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Maintenance

Reputable regional

After almost three decades in airline service, the CF34 remains a cornerstone of regional routes, as Paul E Eden finds
 
Derived from General Electric’s military TF34 turbofan, the CF34 entered airline service as the CF34-3A1 with Lufthansa CityLine in 1992. In fact, the engine had made its service debut on the Challenger 601-1A business jet in 1983, an aircraft type from which Lufthansa CityLine’s CRJ100 regional airliner was derived.
 
An incredible evolutionary path has since seen the CF34 grow in size and output, mounted in its original fuselage position and underwing, while embracing the latest technologies. Dave Kircher, General Manager at GE’s Regional Engines and Services Group, explains: “Since the CF34-3 entered service in 1992, the engine’s technology has advanced significantly. The CF34-8 was modernised with a 10-stage compressor and advanced airfoils; the engine also includes 30% fewer parts and delivers 50% more thrust, with improved fuel efficiency and maintainability compared to the -3.
 
“The CF34-10 was another step change in the model’s evolution, with more thrust – up to 20,000lb on the -10E – and technologies from CFM’s CFM56 and GE’s large commercial engine programmes, including the CF6 and GE90. The -10E has a single-stage high-pressure turbine, advanced wide-chord fan blades, advanced 3D aero compressor and turbine airfoils, and a Chevron exhaust nozzle.”
 
The result is a family of related, but significantly different engine models, requiring specific maintenance support based on subtype and operating environment. General Electric’s own Customer and Product Support team works closely with its CF34 customers to support their individual needs, while the OEM has also developed upgrades, as Kircher describes.
 
“An upgrade package for the CF34-A1 converts it to CF34-1B1 standard with improved fuel burn and climb thrust capability. For the CF34-8, changes to the combustor, high-pressure turbine blades and nozzles are available to improve durability and time on wing. And, since the CF34-10E entered service, GE has reduced its fuel burn by more than 2%, through design enhancements and optimisation on the turbine and other hardware that improve durability.”
 
To better support its CF34 customers, Kircher says GE uses data analytics for more predictive maintenance and better fleet planning. “Our analysts review comparable data across the fleet and look for findings that can be applied to it. This allows us to see around corners and better assist customers with their maintenance schedules. We also hold CF34 operator conferences to keep customers up to date and have regular communication outside the conferences through Fleet Highlights and other meetings.”
 
CF34 expansion MTU Aero Engines supports the CF34 at its Berlin-Brandenburg site. Recognised as a GE-authorised service partner these past 15 years, in 2017 the facility completed its 1,000th CF34 shop visit, and MTU is expanding it by 30% to increase capacity and efficiency. Thomas Needham, Vice President Programs & Sales, MTU Maintenance Berlin-Brandenburg, explains: “We offer a host of tailored and intelligent solutions for CF34 customers, ranging from MRO, through leasing to asset management, and including our on-site support team, as well as engine trend monitoring, accessory and LRU support, and much more.
 
“We have a 24/7/365 AOG and on-site service team. We complete as much work on-site as possible, either on-wing or near wing, saving time and cost for our customers. Unscheduled work usually comes in via our 24-hour support line or by direct arrangement between our customer support teams and the customer.
 
“Scheduled work is organised on the basis of customer requirements, fleet planning and engine performance data. We divide shop visits into two categories. The first covers LLP [life-limited parts] exchange, which is hard-timed and cannot be delayed. LLP refurbishment is performed according to cycles flown – around 18,000 for the CF34-3; 22,400 or 25,000 for the -8E/C; and 25,000 for the -10E. LLP limits for modern engines have been extended in such a way that some engines may only need LLP replacement at the second or third shop visit. Category two is for on-condition visits that return the engine to serviceability, in the form of performance restoration or in response to an unscheduled event. 
 
“Most CF34 shop visits are performed on-condition. Timing these to achieve maximum value and minimal cost is a balancing act. On the one hand, airlines don’t usually want to take an engine off-wing earlier than scheduled, since this generates additional cost, especially if parts with remaining green-time – that is if they aren’t fully worn out – are replaced. On the other hand, if performance is rapidly deteriorating, it’s important to take the engine off-wing before more serious, and cost-intensive, damage occurs. This is where our engine trend monitoring can be helpful. Through monitoring and expert analysis, we recommend the optimal point for engine removal, timing it as part of our fleet management service.
 
“It’s always worth looking at the LLPs’ remaining flight cycles during a visit, and particularly an unscheduled visit. It can make sense to replace them early and avoid a subsequent shop event. In such cases, serviceable used parts can be reused in other engines in the airline’s fleet, perhaps under our mature engines programme, or remarketed by MTU Maintenance.”
 
Needham uses the standard ‘on-wing’ terminology to suggest an engine still attached to the aircraft, but in the case of the CF34-8’s CRJ application, ‘on-fuselage’ would strictly be more accurate. Is there any difference in maintenance requirements between a wing and fuselage-mounted CF34-8? “We do see some differences. The ‘fuselage engines’ are easier to access and more work can be done without removing them from the aircraft, including module removals and exchanges, saving the customer time. But an underwing engine is easier to remove, since it is lifted onto a trolley, so it really depends on the scope of the work or repair needed.”
 
The CF34 is no more or less susceptible to unscheduled failure, including foreign object damage, than any other regional turbofan, although Needham says MTU has observed an issue with the CF34-10E. “The implementation of a recent HPT service bulletin is causing engines to come back into the shop very soon after their last shop visit. We help mitigate the problem by minimising turnaround time, changing engines as quickly as possible, and supplying spare engines as needed through MTU Maintenance Lease Services.” >>
 

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