surse:http://www.flightglobal.com/ blogs/flightblog ger/2009/ 06/breaking- boeing
-postpones-787. html
<http://www.flightgl obal.com/ articles/ 2006/02/21/ 204869/airbus- has-to-pr
ove-a380-wing- is-compliant- after-early. html
Boeing yesterday
<http://www.flightgl obal.com/ blogs/flightblog ger/2009/ 06/breaking- boeing
-postpones-787. html> announced it was postponing first flight of the
787 citing the need to reinforce structure where the wing box meets the
center wing box at the side of body of the aircraft. FlightBlogger takes
a closer look at exactly what the problem is and how Boeing came to
yesterday's announcement.
Because of the need to go back into the detailed design phase for this
fix, combined with the need to fabricate, install and test at component
and at full scale levels, several sources with a direct familiarity to
the situation estimate that the fix will take "months not weeks."
INSIDE:
* What is the problem?
* Historical Precedent
* Timeline
* The Fix
WHAT EXACTLY IS THE PROBLEM?
The issue centers around the wing-to-body join that mates the wing box
(Mitsubishi/ Section 12) and the center wing box (Fuji/Section 45/11).
The center wing box is the combination of two pieces, the center wing
tank (Section 11) and main landing gear wheel well (Section 45). The
area of concern centers on the 18 points where Sections 11 and 12 meet.
Digging deeper, the 18 points in question on each side of the airplane
(36 total) are located on the top panel of the center wing box and run
port to starboard inside the structure of the center tank through to the
other wing. These 18 'stringers' inside the center wing box are matched
by 17 stringers on the wing box, which serve to stiffen the wing skin.
The wing box has 17 stringers, but a source indicates they are
designated 2-18, hence the reference to the 18 points that need to be
reinforced.
The composite stringers, which give the wings its longitudinal
stiffness, are cured during production when cooked in the autoclave and
joined as a single bonded piece with the wingskins.
On the inboard side of the wing box where the 17 stringers end and
connect to the center wing box, each has what is known as a 'stringer
cap' that widens at the end and actually makes the hard connection
between Section 11 and Section 12 on the side of body. The stringer caps
on ZY997 sustained damage, albeit repairable, when the wings were flexed
in late May.
Boeing confirms that small areas of the wing structure separated or
"disbonded" from the wing skin, though declined to specify exactly
where. Sources directly familiar with the situation say the shifting
tension load from the stringer to fastener head also caused damage on
the structure.
HISTORICAL PRECEDENT
In February 2006, nearly a year after A380 had begun its flight test
program, Airbus was conducting testing on MSN5000, the static test
airframe when the wing "ruptured" during ultimate load testing. The wing
was being flexed to 150% of limit load when the wing broke between the
inboard and outboard engines.
At the time, the wing was deflected 24.3 feet at 147%
<http://www.flightgl obal.com/ articles/ 2006/02/21/ 204869/airbus- has-to-pr
ove-a380-wing- is-compliant- after-early. html> of limit load, below the
150% requirement for certification. Airbus said it designed the A380
wing to break just beyond 150% citing strict adherence to its weight
reduction program. Airbus said it demonstrated the structural
improvement, not through full-scale testing, but through further "finite
element models to prove the adequacy of the structure on production
aircraft."
Later that summer, Airbus was required to install a 66 lb wing
strengthening package on the existing A380 fleet, starting with MSN003
<http://www.flickr. com/photos/ hairymonster/ 486229901/> , the first
superjumbo for Singapore Airlines that entered service in October 2007.
The European airframer decided that wings delivered from MSN018 on would
have the modifications incorporated prior to delivery to final assembly
in Toulouse.
Airbus was able to verify the viability of the fix as a part of its
certification documents supplied to the FAA and EASA for final analysis
and approval.
TIMELINE - Updated
Late May
Boeing experiences the first signs of trouble on the static airframe.
During that test, the wings of ZY997 were flexed and the strain
measurements on the stringer caps were reading higher than predicted.
Previously, on April 21st, Boeing conducted the limit
<http://www.flightgl obal.com/ blogs/flightblog ger/2009/ 04/the-road- to-787
-first-flight- --3.html> load test which saw the wings deflected over
17-feet and an equivalent of 120-130% of maximum load.
"We went in and did some inspections and saw a number of things
indicative of what the strain gauges were saying," said Scott Fancher,
vice president and general manager of the 787 program, said on
yesterday's teleconference, implying that the test had left visible
damage to the structure during the late May testing.
The 1G check out of the wing, which was conducted in late-March, would
not have stressed the join hard enough to yield the same results.
Previous rumors
<http://www.flightgl obal.com/ blogs/flightblog ger/2008/ 12/whats- up-with-t
his-wing-delami. html> of delamination from December 2008 still stand as
false and unrelated to the current situation which came directly from
testing this past spring.
Early June
Preliminary analysis showed that the aircraft was still cleared for
first flight, though with a reduced flight envelope. Sources indicate
that the original plan was to fly ZA001
<http://static. flickr.com/ 3382/3490241807_ f6f66520fd. jpg> and ZA002
<http://www.flickr. com/photos/ mitrebuad/ 3643260832/> on their
respective maiden flights to BFI as planned then park the aircraft while
a fix, which was considered to be "relatively minor" at the time, was
developed that would allow an expanded flight test envelope, though
Boeing says this plan was never in consideration.
Scott Carson, CEO of Boeing Commercial Airplanes, said yesterday that
"the airplane could enter flight test with a credible flight test
envelope as [the company] worked relatively minor modifications. "
June 19
Boeing completes final detailed analysis on the stringer caps and
decides to postpone first flight.
"The work done by the team through the week last week narrowed the
envelope to the point where on Friday we determined that to fly would be
such a small envelope for us that it would be an interesting exercise in
having the airplane in the air but not particularly useful in terms of
preparing the airplane for certification, " Carson said.
June 23
Boeing makes a formal announcement of the first flight postponement. The
change in first flight was unknown to many of those closest to the
airplane. As late as the evening of Monday, June 22, sources indicated
first flight had shifted to July 2nd at 10 am after holding
<http://www.flightgl obal.com/ blogs/flightblog ger/2009/ 06/flight- readines
s-review-set- fo.html> at June 30th for more than a week before and
during the Paris Air Show. Boeing says that the July 2nd date was never
formally approved for first flight.
THE FIX
Boeing says it will be several weeks before it announces a new schedule
for first flight and first delivery.
Several tasks have to be accomplished before 787 is cleared for first
flight: 1. Develop the modification & concurrently repair ZY997. 2. Test
the modification on a component level. 3. Install the modification on
ZY997. 4. Conduct full-scale tests on ZY997. 5. Install the modification
on ZA001.
"We have to give the team time to do time necessary to do this job,"
said Fancher. "While we will proceed with urgency, we will not
compromise the process for the sake of schedule."
The fix, once identified, will be able to be installed on the aircraft
in the factory, the flight line and at supplier partners without any
anticipated schedule disruption.
Carson affirmed that the production plan will proceed as planned with a
10 aircraft/month ramp up targeted for 2012.
"At this point, that's our judgment that we will continue with the build
up that we had previously anticipated. "
Concluzia mea:mai au nevoie de cel putin 6luni pentru a vedea si noi primul Dreamliner ruland pentru teste. Partea mai interesanta sa vedem daca acest lucru va duce la o migrare a clientilor catre A350WXB sau nu
Acasa 
