Printed headline: Starting From Scratch
In engine component maintenance, repair—rather than replacement—is usually the less costly option. But when the OEM maintenance manual does not contain a repair solution, an MRO may be tasked to develop one.
This option, in fact, is becoming more practical, according to London-based aviation management consultant Richard Brown, who cites advancements in technologies that are enabling more engine parts to be repaired than previously. “There are new enhancements that can extend the lives of parts, such as new coatings, which help support business cases for repairing versus replacing with new parts,” he says. “Also, OEM price increases have spurred MROs to develop repairs, given a highly competitive aftermarket along with operators seeking ways of reducing engine MRO costs.”
Many factors influence decisions to repair or replace parts, including engine type, fleet age, usage rates, operating environment, route structure and maintenance practices, explains William Cermignani, executive director of Global Services Engineering for Pratt & Whitney. But he also notes the economic case typically is influenced by how airlines operate, inspect and maintain their engines. The “repair or replace requirements” must be tailored to each operator, he says.
Cermignani reports Pratt & Whitney receives repair-development requests for all of the OEM’s engine types, with the quantity of requests related to fleet size, engine utilization and shop visit rates. “We leverage our Global Services Engineering (GSE) Technology Group to extend the capabilities of existing repair technologies or develop new, innovative technologies to repair previously unrepairable components,” he says. “The results of our repair developments are applied to new and mature products.”
Rhonda Sample, repair leader at GE Aviation, emphasizes that along with the OEM, an airline MRO or a third-party shop can independently develop repairs. There are, she explains, multiple ways that the OEM cooperates with an airline or MRO to do so.
“One effective way to pool additional engineering evaluation/substantiation/document-writing resources is through the use of component-repair development agreements. They are bilateral agreements which provide a formal process for the OEM to work with airlines or MROs to jointly develop and substantiate repairs,” Sample explains. “There are also many cases where a very capable airline or MRO simply develops a repair and brings it to the OEM for certification, substantiation and inclusion in the OEM manual.”
For the repair process to be published in the manual, the regulatory requirements that govern system certifications must be met. “A repair solution may be published after the system certification is successful, the process substantiation is complete, and a source is industrialized,” she states.
A third method, Sample notes, includes collaborative work on departure records (DR), which are one-off dispositions on individual parts or defects. In many cases they, too, can result in a permanent published repair scheme. She reports the OEM processed more than 3,000 DRs in 2018 on the CFM56 alone, in support of customer collaboration and cost control. In addition to the DRs, Sample notes that during 2018, the OEM issues nearly 600 new or improved repairs instructions across seven programs—including the Leap.
When to Start
The OEM usually undertakes repair development or an MRO does so itself when it observes a need, explains Clinton Kent, sector vice president for components manufacturing at StandardAero. Among the principal reasons he cites are reducing costs, fleet issues where the part drives early engine removals or shortages of newly manufactured parts. Kent adds that newer engine types also are driving repair development priorities.
“On entry into service, engines will typically commence a period of teething problems,” he says. “When this happens, parts are removed and the OEMs will typically store them, develop inspection criteria and repairs, and reintroduce them to the market.”
Interestingly, Kent points out it may be necessary to create an additional repair scheme, even in cases where one already is described in the manual. For instance, he says a technician carrying out a repair may find a dimension for a part surface or thickness falls outside of the maintenance manual’s repair criteria. “For example, we might measure a crack on a part. The manual might say the repair limit is 0.002 in. If the crack we measured is 0.005 in., we might propose a repair for OEM approval,” he explains.
Once the repair scheme is proposed by the MRO, Kent says the OEM can take one of two approval actions. If the repair process is simple, the OEM might simply approve the repair scheme as presented, he says. “But in some situations, the OEM’s approval process may be more extensive, and the component’s original design may be studied to verify the repair will work. Once the OEM [confirms] that the repair is safe, the MRO would be authorized to go ahead and do the repair.”
Kent adds that if a component fails multiple times and an OEM technical analysis of the repair plan is favorable, that is generally when the procedure meets the criteria for a repair manual listing and becomes part of the existing certified repair documentation. He cautions, however, that all repairs take time to propose, develop, review, approve and conduct. “That can be as little as a few days for simple repairs, to years for more complex solutions. But a good average is 60-90 days,” Kent notes.
According to Thomas Richter, senior director for OEM business management at Lufthansa Technik, a repair-development decision often is based on an analysis of those modules slated for inspection during the next wave of shop visits. “If there is sufficient evidence that a certain failure mode on a particular part results in extraordinary scrap rates and part replacement costs, we would start repair development projects—subject to the OEM’s interest to provide a repair,” he says.
In that regard, Richter points out that Lufthansa Technik performs much of this analysis and decision-making, as well as some of the repair engineering, under joint repair-development programs with the engine OEMs. This, he says “results in a proprietary product,” in which the ownership of the resulting repair depends on the type and extent of the technology, intellectual property (IP), and the resources and efforts contributed by each party.
At the same time, he stresses that Lufthansa Technik also develops repairs independently of its OEM partners under its own European Aviation Safety Agency (EASA) Part 21 certified design/development agency authority. “These repairs are not listed in the OEM manual. We market them on our own,” Richter explains.
“Generally speaking, repair development is a combination of customer need and business case, so we tend to see the most development on repairs for engines with large fleets and on parts with high material costs, such as high-pressure compressors, high-pressure turbines, low-pressure turbines and combustors for CFM56, V2500, CF6-80 and GE90 engines,” says Friedhelm Kappei, head of industrial engineering at MTU Maintenance. “We see a constant high demand for repair development, especially as engines become more mature,” he states, adding that roughly 30% of MTU Maintenance’s repairs are newly developed and account for 50% of the company’s research and development budget.
Alternative proprietary repair development has been offered by the MRO under its MTUPlus program on CF6, CFM56, PW2000 and V2500 engines. Part of the development process, says Kappei, includes an analysis of repair needs and customer benefits, as well as development risks and availability of technology. “We then prioritize repairs that provide the most benefits for our customers,” he says.
When the need for a repair has been identified and the market demand verified, MTU’s experts will begin researching, developing and testing the procedure. If these steps have been completed successfully, the repair will be certified by EASA and/or the FAA.
“As an EASA Part 21 approved design organization, MTU can develop repairs and have them approved as per EASA’s stringent standards,” Kappei notes. “Regular audits and optimization of repair design criteria continually ensure that the procedures are always up-to-date and that high levels are maintained.”
MTU’s proprietary repairs, Kappei emphasizes, are developed independently of the engine OEMs and are competitive with any similar repair schemes in the OEM manuals. However, he stresses, MTU does collaborate on repair development as part of the OEM networks—through parent company MTU Aero Engines. OEM network repair development also incorporates risk and revenue partnership-sharing, he reports.
“Our MTUPlus repairs tend to be more popular with operators who own their assets and fly them for their entire life cycle. Since their focus is more on cost reduction, alternative repairs certainly provide that,” says Kappei.
While operators of maturing engines traditionally are also more open to alternative repair solutions as a way of reducing high material costs during shop visits, Kappei predicts there will be an increasing trend toward new repair solutions on new engines as problems arise following entry into service.
GE Aviation’s Sample, in fact, points out repair development is occurring earlier in the engine life cycle. Among the engines she cites are the GE90-115, GEnx and Leap.
“When engines are early in their life cycle, the OEM’s focus is on fleet dynamics/support, while monitoring cycle accumulation, and responding with repair solutions to minimize disruption to the airlines,” she explains. “In addition, new technology is often required to develop repairs on the new materials and coatings we use to achieve better performance. And, there is more focus on early-life-cycle engines because few repair procedures exist at that point.”