Earlier this week, Boeing asked airlines to remove a batch of eight newly manufactured 787 Dreamliners from service, which prompted their immediate grounding, after the aircraft manufacturer determined that a manufacturing issue was compromising the resistance of an area of the composite carbon fiber structure of the jet.
So far eight 787s – all built in recent years – have been pulled from flight. United Airlines, Singapore Airlines and Air Canada planes are affected by the impromptu grounding, according to a person familiar with the situation.
Boeing confirmed to Air current that he “identified two distinct manufacturing problems when joining certain fuselage sections of the 787’s rear body, which, combined, result in a condition that does not meet our design standards.”
According to those familiar with the problem, an area of the structure at the rear of the aircraft is unable to withstand the maximum stress that would be experienced by the aircraft in service and could fail.
“We have determined that eight aircraft in the delivered fleet are affected by the two issues and therefore need to be inspected and repaired prior to continued operation,” a Boeing spokesperson said in a statement to TAC.
The new issue is the first publicly known case in the jet’s nine-year life that a structural defect with its mostly carbon-fiber airframe prompted Boeing to immediately withdraw the 787s from service. The 787 fleet was immobilized for three months in 2013 following the overheating of the lithium-ion batteries. At that time, the world frame of 787 was only 50 aircraft and the jet returned to service after the company developed a new containment and ventilation system for the batteries of the main and auxiliary power units. inside the electronic bay of the jet.
The source of the newly discovered structural problem was traced to a coupling point inside the rear fuselage between two carbon fiber composite barrels, known as section 47/48, where the two barrels meet with a large partition which covers the pressurized cabin. The parts are fabricated and attached to the rear pressure bulkhead at Boeing’s North Charleston, SC plant, then delivered for final assembly to the nearby company final assembly building or airlifted to Everett, Wash.
Today, the 787 fleet approaches 1,000 aircraft and has over the past decade become the backbone of international air fleets. While long-haul operations are still sharply down since the start of the COVID-19 pandemic, the 787 fleet around the world has seen a stronger resurgence of operations from the April industry trough, compared to older two-aisle planes like the A330s and 777s, but globally. The capacity of 787 is still down 64% from August 2019, according to the OAG. Some of the fuel-efficient two-aisle airliners were reused for all-cargo operations, as travel restrictions drastically reduced international air travel.
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The first of the two issues that give rise to the problem is how the natural spaces of the structure are filled with shims that ensure that the stresses on the cell are supported as they are designed. Boeing has used predictive wedging technology on the 787 program for more than a decade, laser scanning the surfaces around structural joints to automatically generate the wedges needed to fill the voids.
In the case of the eight withdrawn aircraft, the gaps were poorly addressed. On their own, that might not be an immediate problem, but Boeing said a second manufacturing issue caused the jets to be withdrawn. The second problem centers on the inner skin of large monolithic composite drums. On the suspect aircraft, the woven carbon fiber fuselage skin is “supposed to be smooth enough that there aren’t any sharp ridges,” said a person familiar with the issue.
The company “performed an extensive review of the manufacturing data with respect to both the timing and the skin surface profile. Based on this analysis, we were able to determine that the two conditions affected only those eight planes, “said the Boeing spokesman, who added that he had notified the Federal Aviation Administration” and was conducting a thorough review. of the root cause. ”
When the gaps are poorly filled in combination with the roughness of the inner skin, the required structural strength does not meet the limit load requirement. The limit load is the maximum expected stress that the aircraft could be expected to experience in service. Although load limit is not just an air service requirement, every commercial aircraft test program must demonstrate that an aircraft’s structure is designed for limit loads before it can be cleared to fly for the first time. safely.
“The rest of the fleet in service has been determined to reach the carrying capacity limit,” said the Boeing spokesman, who added that a repair is “in the approximate two-week stage” by air. The Boeing spokesperson added that he had “changed our production and verification process to ensure that we are building a compliant product.”
The limit load is a structural requirement far lower than the much more violent ultimate load requirement to withstand two and a half times or 150% of the most severe conditions the aircraft would have ever experienced in flight.
In the longer term, voids left by improper wedging can add stress to certain points of the structure, which can cause the development and propagation of unexpected fatigue cracks. The Boeing spokesperson said its engineers “analyze data on the in-service fleet to determine if action is needed, potentially including more frequent inspections or rework. It could also be determined that no further action is required if the condition is found not to affect the longevity of the structure. ”
The planes were taken out of service earlier this week after the company discovered the problem over the weekend. “Once we became aware of the situation, we immediately contacted the airlines which operate the eight planes concerned to inform them of the situation,” added the Boeing spokesman.
An FAA spokesperson said the US aviation regulator “is aware of the matter and continues to work with Boeing,” according to a one-sentence statement.
“Singapore Airlines is aware that one of our Boeing 787-10 is affected by this technical issue,” said a spokesperson for the airline. “The plane is not in service and we will be working closely with Boeing on a solution.” United Airlines and Air Canada did not immediately respond to a request for comment.
The installation of the chocks on the structure of the 787 was a recurring challenge for Boeing. Prior to the 787’s entry into service in June 2010, improperly fitted horizontal stabilizers temporarily grounded Boeing’s test fleet. And the problem, according to several Boeing aircraft manufacturing engineers and assemblers familiar with the situation, say structural timing is a long-standing challenge for the company’s South Carolina manufacturing operations.
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“Don’t get me wrong, it’s hard to do,” said one engineer. “But they’re so determined to make the rate, sometimes engineering and production don’t line up.” In 2012, when production of the 787 began, Boeing found more than a dozen poorly seated spars, structural stiffeners, inside the same 47/48 section requiring inspections and localized repairs for structural delamination.
“Safety and quality are Boeing’s top priorities; we are taking appropriate action to resolve these issues and prevent them from recurring, ”the spokesperson said.
The recurrence of timing issues on the Dreamliner program comes as Boeing plans to consolidate 787 final assembly operations exclusively in South Carolina. The North Charleston, SC plant that produces the aft fuselage where the structural problem was introduced, builds the section regardless of where the final assembly is completed.
Write to Jon Ostrower at [email protected]