Boeing's New 787 Wings — Amazingly Flexible 564
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.
Nothing new (Score:0, Informative)
"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."
Re:I hope they test it! (Score:5, Informative)
Reason for not testing (Score:1, Informative)
Re:I hope they test it! (Score:5, Informative)
Re:Nothing new (Score:5, Informative)
Re:Nothing new (Score:5, Informative)
Re:I hope they test it! (Score:4, Informative)
One year ago? How about twelve? (Score:5, Informative)
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.)
Errors in post? (Score:3, Informative)
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....
Re:I really don't see the big deal (Score:5, Informative)
Re:I hope they test it! (Score:5, Informative)
My doctorate is in Mechanical Engineering - Materials, in this case fracture mechanics. The fact that the wing is so strong suggests that it may be being over-designed. My graduate structures professor, who worked on the 747, point out that airplanes are designed for what might be called simultaneous mode failures -- there is no point in having the wings significantly stronger than the fuselage, as once the fuselage breaks the wings don't do you any good, you have just been carrying too much material in the wings. The same is true for all sub-systems. Hence, you have to do a very exhaustive analysis of the expected situations and make sure that all of them are appropriately covered, then you add a safety factor.
Typically, fatigue cracking has been the limiting factor in aircraft structures, and has caused numerous crashes. With the experience that has been gained in military programs, we should now know enough to use these composites properly.
Re:I hope they test it! (Score:3, Informative)
Re:Nothing new (Score:3, Informative)
It's true that the A350 will use composites, but to imply that Boeing is trailing Airbus on this ("Nothing new") when Airbus is actually trailing Boeing is just inaccurate.
Re:Nothing new (Score:5, Informative)
Yeah, it kind of reminds me of when Airbus called Boeing's composite barrel design "old fashioned" [nwsource.com]!
Bearing in mind that nobody has produced such a design yet, including Airbus. Until Boeing did it a couple of weeks ago, that is.
The A350 was designed in direct response to the 787, which surprised Airbus in the amount of interest it received (they had at the time placed their bets on the now-troubled A380 program, which may never break even). Saying the 787 copied any of the A350's design or construction methods is getting it completely backwards.
Ornithopter? (Score:4, Informative)
What? (Score:5, Informative)
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.
Re:Who cares if they bend (Score:3, Informative)
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.
It also means they can change the angle of the wing to something less aggressive, since less air needs to be displaced to maintain adequate lift (because, as you say, the plane is lighter). If they didn't do that, the plane would actually have to fly slower in order to maintain a constant altitude.
Re:I hope they test it! (Score:3, Informative)
Once the wing has been tested to a 'century storm' level (case 1 above) - any testing beyond that (case 2 above) is largely of academic interest, it proves very little about the performance of the wing within the required envelope. Also (AIUI), as the overload percentage increases, the strength of the wing starts to depend more on the individual wing's characteristics (I.E. manufacturing flaws that wouldn't be a problem at 130% overload) than it does on the basic design.
787 is a revolution in design and manufacturing (Score:5, Informative)
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
Re:Shopping for planes has never looked more fun (Score:1, Informative)
Airbus: Care for some metal wings?
Boeing Client: No, thank you, I take them like my women.... flexible.
See the difference?
Re:I hope they test it! (Score:3, Informative)
Re:I hope they test it! (Score:5, Informative)
Since you can not make the wing infinitely strong you you put operating limits in it.
One "neat" trick they use involves airspeed. When you start pulling Gs your stall speed goes up. Once a wing is stalled it stops generating lift so it unloads.
Back in the day your airspeed indicator had arcs. The green arc means that your wing will stall before it breaks.
The Yellow arc means that yes you can break the wing if you try.
The Red line means bad things are going to happen.
So when flying into storms the pilot can slow the the top of the green arc and be safe.
BTW a stall at altitude isn't a terrible thing. It is better than breaking the wing.
With this wing it may have an all Green arc.
As to breaking the structure to learn things. Yes but that kind of testing is expensive. If the wings of the 787 pass with a bigger than average margin then I would much rather see them do repetitive tests to see how it does with multiple over stress conditions.
The thing about some of the composites I have dealt with is some don't fail gracefully. I have parts of aircraft deform from stress but not totally fail. In other words it will get you home but she isn't going to fly again without A LOT of work.
I have seen carbon fiber get a good scratch in it and the next thing you know it is in a million part small parts.
Re:I hope they test it! (Score:2, Informative)
"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."
Re:I hope they test it! (Score:5, Informative)
of course their is a downside to most changes.
by deform, you mean yield [wikipedia.org] so, yes if you exceed the limit of carbon fibre you likely have snapped, where as aluminum, you have destroyed the structure of the frame. So if they both exceeded this limit at the same load, the aluminum may allow you to make it through one event.
For this to be obviously safer, you need:
1) the yield points would have to be very close.
2) it must be a single yield event (not repeated yield points, leading to a quick fatigue failure)
3) you must know the event occured so that you will replace the yieldied aluminium part, before the next event.
4) the yield event would still have to be in the yield strength of the aluminum, and not exceed it to the point of failure.
I think that is the issue, all of these are false. Carbon fibre has a much higher yield point, the aluminum wings constantly need inspected for fatigue cracks, and with each cycle they become closer to the point of failure.
With the carbon fibre, as the wing bends, it is probably designed to self limit the load. Since the aluminimum cannot survive the same amount of movement, it cannot self regulate (it bends, which makes it hot, which makes it softer, which makes it bend more which makes it hotter and softer,...)
of course it takes alott of energy to bend carbon fibre also, so it is releasing energy as heat as well. Granted aluminum is a much better heat conductor, so it would naturally transfer that heat better. But carbon fibre is known to stay stronger at high temperatures than aluminum.
Re:I hope they test it! (Score:4, Informative)
Re:Well... (Score:4, Informative)
The point I'm trying to make, and perhaps not clearly (and if so, my apologies--it's been a long day!), is that they could perform the testing at 100% load and still have adequate safety factors in terms of structural performance. The 150% load test assumes a load the aircraft will never experience and then qualifies that the structure maintains its integrity in extreme conditions.
The load rating (i.e. 100% load) is a product of the lowest common denominator of design safety factors throughout the aircraft. Testing beyond 100% load is an *extra* margin of safety because 100% load already incorporates safety factors appropriate for human life.
Liar (Score:2, Informative)
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?
Re:787 is a revolution in design and manufacturing (Score:2, Informative)
Furthermore, there are alot more tools involved than whatever periodical you read seems to claim.
Its quite obvious they simply visited near the end of assembly.
And finally, it won't be rolling out on 7/8/7 because Air Force One is currently being painted, and is overdue, because of paint problems. This means the paint for the 787 has been bumped back as much as several weeks.
The first 787 will not roll out of the paint hangar completed until late july.
Sincerely,
A Boeing Employee
zOMGLOLWTFBBQPONIES!!!! (Score:1, Informative)
Re:I hope they test it! (Score:1, Informative)
Re:I hope they test it! (Score:5, Informative)
It sounds as if Boeing uses a "factor of safety" of 1.5, where the maximum anticipated load is multiplied by the factor of safety to determine the design strength of the wing. The factor of safety is calculated based on the earliest failure mode of the part, so it could simply be that other failure modes than wing deformation and buckling (as seen in the youtube video) are what determines the factor of safety with this new carbon fiber wing.
Re:Well... (Score:5, Informative)
What reasonable is, depends on which field you look at. The same standards do not apply to structural engineering (buildings), civil engineering (bridges, dams), aerospace engineering (aircraft), electrical power engineering (building wiring, electrical distribution systems), etc etc.
The FAA standards are, they set a specific limit load condition calculation for classes of aircraft (light aircraft are different from jet transports carrying people, etc). That's based on performance, operational usage, and the number of people typically carried. There are load cases for limit loads for gust loading (suddenly hitting a headwind when you're already pulling Gs), wind shear, emergency pull-ups, etc. A speed is established, called maneuvering speed, below which nothing you can do to the aircraft is credibly likely to ever cause the aircraft to exceed the limit loads.
Then, you add a 50% safety factor on top of those loads (failure load >= 150% of design limit load), and demonstrate to the FAA's satisfaction that the aircraft meets that ultimate load. For jet transports carrying people, the demonstration requires that you take it out to the 150% load limit and see if it breaks there.
Now, that ultimate load can be expected to cause permanent damage to the wings. Pretty much any aircraft exceeding the design limit load (100%) will get grounded, and anything approaching 150% is guaranteed to have damage. Since the test to 150% damages the test structure for any aluminum aircraft, the usual assumption is that it's a good idea to just keep testing past 150% until it breaks.
But you just need to prove that it meets the 150% for the FAA to be happy.
Designers try to make the failure point slightly, but not too much, past 150% of design limit load. Because adding weight is expensive (operations costs), and as others have mentioned it doesn't do any good for the wing to be stronger if the fuselage breaks first, etc. The loads are all balanced; it's inefficient for things to fail at different points.
These standards are reasonable, for transport aircraft. We know that because large jets are not falling out of the sky due to wing failures. I can't offhand think of the last one that wasn't due to some external cause (collision, etc). There closest incident recently was the American Airlines 587 crash in 2001 (http://en.wikipedia.org/wiki/American_Airlines_F
Re:787 is a revolution in design and manufacturing (Score:3, Informative)
I guess I wasn't specific enough for possible robot readers like yourself. Even though it's common to see "nm", I understand that accuracy is more important than actual communication for some. So try to parse "n.m." instead. Thank you good bye.
Re:I hope they test it! (Score:2, Informative)
The green arc is normal operating speed, the yellow arc is acceptable only in smooth air. The red line (Vne) is *never* to be exceeded.
What you're thinking of is known as maneuvering speed (Va). It is WELL below the max of the green arc and varies by the weight of the aircraft. Also, it doesn't exactly mean the wing will stall before it breaks. It means that full-deflection control inputs (turning the yoke all the way to the right, for example) won't exceed the G limits of the aircraft. So yes, if YOU try to break something off, the wing will stall first, but mother nature could still very well manage it, especially in a storm. Even large airliners fly over or around storms for a reason.
But you're right about one thing - a stall at altitude has to do with the WING producing lift, and has nothing to do with the engine. It's an easy recovery and not a bad thing at all unless it happens close to the ground (during the landing or takeoff phase), since you do lose altitude in the process.
Re:I hope they test it! (Score:4, Informative)
747 vs 787 wing testing (Score:2, Informative)
Re:I hope they test it! (Score:5, Informative)
You are correct that microfine stress fractures are impossible to see in a pure carbon structure. To work around that, every object has a very fine fibreglass layer (070 or thinner) on the outside surface. When stress is applied, the fibreglass shows the stress marks and you can then visually see that something is wrong.
The biggest issue with C/f structures is design life. At the time when I was last working in the industry (mid 90's), they weren't even sure what the maximum life was. There was no data anywhere in the world. The sailplane factories were stating that 10K hours was the minimum and they would test after that (metal airframes were 30K hours before EoL). There were studies being done at Melbourne's RMIT (Australia). The last I heard there was they got to 17K hours before failure of one wing. Given the absurd number of hours a commercial airliner does compared to a sailplane, I would hope and expect that they have done some lifetime studies beyond that. I haven't yet seen any numbers from Boeing about expected airframe life for their pure composite structures.
dreamliner rollout (Score:2, Informative)
http://seattlepi.nwsource.com/photos/popup.asp?Su
Comment removed (Score:3, Informative)