Boeing's latest rework effort on its all-composite 787 jet sees it removing and replacing thousands of improperly coated fastener joints inside the wings on each airliner to ensure protection from lightning strikes.
The work first requires removal of sealant on the aircraft's composite wings, allowing access to thousands of wing fuel and hydraulic system fastener joints that were designed and installed with an improper coating. They have to be removed and replaced to meet Federal Aviation Administration requirements for electromagnetic effects (EME) protection for lightning strikes.
The design flaw was discovered in autumn 2009, but the airframer has waited until now to address it.
Boeing has continued wing deliveries to final assembly, pausing several times in 2010 to allow shipsets to arrive at a higher level of assembly completion. But it opted to push the wing fastener joint rework to change incorporation after assembly, although wings with this design issue continue to arrive in Everett from manufacturer Mitsubishi Heavy Industries in Japan.
There had previously been an issue with incorrectly applied sealant on the wings, necessitating rework, but Boeing has been receiving wings from MHI with correctly applied sealant for some time.
However, the airframer says that it will be required to conduct "a significant amount of resealing work that needs to be accomplished on all 787 wings" as a result of the fastener joint changes.
Boeing says "the overall resealing work is well understood and already a part of the programme's plan". It adds: "This work was identified and planned for prior to the announcement of the programme schedule" in January, which slid first delivery to Japan's All Nippon Airways from early 2011 to the third quarter, following a fire aboard test aircraft ZA002 in November 2010.
FAA requirements for EME protection as part of Part 25 Section 954 and 981 require all joints and fasteners to be installed in a way that prevents any sparking within the fuel that could lead to a catastrophic ignition.
Because the 787's structure is majority composite, which does not conduct electricity like traditional metals, Boeing has had to meticulously design the metallic parts of the aircraft, including the incorporation of an elaborate current return network, to prevent sparks and arcing, as well as withstand lightning strikes.
Those directly familiar with the issue say the test fleet of six 787s has the same configuration as those jets currently requiring rework, but did not need the fastener joint modifications before flying, as Boeing employs a fuel with anti-static additives for test flights preventing any possible spark.
ZA001, Boeing's lead 787 test aircraft, suffered a lightning strike in May 2010, with no trace of damage to the aircraft beyond instrumentation inside the right wing where the bolt was believed to have hit.
Today, more than 35 787s already delivered to Everett will require this rework, including test aircraft ZA004, ZA005 and ZA006, which is likely to be refurbished and delivered as business jets.
The airframer says it has "worked with MHI to develop a detailed plan to accomplish this work to ensure that airplanes already in production are brought up to standard and that future wings are delivered to Everett without the need for rework".
The company is conducting 787 rework operations at Boeing ATS "Factory South", the 40-24 building inside the main Everett factory, as well at its Global Service & Support site in San Antonio, Texas.
Source: Flight International