The pictures shown around informally in the industry look ugly: a myriad of small cracks in the paint around windows, paint peeling off the fuselage, exposed and worn expanded copper foil (ECF), the lightning protection layer visible below the surface paint, unprotected fasteners.
And worst of all—20 Airbus A350s grounded by the Qatar Civil Aviation Authority (QCAA), turning one of the manufacturer’s most important customers, Qatar Airways, into a very unhappy one for the time being. The carrier refuses to take delivery of any additional aircraft from Airbus.
Airbus is adamant that the paint flaws and the ECF damages do not compromise protection against lightning as “we incorporated substantial margins.” Airbus also sees “no effect on the structure of the aircraft” and stresses that “this is not at all an airworthiness issue.”
Most operators appear to agree. Lufthansa and Finnair refer to “cosmetic” issues that have been fixed. But Qatar Airways Group CEO Akbar Al Baker holds a different view.
“We don’t know if it’s an airworthiness issue. We also don’t know that it is not an airworthiness issue. This is also a conclusion that was accepted by EASA inspectors that came in and met our regulators,” Al Baker said at a recent Aviation Club meeting in London. He also criticized that “Airbus has made a very large dent in our widebody operations,” a statement that raises the prospect of claims for compensation.
Now Airbus is hitting back. In a highly unusual statement Airbus wrote Dec. 9: “In the face of the ongoing mischaracterization of non-structural surface degradation on its fleet of A350 aircraft by one of its customers, it has become necessary for Airbus to seek an independent legal assessment as a way forward to resolve the dispute, which the two parties have been unable to settle during direct and open discussions.”
The independent assessment is based on a clause in the contract between Qatar and Airbus that comes into force when the two parties disagree.
“The attempt by this customer to misrepresent this specific topic as an airworthiness issue represents a threat to the international protocols on safety matters,” the manufacturer added. And “while Airbus regrets the need to follow such a path, it has become necessary to defend its position and reputation. Airbus has worked actively with its customers in order to minimize the impact and any inconvenience caused by this in-service surface degradation on the aircraft. These solutions have all been dismissed by the above-mentioned customer without legitimate justification.”
The issue of why A350s operated by several different airlines—including Qatar, Cathay Pacific, Etihad, Finnair and Lufthansa, among others—are experiencing premature paint wear to varying degrees has kept Airbus busy for more than a year. Finally, the company claims it has identified the two main root causes—differences in thermal expansion and lack of adhesion to titanium fasteners—and is working on fixes.
The A350 paint system consists of multiple layers that cover the carbon fiber structure and the ECF on top of it. The first layers are the so-called basic primers—all of which are applied before final assembly of the aircraft. Several more are added after final assembly in the paint shop: an adhesion promotor, an external primer, intermediate coat, the basecoats and the clearcoat.
The important learning for Airbus from all the troubles is that the way paint is applied to an aircraft has to differ greatly depending on whether the fuselage is made of metal or composites. The A350 is Airbus’ first aircraft that has an (almost) all-composite fuselage. Aircraft are exposed to very high temperature differences, leading materials to expand and contract substantially. As Airbus found out, it gets vastly more complicated when different materials don’t react in the same way. And that is exactly what appears to be happening on the A350: the carbon structure essentially does not expand at all; its so-called thermal expansion ratio is 1. For the titanium fasteners, the ratio is 10. For the ECF, it varies between 15 and 40. And for the primer and paint, it is between 30 and 40.
Airbus says that the “thermal cycling”—many times going from hot to cold and expansion to contraction—can lead to early surface wear and even expose the ECF, which then gets damaged further with no paint protection. One reason why the problem has been so significant for Qatar Airways is that its aircraft are exposed to particularly large temperature variations between cruise flight and time on the ground in the Gulf summer.
The other issue a phenomenon called “rivet rash”—the paint does not stick well to the titanium fasteners, an experience shared by Boeing and its 787s.
Airbus EVP of Programs and Services Phillipe Mhun told Aviation Daily that “a wide range of solutions is available in the maintenance manual.” These include local and full repainting of the aircraft as well as ECF repair instructions. There were also “continuous product improvements” and Airbus is sharing “detailed instructions about how to paint.”
EASA inspectors had visited Qatar some months ago, which is when the agency also made the statement quoted by Al Baker. In a new statement, EASA is backing the Airbus view. “Airbus has identified the root causes of the paint issue. Paint process have been further optimized and additional enhancement initiatives have been launched in accordance with these findings,” an EASA spokesperson stated. “We are in contact with Airbus on the matter and are aware that the root-cause analysis has not identified any safety issue that would have an impact on the continuing airworthiness of the affected aircraft.”
The issue is unrelated to the recently published proposed EASA airworthiness directive affecting 13 A350s that lack some heavy ECF patches in some parts of the wing lower and upper cover.
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