43 I MAINTENANCE & ENGINEERING

A decline in engine values on the aftermarket makes it economic for

airlines to acquire time-continued parts and used serviceable material at a
rate that generates savings up several hundred thousand dollars for each
shop visit. The economics for older generation engines are studied.

The economics of using

repaired & serviceable parts
in engine maintenance
T
he use of time-continued parts Jet Engine Management. “This will save sales and marketing for Europe at
and used serviceable material several hundreds of thousands of dollars Magellan Aviation Group.
(USM) is a common cost-saving per SV, depending on the number of There is also commonality of parts
practice in the maintenance of modules worked on and the extent of between the three main PW4000 variants.
mature and older generation engine types. USM used.” The trader or broker is, therefore,
Given the right material acquisition cost There are four or five main categories taking a gamble in buying the used
and the maintenance status and of engine components: life-limited parts engine, disassembling and inspecting the
remaining life of the engine, this practice (LLPs) of the disks and shafts; parts, repairing some parts, warehousing
can generate substantial savings in engine turbomachinery blades and vanes and material until it is sold, and shipping
maintenance costs. The economics of this combustion unit; main cases; accessories parts and modules to the buyer. The
are examined here. and quick engine change (QEC) kit; and engine’s maintenance condition is also a
remaining small parts and components. gamble, since a high percentage scrap rate
“The 80:20 rule applies in the use of will mean a total lower re-sale value of
Economic basis USM and parts in engine maintenance,” parts that get repaired. The process
The economic basis for using USM in says Chris Grey, principal at Aer Auster. generally becomes more worthwhile the
engine material revolves around two “About 20% of the components account lower the market value of used engines.
main issues. for about 80% of the value of an engine “It takes about one week to tear
The first is that the cost of similar USM and parts and materials that will be down an engine, and it requires use of a
engine shop visit (SV) workscopes does in demand from airlines to lower engine specialist facility,” says Grey. “It can cost
not decline as an engine ages. Most of an maintenance costs. This will be most of $50,000-70,000 to disassemble an
engine SV cost is related to purchase or the blades and vanes from the modules in engine. From this, an electronic inventory
repair of materials, parts and the core engine. These are the high of all parts in the engine is produced. All
components. The cost of parts, and in pressure compressor (HPC), combustor, the parts have to be inspected and tagged.
particular engine blades and vanes, does high pressure turbine (HPT), and low All relevant paperwork also has to be
not decline over the 35-45 year period pressure turbine (LPT). The LLPs in these archived, including that related to repairs.
that an engine type is in operation. modules are also in high demand. There are also risks for airlines using
The second main issue is that, as a “It is rare, however, to sell and use all USM, both in the case of engine parts, as
fleet’s size declines due to retirements and LLPs from a disassembled and torn down well as buying complete modules.
fleet disposals, the supply of used engines engine,” continues Grey. “There is little
generally increases. At some stage, engine demand for fan section components,
values will decline to the point where the including the blades, or for low pressure Potential pitfalls
total cost of disassembling the engine to compressor (LPC) blades and In addition to core engine
all the main constituent parts, and vanes/stators, because their maintenance turbomachinery parts and LLPs, there are
repairing some of the material, allows a costs are relatively low, so they offer only other main considerations for an airline.
specialist engine trader to offer repaired a small scope for savings. Some airlines, The first is that the on-wing life of the
parts and components on the market at however, will buy complete fan and LPC engine is not compromised or too short,
an economic rate. Selling USM to airlines modules under the right circumstances. compared to financial saving. There are
exceeds the cost of engine acquisition, There is also some commonality several aspects to this. The first is that
teardown and part repair for the broker, between engine types. For example, the USM might be installed in an engine
while it is significantly cheaper for airline HPC, combustor, HPT, and LPT in the without it being repaired, which risks
operators to buy USM than new parts CFM56-5B are common with the compromising the engine’s predicted
from original equipment manufacturers CFM56-7B. “There is also commonality subsequent on-wing life.
(OEMs). between the CFM56-5C, powering the The second is that repaired USM may
“A specialist engine trader will A340-200/-300, and the CFM56-5B and - be installed in the engine. While this
typically sell repaired USM to airlines at 7B. This includes a lot of LLP material is more expensive, it will extend
70-75% of OEM catalogue list price commonality between the three engine the engine’s on-wing life, but it will still
(CLP),” says Simon Mermod, director at models,” says David Rushe, director of not be as long as that expected with new

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The CFM56-3 and younger variants of the -5B/-
7B are available in large enough numbers to
make the use of USM in engine maintenance
economic. The potential savings extend to
several hundreds of thousands of dollars per
shop visit.

engine types. “Examples are about 100%

for types like the CFM56-5B and -7B, or
the V2500-A5,” says Mermod. “Types
like the CFM56-3 typically have pro-rate
percentages or factors of 50%. This is
because the fleet has imploded, the
number left in operation is constantly
declining, and the large number of
retirements means there is always a
plentiful supply on the market.”
The pro-rate factor is not always the
lowest for oldest engine types. An
example is the PW2000, one of two
engine options on the 757. The 757 is
popular with freight operators, and the
PW2000 is the popular choice with
material. USM will still cost less than new operate for another five to eight years airlines because of the limited number of
parts, and can achieve a similar on-wing before being scrapped do not need to independent maintenance shops available
intervals in the case of some lower thrust have a new set of LLPs installed. for the RB211-535, as well as its
settings and cooler environments. An airline’s demand for USM and relatively high SV costs. There are
Ultimately the overall cost per engine time-continued modules will ultimately relatively few PW2000 operators, with
flight hour (EFH) or engine flight cycle depend on the engine’s last SV, its on- Delta and United being the two largest
(EFC), or actual SV cost should be wing interval since then, its resulting users. Delta is likely to fully utilise the
reduced compared to a workscope using maintenance condition, and the required maintenance life of its engines. This limits
new parts. subsequent on-wing interval. the supply of engines with maintenance
USM also circumvents the need to life remaining on the aftermarket, and
perform full maintenance, saving means that the pro-rate factor of the
maintenance costs. An example is the Engine purchase values PW2000 is relatively high. It has been
case of swapping used modules with The purchase price of engines for known to be close to 100% in some
time-continued or ‘green time’ modules disassembly and salvage, repair and sale cases. Demand for PW2000s and related
taken from a disassembled engine. This is of parts is key to its being economically material will be sustained by the 757’s
be cheaper than repairing or replacing viable for a specialist broker and trader. popularity as a freighter.
parts, and performing full maintenance “The general rule is that purchase value
on the original module. This can generate of an engine on the aftermarket will be
large savings, especially if it avoids pro-rated according to remaining LLP Engine acquisition
replacement of LLPs at high cost, and lives,” says Glenford Marston, chief The most usual route to acquiring
where the required remaining life of the executive officer at Aero Norway. “As a used engines is for specialist traders and
module is a fraction of the lives of the simple example, if the full lives of LLPs brokers to acquire retired aircraft as
new LLPs being installed. for an engine type are 20,000EFC, and entire units from airlines and lessors. In
There are several situations where this the remaining lives of installed parts are many cases the aircraft will be valued at
technique will work, mostly where older half at 10,000EFC, then the engine will the pro-rated value of each of its engines,
engines are being operated, and may only be valued on the basis of a percentage of plus an allowance for the value of
be for a limited number of years before half the cost of a full shipset of LLPs. So, airframe parts, taking into consideration
retirement or for a longer term, but at if the list price of new LLPs is $4 million, the number of the type already retired
low rates of utilisation. This has to and the engine has remaining LLP lives of and the general supply of airframe
consider typical annual rates of 10,000EFC, then the 100% pro-rated material on the aftermarket. This will be
utilisation. These can be as low as 800- market value will be $2 million.” next to zero for types like the 737 Classic
1,000 flight cycles (FC) in the case of If the pro-rate percentage or factor is and 747-400. Their values will, therefore,
some short-haul freighter aircraft, 1,500- 50%, which is more often the case with be entirely based on engine pro-rated
2,300FC per year for short-haul older engine types that are declining in values in relation to remaining LLP lives.
passenger aircraft, and 700-1,500FC per number, then the market value in this The number of 747-400s, 737
year for medium- and long-haul aircraft. case will actually be $1 million. This is Classics and a few other types being
These rates must be considered equal to 25% of the CLP of a LLP absorbed by freight carriers and
against the LLP lives of parts in different shipset. secondary operators is now declining. An
modules of most engine types. Most high The overall issue is that no additional active freighter fleet, however, will
pressure (HP) module LLPs in most value is attributed to the possible value or maintain healthy demand for engines.
engine types are generally 15,000- condition of the remaining material in the The case is different for types such as
20,000EFC, and 25,000-30,000EFC in engine. the 767, A320ceo and 737NG. There is a
low pressure (LP) modules. Pro-rate percentages or factors are strong aftermarket interest in these
Engines or modules that will only relatively high for younger and current aircraft, so their used market values will

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46 I MAINTENANCE & ENGINEERING
Despite the cost of acquiring and repairing core
module blades and vanes, USM can be sold to
airlines at 50-70% of the OEM list price for new
parts. This generates savings of several hundred
thousand dollars at each shop visit, especially in
the high pressure turbine.

putting a CFM56-7B at $3.4 million.

Market values of CFM56-5Bs and
V2500-A5s would be similar, at $1.75-
2.8 million for engines with 50-80% of
LLP life remaining, and $3.5 million for
an engine with 90% of life remaining.
Older types, such as the PW4000-94
and CF6-80C2, would have pro-rate
factors of 50% for engines with
remaining LLP life of 50-70%, putting
market values at $1.8-2.7 million. Either
of these engines with 80% LLP life
remaining may achieve a higher pro-rate
factor of about 60%, and so have market
values of $3.4-3.7 million.

be more than just pro-rated engines. are now being sold by Aviall on a quote
The engine types that are more likely basis. This applies to all parts in the LPT Scenarios
to use USM during maintenance to and the fan shaft. All other LLPs have There are several scenarios where the
reduce engine-related costs include older standard CLPs. use of USM in engine maintenance makes
narrowbody engines. This will include the The 2017 CLP for a LLP shipset is the economic sense.
CFM56-3 in the case of 737-300s and - fan/LPC with lives of 30,000EFC and a The most usual situation is the
400s, many now operating as freighters. CLP of $618,000; the HPC module with teardown of an older example of an old
The PW2000 is another type. lives of 15,000-20,000 and a CLP of engine type, that is no longer being
The PW4000-94 and CF6-80C2, $850,000; a HPT with lives of 15,000- manufactured, to acquire material for use
which power large numbers of 767- 20,000 and a CLP of $676,000; and a in maintenance of an older engine type.
300ERs, about 300 747-400s, about 120 LPT with lives of 19,000-25,000 and a This situation can apply to two
MD-11Fs, and a small fleet of A300-600s CLP of $965,000. scenarios. One is where the USM is
and A310s, are also likely to use USM in The pro-rate factor for the CFM56-3 installed in an engine owned by a lessor,
maintenance and so realise a savings. is generally 50%, and so an engine with and the other is where the engine is
The oldest CFM56-5Bs and -7Bs, and 50% of LLP life remaining will have a owned by the airline.
V2500-A5s powering the A320ceo and market value of about $0.75 million. The third example is teardown of an
737NG fleets, are now over 20 years old. The CFM56-5B and V2500-A5 engine that is owned by an airline for the
There are, therefore, several hundred of power the A320ceo. The CFM56-5B LLP purpose of providing material for its own
each of these aircraft in the later mature shipset has a list price of $3.9 million. engine maintenance shop. “This is rare,
and ageing phases of their maintenance These are split between the fan/LPC with but is currently happening with some of
lives. These can all realise engine lives of 30,000EFC and a CLP of the large US carriers,” says Bill Polyi,
maintenance cost savings with the use of $864,000; HPC with lives of 20,000EFC president and chief operating officer at
USM. This would not necessarily make and a CLP of $950,000; HPT with lives Magellan Aviation Group. “It has been
sense, however, if there was a good of 20,000EFC and a CLP of 1.007 happening recently because of a larger
possibility of these aircraft being utilised million; and LPT with lives of 25,000EFC than predicted surge in SV activity for the
for a period that was at least as long as and a CLP of $1.068 million. CFM56-5B, CFM56-7B and V2500-A5
the on-wing time of engines that had The V2500-A5 has 25 main parts, all because of the continued growth in fleet
received a full workscope that included with lives of 20,000EFC. These have a numbers. There has been a surge in
the use of new material. CLP of $3.84 million. engine shop activity among these three
In addition, the CFM56-5A is The CFM56-7B has 19 parts in four main types, which has caused a delay in
operated in relatively large numbers by a main modules. The fan/LPC module has supply of new parts and materials. We
small remaining fleet of A320-100s and lives of 30,000EFC, the HPC and HPT expect this situation to last for another
about 135 A319s. This engine may also modules have lives of 20,000EFC, and two years.”
be a candidate for using USM. parts in the LPT module have lives of A fourth example is acquisition of a
25,000EFC. These have a CLP of $3.76 brand new or young engine that has just
million. been manufactured and is acquired by a
Engine market values The pro-rate factor of these three broker, trader or an airline with the
The LLP shipsets, the lives of parts in engines is likely to be 90-100%, with specific purpose of being broken to sell all
each main module, and the OEM’s list 90% being paid for older engines and the main parts.
prices provide a benchmark for the likely those with 50-80% LLP life remaining. “The purchase and re-sale value of
market value of pro-rated used engines. This would put the market value of a the salvaged parts would be different in
Starting with the CFM56-3, the full CFM56-7B at $1.7-2.7 million. A high this case, because the re-sale value of all
shipset of LLPs had a list price of about pro-rate factor of 100% is likely for salvaged parts would be greater than the
$3.1 million in 2017. The LLPs for the -3 engines with 90% of LLP life remaining, engine’s purchase value,” says Grey.

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 47 I MAINTENANCE & ENGINEERING
There are certain situations where this workscopes of several engine types. variants: the -3B1, -3B2 and the -3C1. Of
can be economic for the purchaser and Engine workscopes will vary in size, the 734 aircraft in active service, 535 or
trader. Many engine types now provide a depending on engine modules worked on. 73% are equipped with -3C1 engines.
range of thrust ratings, up to 10 in the Using USM in the different modules for The -3C1 can be rated at 23,500lbs,
case of the CFM56-5B/3 series, varying main engine types is the first way to 22,000lbs, 20,000lbs and 18,000lbs. The
from 21,600lbs to 33,280lbs. illustrate possible savings. In the case of large number of retired aircraft includes
Turbomachinery parts are common to all turbomachinery blades and vanes, the several hundred 737-500s that were
thrust ratings. It is possible to buy new main issue relates to what percentage of equipped with -3C1 engines. The -3B2
low-rated variants of engines that are in parts can be repaired, and what has a maximum thrust of 22,000lbs.
the last few years of production, percentage have to be scrapped and Engines rated at 23,500lbs are
disassemble them and sell parts for use in replaced. The main saving for an airline referred to as Class C engines, while
higher-rated variants. will come from replacing scrapped parts engines rated at 22,000lbs and 20,000lbs
Purchase price is based on the original with USM bought from a specialist are referred to as Class B engines. The
thrust rating, so buying an engine at a provider, rather than buying new OEM -3C1 uses the highest standard material.
low rating will result in a price that is up parts at CLP. The HPT is the module In addition, some of the Class C and B
to 30% lower than for the highest-rated whose parts have the highest CLPs and so engines were modified with CFMI’s Tech
variant. “The high demand and value can generate the largest saving. Insertion programme, which used
parts in these engines can be used in all A second way to achieve potential improved turbomachinery hardware that
thrust-rated variants,” says Grey. “These savings from USM is to use time- included 3D blades. The kit increased on-
include the HPT blades and the HPT continued LLPs in the same modules. wing interval and reduced fuel burn.
nozzle guide vanes (NGVs). It is possible A third is to use time-continued The -3’s mature removal interval will
to sell all the parts from a disassembled modules acquired from disassembled depend on the operating environment and
engine for a total value that is close to the engines instead of performing the EFH:EFC ratio. Non-Tech Insertion
purchase price of a high-rated variant, maintenance on existing engines. engines rated at 20,000lbs thrust,
and it can even be higher. Fast-moving The engines examined here are the however, can generally achieve mature
material includes blades and vanes, the CFM56-3, CFM56-5B/-7B, PW4000-94 intervals of about 8,000EFC.
seals, combustor units, seals and LLPs. and the CF6-80C2. Non-Tech Insertion engines rated at
These alone can achieve 95-97% of the 22,000lbs thrust and 23,500lbs thrust
OEM list price on the aftermarket.” will achieve shorter intervals of
CFM56-3 6,000EFC and 5,000EFC.
Out of almost 2,000 737-300/-400/- Category C Tech Insertion engines are
Maintenance cost savings 500s built, 734 of these are still in active thought to generally achieve longer
The best illustration of how use of service. This includes 469 passenger and removal intervals of 9,500-12,000EFC.
USM can save engine maintenance costs 265 freighter and combi aircraft. A core engine SV workscope will
is by using several examples of SV There are three main CFM56-3 either usually be a core restoration or

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48 I MAINTENANCE & ENGINEERING
The CF6-80C2, and other older types like the
PW4000-94, benefit from the large number of
retired units available on the market. This allows
operators of older 747-400s, 767-300ERs and
MD-11s to utilise the aircraft for several years
while minimising engine maintenance costs.

of $965,000, which is $145,000-195,000.

Large savings can, therefore, be made.”
In may make economic sense for an
airline to acquire time-continued
modules. “It is possible to acquire a time-
continued LPT module for a -3 engine for
$400,000-500,000,” says Hobbs. “This
compares to $700,000-900,000 for a mix
of repaired and USM blades and vanes,
about $190,000 for time-continued LLPs,
plus additional costs of other parts and
sub-contract repairs, and the labour
involved. A new shipset of LLPs for this
module alone will cost $965,000.
overhaul. Examining the three modules of The HPT shroud shipset has a CLP of “Another module that may be
the HPC, combustor and HPT will about $268,000. One the same basis, the acquired as a time-continued unit will be
illustrate potential savings. potential saving of 50% parts being the fan/LPC, which will have a market
Aero Norway performs CFM56-3 replaced with USM is about $67,000. value in the region of $550,000 in the
maintenance and SVs, but also acquires Total saving in the HPT module from case of half-life LLPs,” adds Hobbs.
-3 engines for teardown to salvage using USM is this about $675,000.
material for repair to be sold to airlines as The CFM56-3 has a nine-stage HPC.
USM. This includes material used for SVs The whole module will thus include nine CFM56-5B & -7B
performed at the company’s facility. The rotor stages and nine stator stages, some The CFM56-5B and -7B have
USM from -3 engines generally attracts of which will be variable stator vane significant commonality, and most core
45-50% of CLP, in contrast to 65-70% (VSV). “The full shipset of blades in the engine modules are identical between the
for younger generation engines. Tech HPC rotor stages has a CLP of $390,000- two variants. Exceptions are the fan and
Insertion 3D blades, however, fetch a 400,000,” says Marston. “The CLP per LPC. This commonality widens the scope
high percentage value, but will achieve blade of the first two stages is relatively for savings by using time-continued
long removal intervals if that is required. high at $1,000-2,000. It is then a few material and USM.
The CFM56-3 has a single-stage HPT hundred dollars per blade for the The original -5B series has eight
with 72 blades. “The purchase price of remaining seven stages. The cost of repair variants. These were the -5B8 rated at
each HPT blade is $12,500, so a is $120-250 per blade.” 21,600lbs, up to the-5B3 rated at
complete shipset has a CLP of An average repair cost of 25% of 32,000lbs thrust. These have the same
$900,000,” says Marston. “A main issue CLP will mean a cost of $70,000-75,000 hardware. There were two later main
is the percentage fill rate, which is the for 70% of the blades. series. The first was the -5B/P; the /P
percentage of parts replaced with USM. USM purchased to replace the suffix indicated a performance
The remainder will be repaired. If the fill remaining 30% at a cost of $80,000 improvement package that reduced
rate is 50%, then about 36 of the blades versus $120,000 for new replacement exhaust gas temperature.
will be repaired, and the other 36 blades parts. This generates a savings of about The second was the -5B/3, which was
will be USM purchased at a price of $40,000. Similar savings can be made in a production standard that included the
about 50% of the CLP for a new part. the case of the nine stator stages, so a Tech Insertion hardware standard. Like
The repaired 36 blades will cost about total savings of about $80,000 is possible the /P, the /3 programme improved engine
25% of the price of a new part, so about for the whole of the HPC module. performance and on-wing life.
$112,000. There is then the possibility of using Mature engines achieve removal
The saving, however, comes with the time-continued LLPs to gain further intervals of about 10,000EFC, although
USM versus the price of brand new parts savings. This will make sense where the they will be longer for engines rated at
from the OEM. This will be $450,000 for LLPs in a module are almost fully 27,000lbs and lower if they are not
36 new HPT blades. Each USM HPT utilised, and the time required until limited by remaining LLP lives.
blade is about $6,250 per blade, and so engine retirement is substantially less than The -7B series has six variants rated
the cost of the USM is about $225,000. the life limit of new parts. “The market at between 19,500lbs thrust, for the
The saving is this about $225,000.” rate paid for LLPs for the CFM56-3 is -7B18, to 27,300lbs thrust for the -7B27.
The other two main sets in the HPT generally 30-40% of the life value,” says Mature removal intervals will be
module are the NGVs and the HPT David Hobbs, director of engine material compromised to an extent by LLP lives in
shrouds. The NGV shipset has a CLP of sales at Aerfin. “That is, if the LLPs for the core, which are 20,000EFC. The
about $1.535 million. On the basis of an LPT module are required, and those highest-rated engines will have intervals
50% being replaced with USM at a price available have about half the full life of 9,000-10,000EFC, while low-rated
of 50% of CLP, the saving is about remaining, then the rate paid for time- engines can be 12,000-15,000EFC if they
$384,000. continued parts will be 30-40% of 50% are not overly compromised by LLP lives.

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 49 I MAINTENANCE & ENGINEERING
There is a potential for savings of up which has a CLP of $245,000. A fill rate parts is about $160,000. The cost of
to $700,000 when using USM in all core of about 50% means the repair cost for USM for the replaced parts is about
engine modules, and a saving of a further half the units will be about $30,000. The $190,000, and a saving of $80,000 can
$445,000 for the LP modules. other half of the 42 parts can be replaced be realised.
The HPT provides the largest with USM at a cost of about $116,000, The total saving from the HPT,
potential for savings. The -5B and -7B thereby saving about $7,000. combustor and HPC modules in the core
have a single-stage HPT, with 80 blades. The total saving for the HPT module engine is up to $700,000.
CLP for the shipset is about $1.16 will, therefore, be about $420,000. There is also the possibility of an
million. A typical fill rate for HPT blades The combustion section of the airline using time-continued LLPs. This
will be 50%. Repair cost at 25% of CLP CFM56-5B/-7B is a continuous makes sense when the 30,000EFC,
will mean that repairing half the blades combustion module, rather than 25,000EFC and 20,000EFC life limits of
will cost about $145,000. The cost of individual combustion cans. The three the three main groups of LLPs are
replacing the other 50% of blades with main elements are inner liner, outer liner, considered.
USM will be about $405,000, versus a and combustion casing. The casing is “There is high demand for all types of
cost of about $580,000 for replacing rarely repaired, and can be acquired for -5B and -7B material,” says Hobbs.
them with new OEM material. The about $500,000, versus a price of about “Airlines will have to pay a rate of about
potential saving is $175,000 in the case $755,000 for a new unit, a saving of 100% of life factor, and even 120-130%
of HPT blades. about $255,000. for time-continued LLPs on these engines.
The HPT also has a single-stage NGV, If the two liners cannot be repaired, Therefore, if a part has a life limit of
which comprises 21 parts that each have and 30% are replaced with USM, then a 20,000EFC and a list price of $100,000,
a list price of $66,760. The shipset has a small saving of about $40,000 can be and its remaining life is 10,000EFC, then
CLP of $1.4 million, the highest CLP for made. It is, therefore, possible to save the market value will be at least $50,000
any stage of blades or vanes in the engine. about $250,000 in the case of the and up to $65,000.”
In some cases, all parts can be repaired combustion chamber module. Potential saving comes from buying
following a short removal interval, or for The HPC in the -5B/-76B is a nine- fan/LPC or LPT parts when only half the
an engine operated at a low thrust rating. stage compressor, with the first three LLP life is required. In the case of
A relatively low repair cost for these stator stages configured as VSVs. The fan/LPC, buying a complete set of LLPs
items is about $350,000. overall shipset for all blades and vanes will save $350,000-450,000, and in the
In the case of a fill rate of about 50%, has a CLP of about $910,000. The case of the LPT, a complete set of LPT
half of the NGV can be replaced with average repair cost is about 25% of CLP. parts at half life will save $400,000-
USM at a cost of $490,000. This A typical fill rate for the HPC is about 600,000.
generates a saving of $210,000. 70%, so only about 30% of the parts are Lastly, time-continued modules will
The final element of the HPT is the usually replaced with USM or new provide savings for airlines. One potential
HPT shrouds. There are 42 in a shipset, material. The repair cost for the 70% of use is the purchase of fan/LPC or LPT

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50 I MAINTENANCE & ENGINEERING
modules with remaining LLP lives of second stage HPT blades have a shipset repair costs are $75-115 per blade and
5,000-8,000EFC. “These can easily be CLP of $1.02 million and $862,460. $250-727 per vane. The use of USM for
sold by engine brokers and traders,” says On the basis of a fill rate of 50% in the remaining 50% of blades and vanes
Hobbs. “The fan/LPC module on a -5B each stage at a shop visit, half the blades in the LPT will provide the savings. A
engine, for example, with 50% LLP life in the two stages can be repaired at a cost rate of about 70% for USM will generate
remaining can realise about $1.1 million of about 25% of the CLP of new blades. savings of about $175,000 in the four
on the aftermarket. This compares to The repair cost in these two stages is thus stages of LPT blades, and $162,000 in
about $860,000 for a full set of LLPs and about $125,000 and $110,000. the four stages of LPT, a total of about
up to $1.04 million for repair of about The savings comes from using USM $337,000.
70% of the blades and vanes at a repair for the other half of the blades at a cost Clearly there is potential for further
cost of about $660,000, plus another of about 70% of CLP. Thus, the savings savings in the maintenance of other
$380,000 for the purchase of USM and in the first stage will be a cost of modules, such as the combustor and
other materials and parts, and all the $510,000 for new blades, less the 70% HPC.
associated labour of an extensive SV. cost of about $350,000 for USM, which Purchase of time-continued LLPs
is about $160,000. The savings in the provides another opportunity to realise
second stage will be the CLP of about savings. A full shipset of LLPs on the
PW4000-94 $430,000, less the cost of USM at about PW4000-94 has a 2018 CLP of $7.1
There are four thrust ratings for the $300,000, equal to $130,000. million. This is split between $1.37
PW4000-94, between 52,000lbs and The two NGV stages of the HPT have million for the fan/LPC, $2.6 million for
62,000lbs. Most higher-rated engines 34 and 20 units. Total CLP of complete the HPC module, $1.18 million for the
power the 767-300ER and A300-600R shipsets is $728,000 and $714,000. HPT, and $1.94 million for the LPT.
fleets, while most PW4056 at 56,000lbs A fill rate of about 50% might be In the case of using time-continued
power 747-400s. expected by an airline. Repair costs are in LLPs in SV maintenance, LLPs with
The 24 LLPs for engines rated at region of 15-20% of CLP for each part. about half EFC limits remaining can thus
52,000lbs and 56,000lbs have uniform Savings will come from using purchased provide substantial savings for operators.
lives of 20,000EFC. LLPs have uniform repaired parts as USM as an alternative The 15,000EFC and 20,000EFC life
lives of 15,000EFC in the two higher- to buying new parts. On the basis of limits of LLPs in the engine and the
rated variants at 60,000lbs and USM acquired at about 70% of CLP, the typical rates of utilisation mean that most
62,000lbs. A shipset of new LLPs has a saving in these two stages will be in the parts are fully utilised and due for
CLP of $7.1 million. region of $215,000. Total savings in the replacement at an age of about 20 years
Used engines can be acquired on the HPT module from using USM in the two or more.
market at a pro-rate factor of about stages of blades and NGVs will thus be Airlines are likely to pay a rate equal
50%. An engine with about half the EFC about $500,000. This is in the case of to about 70% of CLP, adjusted for
limits remaining will have a market value USM being used in all four stages during remaining life. For parts with 50% of
in the region of $1.8 million. the same SV. EFC remaining, this would be a purchase
Most remaining aircraft and engines The LPT provides another example of cost of $479,000 for the fan/LPC,
are operated on long-haul cycles that potential savings. The module has four $911,000 for the HPC, $414,000 for the
average 7.0-8.0FH. These are with the stages, with 128, 130, 126 and 128 HPT, and $678,000 for the LPT. This
747-700, 767-300ER and MD-11. Engine blades. The blades have list prices of translates into savings compared to the
removal intervals are driven by EFH $1,700-3,300 each, and the entire shipset OEM’s CLP of $889,000 for the fan/LPC,
rather than EFC, and average 15,000- of blades have CLPs of $280,000, $1.69 million for the HPC, $770,000 for
18,000EFC, or 1,900-2,400EFC. $219,000, $232,000 and $423,000, a the HPT, and $1.26 million for the LPT.
There is potential for airlines total of $1.15 million. This totals savings of $4.6 million for all
operating the PW4000-94 to realise The accompanying four rotor stages engine modules. The savings in each
savings in engine maintenance. This can have 40, 44, 38 and 36 vanes. These have module would be greater where
be more than $1.0 million in the case of list prices of $7,500, $5,750, $7,350, and remaining EFC life is less than the 50%
blades and vanes of all four main $8,290. The entire shipset of vanes have used here. These savings will be
modules, and several million dollars in CLPs of $300,000, $253,000, $279,000, particularly attractive to freight carriers
the case of LLPs. and $298,000; a total of $1.13 million. operating the 747-400 or MD-11 for
The PW4000-94 has a two-stage Again, the fill rate may be about another five to eight years, or to
HPT, the first with 60 blades and the 50%, although this will vary and is less passenger airlines that have delayed the
second with 82 blades. The first and predictable for a mature engine. Average retirement of 767-300ERs.

AIRCRAFT COMMERCE ISSUE NO. 120 • OCTOBER/NOVEMBER 2018

 51 I MAINTENANCE & ENGINEERING
for all 154 blades. In the case of repairing An engine with half the LLP EFC
CF6-80C2 50%, and purchasing USM for the other limits remaining will, therefore, have a
The CF6-80C2 is a similar case in 50% of the blades, a USM market rate of market value of about $1.94 million. This
point to the PW4000-94. Both engines 70% will generate savings of about will be split between $542,000 for LLPs
power the same aircraft, similar numbers $300,000 for the HPT blades. in the fan/LPC, $538,000 for parts in the
have been retired, engines remaining in The two HPT NGV stages have a HPC, 357,000 for parts in the HPT, and
service have similar operational and total CLP of $1.33 million. On the same $499,000 for parts in the LPT.
utilisation characteristics, and both can basis of a 50% replacement rate, the In the case of using time-continued
be acquired on the aftermarket at similar possible savings when purchasing USM is LLPs in SV maintenance, LLPs with
pro-rate factors of 50%. up to about $200,000. Total potential about half their EFC limits remaining will
The CF6-80C2 shipset of LLPs has a saving for this module is thus about $0.5 provide about 10,000EFC for the
2018 CLP of about $7.75 million. The million when all blades and NGVs are fan/LPC, HPC and LPT modules, and
parts in the fan/LPC, HPC and LPT considered. 7,500EFC for the HPT modules. If
modules have uniform lives of The LPT presents another purchased at a factor of about 70% of
20,000EFC, and parts in the HPT have opportunity for savings. The LPT has five pro-rate life, potential savings compared
lives of 15,000EFC. The implication is a stages. The CLP for a complete set of to the purchase of new parts at CLP are
market value of about $1.94 million for LPT blades is about $1.32 million, and about $1.4 million for the fan/LPC, $1.4
and engine with 50% of LLP life the CLP for a complete set of LPT vanes million for the HPC, $930,000 for the
remaining. is $1.99 million, for a total of $3.31 HPT, and $600,000 for the LPT. This is a
The CF6-80C2 has mature removal million. On the same basis of a 50% total of up to $4.3 million on the basis of
intervals of about 2,400EFC when replacement rate for the entire shipset of the entire engine’s LLP stack being
powering the 747-700, intervals of about blades and vanes in the module, the replaced with time-continued LLPs.
2,500EFC when powering the 767- potential savings from USM is $497,000. The possible savings with CF6-80C2
300ER and 2,200EFC when powering the The purchase of time-continued LLPs extend from several hundred thousand to
MD-11 at a higher thrust rating. provides another substantial opportunity up to $1 million at each shop visit. This is
The CF6-80C2 has two-stage HPT, for savings. As with the PW4000-94, the possible considering the age of most
and like all other engines, savings are pro-rate factor in the aftermarket for engines that are retired, and the likely
made between the difference of purchasing CF6-80C2s with time- number of years that 747-400s, 767-
purchasing new material and buying continued parts is in the region of 50%. 300ERs and MD-11s will be operated.
USM at about 70% of CLP. Blades in the The 2018 CLP for a complete shipset of
two HPT stages have CLPs of $16,500 LLPs is divided between $2.167 million To download 100s of articles
and $9,500 per blade, and there are 80 for the fan/LPC, $2.15 million for the like this, visit:
and 74 blades in the two stages. This is a HPC, $1.43 million for the HPT, and www.aircraft-commerce.com
total shipset cost of about $2.02 million about $2.0 million for the LPT.

ISSUE NO. 120 • OCTOBER/NOVEMBER 2018 AIRCRAFT COMMERCE