With almost a month since Boeing announced it was forced to ground its 787s for structural reinforcement, the company continues to work to develop, install and test a fix that can get its troubled Dreamliner into the sky after more than two years of delays.
According to a senior program source: “There is good news and bad news. The good news is we know what to fix, and how to fix it. The bad news is the location is a [expletive] to get to.”
Boeing says that revised schedules for first flight and delivery remain under review, as they have been since the company’s June 23rd news conference.
DIAGNOSIS & DEVELOPMENT
While the fix is being developed and a fully revised schedule finalized for airlines, sources at both Boeing and partner suppliers indicate that the existing production plan has slid roughly one and a half to three months for the delivery of Airplane Ten’s components to Everett, even as suppliers continue to prep parts for shipment.
The slip, the sources say, allows Boeing to finalize and test the fix and limit the number of aircraft in final assembly required to undergo the fix in Everett. Boeing previously stated that any fix developed would be able to be installed no matter the location of the parts in the supply chain.
Airplane Eight, ZA101, is expected to begin final assembly operations before the month is out, with parts for Airplane Nine, ZA102, believed to be arriving beginning in early August. The slip, one supplier sources say, could mean that structural components for Airplane Ten, ZA104, may not arrive until October. The customer ZA-designations are non-sequential.
The side-of-body issue was first discovered in late-May during a test that saw lower wing loads than the April 21st test of 120-130% of limit load. The test revealed the weakness in the upper section on the stringer caps of the wing to body join at the side of body of the aircraft.
A corps of Boeing engineers are working 80-hour weeks to design the fix that allows the 787 to fly with a robust flight envelope and achieve FAA certification with 150% of limit load on the wing, sources say.
For the development of the remedial fix, widely believed to be made of titanium, engineers have to design a modification that avoids two potential challenges down the road.
Veteran structural engineers tell FlightBlogger that the key to developing a reinforcement centers around ensuring that the loads that caused the initial problem at the site of the wing stringer caps are not redistributed elsewhere causing a further structural issue.
Second, as the area is stiffened Boeing engineers must take great care to develop a fix that isn’t susceptible to long term fatigue issues that come from the normal structural aging of the aircraft.
These challenges aren’t unique to structural engineering on the 787, in fact, they are part of the normal checklist that comes with developing the solution that is the 3-dimensional puzzle of designing aircraft. This is not to say, however, that solving the problem is any less complex, difficult or time consuming.
INSTALLATION
Several program sources indicate that August is a crucial month for the wing fix as the development phase moves into the installation phase.
Boeing reiterated that its engineers are “working with urgency”, and no internal timeline has been finalized for the testing or duration of the installation of the fix.
Sources say the area that will be reinforced at the side of body is extremely tight and difficult to reach as the installation area of the fix will provide very little room to install the fasteners to secure the reinforcement.
The installation of the fix may begin as early as the middle of August, with installation times around one month for each already assembled airplane, sources estimate.
Boeing has nine 787s at its Everett facility (6 flight test, 1 production, 2 ground test) that have gone through, or continue to undergo, final assembly operations, and structural sections for a 10th (Airplane 8) continue to arrive.
ZA001 is expected to leave the flight line for Paint Hangar 45-03 where the first 787 will undergo installation of the fix.
ZA002 will remain on the Everett flight line and the area around the side of body will be covered with a specially ordered tent to protect the aircraft.
In addition, Boeing has moved the approximately 50-foot long, two-thirds span test wing box, known as the “Dash 18” wing, from the company’s Seattle Development Center to Building 40-23 where 787 static testing has been taking place in Everett.
The company is considering using the test wing box, which was formally broken in November 2008 above 150% of limit load, to test installation methods as a dress rehearsal before modifying the static test airframe and ZA001.
PERMANENCE & PRODUCTION
Even with the remedial fix in the works, a key discussion centers on the future of 787 production and when the permanent fix is designed into the wing to body join.
Sources say a revision of the upper part of the wing to body join is almost certainly necessary to create a permanent long-term solution and eliminate the time consuming installation of the remedial fix.
Boeing says there are about 40 787s in process throughout the global supply chain and a question yet to be answered is the timing of incorporation for the permanent fix.
Boeing has already planned a series of blockpoint changes to incorporate weight reduction and performance improvements into the design of the aircraft. The first major blockpoint was for ZA100, the first production 787 (Airplane 7), with the next expected to follow around Airplane 20.
Airbus faced a similar challenge when the A380 wing ruptured below the 150% mark in 2006 forcing the European airframer to modify aircraft already in final assembly. Airbus eventually incorporated its own remedial fix into A380 production before the wings were delivered to Toulouse, however the company has had to redesign the effected area as a long-term solution.
Photo Credit Fortune Magazine
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This post originally appeared at Flightglobal.com from 2007 to 2012.
