After almost three decades in airline service, the CF34 remains a cornerstone of regional routes, and its latest-technology variants are still being delivered on new Bombardier and Embraer jets. With OEM support, the MRO industry looks set to provide CF34 support for decades to come.
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 per cent fewer parts and delivers 50 per cent 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 per cent, 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.”
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 per cent 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 an 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.”
The world’s first GE-authorised independent CF34 MRO provider, StandardAero offers an expansive range of services focusing on the -1, -3 and -8 engines.
The company’s Winnipeg, Canada facility has completed in excess of 2,500 CF34 engine and module work packages and Eric Recksiedler, CF34 program manager, provides an overview of the -3 and -8 maintenance schedules to which it typically works.
“The CF34-3B1 fleet is mostly past the 30,000 LLP shop visit, and we’re now seeing engines at 36,000 cycles, in for replacement of 18,000 LLP for the second time. Many have been altered from their original shop visit rhythm after used serviceable LLP were installed at 22,000/25,000 or 30,000 LLP events.
“CF34-8C1 engines converted to -8C5B1 configuration at around 9,000 cycles, through replacement of their core HPC/HPT modules, are now seeing fan/LPT LLP shop visits at the 25,000 event, while those beyond 25,000 are approaching their second HPC/HPT LLP replacement shop visits at a 34,000 event.
“We’re seeing some new-build -8C5B1 engines reaching midlife performance events and significantly more hitting their 25,000 LLP event. The new-build -8C5 engines are divided between those seeing their first or second performance events, although some fleets are beginning to hit their 25,000 LLP events.”
Recksiedler reckons the CF34 is maturing as expected, although he observes that CF34-3 flight hours, and 2018/19 shop visits are somewhat higher than forecast. In terms of unscheduled work, he says:
“There’s always some degree of FOD and DOD [domestic object damage, caused by engines ingesting aircraft-related hardware] events. On the CF34-8 we’re also seeing combustion liner dome baffle liberation, HPT blade failure and HPC vane shroud pin liberations. These failure modes are known in the fleet, and most operators have adjusted their maintenance plans to address them.
“There are also a number of part configuration upgrades related to combustion liner dome, HPC vane hardware and Stage 2 HPT blades. They’re pretty important if an operator wants to remove known failure modes and improve engine reliability.”
Recognising the importance of quality record keeping, MTU’s Thomas Needham notes: “Records management can be a complicated business across the entire industry, not just for CF34 engines. Parts traceability can be a major issue, with many follow-on asset owners requiring back-to-birth documentation for life-limited parts, and the more times an engine changes hands, the trickier this can become.”
Eric Recksiedler says StandardAero sees ‘pretty detailed’ record-keeping for the CF34-8, running into very few problems when it comes to the data required for maintenance. But that’s always the case for the CF34-3.
“There have been some issues with records on previous fan blade maintenance. This is owing to a relatively recent service bulletin that drove the need for operators to identify fan blades on which a particular maintenance activity had been performed. So, it isn’t a traceability issue, it has more to do with very specific maintenance having been performed on the fan blades during previous maintenance events.”
Records are equally essential for the UK’s AerFin, which holds a particularly large stock of CF34-8E components, as well as complete engines.
Director of sales and marketing, James Bennett, says the CF34 is typical of its engine and airframe components business.
“Part of our technical due diligence mandates that all technical documentation is fully signed off before we sign any purchase agreement. The fact that we’re buying aircraft fleets this often means a forensic reconstruction of the documentation is required, and while that’s labour intensive, it’s crucial to ensuring the assets are marketable. Without the documentation required to satisfy our airline and MRO partners, the parts potentially have little value.”
In October, the CF34 will have been in airline service 27 years, and yet it is still selling factory fresh on the ARJ21, the latest CRJ models and last of the original E-Jets. Given its reputation for reliability and widespread employment, it’s reasonable to expect the CF34 to thrive for another 40 years or more.
What does General Electric expect its CF34 support to look like in 2059?
“We’re committed to supporting the fleet throughout its life cycle,” Dave Kircher says.“GE works with its suppliers to ensure critical parts remain in production and we utilise component repair and used serviceable parts to meet customer needs.”
And that’s decades’worth of good news for CF34 operators, MROs and parts suppliers.
Visit geaviation.com/bga/engines/cf34-engine for more information.