Excerpt: "Mitsubishi Aircraft has introduced a stretched variant to its MRJ regional jet family and unveiled extensive design changes, including using aluminium instead of carbonfibre composites for the aircraft's wings.
With the aluminium wings, the company moves away from its earlier aim of using significant amounts of composite materials for the airframe. The result is that the only remaining composite parts will be the empennage, horizontal tail and vertical tail, amounting to 10-15% of the total airframe.
The change will allow its engineers to develop an optimum wing for the MRJ90 and minimise the deterioration of range performance for the stretched version. The biggest benefit will be for the MRJ70, which will weigh less.
"This will allow weight reduction through structural changes, allowing for larger winglets and resulting in a reduction of block fuel [consumption] and take-off performance improvement," says Mitsubishi."
Given Mitsubishi's role in the wings of 787, what, if any, can one infer from this recent design change with regard to 787?
Dynamicsguy From Australia, joined Jul 2008, 767 posts, RR: 8 Reply 2, posted (3 years 8 months 1 week 1 day 19 hours ago) and read 4159 times:
Quoting Cerecl (Thread starter): Given Mitsubishi's role in the wings of 787, what, if any, can one infer from this recent design change with regard to 787?
I'm pretty sure the news has been posted before.
What can one infer? I don't think very much. Boeing themselves have said many times that the benefits of composites on the 787 don't scale as well for a 737-sized airplane, so maybe the situation is even worse for a regional jet.
From reading between the lines of the article, it sounds like the move away from composites was due to either the non-recurring engineering cost or the cost of production infrastructure. Either of those two factors may have pushed them towards a single wing design for the whole family if they'd stuck with composites.
Switching to aluminium may allow them to tailor the wing for each family member more cheaply. One reason for structural changes to be easier and require a shorter lead time is that you don't have to lock in your engineering early enough to be able to make layup mandrels for your composite parts. All speculation, of course.
Even without those specific drivers their trade studies may have pushed them to aluminium anyway. Composites have their benefits and drawbacks and they have to be balanced. With all of the other non-composites related changes it sounds like they've been doing plenty of trade studies, and the material change is one of them.
Keesje From , joined Dec 1969, posts, RR: Reply 3, posted (3 years 8 months 1 week 1 day 19 hours ago) and read 4121 times:
Little implications for the 787 I guess. The design is basicly done & tested. Looking a bit broader I think just like MHI other companies will be more carefull betting the house on CRFP then they were 5 yrs ago. It's not the holy grail for every aerostructure.
20 yrs ago I was teached the complications and risk associated with CRFP. I've seen them all come by in recent yrs. (hopefully damage detection, certification and repair stay away).
When the 7e7 was born many started to dismiss/ ridicule any reference to risk using extensive CRFP. Nowadays many see that a good piece of aluminium has its advantages regarding pressure loads, predictable quality and manufacturing.
I would not be surprised if the A350 XWB ends up including 50% composites instead of 53% because of lessons learned in recent years.
Parapente From United Kingdom, joined Mar 2006, 1315 posts, RR: 10 Reply 4, posted (3 years 8 months 1 week 1 day 19 hours ago) and read 4017 times:
It becomes easier and easier to see why "open rotor" is a must for the 737/320 replacement if they are going to get the necessary leap in performance demanded.Of course any new plane will be more efficient,but it looks like it will be primarily Al or AlLi so shedding weight will not be easy.
If the "open rotors" are at the back as most people suggest it does open up the possibility of some new thinking on the wing.If for instance it had some "super" high lift devices (but no drag penalty in flight) this could result in both smaller (low drag) wings and less T/O power required - only a thought.
SEPilot From United States of America, joined Dec 2006, 6258 posts, RR: 39 Reply 5, posted (3 years 8 months 1 week 1 day 18 hours ago) and read 3889 times:
A close reading of the article shows that the primary motivation seems to be the fact that changes are much easier and cheaper with Al than with CFRP. This makes a lot of sense; with CFRP, if you want any differences between two different versions you need two sets of molds, which are very expensive. They wanted to be able to optimize the wing for each version, which with CFRP would require different molds for each one. But with Al it is much easier to tailor the design to each version. This plus the fact that the weight savings of CFRP for an aircraft this size are much less significant than for a larger one makes it much easier to go back to Al. So what is the implication for the 787? Not much; I still believe that CFRP is going to prove highly desirable, not so much for weight savings as for maintenance savings. This is going to take a while to establish, and in the meantime designers are still faced with the task of designing a plane that will find acceptance in the marketplace at a price that will bring them a profit. The safer and more conservative choice is still Al, especially for smaller planes. This will not change until the 787 and A350 have proved themselves; but someone had to go first and Boeing had the guts to do it.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
Lightsaber From United States of America, joined Jan 2005, 10682 posts, RR: 100 Reply 6, posted (3 years 8 months 1 week 1 day 16 hours ago) and read 3689 times:
No implications for the 787.
I'm excited the MRJ has grown a little.
Quoting Dynamicsguy (Reply 2): I'm pretty sure the news has been posted before.
But the thread died quickly.
Quoting Cerecl (Thread starter): The result is that the only remaining composite parts will be the empennage, horizontal tail and vertical tail, amounting to 10-15% of the total airframe.
I was under the impression a little more was being left composite.
Quoting Keesje (Reply 3): When the 7e7 was born many started to dismiss/ ridicule any reference to risk using extensive CRFP. Nowadays many see that a good piece of aluminium has its advantages regarding pressure loads, predictable quality and manufacturing.
CFRP is mature. The problems with the 787 were program management (in my opinion). In my opinion there is just as much risk sticking with aluminum and having an airframe too heavy to compete long term.
Quoting Keesje (Reply 3): I would not be surprised if the A350 XWB ends up including 50% composites instead of 53% because of lessons learned in recent years.
Ok, I'm not going to quibble about 3%. I'd agree there could be some shift back.
MSNDC9 From , joined Dec 1969, posts, RR: Reply 7, posted (3 years 8 months 1 week 1 day 14 hours ago) and read 3512 times:
Quoting Cerecl (Thread starter): Excerpt: "Mitsubishi Aircraft has introduced a stretched variant to its MRJ regional jet family and unveiled extensive design changes, including using aluminium instead of carbonfibre composites for the aircraft's wings.
Exaclty how do you make the leap from a design consideration in the MRJ to the 787?
Stitch From United States of America, joined Jul 2005, 26705 posts, RR: 83 Reply 8, posted (3 years 8 months 1 week 1 day 14 hours ago) and read 3433 times:
Yup, it looks like MHI is doing it more for convenience than any belief/fear that CFRP is "not ready for prime time" in a major aerospace structural application.
Part147 From Ireland, joined Dec 2008, 351 posts, RR: 0 Reply 9, posted (3 years 8 months 1 week 22 hours ago) and read 3105 times:
Quoting SEPilot (Reply 5): but someone had to go first and Boeing had the guts to do it.
Well said, alas historically, others have not faired so well after 'going first' - the Comet, Concorde, etc... maybe those who get a bit of a head-start don't always benefit as much as they could/should.
I think many other manufacturers have a great opportunity to close the gap between themselves and Boeing and perhaps even Airbus as a result - by opting to use less CFRP for the more 'user-friendly', recycleable aluminium.
Time will tell
It's better to ask a stupid question during training, rather than make a REALLY stupid mistake later on!
Rheinwaldner From Switzerland, joined Jan 2008, 2066 posts, RR: 6 Reply 10, posted (3 years 8 months 1 week 20 hours ago) and read 3001 times:
I don't think that there is any implication with the 787. Even the CFRP prospects in general are not hampered.
Much more this move could mean, that beside Boeing and Airbus no other manufacturer is capable enough to stem large scale CFRP projects. The industrial application of CFRP in the area of wings and fuselages requires a lot of research. In this area the smaller players lack the power of Boeing or Airbus.
Don't infer from the 787-experience that CFRP will not be the future. The 787 lacks many of the promised ability that would be expected from the use of CFRP.
More and more I think that the 787 is a stop gap plane on the way to a bright CFRP future. Yes, it succeded brilliantly on the market. But other than that it is a capital example of over-confidence. The innovation leap was far too big to be handled seriously. The efficiency gains are only marginal compared to the efforts that were put into that plane. As of now it seems that the full efficiency gains are contributed by the engines and not by the usage of CFRP. This is a complete failure to roll-out the promises made by CFRP.
I have not seen one source (also very recent ones) that does not clearly say a CFRP structure part is 20..40 % lighter than a comparable aluminium part. I can only assume that this weigth saving ratio is even established since decades in those areas that saw CFRP applications before (rudders ...). So why does the 787 not deliver this mark? As I said, it likely has more to do with the 787 than with CFRP.
Even the A380 is able to gain a relative weight reduction of 26% for the CFRP parts(http://www.reinforcedplastics.com/view/1432/composites-lift-off-in-primary-aerostructures/ : 16% of total weight is CFRP (25% other source) which reduces the weight compared to an all-alu plane from 185 to 170 tonnes).
The following achievements (listed e.g. in this link http://www.eads.net/1024/en/madebyeads/possibilities/composites.html ) can not be found on the 787:
- Up to 40% weight savings
- Autoclave-less production
- Reinforcements can be sewn onto the carbon fibre fabric to give it a three-dimensional structure
I think in 50 years the 787 will be remembered as a pioneer-aircraft that explored a (too) big (at once) chunk of new land, did receive ludicrous market attention but did not satisfy the fullness of expectations that come from CFRP.
On this forum it is my impression that the CFRP hype has cooled down extremely since the 787 stalled. But I would not attribute that to CFRP but to the 787.
Quoting Dynamicsguy (Reply 2): Either of those two factors may have pushed them towards a single wing design for the whole family if they'd stuck with composites.
A very easy tailoring to changing strengths was always rated as big CFRP advantage. What happened here?
Quoting SEPilot (Reply 5): This makes a lot of sense; with CFRP, if you want any differences between two different versions you need two sets of molds, which are very expensive.
Only if your mandrel is on the wrong side of the part, that you build. E.g. in the case of fuselage barrels the inside mandrel is an example that prohibits easy configuration changes (likely the 783 is a victim of that fact). With an outside mandrel the number of local layers can be controlled very easily. For each subtype of fuselage the tape laying machine simply is loaded with another programme.
Quoting SEPilot (Reply 5): This plus the fact that the weight savings of CFRP for an aircraft this size are much less significant than for a larger one makes it much easier to go back to Al.
Why should the weigth savings not scale down? If the same material mix is applied I would expect an exactly identical weight saving contribution of CFRP.
SEPilot From United States of America, joined Dec 2006, 6258 posts, RR: 39 Reply 11, posted (3 years 8 months 1 week 19 hours ago) and read 2984 times:
Quoting Rheinwaldner (Reply 10):
Why should the weigth savings not scale down? If the same material mix is applied I would expect an exactly identical weight saving contribution of CFRP.
This may actually apply more to the fuselage than the wing. In the fuselage there is a minimum thickness required for damage resistance, which for smaller airframes is more than is required for actual strength, and so you don't get the same weight savings. I have not seen any comparable arguments about the wing, but there may be some.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
Stitch From United States of America, joined Jul 2005, 26705 posts, RR: 83 Reply 12, posted (3 years 8 months 1 week 18 hours ago) and read 2867 times:
Quoting Part147 (Reply 9): Well said, alas historically, others have not faired so well after 'going first' ...maybe those who get a bit of a head-start don't always benefit as much as they could/should.
And sometimes, they do benefit from going first - Boeing's 247 is generally considered to be the first airliner placed into service that brought a number of advances together (all-metal semi-monocoque construction; fully cantilevered wing; retractable landing gear; autopilot; etc.) and it laid the groundwork for a pretty successful run of commercial airliners from Boeing.
Cerecl From Australia, joined Jul 2008, 647 posts, RR: 0 Reply 13, posted (3 years 8 months 1 week 7 hours ago) and read 2637 times:
Thanks to everyone for their reply, except perhaps this
Quoting MSNDC9 (Reply 7): Exaclty how do you make the leap from a design consideration in the MRJ to the 787?
I did not "leap", I specifically let open the possibility that there may not be any connection. If you took more time to read the question instead of "leaping" to chastise maybe you would have seen that.
I'll bite on this one. The 787 does use out-of-autoclave technology for primary structure.
Quoting Rheinwaldner (Reply 10): Quoting Dynamicsguy (Reply 2):
Either of those two factors may have pushed them towards a single wing design for the whole family if they'd stuck with composites.
A very easy tailoring to changing strengths was always rated as big CFRP advantage. What happened here?
The advantage of CFRP is you can tailor the fibre directions to the load paths, but that was not my point.
It requires more engineering effort to design and analyse for CFRP making it more expensive to do the engineering. That ply tailoring is more involved that just changing aluminium skin thicknesses, and then when you analyse the structure there is more effort to analyse for all failure modes. There may have only been enough money in the budget to do a single CFRP wing design. With aluminium that budget may stretch to more variations on the wing design.
CFRP parts also require layup mandrels for each composite part. These are expensive pieces of tooling, so again it could be a matter of cost. It would cost too much to make separate sets of tooling for different variants of the wing, so instead they may have had to stick with a single wing design with a single set of common mandrels. If you have composite parts inerfacing with composite parts then you can't have a "right" side for all of the mandrels, though it may allow for larger parts defined by the outer mould lines to share madrels across designs.
Sponsor Message: 
From Australia, joined Jul 2008, 647 posts, 
From Germany, joined Nov 2006, 4248 posts, 
From , joined Dec 1969, posts, 
From United Kingdom, joined Mar 2006, 1315 posts, 
From United States of America, joined Dec 2006, 6258 posts, 
But the thread died quickly.
I'd agree there could be some shift back.
From Ireland, joined Dec 2008, 351 posts, 
From Switzerland, joined Jan 2008, 2066 posts, 
Printer friendly format 
