Boeing on Tuesday disclosed a new manufacturing quality issue with the 787 Dreamliner, this time with assembly of the airplane’s horizontal tail in Salt Lake City. The disclosure comes after last week’s revelations of quality control problems at Boeing’s South Carolina plant affecting the 787’s aft fuselage.
Boeing also released data Tuesday showing the order backlog for the 737 MAX has been reduced this year by almost 1,000 jets.
During fabrication in Salt Lake of the 787’s horizontal tail — known as the stabilizer — engineers discovered earlier this year that “certain components were clamped together during the build process with greater force than specified,” potentially leaving the structure with gaps between components wider than the five-thousandths of an inch that’s allowable in the specification, Boeing said.
Boeing spokesperson Jessica Kowal pointed out that the gap tolerance required is only slightly more than the thickness of a sheet of paper, which is about four-thousandths of an inch. Such gaps are typically filled with small pieces of material called shims.
This flaw, which Boeing said was identified during an internal audit conducted in February, “may lead to premature aging” of the horizontal tail structure.
Kowal said none of the affected 787s currently in service with airlines around the world “are within a window when they would experience this aging,” and so “this is not an immediate safety of flight issue.”
“We are correcting the issue on airplanes that have not been delivered,” Kowal said. “The rework generally involves removing fasteners at the affected locations, applying a calibrated clamping force, measuring for any gaps and shimming if required.”
“Analysis is underway to determine if action is required on the in-service fleet,” she added. “Following an assessment of the manufacturing process, a total of 893 airplanes are believed to be affected.”
That’s the vast majority of the 982 Dreamliners Boeing has delivered.
As with the aft fuselage quality control problem, the new problem means delivery of 787s, already hit by the falloff in demand from the global pandemic, has been further slowed as Boeing conducts inspections of completed jets.
Though the build 787 rate is still nominally 10 jets per month, Boeing delivered just four in April, none in May, three in June, two in July and four in August.
In South Carolina, Boeing identified two separate quality defects in fabrication of the aft fuselage, both at the join between the pressurized section that is the rear of the jet’s passenger cabin and the unpressurized and tapered barrel section behind it, which is where the jet’s horizontal tail is attached.
One of the South Carolina flaws — shims used to fill gaps in the aft fuselage where the two sections are joined were the wrong size — was discovered in August 2019 and corrected on jets built since then.
The second flaw, discovered last month, revealed that the inner surface of the fuselage at the join was insufficiently smooth.
When analysis showed that the combination of the two flaws — wrong-sized shims and a non-flat inner skin surface — could together create unacceptable gaps at that fuselage join, Boeing last month was forced to ground eight 787s in service with various airlines, including United, Air Canada and Singapore Airlines.
A Federal Aviation Administration (FAA) engineer, who works on commercial airplane safety issues but cannot be identified because he spoke without agency permission, said Tuesday that although planes have been grounded in the past when in-service accidents revealed design flaws, “grounding airplanes for manufacturing flaws is unprecedented and unbelievable.”
Boeing said Tuesday that since February it has been inspecting every complete but undelivered 787 for horizontal tail gaps. And it is also now inspecting those jets for the unacceptable roughness of the inner skin at the aft fuselage join discovered last month.
The company said it expects these inspections to continue to slow 787 deliveries “in the near-term.”
Boeing is still consulting with the FAA and working out the implications for jets in service of all three manufacturing flaws.
“We continue to analyze and try to understand the scope of the issues,” Kowal said.
As with FAA oversight of the certification of new airplanes, the safety agency delegates most of the oversight of manufacturing work at all Boeing’s commercial airplane plants to Boeing engineers designated as FAA representatives, who are overseen by Boeing managers.
Last year, Boeing announced a sweeping transformation of its standard quality control procedures and its intent to eliminate about 900 quality inspector positions.
At the time, Boeing justified that move by citing the use of automation, and specifically “smart tools” that would enable the fabrication of precise shims to fill gaps.
Over the Labor Day weekend, the FAA said in a statement that it is investigating the 787 manufacturing flaws, adding that “it is too early to speculate about the nature or extent of any proposed Airworthiness Directives that might arise.”
At the beginning of the 787 program, Boeing outsourced fabrication and assembly of the jet’s horizontal tail to subcontractor Alenia at a plant in Foggia, Italy. However, major quality issues there caused multiple delays. In 2012 when the second Dreamliner model, the 787-9, was introduced, Boeing opened its own horizontal tail assembly plant in Salt Lake City.
The horizontal tail work was eventually taken away from Alenia altogether so that all the 787 stabilizers are now made in Utah.
More MAX cancellations
Boeing on Tuesday also released its jet orders and deliveries figures for August. The data shows that another another 91 orders for the still-grounded 737 MAX have either been canceled or are considered at this point unlikely to be fulfilled.
That brings the total of 737 MAXs either canceled outright or removed from the official backlog to 955 aircraft so far this year.
August activity consisted of 17 outright cancellations of the MAX, a dozen by major lessors Aercap, Aviation Capital and GE Capital Aviation Services, two by the carrier Icelandair, and three by unidentified buyers.
Boeing also removed an additional 74 MAXs from its official backlog.
Although the order contracts for these aircraft are not formally canceled and are still under negotiation between Boeing and the buyers, the jetmaker considers the orders unlikely to be fulfilled at this point and so accounting rules require that they no longer be counted in the backlog.
Ten 787 Dreamliners were similarly removed from the backlog as dubious, likely due to the dramatic COVID 19-induced drop in demand for planes.
For the first time this year, Boeing did notch five new orders for the 737 MAX in August: two for Enter Air of Poland and three for an unidentified customer.
The net result is 433 outright MAX cancellations or conversions to other models this year and 522 orders now removed from the official backlog as too dubious to count.
The MAX order backlog is now cut to 3,408 airplanes. This compares to the Airbus order backlog for the rival A320neo, which at the end of August stood at 6,034 airplanes.
Boeing’s data also confirmed that EVA Airways of Taiwan last month replaced its order for seven of the largest Dreamliner model, the 787-10, with an order for three 777 freighter jets and four smaller 787-9s.
Including all jet models, Boeing’s 2020 net order tally, after accounting for new orders, cancellations and those removed from the backlog as no longer solid, stands at negative 932 airplanes.
In contrast, Airbus has won a net order tally of 303 aircraft this year after cancellations.
Boeing said Tuesday its official backlog for all models is 4,387 jets. Airbus cites its backlog at 7,501 jets.
In addition to the four 787 passenger jets delivered in August, Boeing also delivered two 767-based KC-46 military refueling tankers, two 737-based P-8 anti-submarine planes, two 767 freighters and three 777 freighters.
So far this year, Boeing has delivered just 87 jets.
That compares to 276 jet deliveries at this point last year. In 2018, before the MAX was grounded, Boeing had delivered 481 aircraft by the end of August.
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