Boosting engine performance

Intricate, complex and essential. Keeping aircraft engines fit for action is key to the global airline industry, as Bernie Baldwin discovers.

Used serviceable material is particularly popular with airlines that intend to retire an engine or aircraft type in a planned timeframe as it of ers significant savings over new components.
All photos MTU Maintenance unless specified

Many of us will have seen an aero engine without its nacelle and marvelled at how its plethora of parts is put together – pipework, electronics boxes, casing and more. While on any aircraft there are a number of components and systems, large and small, which are considered ‘mission critical’, there are none more so than a part that will render the
engine inoperable.

Caring for engines is one of the most vital maintenance tasks. However, in doing so, independent maintenance, repair and overhaul (MRO) providers or airline maintenance departments also need to keep an eye on costs. That’s why new engine repairs – including fans, propellers, hot section, the use of better materials and so on – continue to be developed in order to lessen the need for potentially much more expensive new replacement parts.

Tim Mathis, general manager of StandardAero Component Services’ Cincinnati facility in Ohio, picked out one area that has caused concern. He says: “The biggest impact to the industry lately is corrosion repairs either by welding, cold metal transfer, spacers or bushing repairs. Significant corrosion on large aluminium cases can cause extremely costly replacement parts for a defect that af ects a minimal amount of the component. For example, a fan frame shroud could be rejected for corrosion of a mounting hole in the past, where the repair shops can now machine out corrosion and install a metallic bushing to extend the part life.”

While the International Aero Engines (IAE) V2500 is most often found powering Airbus A320 Family airliners, it also equips the McDonnell Douglas MD-90. The Embraer KC-390 transport aircraft is the first military application for the two-stage bypass engine.

High-tech repairs

At Pratt & Whitney Canada, new and innovative after-market repair technologies improving product cost, reliability and safety, continue to be developed. The company reports: “These are being focused across all facets of our MRO business. A few examples are repair and laser additive after-market manufacturing, new inspection methodologies and cleaning and stripping processes that have been shown to extend component repair life. The key is meeting customer maintenance programme objectives.”

Martin Friis-Petersen, senior vice-president MRO programmes at Hanover-based MTU Maintenance, highlighted the company’s development of alternative proprietary repairs for clients as a cost-ef ective alternative to purchasing new parts: “Customers also benefit significantly from extended component life, reduced fuel burn and lower scrap rates compared to other solutions on the market, he says.

“Our high-tech repairs are interesting for operators who own their assets throughout the entire lifecycle. On current generation engines, MTU has a large number of repairs and repair processes available for various engine types. For instance, our V2500 Select One HPC Airfoil Repair provides extremely competitive repair cost and remarkable potential for fuel burn reduction, Petersen adds.

Jochen Mast, head of sales support and marketing at Lufthansa Technik AERO Alzey (LTAA), says that while repairs to engines do get carried out in the regional aircraft engine area, those designed by the DER (designated engineering representative) at an MRO provider, and approved only by that DER, are less common.

There is greater demand for repairs to engines such as the CFM International CFM56 and IAE V2500 because they are among the most widely used turbofans.

“The reasons for this are twofold, he adds. “The main reason is that the airlines do not accept them. In order not to jeopardise their warranties with the original equipment manufacturers (OEMs) or due to lease return requirements, they stick to OEM-approved repairs. Also, the comparatively small sizes of most regional airlines means they do not have the leverage to pressure the OEMs or lessors to relax their DER policies, nor would they – in most cases – have the engineering power to assess third party DER repairs.

“This lack of interest by the operators is further amplified by the much smaller volumes of regional engines, compared with narrowbody engines like the CFM56 or V2500, which also renders the development of more sophisticated DER repairs uneconomical for independent MROs or repair sources,” Mast adds. “Hence, our repair development is always in very close co-operation with the OEMs.

“For all high-cost items rendered scrap, as per the manual limits, we strive to find ways to bring them back in serviceable condition, for example, by jointly assessing the possibility of repair limit or process extensions with the OEM on a single part and case basis.

“We also regularly propose new repair procedures to the OEM. They are then collaboratively developed and brought into the engine manuals as OEM-approved repair procedures and thus sustainably reduce the cost of engine repairs for our customers,” he continues. “We are constantly developing new on-site repair procedures, allowing us to perform engine repairs which usually require a shop event to be performed on site (for example, an oil smell in cabin fix for the CF34-8) and thus we save our customers a lot of time and money.”

Pratt & Whitney Canada’s PT6A powerplant has been used in a diverse range of aircraft including the Short 360, Air Tractor AT-802F Fire Boss, Embraer A-29 Super Tucano and Israeli Aircraft Industries (IAI) Arava.
Pratt & Whitney Canada

Unlocking potential

If repairs cannot be carried out and new replacement parts are too expensive or inappropriate for an engine due to the stage of its lifecycle, there is the possibility to fit parts which have been used, but which have a known amount of life left in them. This used serviceable material (USM) mostly comes from the parting-out of an engine which has reached its life limit, even though some of its components have not.

Mast says numerous teardowns have already been performed at LTAA and he expects the number to increase over the next few years: “This allows LTAA, as an OEM-independent provider of MRO services, to offer more attractive pricing by using a higher share of used material.

“Customers using parts from a teardowns can benefit from the significantly cheaper prices compared with new parts, which is even more attractive if an engine needs to be custom built to achieve defined conditions, such as a certain remaining time-on-wing or lease return requirements,” Mast adds.

According to Troy Forrest, vice president of engine trading for StandardAero Airlines & Fleets, the Canada-headquartered company makes extensive use of used serviceable material (USM) “to generate cost savings for our operators, where the use of such parts is allowed under a customer’s maintenance policies” He explains the company’s USM usage in more detail: “In certain cases and for certain workscopes, USM can account for over 50% of parts replacement costs, with such components regularly offering savings of 50% or more, compared with new parts lists prices. These savings are augmented by the additional cost benefits generated by StandardAero’s ‘repair vs. replace’ philosophy. The use of USM and our component repair and overhaul capabilities allows us to mitigate any new material supply chain issues, thereby minimising turnaround times.”

MTU Maintenance staff work on a General Electric GE90. The turbofan is fitted to an AeroLogic Boeing 777F.

Innovative approach

Pratt & Whitney Canada offers its SMART maintenance solutions for turboprop engines. The company reported: “Whether it’s a capped-cost parts programme, flat-rate overhaul, engine exchange (for a zero-time since overhaul engine) or an engine upgrade, there are multiple solutions that can help our customers reduce the cost of an overhaul.”

For USM acquisition and sales, Pratt & Whitney Component Solutions is the entity that does this work for smaller operators. This allows the company “to work with customers on workscope, build standards and the associated incorporation of this material to optimise fleet performance while lowering cost of ownership”.

A similar story can be found at MTU Maintenance, said Friis-Petersen: “Used serviceable material, gained from teardown engines, is something we use extensively in our independent, customised MRO services as a way of reducing material costs for operators. These types of service are in high demand.

“One way of doing this would be as part of a mature engines programme – SAVEPlus – across a large fleet; retired engines can be torn down to ‘feed’ the remaining active fleet with USM instead of installing brand new and more expensive parts. This is especially true if operators have a remaining flight period in mind and the cost of new parts would be out of proportion to the time the engine will continue to be flown. Bearing in mind that material costs can really add up, any reductions here can have a big impact.”

Friis-Petersen adds: “When it comes to smaller fleets or single engines, USM can be sourced by the MTU team and used during a shop visit. MTU is also able to use ageing engines from its own lease pool as a natural pipeline of engines being dismantled for USM support.”

As previously noted, repair and overhaul processes and techniques continue unabated. Taking an overarching view of the industry, the companies unveil what the next developments in support programmes for engines might cover.

More than 30,000 examples of the CFM International CFM56 have been produced to date. Cumulatively, the powerplant has spent the equivalent of 91,000 years in flight.

“There is a lot going on in the engine MRO market at the moment,” Friis-Petersen notes. “We need to deal with growth, tight capacity, increased OEM presence and increasingly complex customer needs – and we need to do it in a fast and flexible way. For that, MTU is driving technological advancement forward, for example by developing our engine trend monitoring and fleet management further.

“Gone are the days of standard MRO. Managing fleets in the sense of reducing the engine lifecycle costs, based on our long-lasting technical expertise and capabilities along the value chain, is core in the ongoing MTU digitalisation and innovation initiative.

“We believe we are the leader in customising services to each and every engine in the fleet, pro-actively maximising engine usage and significantly reducing cost for customers. We are proud to be engine experts and we will work hard to keep things this way, to be competitive and to offer the best solutions to our customers.”

Giving StandardAero’s take on the future is Randy Mengel, vice-president and general manager of StandardAero Airlines & Fleets’ Maryville, Tennessee, MRO facility. He says: “The importance of engine prognostic health management (PHM) will continue to grow as operators seek to maximise onwing reliability while minimising support costs. Effective engine health monitoring and data assessment will therefore be a key enabler to this trend. The ability of MRO providers to offer cross-fleet services is also likely to become ever more important, with operators preferring to simplify their maintenance activities by relying on a single support provider, rather than multiple shops.

“Technology-wise, the trend towards more electric aircraft is likely to highlight the importance of MRO providers being able to offer the customer a broad set of capabilities, spanning not only ‘big engine’ turbomachinery but also power systems, controls and APUs.”

LTAA’s Mast focuses first on support for new engines. He says: “We believe that the trend to sign up for hourly programmes at the time of engine acquisition will continue. From a risk perspective, this makes sense as the airlines can plan with more or less guaranteed maintenance cost and do not have to worry too much about the teething issues that new engine types (incorporating new technologies) usually exhibit, besides maybe the operational hurdle any engine change causes.

“These programmes are like an insurance and operators seem to be willing to pay the inherent risk surcharge for having the peace of mind in the uncertain juvenile phase of an engine type,” Mast continues. “As the engine types mature in their lifecycles, however, such programmes lose their competitive edge. The risk of unforeseen technical issues is reduced over time and other support programmes – like fixed prices for defined work scopes or programmes based on the actual manhours and material consumed (T&M – time and material programmes, with and without capping) – become more attractive.” That’s the future. As for now, the breadth of offerings to ensure the airworthiness of engines is certainly comprehensive.