backtop


Print 75 comment(s) - last by Masospaghetti.. on Aug 7 at 10:02 AM

Engineers on the project say wing design flaw will prevent test flight in 2009

Boeing's 787 “Dreamliner” has been more of a nightmare for many at Boeing as the project has cost significantly more than expected and is still two-years late (and counting).

Another problem in the 787's design has been found, this time in the wings. During tests to certify the aircraft, damage to the wings and wing box of the 787 was found. The damage was delamination of the composite sheets covering the wings under stress.

The Seattle Times reports that the structural flaw in the Dreamliner was discovered in May during ground tests that bent the wings upwards to simulate stress during flight. The stress at the end of rods used to stiffen the upper wing skin panels caused the composite plastic material used in the wings to delaminate.

The damage to the wing occurred just beyond the Dreamliner's load limit, described as the maximum weight the wing is expected to bear in service. The Seattle Times mistakenly reported last week that the damage occurred just over the wing's ultimate load, which is 50% higher than the in-service limit load the wing is expected to endure. The limit load is the FAA test target and proves that the problem with the design of the wing is worse than originally believed.

The plane could have flown after the wing damage, but the test flights would reportedly have been severely restricted. The damage the wing sustained is reportedly not severe enough to have caused any sort of catastrophic failure had it happened in flight.

The design flaw and time needed to devise and implement repairs on the fleet means that the test flight will not likely happen this year according to one engineer on the project. The test flight was delayed in late 2008 to Q2 2009.

The damage to the wings extends inside the fuselage of the aircraft as well making repairs more difficult. The failure in the wing and the wing box is not the fault of Fuji Heavy Industries, who manufactures the components for Boeing. That means Boeing is solely responsible for any cost overruns and time delays because of the issue.

The fix has yet to be certified but could involve engineers creating a U-shape cutout in the end of the upper wing skin stringer and then refastening the reshaped stringer ends with new titanium fittings.



Comments     Threshold


This article is over a month old, voting and posting comments is disabled

RE: Confused...?
By Mclendo06 on 7/31/2009 10:32:01 PM , Rating: 2
Even if a plane will pretty much never see that load, you have to design to the FAR specifications. Period.

I'm honestly not very surprised by these issues. The 787 is the biggest leap in commercial aircraft design since the Concord. No plane has ever used composites for so much of the structure. The design is completely different. Delamination is going to be an issue with laminated composites, but they are generally better understood than woven composites, not to mention that techniques for their manufacture are further along, both of which make them a lower-risk choice overall.

The 787 is only the start in the world of composite aircraft. Once Boeing gets these kinks worked out they are going to be lightyears ahead of any other producer of commercial air transports.

One other thing - the 777 failed at 154% of maximum design load in its static test - http://www.youtube.com/watch?v=pe9PVaFGl3o - an overdesign of only 2.7%. Boeing knows how to analyze complicated structures just as well as anyone. The only problem is that failure of composites is an order of magnitude more complicated than the failure of metal...


RE: Confused...?
By Amiga500 on 8/1/2009 7:29:48 AM , Rating: 1
You think I don't know all about the FARs and JARS?

For test aircraft (i.e. not going to be used to carry passengers!), they do not have to meet the FARS/JARS. If you could guarantee meeting the regs prior to a test program, why have a test program at all? ;-)

Boeing were scared to even get the thing into the air with a restricted envelope of >2g. Says enough to me.

Oh, and you don't have to tell me about the complexity of modelling composites. Been, seen and done. I am of the opinion the 787, A350 and CSeries are a generation too early. Composites are simply not ready for the big time yet... too many unknowns, and too many inherent manufacturing problems with current processes.


RE: Confused...?
By Mclendo06 on 8/1/2009 8:00:26 PM , Rating: 2
Oh, I'm sure you do know about the FARs. Sorry, I wasn't trying to infer that you didn't. My comment was meant to be more tongue-in-cheek. I should have worded it differently.

I disagree that it's too early for a composite airplane. From discussions I've had the 787 is designed pretty conservatively overall. Yes, there will be growing pains, but everything I have seen indicates that Boeing is going to great lengths to ensure that these growing pains don't lead to catastrophic failures. The lessons they learn and the expertise their engineers are gaining will make the next composite aircraft that much better.


RE: Confused...?
By ikkeman2 on 8/7/2009 2:19:24 AM , Rating: 2
so you'd prefer a "potemkin" first flight (copyright leelaw) like their roll-out.

remember they rolled out a shell some two years ago and the uppper echelon claimed their (wet)dreamliner would be "structurally complete" in mere weeks... I guess even Boeing couldn't allow for another pr stunt like that.
They identified an error, tried to find a solution - found they had no option but a repair and decided (to do the right thing and) to implement the repair befor going forward.
Kudo's to Boeing for doing the right thing, instead of the looking good option.


"Folks that want porn can buy an Android phone." -- Steve Jobs

Related Articles













botimage
Copyright 2014 DailyTech LLC. - RSS Feed | Advertise | About Us | Ethics | FAQ | Terms, Conditions & Privacy Information | Kristopher Kubicki