Журнал - The Engine Yearbook 2005

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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

You’re not just getting a part.

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your needs.

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.

As an MRO business, we are driven to deliver operational reliability, superior cycle times, and the most

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United parts and United people: It’s a partnership designed to keep you flying at your best.

So visit unitedsvcs.com or call 650-634-7977 today. And meet a few more people who want

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–GregHall

Senior Vice President

United Services

ATE&M_Components 8/2/04 2:06 PM Page 1

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

make one- to two-hour flights as

many as 10 to 12 times a day.

EYB2005_1 7/9/04 8:44 am Page 10

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.” ■

EYB2005_1 7/9/04 8:46 am Page 11

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.

n the 20 years since the launch of

the 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

EYB2005_1 7/9/04 9:29 am Page 12

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

021300 PWLCE rel cgs 2/6/04 1:54 PM Page 1

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

EYB2005_1 7/9/04 8:51 am Page 14

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.

EYB2005_1 7/9/04 8:52 am Page 15

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.

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

EYB2005_1 7/9/04 8:52 am Page 16

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.

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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

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