The MRO industry is preparing for more composite repairs as next-generation aircraft enter service
The maintenance, repair and overhaul (MRO) industry is gearing up to service an increasing number of airliners employing a much higher share of composite materials. The introduction of the , the and—less expectedly—the and the 737 MAX is causing MRO service providers to invest in new equipment and technician training. The changes, however, remain evolutionary rather than revolutionary, as many MROs have developed a high level of expertise since the 1970s.
“What has changed is that composites have evolved from being used in secondary structures, such as radomes and fairings, to being utilized in semi-critical control surfaces and most recently in primary critical structures such as the fuselage and wing box,” Richard Brown, principal consultant with aviation consultancy firm ICF SH&E in London, says. However, so far the bulk of demand for composite repairs is driven by the existing “metal” aircraft being delivered such as Airbus A320s andand and that feature composite structures in areas such as nacelles and cargo doors, Brown argues.
The reasons for repairs are unlikely to change. Composite repairs primarily are needed due to incidental damage to the aircraft. Boarding bridges, fuel trucks and other ground equipment can hit aircraft. Lightning and bird strikes are other well-known causes.
Industries Engineering & Maintenance (AFI KLM E&M) sees a real change in where the repairs will have to be performed. The company already performs repairs on wing, without taking down a component or panel. “We choose to do so to make logistics easier and shorten the turnaround time,” James Kornberg, products and business development manager for aerostructures, explains. This has been the case for thrust reversers, for example. “But now we will have no choice—we'll have to make primary structure composite repairs on-wing, outside of our workshop,” he points out.
This can make turnaround times challenging. “Composites take longer to repair because of the curing time required for the adhesives; for some adhesives this is a minimum of 12 hr.,” Bas Gouverneur, head of aircraft engineering at, says. This is particularly the case for A-checks or night stops where the ground time of the aircraft ranges between 12 and 24 hr. In addition, it may be difficult to maintain the correct minimum temperature for the repair or to protect the area from rain, he notes.
Christian Sauer,'s manager for engineering, airframe-related components services, also sees a critical aspect in the on-time availability of a repair process and material in aircraft-on-ground situations. Technik recently developed an automatic system using a stationary robot for quicker repairs. The idea is to automate the panel repairs in monolithic and sandwich structures, mainly for the aircraft fuselage and wing structures. This approach cuts repair time by about 60%.
Lufthansa Technik is working on a mobile version of the equipment under the “Caire” research and development project that runs until 2015. Technicians will then be able to take equipment out to damaged aircraft.
Meanwhile, archrival Air France Industries is planning a new composite aerostructure repair center at its Paris Charles-de-Gaulle base. “The idea is to be as close as possible to the aircraft,” Kornberg said. The €40 million-plus ($55 million-plus) facility will be inaugurated in the summer of 2015. It will regroup existing capabilities, such as those now located in Le Bourget and add equipment and human resources. The 215,000-sq.-ft. repair center will employ 200 technicians from the beginning. Equipment will include autoclaves, non-destructive testing devices, surface treatment installations and sample testing laboratories.
The target turnaround time (TAT) for a complex repair—like a thrust reverser overhaul, which today can take two months—will be halved. A reduced TAT allows for a smaller inventory, Kornberg emphasized. At the new maintenance facility, the company will also carry out research and development projects to develop “new, high-added-value solutions.”
As an example of the complexity of the repairs AFI KLM E&M can perform, Kornberg referred to an Air Francethat had its tail cone damaged by an A330 wing tip in 2010. Airbus suggested replacing the carbon-fiber part. “They eventually approved our repair solution. Thanks to our experience, we saved time and money,” Kornberg says.
He emphasizes that few maintenance organizations can undertake such complex repairs, which begin with thorough engineering work. A complex repair has to be approved internally, with AFI KLM E&M's Design Organization Approval (DOA) or via the OEM. There is even a trend toward fewer players, as these repairs tend to become more and more complex, Kornberg adds.
The industry also is putting some effort into training. “Airframers have been working with specialist schools and MROs to train technicians on the latest bonding and bolt repair techniques,” Brown says. At AFI KLM E&M, in addition to hiring new employees specializing in composites, technicians are being transferred from metal specialties. “But training is not enough; these technicians need maximum practice, and this is possible thanks to our high level of activity,” Kornberg says.
Lufthansa Technik's Sauer does not see a hiring wave approaching, but selected specialists will be added. “Different skills, yes; one reason for this is that we prefer bonded repairs (versus bolted repairs), and bonded repairs strongly depend on the skill level of the mechanic,” Sauer says.
SR Technics' Gouverneur agrees that hiring new specialists is not the main issue. It is more about providing today's employees with the additional training required. “Improvement of skills is key, due to the many varieties of composite materials,” he says.
Kornberg estimates it will take five to seven years for all 787 stakeholders—the manufacturer, operators and MRO service providers—to have a good idea of how composites perform on the new-generationtransport. One useful piece statistic is the thrust reverser removal rate, he suggests.
Although the 787 and the A350 are bringing a dramatic increase in terms of composites use, they are not the only ones that will increase the volume of composites repairs. Kornberg mentions the Airbusand the Boeing 737 MAX, too. Their engine nacelles will be larger, and ground clearance will be smaller, he says.
However, contrary to the general belief that the composite content of airframes will continue to increase, Sauer predicts metal will come back in some way.
“I personally think that we have seen the peak in usage of carbon-fiber reinforced plastics (CFRPs),” he says. In his view, airframers will move to a more selective usage of CFRPs, creating metal-CFRP hybrid designs. He believes that “CFRP will be used where its benefits can really be used.”