that flies and it's not silver.Equine Mammals Are Considerably Smaller
these little things called rivets, which appear in many lines along a metal airplane wing, cause enormous stress concentrations. Which lead to microcracking, under the rivet. Which leads to corrosion. Which leads to failure modes hard to see with the naked eye.
Composites, while not completely inert (IE, they will corrode when bound to certain metals) are not riveted: rather they are much larger homogenous entities without the stress concentrations. Lighter and flexible to boot.
...for 99 cents, and they could make back a big part of the cost of the test...
before posting?
/.er able to come up with a legitimate concern would be able to document it with the necessary math and physics, and not merely throw an offhand remark against the wall to see if it sticks.
Boeing and its engineers have been doing this for a while, and I trust they've considered exactly what effects wing bending has on performance, and it is not a problem. Any
I suspect that the limit to lift in controlled flight would be due to aerodynamic stall, not wing bending.
"National Security is the chief cause of national insecurity." - Celine's First Law
Actually, there was not a different in diameter. It's just that one of the cylinders hadn't been supported properly for a couple days and became oblate. It was still the right size, just not the right shape. So they jacked it back into shape and connected it. It wasn't difficult.
Your comments about holes in planes ("ramp rash") are also off base. Boeing has two patch kits, one which can be applied in a very short time, the other which takes something like 36 hours to cure. Boeing has shown to the airlines that fixing small holes from collisions with trucks won't be a problem.
http://lkml.org/lkml/2005/8/20/95
This clearly has nothing to do with aircraft performance but rather is designed to punish Airbus (EAS) for their 148% failure. An not in the industry but rather in the public perception which is a random and important part of aircraft success. I'm sure if one would the clock back to the launch of the 747 that the other players in that early market spread all sorts of rumors, it'll never fly, it's drop out of the sky, you'll suffocate etc etc. The 380 will sell so will the 787, both maiden commercial flights will be on slashdot.... both will crash at least once.
Another thing to think of, is that pole-vaulting poles have been made of composites for years. The first ones were bamboo, then aluminum, the fiberglass and more recently (cir. 1995 or so) carbon. If you have ever seen pole vaulting, you know why I bring it up, the poles bend almost to the point where their ends can touch, and are generally 12-20' long. I did this sport in highschool... what a thrill it was to have the pole throw you up in the air.... unless it breaks (shoulnt have jumped on an under-weighted and 3 year old pole!).
Tm
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Yes... an all-composite plane is great and fantastical and yadda yadda, but has Boeing ever heard of sharing? A couple years ago I needed carbon fiber for my college senior project and it was all but impossible to find because of the 787 and the JSF (thank you Ebay). I'm all for making planes that fly better or don't crash as much and whatever, just leave some freaking material for the rest of us. Carbon fiber is wonderous stuff, stop hogging it!
I think 2 should be enough.
Thank you, I'll be here all week. Don't forget to tip the waiters.
To do list for Windows
Mod parent up - Informative
The only carbon fibre I have around here is a $1000 flyrod and I'm not going to test that.
Engineering is the art of compromise.
Gravity is a myth: the earth sucks.
Engineering is the art of compromise.
Do a little research on how metal wings fail before spouting off. Look at any previous test to failure on traditional wings.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
In 1969 I went to work for Boeing at their 747 plant in Everett. A monumentally huge plant, each of its two assembly lines could roll out a 747 every 7 days. All wings were fabricated on-site using the latest technologies: laser-aligned jigs and robotic rivet machines. They had such stiffness and strength that the wingtips in the static test facility could reportedly be pushed & pulled upwards by hydraulic rams & cables more than 30 feet above their nominal resting levels before the first components started to fail (spars deforming, rivets shearing, ...). I don't know how many G's would be required to produce that much deflection, but I'm sure the number would be more common to modern fighter aircraft than airliners. I've never felt safer than when flying in a 747. If the 787 carbon fiber wing really outperforms a 747's aluminum "slab", I'm going to enjoy flying on the new bird.
sorry, I didn't see the first sentence.
The Kruger Dunning explains most post on
I have seen some of this testing done at the University of Idaho. It is pretty amazing to see large wing sections bending and flapping as described. I know previous versions of this carbon wing have been "accidently" tested to the breaking point. I would put money down to say the wing can withstand touching the fuselage. Very interesting indeed.
Any transportation device should be as light as possible while meeting the requisite safety and non-weight performance requirements. If you save 10% of the weight of the plane due to lighter wings (and possibly lighter fuselage) you increase it's capability in one or more of these areas:
Fuel consumption
Capacity
Speed
Maneuverability
Long term maintenance
IF the wings actually met two or three times as much as they needed to, the odds are very high that they could be lightened significantly.
Mass is possibly the single most critical aspect in transportation. Given the choice between spending 3500USD more on a vehicle that was 30-50% lighter versus spending that 3500USD on the same vehicle but with hybrid drive systems, I'd take the lighter one every single time.
And for those who want to talk about "safety" of mass it's false. Mass is not what makes a car safer, it's the size. More energy absorption decreases the impact force to your body.
My Suburban burns less gasoline than your Prius.
Here are new photos of the first 787 before paint.
787 Photos
30% off web hosting. Coupon code "SLASHDOT".
What is the point of having all that cool test equipment and cameras if you can't break stuff ?!?
;)
hehe, 30 years later i still remember a trip to the local power station that had the test equipment for powerlines and stuff. They crushed a large ceramic insulator til it blew up. Took some insane amount of pressure like 20000 psi. Quite spectacular. They had a rig for pulling apart a powerline too, we would have killed for that test
How long before flight control surfaces that function by deforming or bending specific areas of the wing
I was under the impression that carbon fiber was actually renowned for being inflexible and tending to shatter, rather than deform (at least from my experience with motorcycle fairings and carbon fiber rims). Is there a less-rigid mix of CF? If so, why is it not used in racing products?
Trust me, as hellish as being cooped up in a plane for 16 hours sounds, getting cooped up in a plane for 10 hours, then three hours in a shitty airport, then getting on the plane for another 7 hours is worse.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
I'm a non-practicing ASE and was wondering how lightning might impact the wing and/or fuselage? http://www.sae.org/aeromag/features/aircraftlightn ing/ In other plastics, arcs caused by lightning opens holes and makes the material brittle. That would be bad for a wing in a thunderstorm for obvious reasons.
.... hummmmmmmm./
Makes me pause and say
Looks like some foil or layers of conducting material is embedded in the wing/airframe. http://www.dexmet.com/Lightning-Strike-Protection
Ever notice the number of times that ultra-expensive carbon fiber racing yachts tend to break in conditions far less stressful than what they are apparently rated for? The super-dooper CF mast snaps, or the hull cracks or something. Examples that come to mind are the maxi-yachts taking part in the Sydney-to-Hobart, or the sinking of the australian CF entry 'AUS35' in the America's cup about ten years ago. And yet aluminum-masted yachts in the same weather conditions make it through.
hers a linky to the rollout of the dreamliner in the middle of the nightb ID=2642&page=1>itle=First%20787%20Dreamliner%20& css=gtitle.css&pubdate=06/26/2007
http://seattlepi.nwsource.com/photos/popup.asp?Su
> They have come a long way in wing flexibility.
The Boeing B-52's wings flex up 10 feet at the tip from parking to take-off speed. They've been that way for 55 years. Let's hope they've come a long way since then, carbon composite or no.
The Buff also gets a foot longer at cruising speed as compared to parked. Will Boeing build more foot room into the 787? Not bloody likely. "Call that progress? Because I don't." -- Marvin the Paranoid Android
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
These are 3D objects. Think about twist.
When the leading edge rises more than the trailing edge, you may get extra lift. If it stalls, you may get drag that pushes the wing backward.
If you do lose lift, things may be even worse! Then the wing snaps back, only to regain the forces that were bending it in the first place. This can set up an oscilation, like the one which destroyed the Tacoma Narrows Bridge.
Reminds me of a joke my Israeli colleagues sent me a couple of hours after Sep 11
20 First class airline tickets 100000 dollars
4 Airliners 800 million dollars
2 Skyscraper 2 Billion dollars
Palestinian children smiling (this had a picture from UNICEF) - Priceless
I guess having bombs go off every month gives you a sense of humor regarding other peoples tragedies.
**Life is too short to be serious**
The autopilot tried to keep the airplane level and on course by turning the control wheel to the left, balancing the asymmetry causing the plane to want to roll right. This worked for several minutes although it required the autopilot to turn the control wheel more and more to the left. Eventually the autopilot had turned the wheel to the maximum and the aircraft began to slowly roll to the right.
WTF?
That autopilot is dangerously defective. A dead engine is something it should handle; this isn't something fucked up like misrouted wiring or hydraulic lines.
So you lose lift. The wing flexes back the other way. Being in motion, it doesn't suddenly stop. It flexes past the origin.
It can keep doing this, flapping away, until damped by various loses like the generation of noise and heat.
Problem is, damping might not happen. You still have that force that bent the wing in the first place. Like a kid kicking on a swing, or like the Tacoma Narrows Bridge in the wing, the wing may deflect more each time. The movement grows until the wing snaps.
Of course, you might not lose lift. Think in 3D. If the wing twists, it may generate more lift.
That's shot from a cheap little plane flying along the coast, multiple miles away AFAIK.
The camera must have been insanely expensive. You'd need a huge lens. Then, you'd need either a motion stabilization mount or a very fast shutter speed. Fast speed means you need a huge sensor to reduce the noise.
Is it free hardware? Free as in "speech", not "beer".
If it has been determined that 150% is "safe enough" then designing it for 300% is expensive and heavy.
I see that in electrical equipment. Motors from 30 years ago have some parts that are heavily overdesigned. New ones have every part build to about 105%, and are much smaller, lighter, and more efficient.
So it is with planes. Build every part to the required safety margin and no more. Then you will get weight, price, and efficiency benefits.
The problem is that carbon fibre is relatively new at this use. The engineers don't fully know its capabilities. In order to design it to the minimum safety margins the "break" test could be really informative. Unless they do, they don't know if it will actually withstand 155% or 500%.
FLIGHT/NAVIGATION INSTRUMENT(S)..INATTENTIVE..PILOT IN COMMAND
I may be wrong, but won't lightning strikes be an issue for composite wings? I remember seeing some pictures from tests showing the effect and I amazed at the level of damage caused, compared to metal.
The article didn't mention it and I have yet to see anyone else mention it (may be filtering too high)
-SK
Not being an engineer, maybe someone with more (or less :-) qualifications can answer this:
How relevant is a slow steady application of stress on the structure?
That does not seem to represent the real life bouncing that turbulance applies to a wing. With the right amount of fuel in the wings, weight in the plane and a string of conveniently lined up 'pockets of air' (wind sheer, thermals, etc.) I could easily imagine a wing getting loaded very quickly to extreme amounts of pressure.
What kind of testing is done to determine / limit oscillations leading to both premature metal fatigue and positive feedback loops?
I'm in my right mind and I have the answer to everything!
All I want is a frickin' laser on top of a frickin' 787!
Strong is good. Flexible ... well, there could be problems. Because you can bend the wings up more before they will (theoretically) break might imply that their structure has lower stiffness. That might lead to a lower natural frequency of structural vibration which might, in turn, become low enough to couple to flight control loop frequencies.
Have gnu, will travel.
I read that.
You should not need to disengage the autopilot over the loss of one engine. This is dangerously defective. WTF?
While investigating a failed engine, the last thing a pilot needs is the extra stress of having to take over from the autopilot.
What do you learn? Lots of stuff.
;).
1) You learn how the wing breaks when put under that sort of load.
2) You learn how this particular batch of wing breaks when it's new.
3) You get a chance to find out that the test environment is not good enough to cope with a wing breaking
And if another wing ever breaks, and you have the broken wing pieces, you'd probably be in a better position to figure out what happened than if you never broke the wing in the first place. Then if really desperate and clueless you can then attempt to break a new wing of the same batch. If it breaks at a different load or a different way, then you might have your "Aha moment".
Now whether it's worth it or not is a different matter. Since the plane is far more likely to crash/fail for other reasons than a wing failing. When was the last time a plane crashed primarily due to the main wing breaking (not flaps failing or engines falling off or something smashing into the wing and breaking it)?
The load at the wingtip is probably the more dramatic one as far as video is concerned, but it's only one of many - 1/3 span is another.. The "thumper" test is also pretty cool; that's were they intoduce a small periodic driving force to various parts of the wing and measure it's response.
A goal is a dream with a deadline
Federal regulations also require that rate of load application be considered as well, so your instincts are correct. These days, a power-spectral-density model is used to access turbulence response for "Part 25" (commercial) aircraft. You can also introduce a periodic driving force on a wing for purposes of testing using devices known as "thumpers".
I know I'm only scratching the surface here, but I just wanted to let you know that you accessment is correct, and those test are done.
Follow this link: http://rgl.faa.gov/ Click on Federal Aviation Regulations and hunt for 25.341, from there, you should be able to find more data on the PSD model currently in use.
A goal is a dream with a deadline