By DONNA DOLEMAN, Engine Air Magazine

“The CFM56 is an eminently reliable engine,” Graeme Peppler accurately pointed out in the fall 2008 issue of Engine Air. Even so, with nearly 19,000 CFM56 engines flying today and approximately 400 million cumulative flight hours logged, members of the CFM56 family require not only routine maintenance but also the occasional special repair.

In addition, with an unprecedented number of units in service, operators always are seeking better and more cost-effective ways to keep their CFM56 engines out of the shop and in the air. To that end, three of the world’s leading maintenance, repair, and overhaul (MRO) providers are finding creative ways to provide added value to their CFM56 customers.


MTU Maintenance is a part of MTU Aero Engines and, as such, is an original equipment manufacturer (OEM) for a wide range of engines, although not the CFM56.  The company has gained much of its MRO know-how from the development and production of new engines, and this also is key to its strength in repair development.

MTU Maintenance advertises that its motto is “repair beats replacement.”  According to Katia Diebold-Widmer, Head of Marketing at MTU Maintenance, “MTU Maintenance and MTU Aero Engines combined have a strong technical and engineering experience based on our OEM know-how, which includes, for example, materials, development, and design, as well as benefits from participating in military programs.

“In addition,” she continues, “our long experience as an independent provider of engine MRO services, which includes system competence, customized workscoping, Engine Condition Monitoring (ECM), and analysis of repair effects on engine performance on-wing, adds considerable MRO know-how to our OEM expertise.”  With a worldwide network of engine MRO shops, the MTU Maintenance group added the CFM56 to its MRO offerings in 1999. The first step was the establishment of a CFM56-7 repair and overhaul center in Hannover, Germany.

Overhaul of the CFM56- 3 began in Vancouver, Canada, a year later. And, in 2003, MTU Maintenance added a CFM56-3 facility in Zhuhai, China, which now also handles MRO for the CFM56-5B and -7.  It is this experience that enables MTU Maintenance to develop new, cost-effective repairs for a wide variety of engines – among them, the CFM56 engine series.

In particular, the company specializes in recovering highvalue parts, such as high-pressure compressor (HPC) and high-pressure turbine (HPT) airfoils. After repair, these like-new parts are installed in engines in lieu of expensive new replacements. As an example, a new high-tech MTUPlus CFM56-7 airfoil replacement currently is under development and should be introduced by the end of this year.

The repair combines a split vane repair with the usage of improved proprietary coatings that result in increased component life, improved performance, and longer onwing times. As a result, MTU Maintenance will be one of the first companies worldwide offering a competitive portfolio of repairs reducing scrap to zero.

Diebold-Widmer describes MTU Maintenance’s success. “We have repair development teams based at all our sites for standard repairs, as well as dedicated teams specializing in the development of complex, piece-part repairs (a program known as MTUPlus) at our locations in Germany.  All in all, approximately 1,100 engineers across all engineering disciplines – manufacturing, materials, technology, structures, etc. – are working within MTU, both on the OEM and the MRO sides. We have all the necessary repair testing technologies available, too.”

Repairs are developed according to a gating process, in order to ensure that both customer objectives and cost effectiveness are achieved. Besides customer requests, top management also drives development initiatives and projects. Furthermore, MTU cooperates with universities and research institutes, and it works directly with other MRO providers, such as Lufthansa Technik with whom it shares an equal-share joint venture, Airfoil Services Sdn. Bhd. (ASSB), located in Kuala Lumpur, Malaysia.  “Existing designs may be improved by new high-tech repairs, which sometimes have shown better performance than the original OEM design,” says Diebold-Widmer.

“As an example, we have customers that are currently flying with our newly developed MTUPlus ERCoatNT, which is an erosion-protection coating developed for high-pressure compressor airfoils. This coating’s use is not restricted to any particular engine type, although it is primarily intended for engines exposed to the risk of heavy erosion by sand.”

MTU Maintenance is focused on customer-tailored services, Diebold-Widmer adds. “We establish a customized ‘Shop Handling Guide’ by customer and, within that range, offer tailored workscoping for each engine due for maintenance in our shop. This would typically include special workscopes driven by specific operations, such as for airlines operating under ‘severe environment,’ such as in the Middle East, China, and India.

Another example is CFM56-7 specific repair workscopes, which are conducted either in the shop or sometimes on-wing, in order to increase [aircraft] time on-wing until the first heavy shop visit. This includes compressor top and bottom case repair, the HPT blade rollover program, and fan case replacement.”  MTU Maintenance aims at developing new repairs that offer significant customer advantages. For the customer, this may mean cost savings as a result of repairing instead of replacing parts with new OEM engine parts or performing designated engineering representative (DER) repairs instead of OEM repairs.

Longer on-wing times due to better endurance and/or performance also contribute to lower cost of ownership throughout the engine’s lifecycle.  In order to integrate customer requests for specific repair developments, MTU Maintenance regularly organizes a Repair Colloquium with its customers.

At these meetings, MTU Maintenance representatives present their latest developments; they also organize separate sessions to analyze the customer’s specific needs in terms of repair.  For example, they suggest that customers bring along samples of scrap parts so MTU Maintenance engineers can further analyze what can be done.


Lufthansa Technik’s special experience in maintaining, repairing, and overhauling aircraft engines comes from over 50 years as an airline operator. The company’s depth of experience is perhaps best illustrated by the fact that General Electric (GE) used Lufthansa Technik’s know-how in developing its own repair program for GE CF6 series engines. Moreover, Lufthansa Technik is the only independent engine shop worldwide to overhaul the full series of CFM International turbofans – including the CFM56-2C, CFM56- 3, CFM56-5A, CFM56-5B, CFM56-5C, and the CFM56-7B – according to Wolfgang Reinert, International Media Relations.

In the mid-1990s, Deutsche Lufthansa AG’s former engineering division became Lufthansa Technik and expanded its MRO offerings beyond Lufthansa Airlines to all aircraft operators. Thomas Böttger, Director Customer Service, Engine Services Division, says that this experience as an operator is part of what makes Lufthansa Technik unique.  “There are so many challenges for airlines. Because we know overhauling engines represents a big cash expenditure, we focus on keeping the engine on-wing longer.”

Mr. Böttger continues, “Our Airline Support Team (AST) can often help operators avoid those expensive in-shop engine overhauls and removal of the engine from the wing.”  Lufthansa Technik offers an extensive global support network for on-wing repair and maintenance to keep the engine in the field longer.

With qualified CFM56 mechanics located in Melbourne, Australia; Johannesburg, South Africa; Tulsa, Oklahoma; Buenos Aires, Argentina; Hong Kong, China; Dublin, Ireland; and Frankfurt, Germany, the company is able to respond rapidly to customer needs. Reinart notes that Lufthansa Technik also is in the process of developing a location in the Middle East with a partner.

“These satellite locations all have qualified, experienced mechanics, tooling, and equipment to support our customers onwing,” Böttger states enthusiastically. “The structure and model vary in that some locations are large, while others may be smaller or on location. But all the sites have personnel able to go anywhere in order to respond on a moment’s notice to a customer’s on-wing needs.”

The driving strategy for customer support is to develop more solutions in order to keep engines on-wing as long as possible. “We are not in the business of selling materials as are most OEMs,” Böttger emphatically points out. “Many times, engines are still good for thousands more cycles, but a problem drives it to the shop. Our goal is to fix those problems on-wing so the customer can avoid that shop visit.”

Lufthansa Technik has developed some breakthrough CFM56 restorations. One of them addresses a well-recognized problem with the variable stator vane (VSV) bushing in CFM56-5B, -5C, and -7B engines. The bushing is designed to allow a limited range of motion, but when it becomes worn, vanes can come in contact with rotating blades, which potentially could lead to an HPC blade failure.

A CFM International Service Bulletin was issued to address this problem.  When Lufthansa Technik’s customers found that the bushings were wearing at around 24,000 engine flight hours, while the engine itself was still good for more cycles, its AST developed a procedure whereby mechanics are able to replace the worn bushing off-wing but at the customer’s site within 4 days or less. Understandably, customers are very receptive to such costeffective solutions, “because it gives the engine another 2 to 3 years without a shop visit,” explains Böttger.

Among the more than 100 CFM56 solutions developed by Lufthansa Technik’s AST are on-site replacements at customers’ facilities of single HPT blades or blade sets and the Number 3 bearing air/oil seal, which occasionally has been found to wear and cause the smell of oil in the aircraft cabin. Oil smell detection with an innovative Aerotracer, another AST product, helps identify this specific problem and avoid unnecessary engine removals. Similar solutions include the on-wing fan disc, LPC module, and bearing Unit 2 module replacements. These all can save the customer shop visits.

Lufthansa Technik’s commitment to customer-focused solutions is supported by over 4,000 mechanics and engineers located around the world – and those numbers do not include additional technical personnel who support components parts and repairs. “We have a 24/7 Engine Operations Center located in Frankfurt that coordinates everything necessary to serve the customer, from logistics to hotel rooms for personnel responding to a call,” Böttger states. “Of course, we also have personnel on-site at some customer sites, and our satellite facilities have the freedom to just respond to a local call.”


Pratt & Whitney Global Service Partners (GSP) offers the largest commercial MRO service network in the industry, with six engine overhaul centers and eighteen repair facilities located worldwide. A CFM56 facility in Norway is operational now, and there will soon be three Pratt &Whitney GSP engine centers with CFM56 capabilities once facilities in China and Turkey are complete.

In addition, there are twelve Pratt & Whitney Global Repair Unit (GRU) sites that support repair work on CFM products.  In February 2006, Pratt & Whitney in Hartford, Connecticut, established Global Material Solutions (GMS) in order to develop its own parts for use in CFM56-3 overhaul and repair. “We are an OEM with more than 80 years of aviation history,” says Paul Shook, Program Director, Global Material Solutions.  “The offering of GMS products is the result of feedback from customers looking for options coupled with outstanding quality and competitive pricing.”

In a groundbreaking change to typical MRO offerings, GMS has become the first and only company to receive U.S. Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA) certifications for alternative life-limited engine parts, which historically only have been available from the original Type Certificate holder and its licensees. Life-limited parts include an engine’s major rotating parts, such as shafts, disks, and seals. Examples of life-limited parts offered by GMS are the fan shaft; booster spool; HPT front seal, disk, and front shaft; and LPT shaft.

Shook explains some of the reasons for the program’s success. “Now, more than ever, our customers want and need customized solutions that deliver the best value possible. And, GMS offers extraordinary value with our FAA- and EASA-certified GMS life-limited parts for CFM56-3 engines, combined with focused customer care and a growing worldwide service network.  “In total,” Shook declares, “nineteen GMS life-limited parts are now certified under FAA and EASA Supplemental Type Certificates (STCs), and there will be a total of eleven GMS gas path parts certified and available later this year.

These gas path and life-limited parts represent more than 80 percent of the material value of an average overhaul. GMS regulatory certifications result from numerous engine and rig development and certification tests and represent the first-ever granted for alternative life-limited engine parts.  Ultimately, some thirty life-limited and gas path parts will be available from GMS.  “This strategic initiative,” according to Shook, “offers customers choice and value, enhances our service offering, and complements Pratt & Whitney’s OEM capabilities.

GMS is a response to strong customer interest in alternatives to CFM International-produced materials. We offer customers operating CFM56-3 engines a comprehensive and dependable choice in their material requirements, whether new, repaired, or serviceable. Our material is backed by Pratt & Whitney’s technology, quality, and customer service. Customer interest has been high and continues to exceed our expectations.”

GMS started by introducing new parts for CFM56-3 engines, and additional engine models will be evaluated based on customer demand. GMS provides parts and services through GSP and through independent repair facilities, as well as directly to airline customers. A business model called OEMRO combines Pratt & Whitney’s OEM capability and MRO flexibility, Shook says. “GMS is an important part of this model – complementing our existing offerings for CFM56 engines,” he explains. “In addition, our customer service team continues to work closely with customers to plan for the integration of our GMS parts into their fleets based on their specific needs.”


Today, operators may choose from a growing number of options for the maintenance, repair, and overhaul of their CFM56 engines. These choices have been expanding over the past 10 years and now are accelerating, as providers add more CFM overhaul capabilities, develop creative repairs, and offer new on-wing services and STC-approved life-limited parts.

These trends are likely to continue in today’s competitive aftermarket environment. And providers will continue to experience successful growth as a result of their ability to focus on particular customer needs and develop market-driven repairs, parts, and services. As always, customer selection criteria will include cost-effectiveness, reliability, and responsive customer support.

Images Courtesy of CFM International. Copyright 2013.