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Issues With Newest Engines Provide Early MRO-Proving Opportunities

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Inside MRO 
Cargolux Boeing 747-8F.Boeing
The GEnx entered service in late 2011 on this Cargolux Boeing 747-8F.

Issues With Newest Engines Provide Early MRO-Proving Opportunities

Network partners are gaining early insight into MRO work they will be handling as new-generation engines mature.

Sean Broderick | Aug 30, 2017


The engine maintenance boom that many providers are enjoying has nothing to do with the models grabbing headlines. As engines such as the CFM International Leap and Pratt & Whitney PW1000G attract attention—not all of it good—during their entry-into-service phase, MRO providers, led by the engine makers themselves, are quietly cashing in on investments made decades ago. Mature programs—the CFM56, V2500, Trent 700 and GE90, among others—are delivering strong aftermarket returns as shop visits soar, thanks to strong traffic demand and high aircraft utilization. 

Meanwhile, GE, Pratt & Whitney, Rolls-Royce and their risk-sharing partners are working to get the newest generation of engines into service and operating reliably. Part of the effort includes laying the groundwork for an aftermarket boom that is years away.

As of early August, Pratt was supporting 75 aircraft powered by its PW1000G geared turbofan (GTF)-series engine—59 Airbus A320neos with PW1100Gs and 16 Bombardier C Series with PW1500Gs. The PW1100G service entry has been marred by reliability problems, necessitating redesign and retrofits of several parts—notably combustor liners and No. 3 bearing compartment oil seals. 

While most in-service engines received oil-seal upgrades on-wing this spring, new engines and others needing more extensive work have been pulled into shops, generating most of the off-wing GTF work. 

While the problems have not been good news for Pratt, Airbus or operators, the work is giving the engine OEM an unexpected opportunity to test its support plans.“When we were looking at the No. 3 bearing-seal upgrade and removal, we developed workscopes and validated them,” says Eva Azoulay, Pratt’s vice president for engine services. “One of the other network shops may have an idea to do it better or faster. We test that and then roll it out across all the facilities.”

While none of the off-wing work has risen to performance-restoration level, let alone a full overhaul, pulling engines into shops is allowing Pratt’s aftermarket specialists and engineers to validate assumptions on in-service engines. 

“It has given us a great opportunity to go in and prove out our tooling, our manuals, our overhaul processes,” says Tom Bode, general manager of the Pratt & Whitney Columbus, Georgia, engine center. “We’ve had the opportunity to go into very detailed process reviews for each section of the engine.”

Getting early peeks at engines pulled off-wing is also helping Pratt validate not just repairs themselves, but their prioritization. Pratt dispatches go-teams of engineers to look closely at engines pulled in from revenue service, gleaning valuable information that cannot be replicated in a simulation. 

“No matter how much effort you put into modeling and design, you learn a lot about how the parts actually wear,” Bode says. “We’re getting a chance to see some of that early.”

The lessons learned are not being kept close to the vest. Columbus is one of five announced overhaul shops in Pratt’s GTF network. MTU Aero Engines and Japanese Aero Engines Corp. are open for business, while Lufthansa Technik is expected to see its first GTF in the fourth quarter. The fifth, Pratt’s Eagle Aero Engine Services joint venture with SIA Engineering Co. Ltd., a dedicated PW4000 shop, will add PW1100G work in 2019. Bode’s team interacts with its counterparts in the other locations weekly, trading information gleaned from the shop floor.

Lufthansa TechnikTrent XWB

Trent XWB overhauls will be performed in at least seven locations.

The PW1000G’s competitor, the CFM Leap, is having a smoother entry into service. While every engine OEM’s goal is to have high utilization out of the box, CFM executives made boosting aircraft availability a primary focus of the Leap program, and early feedback suggests they are hitting their marks.

The Leap 1A, which powers the Airbus A320neo family, entered service in August 2016. Daily utilization had surpassed 10 hr. by July 2017 in a mix of short- and medium-haul operations.

The Leap 1B, the exclusive Boeing 737 MAX engine, started revenue service in May, and launch customer Malindo Air quickly put its two aircraft into service for 8 hr. per day on average. 

“The first operations have gone really, really smoothly,” CFM Executive Vice President Allen Paxson says.

The one major post-delivery issue with the engines was traced to a manufacturing problem on Leap 1B low-pressure turbine disks. Safran, which shares Leap construction with GE as a CFM joint-venture partner, discovered a production quality defect on a disk during assembly. About 30 engines were singled out as possibly having a disk from the affected batch, and CFM is working with Boeing “to minimize flight-test and customer-delivery disruptions,” says Francois Bastin, Safran’s executive vice president and CFM program manager. 

Meanwhile, entry into service of Rolls-Royce’s newest Trent family member, the XWB that exclusively powers the Airbus A350 family, has been largely trouble-free. Most engine removals over the first 30 months have been to stagger the on-wing life of a particular aircraft or to collect in-service data, the OEM says.C Series

Full-flight sensor data from the C Series is providing Pratt & Whitney unparalleled insight.

“[We] have had a few maintenance issues that are perfectly normal, but we haven’t had any serious issues,” Rolls-Royce Chief Executive Warren East told analysts earlier this year. “Because it’s early in its life cycle, we’ve been pulling them in a little bit more regularly than we will be doing when they’re in normal service. And so, if there was anything untoward, I’m sure we would be spotting it.”

Airbus on July 26 handed over the 100th A350 and is on track to ramp up production to 10 per month by the end of 2018. It delivered 49 in 2016, battling cabin supply-chain issues along the way.

Rolls, which attaches long-term service agreements to about 90% of the engines it delivers, has designated seven shops as Trent XWB MRO providers, including its Derby facility and joint-venture partners Hong Kong Aero Engine Services Ltd., Singapore Aero Engine Services Ltd. and N3 Engine Overhaul Services. The other three are third-party MRO providers Delta Tech Ops, Mubadala Development Co. and Air France Industries-KLM Engineering and Maintenance (AFI-KLM E&M). 

The AFI-KLM deal, announced in June and that had been several years in the making, puts Air France-KLM’s A350 engines—the airline has 25 firm A350 orders and 25 options—under Rolls-Royce TotalCare agreements. In return, AFI-KLM E&M joined Rolls’s MRO network and is developing repairs for Trent XWB and the Trent 1000 parts, including low-pressure compressor shafts and combustion chambers.

Rolls is supporting partners with training, technical expertise and hardware as they ramp up for overhauls, which are not expected for several years. “We do not have any planned engine inductions and don’t have any for some time to come,” the company says.

The Trent XWB’s early experience stands in contrast to its counterpart for the Boeing 787, Rolls’s Trent 1000. The engine has been beset by a “handful of issues,” East noted on a July earnings call. The most significant: corrosion-related fatigue cracking of intermediate-pressure turbine (IPT) blades. The issue, discovered in early 2016 at Trent-powered 787 launch customer All Nippon Airwaya, is the main focus of a sweeping parts upgrade and engine swap program. The European Aviation Safety Agency (EASA) and the FAA have ordered that engines showing excessive corrosion be pulled from service and repaired in a shop visit. Rolls-Royce has developed a more corrosion-resistant blade and is rolling it out. EASA and the FAA this year have also ordered fatigue-related checks on high-pressure turbine blades and inspections of intermediate-pressure compressor rotor seals.

“Some parts of the engine are turning out not to last as long in service as [expected for] their original design lives,” East explains. “As with any mechanical components, they wear out. And. . . it turns out on inspection that we had to replace them sooner rather than later.”

The issue has caused several airlines to ground 787s while Rolls pushes improved parts into the fleet. The OEM says it is spending about $70 million on unexpected “technical provisions” for its in-service fleet this year, with about half going to Trent 1000s. 

“We think [it] is sufficient at this stage,” says Chief Financial Officer  Stephen Daintith. “It will depend on how the operational issues unfold over the balance of this year, but right now, we think we’re adequately provided.”

Longer-term, Rolls is integrating new technology, some gleaned from the Trent 1000 and some from the  Trent XWB, into the model’s next iteration, the Trent 1000 Ten. The engine’s primary target is a 3% reduction in specific fuel consumption (SFC). The Trent 1000 has seen two sets of improvements, Package B and Package C, targeting SFC and the higher thrust ratings needed for the Boeing 787-9. The 1000 Ten, which Rolls says has only about 25% parts commonality with the Trent 1000 Package C, features a further thrust increase for the 787-10 but is available on any 787 model.

The first Trent 1000 Ten-powered 787s are slated to enter service later this year, and early-build engines will require at least some in-service modifications. Rolls in early August petitioned the FAA for a temporary exemption from smoke-emission limits,  informing the FAA that it could not meet smoke-emission levels “at some thrust settings.” The OEM notes that it meets the smoke-number standards “at the four landing and takeoff operating mode points,” meaning there is no effect on airport-vicinity air quality. It asked the FAA for an exemption through 2019 to develop a design change and modification plan for in-service engines.

Customers that chose GE’s GEnx-1B to power their 787s have not escaped in-service headaches. Last year, operators completed mandatory fan-case modifications to keep fan blades from rubbing when the powerplants ingest ice or other debris. The changes, recommended by GE, required grinding down abradable material that runs along the shroud inside the fan stator casing assembly, in front of the fan blades. The modification was needed on some 330 GEnx Performance Improvement Package (PIP) -2 configuration engines flying on 787-8s and -9s.

The airworthiness directive, issued by the FAA and adopted by EASA, was the last in a series of fixes triggered by a January 2016 incident in which a Japan Airlines 787 experienced an inflight shutdown after flying through icing conditions. The shutdown was caused when ice formed on the No. 2 engine’s blades and was ingested. The fan blades moved forward slightly in response to the ingestion, as designed, but they also rubbed on the abradable seal inside the casing. The other engine on the affected 787 was a PIP-1 build, and made it through the incident with minor damage.

GE issued service instructions in March and April outlining procedures to grind down the material inside the casing to give fans more room when they ingest ice or other debris. GE also called for aircraft with two affected engines to have at least one repaired or replaced with a compliant engine. The FAA in April mandated the so-called “de-twinning,” giving operators an Oct. 1, 2016, deadline. A production-line update was put in place soon after the problem was identified.

Source: Aviation Week Commercial Fleet & MRO ForecastNew Engine Fleets

The GEnx series was involved in a different icing issue that affected both 787s and GEnx-2B-powered 747-8 operators in 2013. High-altitude ice crystal icing—small ice crystals formed in large thunderstorms, accumulating in an engine’s core—caused temporary power losses on several flights, leading to altitude restrictions until a fix was developed. GE initiated a software change that detects the crystals and opens bleed valve doors to eject them before they enter the core, giving regulators the confidence to lift the restrictions.

GEnx-series launch customer Cargolux, which put the engine into service in late 2011 on a 747-8 freighter, surpassed one million flight hours earlier this year. 

“Our confidence in the GEnx has paid off well, even if we had to work around some teething problems with the engine that are perfectly normal for such an innovative design,” says Onno Pietersma, the airline’s executive vice president for maintenance and engineering. “GE’s support team has been extremely helpful in getting things on track.”

Early in-service issues on their latest models have given engine OEMs ample opportunity to leverage emerging data-analytics capabilities. GE Aviation shifted to the company’s internally developed Predix platform in late 2015, and the GEnx family was among the first fleets to feed data into the new system. 

Rolls-Royce in June cut the ribbon on its Airline Aircraft Availability Center, which serves as the hub of its real-time in-service support effort. “For example, a new real-time collaboration system lets engineers working on engines around the world share live pictures from inside an engine with the team at the center and receive their advice on the next steps to take,” Rolls says.

The combination of the GTF and the C Series is giving Pratt its most extensive analytics opportunities yet. Pratt and Bombardier teamed up to equip the aircraft with full-flight data-feed capability, which the engine-maker is using to monitor its powerplants. Pratt’s eFast service, an evolution of Pratt Canada’s flight data acquisition storage and transmission (Fast) offering, links the aircraft’s health management unit with the ground.

“Full-flight data capability provides a much greater database and understanding of how the product is performing,” says Pratt’s Azoulay. “As we are seeing things, either in flight or in the shops, our teams are rapidly able to look at that dataset and try and understand, ‘Could we have seen that coming? Are we seeing something we should be monitoring to prevent a future occurrence?’ Right now it’s about leveraging that great wealth of full-flight data on this platform and learning what additional algorithms or capabilities can we build in the future that go beyond the hot-section trending we’re doing today.”

While Bombardier’s health-monitoring system provides a convenient package to support data-driven diagnostics, all of the new products are providing unprecedented data and, by extension and insight.

“The sheer numbers of sensors that we have on these platforms and the availability of the data out of our engines is allowing this,” Azoulay says. “At this stage, it is about leveraging the data to make links between the things we’re seeing in the field and the engine’s performance. As we see these different events—the combustor, the seal—we’re able to go backwards and see if we can see trends.”

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