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ABOUT
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framecheck2005 9/9/04 2:03 pm Page 3Commercial aero-engine MRO outlook
— a new dawn? 2
Cutting total ownership costs with
the PW6000 8
Reducing maintenance costs on
the V2500 12
Managing the costs of engine ownership 16
Engine maintenance costs 20
Engine trading and value trends 26
When should part-life engines be built? 30
Sharing the customer’s vision 34
Managing the maintenance of
leased engines 38
Upgrading GE’s maturing engines 44
The aero-engine aftermarket and
opportunities in gas path diagnostics 48
Are your engines really as healthy as
they seem? 54
Filtration technology for gas turbine
engine fuel and lubrication systems 60
Economic aspects of maintaining
engine efficiency 64
Advanced repair and coating technologies 68
Titanium impeller welding 72
The latest in aerospace testing equipment 76
Automated repair and overhaul of
aero-engine components 80
Third-generation high-speed grinders 84
Adding capabilities to suit customer need 88
Engine overhaul survey — worldwide 92
Non-overhaul specialist engine repair
companies 103
Directory of major commercial aircraft
turboprops 110
Directory of major commercial aircraft
turbofans 112
C O N T E N T S
An Aviation Industry Press publication EDITOR Paul Copping [email protected] STAFF WRITERS Martin Fendt [email protected] Niall O’Keefe [email protected] PRODUCTION MANAGER Phil Hine [email protected] CIRCULATION & SUBSCRIPTIONS
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[email protected] PUBLISHING & SALES ASSISTANT
Pervinder Singh [email protected] PUBLISHER & SALES MANAGER - USA
Simon Barker [email protected]
MANAGING DIRECTOR Paul Copping [email protected]
The Engine Yearbook is published annually. Aircraft Technology Engineering & Maintenance (ISSN 0967-439X) is published 7 times per year
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Aviation Industry Group Ltd.
ENGINE YEARBOOK 2005
ENGINE YEARBOOK 2005
Commercial aero-engine MRO outlook
— a new dawn?
Aviation is facing significant
uncertainty with
fundamental challenges to
profitability, yields and
traditional business models.
David Stewart, principal,
AeroStrategy offers us some
clear thinking concerning
the aero-engine aftermarket
when the outlook would
appear to be uncertain.
O
ver the past few years, AeroStrategy has developed a commercial maintenance, repair and overhaul (MRO) market forecast with the assistance of more than 20 airlines and global MRO suppliers. Its intention is to help dispel some of the uncertainty, to address some of the unresolved MRO concerns and to assist in answering some basic questions, such as: “When will demand spring back? How many aircraft will be permanently retired? How many parked aircraft will return to service? How will increasing engine size and reliability influence demand? How rapidly will the market grow? Which aircraft types, engine models and regions will lead the way?” Beyond facts and figures, AeroStrategy also provides its perspective on evolving and critical supply-side trends which will shape the engine MRO market for years to come.Market growth
AeroStrategy estimates that commercial jet aircraft with more than 35 seats generated MRO demand worth $35.8 billion in 2003. This is spread across five
primary market segments: off-wing engine overhaul; airframe heavy checks (C and D checks); component overhaul and repair; line maintenance (including A, B and overnight checks); and major airframe modifications, including cargo conversions, avionic upgrades and IFE modifications.
AeroStrategy calculates that MRO demand will reach $60 billion in 2013, implying an annual growth rate of 5.3 per cent (in constant 2003 US dollars, not accounting for future changes in labour rates or spare parts costs). Four key trends underpin this prediction, as follows:
● Air travel growth will average 4.7 per cent over the next decade, fuelling an expansion in the active air transport fleet from 16,000 in 2003 to 23,360 in 2013.
● The airline industry imperative to contain MRO expenditures will be challenged by the MRO
requirements generated by the unprecedented number of aircraft — in excess of 5,000 — delivered between 1998 and 2002, that are only now generating their first heavy maintenance events.
Figure 1:2003 Commercial
MRO market - $35.8b
source: AeroStrategy Modifications Engine overhaul Line maintenance Component Airframe heavy 8% 35% 22% 21% 14% EYB2005_1 7/9/04 8:34 am Page 2ENGINE YEARBOOK 2005
● Over 600 of the 2,000-plus inactive aircraft fleet will return to service in the next four to five years, with many of the young aircraft parked during the 2001-2002 industry crisis returning to passenger service and with more than 200 parked aircraft being converted to freighters. ● Daily aircraft utilisation will be
nearly 10 per cent higher in 10 years’ time. This will occur for three reasons: the expansion of high-utilisation low-fare carriers; the pressures they place on traditional airlines to increase the economic productivity of their major assets; and the fact that many airlines are now operating at relatively depressed levels of utilisation.
Demand for engine overhaul
For the sake of this forecast, engine overhaul costs includes the costs of all major engine shop visits and the costs of changing the life-limited parts (LLPs). It excludes the costs of minor shop visits, inventory costs,
unscheduled events, one-off campaigns and engine upgrade programmes.
Using this definition, engine overhaul
is the largest segment of the commercial MRO market, currently valued at $12.4 billion. The largest engine submarkets are the CF6-80C2, CFM56-3 and
PW4000-94, the only ones with activity exceeding $1 billion each. Pratt & Whitney engines, despite the rapid reduction of the venerable JT8D fleet, generate the highest proportion of overhaul demand — 29 per cent, due to their still sizable installed base. CFMI, GE and Rolls-Royce engines generate 26, 24 and 14 per cent of overhaul demand respectively.
For the period 2003-2013,
AeroStrategy forecasts that demand will increase at 6.3 per cent per annum. This high rate of growth is driven by a number of key factors:
● Fleet growth: AeroStrategy’s forecast shows an underlying aircraft fleet growth of 3.8 per cent per annum and engine fleet growth of 3.4 per cent. In particular, the spate of aircraft deliveries in the late 1990s will provide the impetus for a jump of over 20 per cent in shop visits in the near future, from about 8,400 in 2003 to almost 10,300 in 2005. The start of this sharp increase in activity is already being witnessed, most particularly in the CF34 market where GE and its service centres have begun to spool up for a ‘tsunami’ wave of shop visits. ● Engine utilisation growth: the drive
by low-fare carriers and traditional airlines alike to improve asset productivity means that average engine utilisation will grow at about one per cent per annum. The combined impact of fleet and utilisation growth results in a 4.9 per cent per annum rise in engine utilisation.
● Improved reliability: this engine utilisation increase is offset by improved engine reliability. The average time between shop visits for the entire engine fleet is set to increase from 8,900 hours to 10,400 hours over the 10-year forecast period. This results in the number of shop visits showing a lower rate of growth of 4.4 per cent per annum.
● Increased shop visit cost: the average shop visit cost for the fleet
In 2013,CFMI engines will
generate most engine overhaul
demand at 27.5 per cent,closely
followed by GE (26 per cent),Pratt
and Whitney (19 per cent) and
Rolls-Royce (16 per cent).
ENGINE YEARBOOK 2005
is expected to rise from about $1.5m to $1.75m. This increase results from the growing number of new, large and sophisticated engines such as the GE90, Trent 700/800 and PW4000-112 that will start experiencing shop visits, and the fact that many of the engines delivered in the late 1990s will be facing their first significant LLP replacement requirements at the back-end of the forecast period. The fastest growing engine models include the CF34-3B, 5B, CFM56-7 and V2500 — no surprise, given the growth of regional airlines and the robust outlook for the preferred aircraft of the low-fare carriers, the A320 family and the 737NG. A few larger engines — the CF6-80E, GE90 and Trent 700/800 — will see significant growth as well. Overhaul spending on these extremely reliable and relatively young engines will rise by more than 15 per cent per annum, as their first shop visits for LLP replacement take place later in the forecast period.
By 2013, six engines will each generate more than $1 billion per year in MRO demand, with the CF6-80C2 leading the way, followed by the CFM56-3, CFM56-5B, CFM56-7,
PW4000-94 and V2500-A5/D5. Partially offsetting this growth is the inevitable decline in some currently significant engine markets. The JT8D, JT9D, CF6-50 and RB211-524 will be hit by a double whammy — not only will the associated aircraft rapidly retire, they will also create a supply of cheap surplus engines that will, in some instances, make them cheaper to replace than to overhaul.
In 2013, CFMI engines will generate most engine overhaul demand at 27.5 per cent, closely followed by GE (26 per cent), Pratt and Whitney (19 per cent) and Rolls-Royce (16 per cent).
Engine overhaul supply
On the supply side, the OEMs have already developed a strong aftermarket presence, albeit with varying strategies. Led by GE, they account for a total of 43 per cent of the aftermarket. In the future, AeroStrategy expects the OEMs to maintain this strong position because of the strategic advantages that they have and seek, such as:
● Their ability to make the significant investments required to support the overhaul of today’s highly
sophisticated engines; ● Control and development of
technical information and repair schemes;
● Control of spare parts, which represent about 60 per cent of the cost of engine overhaul;
● Their ability to bundle new engine sales with long-term support contracts; and
● Retaining an established global network of support facilities. Airlines and airline-affiliated suppliers similarly account for 44 per cent of the aftermarket although 30 per cent is ‘in-house’ work and 14 per cent is for third parties.
AeroStrategy expects the amount of engine overhaul accomplished by airlines to decline over the next decade for the simple reason that airlines will find it increasingly hard to justify the very-high investment required to establish engine overhaul capability, especially for the new, large engine models.
Figure 3: Engine overhaul demand by engine ($12.4b)
source: AeroStrategy CF6-80C2 16% CFM56-3 16% PW4000-94 9% JT8D-200 5% JT9D 5% V2500 5% RB211-535 5% CFM56-5C 4% PW2000 4% RB211-524GH 4% Other 27% EYB2005_1 7/9/04 8:40 am Page 5
ENGINE YEARBOOK 2005
Independent suppliers, led by MTU and IHI, have 13 per cent of the market. The growth and competitiveness of the OEMs and airline-affiliated suppliers during the 1990s caused difficult times for the independents, and their market share declined. It would appear that life for the independents will not get any easier over the next decade given the high entry barriers in the engine overhaul market, especially for the newer engines.
However, independents such as Standard Aerospace and MTU (both now under new ownership) who combine financial strength and excellent performance will remain strong competitors.
Market trends
Several developments are reshaping the engine overhaul market. First and foremost in the minds of many is parts manufacturing approval (PMA). With airlines pressuring OEMs to keep spare part prices down and service levels up, the penetration of PMA parts will persist. Engine PMA parts, once consigned to burner cans, accessories and low value-added parts, have entered the gas path in many locations where high-value parts are found. AeroStrategy estimates that the available market for engine PMA today is $650m, of which PMA suppliers will
capture about $150m. AeroStrategy analysis also shows the potential impact of PMA on OEM parts volumes is relatively low, primarily because of a combination of the relatively low number of parts that are suitable for PMA and a continuing uncertainty among some airlines on the acceptability of PMA. The real threat of PMA to OEMs is pricing pressure. The PMA phenomenon, combined with an increase in use of DER repairs, will challenge OEMs to rethink the “razor-razor blade” paradigm—where spare parts profits subsidize engine development—that has long underpinned the aero-engine business.
Secondly, OEMs are continuing to use licensed service centre networks and joint ventures to enhance their positions in the aftermarket rather than invest in their own facilities. Consider two recent examples: the establishment of N3, a joint venture between Rolls-Royce and Lufthansa Technik, and GE’s licensing of several well-known suppliers to service the CF34 in competition with its own maintenance centers. These moves occurred while OEMs were closing engine overhaul facilities, suggesting they are emphasising return on assets over revenue growth. The clear benefit of this approach by the OEMs is protecting their control of spare parts distribution while enabling them to build greater local presence across the globe with less required investment.
Thirdly, mergers and acquisitions among independent suppliers will continue apace. Witness the Carlyle Group investing in Avio, KKR purchasing MTU and 3i buying SR Technics. Some consolidation will probably occur at the “second-tier” of the engine sector, possibly creating new, independent entities that can more effectively compete with the OEMs.
Finally, most industry observers believe that the engine overhaul sector is suffering from over-capacity. Whilst some of this slack will be recouped via the expected increase in demand in the short-term, profit margins for some engine models will suffer until supply-demand imbalances are rectified.
Conclusion
The outlook for the commercial engine MRO market over the next 10 years is a story with two strong themes: demand growth driven by fleet demographics and
Figure 4: Engine demand by engine type ($23.6b)
source: AeroStrategy CF6-80C2 14% CFM56-3 9% PW4000-94 8% CFM56-7 8% V2500 8% CFM56-5B 4% GE90 4% CFM56-5C 3% Other 36% CF34-3 3% Trent 800 3%
Figure 5: 2003 engine overhaul supply share ($12.4b) source: AeroStrategy OEM 8% In-house 30% Airlines 3rd party 14% Independents 13% EYB2005_1 7/9/04 8:40 am Page 6
ENGINE YEARBOOK 2005
significant changes in supply. Airlines have become significantly more focused on costs and value. What they require from suppliers is still evolving. What is certain is that they will seek to reduce the projected 6.3 per cent annual growth in engine MRO expenditures through greater outsourcing, innovative commercial agreements, closer management of repair scope and greater use of alternative parts and repair sources. In addition, airline alliances such as SkyTeam and Star will increasingly seek to use joint purchasing and work sharing to realize cost synergies.
MRO providers must adapt to succeed. As airlines increasingly focus on the transportation aspect of their business, MRO providers can count on heightened demand for broad aircraft support capabilities, enhanced asset management skills and improved productivity. In the final analysis, the new value propositions yet to be developed by an increasingly global supplier base will make the biggest impact on the future size and shape of the MRO industry. ■
ENGINE YEARBOOK 2005
Cutting total ownership
costs with the PW6000
Pratt & Whitney expects to
regain a position of
prominence in the market for
100-passenger airliners due
to the low capital and
maintenance costs of its new
PW6000 engine. Tom Pelland,
PW6000 programme
director, explains why.
“T
he PW6000 will maximiseairline profitability by lowering acquisition and maintenance costs,” says Tom Pelland, PW6000 programme director. “The engine will provide low cost of ownership because it has significantly fewer parts than comparable engines.” The PW6000 will not have to make a shop visit until six to eight years after entering service. Pratt & Whitney designed the engine to keep engines on-wing for 10,000 to 12,000 flight cycles and 15,000 hours.
Pelland says the PW6000 is the only engine designed specifically for low acquisition and maintenance costs in the 100-passenger market segment. “An engine with low capital costs and low
maintenance costs is more optimal for shorthaul operations than a complex engine that may be more fuel efficient. Both the low acquisition cost and low maintenance costs are made possible by an engine design that minimises the number of parts and maximises time on wing.”
The PW6000 is on track for FAA certification in the fourth quarter of 2004 and entry into service as early as December 2005 on the Airbus A318.
Two versions of the engine are to be certified: the PW6122A with 22,000lb (10,000kg) of thrust; and the PW6124A with 24,000lb (11,000kg) of thrust.
The PW6000 series is designed to provide robust engines for aircraft operating in the demanding shorthaul, quick-turnaround environment. Aircraft powered by the PW6000 will make one- to two-hour flights as many as 10 to 12 times a day. The design of the PW6000 reflects the suggestions and recommendations of customers. From the beginning of the development programme, Pratt & Whitney gave customers a significant role in the design, development and testing of the engine.
Pratt began soliciting feedback from customers from programme launch in September 1998. Many of the ideas for improved maintainability came from a series of customer focus events. Pratt says customers made it clear from the beginning that they wanted an engine with low acquisition and maintenance costs and extended time on-wing. The company responded with an engine design based on the concept of simplicity.
The PW6000’s simplicity starts with a configuration that includes only 15 stages — a fan, four low-pressure compressor stages, six high-pressure compressor stages, one high-pressure turbine stage and three low-pressure turbine stages. This compares with 18 stages on the Pratt & Whitney JT8D-200 and as many as 19 on other
competitors’ engines. With fewer stages, the engine has 30 per cent fewer airfoils than competitive engines. This means significantly lower maintenance costs since experience has shown that airfoils account for 60 per cent of maintenance material costs on most P&W engines.
This is especially important with regard to the airfoils used in high volume at engine overhaul. The PW6000 has only half as many of these high-volume airfoils as its major competitor. These are the parts in the hot section of the engine - high-dollar, high-volume parts that are significant drivers of total maintenance costs.
Maintenance is also simplified because of the design of the line replaceable units (LRUs), which are replaced while the engine is on-wing. The LRUs are arranged in a single
Leon Lau – Technician Component Maintenance
Tony Silva – Supervisor Engine Maintenance Brian Dunn – Technician
Component Maintenance Joanne Borg – Supervisor
Engine Maintenance
Henry Clemings – Technician Component Maintenance
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You need United and our host of avionics and component support solutions, from loans and exchanges to repair services for your B777/747/767/757/737 and A320/319 fleets.
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United parts and United people: It’s a partnership designed to keep you flying at your best.
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30 minutes or less. The goal is to be able to replace all LRUs within 15 minutes, by the time the engine enters service.
At the customer focus events, Pratt introduced airline and lease company representatives to the way engine controls and externals could be replaced quickly. Demonstrations included replacing a number of externals, such as the igniter plug, fuel filter, starter speed sensor and hydraulic case drain filter.
Replacement times for these LRUs and others in the demonstrations ranged from three to 11 minutes. At these hands-on events, airline engineering and maintenance representatives were able to make suggestions during actual
maintenance procedures. During these sessions, customer
representatives offered upwards of 50 requests for improvements in the design.
Consequently, Pratt engineers went back to the drawing board to
incorporate many enhancements to improve maintainability, such as the following:
■ No requirement to rig the variable vanes, TCC actuator or the 2.5 bleed system: a typical feature of past engine designs;
■ Modular, compact gearbox and cored gearbox passages which reduce the amount of external plumbing;
■ Fuel pump and fuel control mounted on single fuel manifold, eliminating fuel inlet and outlet tubes for quick replacement; ■ External arrangement identical for
left- or right-hand engine installation;
■ All borescope inspection ports on high-pressure compressor optimised for easy access from the ground; ■ Reusable face seals at all LRU
interfaces;
■ Flex joints to be employed in the starter and ECS ducts to allow removal of LRUs without removing the ducts; and
■ Fuel, oil and hydraulic filters should be located in same area and be accessible from the ground. In addition, an innovative approach to engine diagnostics provides engine monitoring reports that are printed in clear language for efficient
troubleshooting on the flight line. Messages printed in the cockpit use the same abbreviations as seen in the engine manual and engine maintenance manual. Reports will provide the suspect component’s name and
functional identification number as part of the message. Instead of using a code, such as ‘En-4004EN,’ for example, the message says, ‘OIL TEMP SNSR.’
Maintenance costs will also be lower because of the uniformity of the life spans of the major rotating parts. All life-limited parts (LLPs) have a uniform life span of 25,000 flight cycles. On competitors’ engines, various LLPs need to be replaced at different times — one at 10,000 cycles and another at 15,000 cycles. But on the PW6000, all of the LLPs are designed to last until 25,000 cycles, simplifying maintenance and fleet management for operators.
Another key factor contributing to lower maintenance costs is the high debris rejection rate of 95 per cent. A number of design features prevent
ENGINE YEARBOOK 2005
layer, which means they do not have to be removed to swap a part. The configuration of the LRUs means that most of them can be replaced in 15 minutes or less using a minimum number of hand tools. At a customer focus event at Bradley International Airport in Pratt & Whitney’s home state of Connecticut, the company demonstrated that 75 per cent of the LRUs could be replaced in 15 minutes or less - and that 90 per cent required
The PW6000 series is designed to
provide robust engines for
aircraft operating in the
demanding
shorthaul,quick-turnaround environment.Aircraft
powered by the PW6000 will
make one- to two-hour flights as
many as 10 to 12 times a day.
ENGINE YEARBOOK 2005
debris from entering the core of the engine and causing parts to wear prematurely. As a result, the high debris rejection rate maximises time on-wing. A number of design features contribute to the high debris rejection rate. The fan blade design incorporates high root stagger to prevent debris from entering the engine core, and a low aspect ratio and wide-chord design provide resistance to foreign object damage. In addition, the full annual bleed provides maximum opportunity for core dirt rejection, and the bleed’s position behind the rotor takes advantage of low-pressure compressor centrifuging of dirt for maximum debris rejection.
Time on-wing is also extended because the PW6000 runs at lower temperatures than other P&W engines. The cooler operating environment in the high-pressure turbine means key parts will last longer. This section of the engine runs cooler by as much as 300˚F (149˚C) than the same section in other P&W engines. Another factor affecting time on wing is the exhaust gas temperature (EGT). The ability of the PW6000 to retain ample EGT margin over an extended time period is one of the features that allow the engine to reach 12,000 flight cycles before being pulled off wing for overhaul. The engine will effectively never be pulled off wing for reaching the EGT limit during typical operation.
As a result of these improvements, maintenance costs will be considerably lower than for engines competing with the PW6000. Costs are projected at 30 per cent less per engine flight hour than the competing engine on the A318 and 40 per cent less per engine flight hour than the competing engine on the
Boeing 717. These calculations are based on the engines flying at their design mission.
Another money-saving factor for aircraft operators is the environmentally responsible design of the PW6000. Advancements in the control of noise and emissions will have a positive impact on operating costs while responding to societal concerns. The engine meets all current and planned noise and emissions requirements of the International Civil Aviation
Organisation (ICAO). Cleaner-burning engines will enable aircraft to escape emissions-related surcharges and avoid premature retirement from failure to meet future standards. In fact, emission levels are not only below the ICAO requirement for December 31, 2003, but are also well below the requirement to take effect December 31, 2007.
The PW6000 will meet Stage 4 noise requirements, which become effective in January 2006, with substantial margin. This means the engine will enable operators to continue to comply with noise regulations for a long time to come. A number of design features are responsible for controlling the noise, including a long-duct nacelle with a forced mixer.
The PW6000 will enter service as a mature engine due to an unprecedented amount of development testing. This accumulated testing will be equivalent to four years of airline operation.
Through June 2004, PW6000 development engines had successfully completed more than 560 hours of flight tests aboard Pratt & Whitney’s Boeing 720 flying test bed and more than 350 hours on two Airbus A318 aircraft. By late 2005, development engines with the entry-into-service configuration will exceed 12,000 cycles of testing.
During flight tests on A318 aircraft in 2002 and 2003, all planned test
objectives were achieved and engine reliability was excellent. No engine removals were required throughout the A318 flight test programme. PW6000-powered A318s have flown at several major and regional air shows: the Berlin, Farnborough and Malta air shows in 2002; and Mexico’s Aeroexpo and the Paris Air Show in 2003.
The development programme has applied the lessons learned from developing engines for stringent ETOPS (extended twin-engine
operations) requirements. The PW6000 has benefited from the development of the PW4084 for the Boeing 777, which earned 180-minute ETOPS approval before entry into service. “The PW6000 is being built to ETOPS standards to boost its first-time quality,” says Dennis Enos, vice president for commercial development programmes at Pratt & Whitney. “This demanding level of testing will result in exceptional reliability, ensuring low cost of ownership over the lifetime of the engine.”
In addition to soliciting input from customers during development, Pratt & Whitney has worked closely with key suppliers to address
manufacturing issues. Howmet produces turbine exhaust,
intermediate and diffuser cases as well as compressor airfoils. Hamilton Sundstrand is manufacturing the FADEC and gearbox. One risk-sharing partner, MTU Aero Engines, is responsible for the low-pressure turbine and high-pressure compressor, and another, Mitsubishi Heavy Industries (MHI), produces the diffuser and associated hardware.
“We’re enthusiastic about the capabilities that the PW6000 will bring to the 100-passenger aircraft market,” Enos says. “We have designed, developed and tested the engine based on customer input and
recommendations. This effort has produced an engine that will set a new standard for maintainability, durability and low cost of ownership.” ■
ENGINE YEARBOOK 2005
Reducing maintenance
costs on the V2500
The reduction of direct
operating costs has been a
key focus for the airline
industry for some time and
in today’s environment its
importance is even more
pronounced. Engine
operating costs in general
and engine maintenance
costs in particular are prime
movers in this regard. Chris
Davie, director of aftermarket
business planning for IAE,
discusses the company’s
total maintenance
cost-reduction programme.
I
n the 20 years since the launch ofthe V2500 engine programme, IAE has launched many initiatives to sustain the competitive advantage of its engines. Regular operator conferences organised by IAE have provided an excellent forum for V2500 customers to discuss ideas for improvements in operating practices with the OEM and other operators.
Against the backdrop of an airline industry battered by the post-9/11 slump, war in the Middle East and SARS, cost reduction has become even more important to airlines, and operators have consequently sought IAE’s assistance in optimising V2500 maintenance costs. The advent of low-cost carriers has also spurred the process. IAE’s increased focus on maintenance cost has resulted in the total maintenance cost reduction (TMCR) programme for the V2500 engine series, which was initiated in 2000 to address the growing customer need for lower cost of ownership.
TMCR is a significant programme that identifies key maintenance cost drivers and addresses these issues through a prioritised system that delivers
substantial, tangible and timely benefits to its expanding fleet of airline
operators. It is not only existing customers who benefit from TMCR, since IAE’s customer-focused initiatives are of considerable interest and potential benefit to new customers such as the low-cost carriers, 70 per cent of whom have selected the V2500 for the A320.
The following highlights the framework of the TMCR programme, outlines some of its achievements so far and explains IAE’s vision in going forward:
What is TMCR?
TMCR is a continuous improvement programme designed to make the V2500 engine easier to maintain and to give it longer on-wing life. The programme was launched in 2000 and has resulted in an estimated 25-30 per cent
reduction in average first shop visit costs for new engines being delivered today. Since the TMCR initiative came about through discussions between IAE and its customers, operator input plays a key role in the programme. A project team comprising members from each of IAE’s shareholder companies — Pratt &
Whitney, Rolls-Royce, the Japanese Aero Engines Corporation and MTU Aero Engines — along with a dedicated IAE programme management resource has guided the TMCR initiative over the past three to four years.
The partnership between the V2500 operators and IAE is the basis for the success of the TMCR initiative and, during regular powerplant maintenance advisory group (PMAG) meetings and telephone conference calls, customers were involved in the definition of the project to: ensure the right focus to reduce maintenance costs, improve bottom lines and understand customer needs.
Elements of the TMCR initiative
To identify, understand and prioritise the key maintenance cost drivers the TMCR team uses three sources of information: a sophisticated computer analysis of invoices to understand where customers incur the greatest maintenance costs; visits to engine workshops and strip reviews; and annual feedback from the PMAG.
Invoice analysis has been the cornerstone of dissecting and
THE TEAM THAT STAYS IN THE AIR LONGEST WINS.
Every person, every service, every process at Pratt & Whitney Aftermarket Services is dedicated to keeping your planes in the air. Because at the end of the day, the measure of a great maintenance partner is its ability to lower operational costs. Call us. We can create a program that works for your needs and keeps your business flying. Pratt & Whitney. SMART SERVICES FOR A TOUGH WORLD.
www.pw.utc.com
ENGINE YEARBOOK 2005
understanding exactly how the costs for overhauling a V2500 engine arise. A significant volume of invoices from many V2500 customers have been used to determine the key cost drivers, thereby permitting priorities to be established in order to address those issues that give ‘the biggest bang for your buck’. IAE has developed its own IT tools to assist in this, and is focused on extending this activity in the future. Engine strip reviews have also been undertaken in order to identify the components and system-level distress modes that have either caused or contributed towards engine removal or have resulted in the scrapping of parts. Furthermore, maintenance practices have been studied in relation to specific workscopes, and acceptance limits for wear and damage have also been assessed.
PMAG is an annual conference at which airlines, lessors, MRO providers, IAE’s own technical community, Airbus, Boeing and key accessory and nacelle suppliers meet to discuss the subject of maintenance costs. It has proved useful to obtain feedback from conference participants on the prevalent issues and
thereby determine where IAE should be focusing its attention. Additionally, PMAG allows IAE to brief powerplant engineers on its progress in reducing maintenance costs, at the same time obtaining direct feedback from front-line customers.
The annually-updated milestone plan, jointly developed with IAE’s customers, defines the next steps in the
programme, and the following ‘levers’ have been identified as those that can reduce maintenance cost:
■ Repair development — reducing the quantity of new material required; ■ Acceptance limit extension —
optimising the strip levels required; ■ Workscope development —
minimising labour hours spent during overhaul;
■ Engine hardware improvements — improving reliability, time on wing and scrap rates;
■ Maintenance management tools — optimising the timing and level of maintenance activity (eMMP); and ■ Spare parts — optimising pricing
structures in cooperation with suppliers.
The prioritised list includes budgeted activities and completion milestones for each TMCR project. Over the last three to four years, IAE has concentrated on prioritising these projects so that overhaul shop cost reductions can be realised now while time on wing is improved. All these levers have been employed to drive down maintenance costs and bring a real $ per engine flying hour benefit to the customer.
TMCR achievements to date
IAE projects a 25 to 30 per cent reduction in first shop visit cost relative to what it would have cost without the benefit of the TMCR programme for engines delivered today. These engines benefit from all the significant bill-of-material changes developed and implemented over the past several years in conjunction with all the other improvements that are available to the existing in-service fleet. Considering different engine configurations and workscope application of engines already in service today, IAE’s calculations show a potential TMCR benefit of up to 20 per cent over previous overhaul costs for a first shop visit.
Most of the projects in the first phase of the TMCR initiative focused on the core engine; the high-pressure compressor (HPC); and the combustor and the high-pressure turbine (HPT).
HPC — new repairs and new parts
Historically the V2500 HPC module was a key driver for engine
maintenance costs. Bill-of-material improvements addressing these drivers are now available and new production engines are now capable of longer engine runs which translates into significant cost savings. Significant progress has also been made in reducing HPC module repair costs, both through repair development and acceptance limit extensions.
Combustor — new hardware and
new limits
To increase engine on-wing life IAE sought to introduce new combustor wear limits, since many engine removals were combustor driven due to a combination of aircraft
ENGINE YEARBOOK 2005
maintenance manual (AMM)
exceedence and convenience engine removal when repeat inspection was monitoring distress. To extend the reliable on-wing life of the V2500 engine, IAE issued revised AMM borescope limits on all standards of combustor hardware in July 2002. These new limits essentially doubled the amount of allowable guide burn-back, which triggers the initial ‘on watch’ repeat inspection condition, and increased the time intervals between borescope inspections specified for particular levels of distress of fuel nozzle guides (deflectors) and burner liner segments. IAE further relaxed these combustor limits in 2002, permitting greater burn back on specific fuel nozzle guides (non-igniter positions). Additional activity was completed in 2003 which included sea-level and altitude testing to further relax limits on the combustor (including igniter positions of the fuel nozzle guides) thereby allowing improved on-wing time.
HPT — new airfoils and new repairs
HPT blades are the focus of improvement in HPT module maintenance cost. Ongoing
improvements to HPT blades result in better performance in harsh
operations as well as improved stress corrosion resistance. Furthermore, in a joint project with Pratt & Whitney’s Connecticut Airfoil Repair Operations (CARO), the largest provider of V2500 turbine airfoil repairs, IAE has developed new repairs resulting in significant scrap reduction. IAE also plans to release a new configuration stage 1 HP turbine blade in 2004 which will significantly improve the on-wing life of engines operated in severe conditions, such as 33,000lb takeoff thrust and/or operations in harsh environments. It will also offer further improved
repairability/reduced scrap rate for lower-thrust applications.
Going forward
The improvements described show IAE’s commitment to continuously reduce the maintenance costs of the
V2500 engine in cooperation with its partners, customers and operators. Many projects have already delivered benefits, but there are still many other opportunities to be explored. Projects in the 2004 programme include a new HP compressor stage three blade, relaxed chordal width limits on the existing blades and the development of a new plasma spray repair process on the HPC drum.
Another major part of the 2004 project plan is to validate the
estimated TMCR cost reductions. The work involved in validating the benefits of TMCR projects such as new repair schemes, acceptance limits and so on can be arduous since much data is required to obtain trends that reflect a true picture, recognising the variations between different airline operations and overhaul shops. Validation of many of the benefits has been achieved as outlined above, but IAE is determined to fully realise the projected benefits and is pursuing a rigorous validation approach both at the micro and macro levels.
Essentially, IAE will continue to gather and analyse invoices, send engineers to overhaul shops and host PMAG forums in order to further reduce maintenance cost at every level. In partnership with the industry an ongoing substantiation of what has and has not worked well is in essence IAE’s determined approach. From the analysis carried out to date, measured invoice costs are coming down, engines are having fewer premature removal causes and proactive approaches to engine management are being implemented with great success
While there may be a limit to the potential to remove cost from maintenance because of the law of diminishing returns, IAE still expects to identify many more projects. Where much of the activity to date has centred on driving down the cost associated with the first shop visit of V2500 engines, more can be gained from looking forward and widening the scope of current activity.
IAE is working ever more closely with its suppliers of engine accessory units and nacelles components in order
to achieve $ per engine flight hour reductions across the whole
powerplant. Similarly, increased activity is being undertaken to proactively reduce the cost of second, third and subsequent shop visits through a programme of soft-life extension and repair development on low-spool modules. In addition, the next generation of IAE eMMP will deliver further substantial benefits to help airlines optimise their maintenance activity.
The success of the TMCR initiative has initiated a continuous
maintenance cost improvement process that will be followed by new activities to support IAE’s vision of offering the leading and most advanced powerplant solution in the 150-seater market sector. Helping airlines to meet their targets in terms of reduced operating cost improves relationships with existing customers and helps grow the V2500 customer base. Today more than 100 customers rely on the V2500. World-class reliability and low maintenance cost combined with low fuel consumption should ensure IAE’s leading market position. From 1998 to 2003 IAE won nearly 60 per cent of all the engine orders from customers buying Airbus A320 family aircraft. This might be the best proof of the effectiveness of IAE’s TMCR initiative at a time when the majority of orders come from
low-cost carriers. ■
Many projects have already
delivered benefits, but there are
still many other opportunities
to be explored. Projects in the
2004 programme include a new
HP compressor stage three
blade, relaxed chordal width
limits on the existing blades
and the development of a new
plasma spray repair process on
the HPC drum.
ENGINE YEARBOOK 2005
Managing the costs of
engine ownership
While engine overhaul costs
will normally be the largest of
any airline direct maintenance
costs, other costs associated
with engines need to be
carefully considered if total
airline expenditure is to be
minimised. Rudiger Urhahn,
vice president engine services
centre, SR Technics gives
valuable insight into the
elements, drivers and
management tools used in
managing engine life cycle
costs.
E
ngine overhaul is the largest segment of the commercial MRO market, currently valued at $12.4 billion and predicted to rise to more than $20 billion by 2013 (source: AeroStrategy). But these costs, though substantial, are not the only costs associated with engine ownership. At a time when airline fuel costs are rising and fare margins falling, the lowering of engine life-cycle costs can make a huge contribution towards airline profitability.In order to support operators and owners alike in achieving the lowest costs, most MROs have extended the scope of engine maintenance cost management to ‘life-cycle cost management’. The term covers all relevant cost factors associated with aero-engines and is an approach intended to manage such costs
comprehensively — a distinct change from previous optimisation models which focused on only a limited number of cost elements.
Engine ownership cost elements
Life-cycle cost management
addresses all cost elements that add up to the overall cost of owning and operating engines, aiming to minimise overall cost while maximising spend
predictability. It is intended to include the following:
■ The cost of acquiring and financing operational engines, spare engines and spare parts;
■ Operational costs such as those associated with fuel burn as well as the engine maintenance costs incurred on-wing and in the overhaul shop as required by specified engine management programmes and defined asset management policies.
■ A financial provision for unplanned events which cannot be anticipated by airlines.
There is no rule of thumb for simple inter-airline comparison of these costs, as major differences apply even amongst operators of similarly sized fleets.
Although various elements can be assessed individually, it does not usually make sense to add these together and then compare the bottom lines, since a number of operator-specific factors can distort the actual costs. And, in view of the complex relationships between cost elements and parameters, life-cycle cost management cannot be considered an exact science. Nevertheless, with careful consideration
and individual assessment of different, often operator-specific circumstances, an accurate prediction of cost does become possible.
While the cost of financing may be incurred before the equipment is brought into operation, the operational costs kick in at the time of entry into service.
Operational costs are derived from the fuel burn, engine maintenance costs, inventory costs (including spare engines) and the costs associated with the performance of line maintenance activities. Other costs, such as those associated with engineering and logistics support are incurred in the day-to-day management of airline fleets and these too must be included in the total cost.
Newly designed life cycle cost programmes give operators and owners the choice of outsourcing most operational elements to independent partners — but what exactly are the cost elements, what are the drivers, and which tools exist to reap the benefits from these programmes?
Financing costs
Whereas operational costs include both ‘fixed’ and ‘variable’ elements, the cost of financing is basically fixed and determined when a particular fleet is selected and
ENGINE YEARBOOK 2005
financing and depreciation options are chosen. Here, the leasing of aircraft and engines is an alternative to the purchasing and financing of assets. Operator-specific policies on depreciation and cash-flow do vary between operators but they do not usually vary substantially within the timescales that an engine is with an operator. Furthermore, the financing of engines is most normally part of an aircraft deal. Nevertheless, when selecting an engine type, careful consideration must be given to the refurbishment costs.
Spare engines
Spare engines may or may not be included in the fleet acquisition deal, and several arrangements are available to satisfy the need for such engines. The number of spare engines required to support a fleet and the subsequent investment required depend on a number of different factors including: the on-wing time which can be achieved for a particular engine type, the average turnaround time that is required by the engine maintenance provider, and the supplemental costs associated with ‘exchange material’ to further reduce turnaround times. The ‘pooling’ of airline engine fleets can significantly reduce spare engine requirements. Furthermore, it allows operators and owners to enjoy an additional source of income if they provide engines to MRO managed pools when they have no need for them.
Maintenance reserves
The costs of planned off-wing engine maintenance may be considered variable over the lifetime of an engine, gradually increasing and then levelling out with increasing engine maturity. Such costs should be provided for by reserves. While aircraft and engine lease contracts will normally specify that such reserves must be accrued, they do not necessarily limit the exposure of the operator, which might therefore have to consider putting aside additional provisions. The actual cash drawn down for off-wing maintenance will depend on the structure of ownership
agreements and internal management philosophies.
Additionally, an operator will need to consider provisioning for the
unforeseeable, which may result from foreign object damage, in-flight shut down, outstation engine removal or mandatory modification campaigns. These usually occur randomly, but may give rise to substantial costs that can threaten the financial health of an operator. Here, an operator will need to allow an appropriate ‘insurance’ coverage depending upon the profile of its operating network, engine characteristics and the relevant reliability programmes.
Fleet size
The size of a fleet matters when determining costs since economies of scale will apply. However, for many operators the question becomes ‘How can my costs be best leveraged to reflect any economies of scale that might apply?’ With the exception of volume rebates, the cost of financing may simply mount up with increasing fleet size. Operational cost may vary significantly from small to larger fleets. Fleet size and homogeneity define the optimum organisational set-up to manage fleets within an operation. As a general rule, mixed fleets cause significant complexity at higher cost, whereas a varying age of engines of one type within a fleet may not increase costs substantially. As a core benefit to its customers, an MRO may bundle the fleets of its airline operators together, thereby making best use of the economies of scale and offering the best possible prices.
Maintenance contract options
Often quoted and discussed, ‘by-the-hour’ maintenance agreements comprise well-defined service and maintenance packages, for which the financial exposure is, to a large extent, transferred to the MRO provider. MROs may utilise economies of scale to offer attractive rates that provide an added value to the operator. The benefits though, can be applied to all fleet sizes, starting from single aircraft fleets to ‘pool’ fleets, which combine the operational fleets of more than one operator. They clearly address the requirement of operators and owners of the equipment and their financiers and lessors for accurate financial predictability. Alternatively, operators may also choose
straightforward time and material
arrangements for their engine
maintenance, in which case they have to put aside and manage suitable provisions.
It is important to realise that life-cycle cost management programmes do not necessarily equate to a ‘by-the-hour’ maintenance arrangement, since a ‘by-the-hour’ programme usually addresses only the operator-relevant maintenance cost aspect. A life-cycle cost programme comprises a combination of service elements and may go far beyond the scope of maintenance cost.
Purchase and lease of assets
When choosing to lease or purchase a used aircraft fleet, an operator needs to select the best engines with respect to their physical condition, performance margins, modification and technical records status. An operator will also need to make sure that appropriate access to
maintenance reserve funds is granted. Additionally, it is important to be aware of return conditions agreed
The effective management of
life-cycle costs does not necessarily
require the lowest possible shop
visit rate.Instead,it is more
important to ensure that
hardware costs are minimised by
targeting a balance between
on-wing time and shop visit cost.
with a lessor since they can have significant impact on the cost of ownership, driving certain provisions which need to be put aside.
Furthermore, operational costs need to be predetermined in light of reliability and maintenance cost guarantees. Appropriate attention also needs to be given to the ongoing management of these warranties and guarantees, which is a service also provided by MROs.
Sourcing
It is essential not to give away leverage too early by, for example, entering into a long-term
maintenance agreement that is linked to a fleet purchase. Instead, a careful assessment of the options available with various different MRO partners is recommended. An operator may consider leveraging economies of scale with an expert provider and minimising organisational costs by sourcing services out to qualified partners. Apart from the case of very large fleets, economies of scale that apply to maintenance usually result in a preference towards sourcing from an MRO. The MROs seek the very best in terms of managing turnaround times, exchange pools, spare engine pools, materials and labour efficiency. The costs for unplanned events are more balanced with larger fleets. When considering the sourcing of MRO capabilities it is important to find partners who can manage fleets along proven reliability concepts and who can provide maintenance programmes which
combine workshop and on-wing experience. In order to reduce operational risk it is important for an operator to establish that an MRO provider has an appropriate track record before making a final selection.
Balancing on-wing time and shop
visit costs
The effective management of life-cycle costs does not necessarily require the lowest possible shop visit rate. Instead, it is more important to ensure that hardware costs are minimised by targeting a balance between on-wing time and shop visit cost. The determination of this optimum requires both workshop experience and an understanding of operator-specific information. Whilst an operator’s environment and utilisation are difficult to change, costs may be lowered by swapping aircraft between routes to ensure that they are all subject to the same variety of operational conditions. The careful application of takeoff de-rate and other de-rate power settings definitely helps to reduce operational costs. Furthermore, engine lives can be extended when pooling options are exercised with other aircraft fleets, when it is possible to lower takeoff power settings and
accumulate additional flight hours. MROs can facilitate such pooling when they maintain several airline fleets some of which use an engine type at a high takeoff power setting and others a low power setting.
Trend monitoring
The determination of the optimum removal time for an engine can be made easier by using sophisticated trend monitoring software. It may be used in conjunction with engine stagger and modification policies thereby considering the entire cost envelope and all opportunities to reduce cost. MROs now base their life cycle programmes on experience-validated on condition concepts. These concepts can be customised to target the optimum balance of on-wing time and shop visit costs and can add significant experience to
ENGINE YEARBOOK 2005
standard off-the-shelf monitoring concepts.
Maintenance programmes
Maintenance programmes influence the operational reliability and efficiency of engines by addressing EGT margin, fuel burn and optimum on-wing times in relation to life limits, cost and utilisation. The MROs will offer specific maintenance programmes and the operator’s choice of MRO can therefore significantly affect overall costs.
Turnaround times
Shop turnaround times (TATs) directly influence the cost of engine ownership, since they drive the requirement for investment in spare engines both in the short- and long-term. Today, MROs are prepared to offer specified turn-around time programmes with balanced spare part exchange costs. These programmes usually cover dedicated fleets and require planned, staggered inputs which enable advanced planning to support a reduction in TAT to about 35 to 40 calendar days for narrowbody engines and 40 to 50 calendar days for widebody engines.
Selecting MRO support
Today, life-cycle programmes are offered by many MROs, and they address all of the aforementioned cost elements and normally provide access to the required tools. In order to provide efficient life-cycle cost management, financial acumen is essential and providers of such solutions need to be able to influence the entire cost envelope of engines, their line replaceable units and spare parts inventories. Furthermore, such programmes need to be customised to address the needs of the individual operator.
Depending on the operator or owner requirements, the scope of such programmes can range from assistance in selecting an aircraft or engine and associated services and end when an aircraft or fleet of aircraft is phased-out and re-marketed. Life-cycle programmes are of particular interest to engine
ENGINE YEARBOOK 2005
owners since multiple transfers of both aircraft and engines will take place on a leased aircraft fleet and such programmes are designed to share and optimise the cost and risk of operation and maintenance.
While it is clear that the design and inherent reliability of an engine will influence costs, they are also directly influenced by the MRO through the reliable accomplishment of repairs, assembly routines and the consequent shop turnaround times. Fast in-house repair cycles reduce costs by avoiding investment in pool materials and enable high turn rates on materials. This enables MROs to offer attractive spare part exchange fees. Extensive MRO in-house repair capability also reduces vendor costs, while improving the MRO cost structure through the efficient use of fixed assets.
Effective and accurate fleet planning schemes supported or managed by an MRO allow for an optimum allocation of resources, resulting in attractive rates and charges to the operator. Predictability and efficiency can even be enhanced by combining these fleet management aspects with on-line trend
monitoring features and on-site inspection, line maintenance and logistics support, all provided by one source. Generally speaking, optimal life-cycle cost programmes will be achieved when the MRO provider and the operator (or owner) share a close involvement in fleet
management, and where the provider can offer significant operational experience and unique systems. The range of influences on engine ownership costs is so extensive that there is no ‘one size fits all’ solution. Instead there should be a tailor-made solution for each operation - and the best people to provide this are qualified MROs.
From the operator’s perspective, managing engine ownership costs requires a long-term view, backed by good financial acumen. Key factors include: outsourcing sub-fleets to minimise complexity and using MROs to leverage scale. Risk-sharing programmes should be arranged with qualified partners and may be
A good MRO should support all aspects of its customer’s needs with in-depth knowledge, proven experience of aircraft/airline operation, integrated capabilities, complete independence from outside influence, significant leverage with quality OEMs and good financial acumen. Indeed, as aircraft and engines have become more complex, a good MRO has become a valuable asset in its own right. ■ covered by-the-hour contracts or
time and material agreements that address performance guarantees, engine life-cycle programmes, asset management and/or inventory reduction through the economies of scale. Contracts, especially short-term agreements, need to be monitored very closely while engine fleets and life-cycles should be intimately understood.
Rely on the repair and overhaul experts who know the product best – the original designer and manufacturer. Woodward’s value-added custom solutions lower your cost of ownership. Our technical expertise, engineering and analysis, unmatched environmental test facility, and global support network provide increased
component on-wing time, the highest quality levels, fastest turn times, and most cost-effective service in the industry.
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+1 815 877 7441 • www.woodward.com EYB2005_1 13/9/04 1:50 pm Page 19
ENGINE YEARBOOK 2005
Engine maintenance
costs
Engine maintenance costs
can account for a third of
total aircraft maintenance
costs. Understanding how
engine maintenance costs
come together is therefore
essential to any airline. Dr
Olaf Rupp, manager product
support engineering GE/CFM
for MTU Maintenance
Hanover throws some light
on the subject.
F
or airlines, the assessment and selection of new aircraft and engines is an important part of business planning. During this process, understanding the life-cycle costs of the whole system as well as the subsystems, such as the engines, is a key factor. Maintenance accounts for about 10-15 per cent of the direct operating cost of an aircraft but the exact figure will depend upon a number of parameters such as the aircraft model, the engine type and the nature of the operation (see figure 1). Total aircraft maintenance cost can be broken down further into line maintenance, heavy maintenance, component maintenance and engine maintenance. The distribution of costs between these centres varies once again depending on a number of factors. But engine-related costs can add up to as much as a third of the total aircraft maintenance cost.Elements of engine maintenance
cost
Engine maintenance costs (EMC) divide into those encountered on-wing and those experienced off-wing. On-wing maintenance costs are not only
influenced by pure technical issues such as the engine type and any modifications that may be necessary, but they will also be affected by the philosophies that an airline applies to its line maintenance. This article focuses on the off-wing element of maintenance cost and the parameters that influence it.
When an engine is removed and goes into a shop for refurbishment, the primary cost factor of the shop visit is the material cost. Approximately two thirds of the costs of an engine shop visit come about through the
replacement of material. If life-limited parts (LLP) need to be replaced the material cost element will increase further. Only about a quarter of the shop visit costs can be attributed to parts repair, leaving a relatively minor portion to the labour involved in disassembly and assembly (see figure 2).
The biggest portion of the material cost is attributable to airfoils. The high-pressure turbine (HPT) airfoils have significant influence on cost, with individual vanes costing as much as $15,000 and blades costing as much as $7,000 each. Where the cost of
The influence of some factors
that affect EMC,for example the
hours-to-cycles ratio and thrust
de-rate can be calculated
scientifically.
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ENGINE YEARBOOK 2005
replacing high-pressure compressor (HPC) airfoils may be low for mid-European operators, those airlines operating in the Middle East may experience significant cost from this source. Engines operated in a sandy and/or erosive environment can cause HPC scrap rates to approach 100 per cent. Typically, the largest portion of the parts repair cost is also associated with airfoils since high-tech repairs, such as rejuvenation or split vane repairs are required to get these parts back into a serviceable condition.
Factors influencing EMC
As already mentioned, numerous factors influence EMC: the hours-to-cycles ratio; the thrust de-rate applied during takeoff; environmental
influences such as temperature and pollution; line maintenance procedures; and ETOPS operations requirements, to name just a few. These are all factors that are related to a specific operator whereas other factors, such as parts repair capabilities, need to be
considered by an airline when choosing a maintenance provider. Ultimately, however, material prices and therefore a
significant part of EMC is decided by the engine OEM.
The influence of some factors that affect EMC, for example the hours-to-cycles ratio and thrust de-rate can be calculated scientifically. The influence of other factors such as ‘pilot factors’ are considered to be ‘soft’ and are near-impossible to estimate. Nevertheless, they may have significant influence on how frequently an engine has to go into a shop and how expensive the shop visit is.
Engine operation
Engine operation is the main influence on how much an engine and its constituent parts are stressed, thereby having a large influence on engine deterioration and EMC. The effects of the hours-to-cycles ratio and the thrust de-rate are typically easy to estimate. When an engine is operating two hours per cycle and a 10 per cent effective de-rate is being applied, the EMC per engine flight hour can be assumed to be 100 per cent (see figure 3). If the effective de-rate being used on the engine decreases to about five per cent, there will be an increase of EMC per EFH of some 14 per cent. If the de-rate stays at 10 per cent, but the hours-to-cycles ratio changes to four hours per cycle the EMC per EFH will reduce by some 22 per cent. Obviously, the figures quoted in this example will never be absolutely correct, since in real life more than one parameter will change, but they do provide a good indication of how the hours-to-cycles ratio and the thrust de-rate can influence EMC. In some maintenance contracts, such as by-the-hour contracts, changes in engine operation during the contract period are addressed through the use of tables which show how much the cost per flight hour will change if, for example, the operator uses more or less takeoff de-rate.
Line maintenance procedures can also influence EMC but the extent of this influence depends upon the operator. For example, MTU
Maintenance once discovered that an operator of CF6-80C2 engines experienced positive results when it introduced coke cleaning. The main engine removal reason for this
