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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.



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RE: Confused...?
By bjacobson on 7/31/2009 12:21:39 PM , Rating: 2
Even with all the design hurdles to overcome, this is one heck of a plane. 20% fuel savings over the 767...


RE: Confused...?
By BZDTemp on 7/31/2009 4:50:53 PM , Rating: 5
1. Lets see that come to life - so far it is just computer predictions.

2. Advancement in engine tech is likely to account for big savings. Maybe even more than the optimized weight and aerodynamics.

The A380 uses less fuel that the current 747's so of course Boeing should be able to make the Dreamliner use less than a 767 - after tech has moved a long nicely these last years.


RE: Confused...?
By knutjb on 8/1/09, Rating: -1
RE: Confused...?
By Amiga500 on 8/1/2009 7:33:06 AM , Rating: 1
quote:
Even with all the design hurdles to overcome, this is one heck of a plane. 20% fuel savings over the 767...


You might be interested to know that if a propfan engine were used, fuel savings would be 50% over a 767!

(and that is from the 1980s NASA propfan tests... wait and see how the updated tests perform)


RE: Confused...?
By knutjb on 8/2/2009 4:26:52 AM , Rating: 1
I was too noisy in that application. Some of the blade tech made it's way into turbo props. Turning at lower speeds on turbo props, the noise difference wasn't an issue. I haven't seen if they have revisited it. It was prettycool looking.


RE: Confused...?
By ikkeman2 on 8/7/2009 2:00:20 AM , Rating: 2
and a cessna citation uses even less fuel, while going only a few hundred instead of a few thousand miles at only a few hundred instead of almost a thousand miles an hour...

- what's your point.


RE: Confused...?
By Masospaghetti on 8/7/2009 10:02:33 AM , Rating: 2
There are other very significant issues with using a propfan - and while ultimate efficiency is better, noise is an issue and so is safety -- I wouldn't want to be in that plane when you have a prop blade separation.

To give you an idea of how much energy these blades would have if they separated, a traditional turbofan with a kevlar-reinforced cowl sometimes cannot contain a separated turbine blade - there have been instances where the blade has literally severed the entire fuselage of the plane in half and wedged into the other engine. Now imagine what would happen if there was no cowl at all...

Personally I would love to see more competing technologies for engines, everything uses turbofans now and its kind of boring - bring back the supercharged 28-cylinder Wasp Major radial!!


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