Журнал - The Engine Yearbook 2005

Подождите немного. Документ загружается.

ENGINE YEARBOOK 2005

STS has a fully digital array that

integrates the power lever transmitter

(handles), controller and receiver

(actuator) into a compact, low-cost,

two-component package. This

arrangement greatly decreases system

complexity and maintenance costs.

The main components of the power

lever control system include:

● The ‘smart throttle controller’, a

software program running on the

test cell host computer that provides

power-lever angle commands to the

smart motors and allows for

Ethernet communication between

components and optionally to the

customer’s control system. Part of

the controller is the ‘smart throttle

operator interface’, an 8in touch-

screen. The screen is mounted on

the control console for ease of use.

An optional desktop lever is

available to control throttle position.

The lever incorporates dual handles

to operate both the engine power

lever and the fuel shut-off lever.

Optionally, a game joystick or other

digital input can be used as the

operator interface.

● The ‘smart throttle motor’ mounted

on or near the engine for hydro-

mechanical engines, drives the

engine throttle cable through push-

pull cables. For FADEC engines, the

smart motor is fitted with a

‘resolver’ and is mounted on or near

the engine, or in the cabinets of the

control room.

STS theory of operation

ASE’s STS makes it possible for test cell

operators to control the throttle of an

engine under test in an engine test cell.

STS contains an industrial motor which is

typically mounted on the engine adapter

and is operated from the control console.

A touch-screen interface is provided for

normal operation and an optional handle

may be installed. This system conveys

commands to the smart throttle motor

over an Ethernet link. There is also a

dedicated hardwired connection which

makes it possible to return the engine to

idle under any circumstances. In addition

to the hardwired ‘return-to-idle’ switch, a

hardwired ‘return-to-cut-off’ switch is

available for engines that require this

position setting.

STS software converts the requested

throttle position into commands that are

processed by the smart motor. The

software receives the throttle movement

request from the operator through the

touch-screen or the power lever handle.

The commands are sent to the smart

throttle motor over the Ethernet network.

STS software monitors the throttle

position, the status of the communication

link with the motor and other status

conditions of the smart throttle motor.

STS software provides the routines

required to: rig the smart throttle motor;

setup preset throttle positions; set the

speed of movement of the smart throttle

motor; override the idle stop; and monitor

movement of the smart throttle motor.

The smart throttle motor contains a

processor which accepts commands

from the controller, compares them

with position data from an encoder in

the motor, and then turns the motor at

the speed and direction that is

appropriate to take the output to the

required throttle position.

For non-FADEC engines the smart

throttle motor is fitted with a gearbox to

reduce output shaft speed and increase

output shaft torque, to match the

torque/speed requirements of the engine

power lever input shaft. The shaft from

the gearbox of the motor drives a

mechanical linkage that drives the

throttle on the engine. Each adapter

using this control arrangement has a

linkage that is appropriate to the engine

and adapter: either a push-pull rod or a

push-pull cable. The smart throttle motor

for FADEC engines is equipped with

precision ‘resolver’ outputs to produce

the electrical control signals required by

engines with electronic fuel controls.

In order to provide backup control, in

the unlikely event of a communication or

host computer failure, the STS is equipped

with a back-up hardwired circuit that can

order the processor in the smart throttle

motor to return to the idle or cut-off

position. This RTI/RTCO is possible even if

the communication cable to the smart

motor is severed, because the command is

resident in the smart motor processor.

Other STS features include: display of

the power lever angle on the smart

throttle touch-screen; a rigging

procedure with simple touch-screen

commands (no pots or amplifiers to

adjust); idle stop override actuated by a

soft push button to allow movement

beyond the set-point; the return of the

motor to idle position stored in non-

volatile memory whenever proper

communication is lost or if the

emergency idle command is received;

and five programmable preset throttle

positions with programmable throttle

slew rates. ■

EYB2005_3 7/9/04 2:14 pm Page 79

ENGINE YEARBOOK 2005

Automated repair and overhaul of

aero-engine components

The maintenance, repair and

overhaul (MRO) of aero-

engine components consists

of a chain of different

processes. At present the

supply industry is providing

improved machining

equipment to automate the

individual process steps.

Claus Bremer, president of

BCT, describes how adaptive

CNC technologies can

automate the single repair

processes and, at the same

time, optimise the efficiency

of the entire MRO chain.

utomated repair processes

and adaptive machining

strategies constitute

important elements in today’s aero-

engine MRO industry. Currently, the

repair of blisks is a central issue

whenever consideration is given to

replacing bladed stages with blisks;

the feasibility of such a step hinges

on the available capabilities for the

automated repair. Manual repair

operations cannot be applied to state-

of-the-art blisks - especially for

welding and reprofiling tasks -

because of their unsatisfactory

reliability, quality and

competitiveness. Automated repair is

therefore a key factor when

proposing the use of blisks in

military and commercial aero

engines. Standard repairs are also

influenced by these innovative

approaches. Currently, most of the

processes for the MRO of engine

components are carried out manually.

In many cases, however, manual

operations are not satisfactory from

the points of view of cost and

reliability. Another common problem

is that the components such as blisks

and impellers, are too complex for

efficient manual treatment and

require automated repair systems.

Adaptive machining methods can

compensate for part-to-part variations

as well as inaccurate clamping positions

and keep the tolerances for the actual

parts to a minimum. The geometrical

adaptation of the numerically-controlled

(NC) paths to the actual part geometry

is performed automatically using in-

process measuring techniques,

mathematical best-fit strategies and

adaptation methods. The adaptive

systems are integrated into standard

welding machines and machine tools as

well as into the existing CMM, CAD,

CAM and CAQ environments.

The MRO steps which are especially

time consuming and require a high

degree of accuracy are inspection,

welding, milling and polishing. The

chain of automated repair processes for

aero-engine components is, in most

cases, as follows: first the parts are

visually and CMM-inspected to check

their general reparability and to

identify and locate the damage. Then

the damaged areas are cleaned using NC

machining processes in preparation for

the material addition process. Material

addition is carried out using NC laser-

welding methods. As a last step, the

welded areas are reprofiled (using

milling tools) and polished (using

flexible grinding wheels) on NC milling

equipment.

Single blades

The restoration of tips and edges is a

standard repair for compressor and

turbine blades. For these type of parts

and repairs, reliable NC equipment and

adaptive application software are

available for NC laser-cladding as well

as for NC machining for cleaning,

reprofiling and polishing. Any 3-

dimensionally-shaped blade can be

processed. The nominal geometry

(master geometry) is provided by

automatic reverse engineering of a new

or refurbished blade, using the regular

touch-trigger probe of the machining

equipment. The same equipment can

also be used for various other repairs,

such as for the refurbishment of

shrouded blades (e.g. knife edge seals,

interlock faces) and nozzle guide vanes

(e.g. airfoils, platforms), the tip repair of

blisks, and so on.

The adaptive application software

packages plus standard 5-axis

machining equipment form self-

sufficient, workshop-oriented repair

stations for the automated restoration of

single blades resulting in end-finished

blades. The software solutions allow the

user to ‘program’ new types of blades

or to modify the machining strategies

by themselves. This self-sufficiency

speeds up reaction time and reduces

costs. When the adaptive approach is

taken, moreover, the use of expensive

calibrated fixtures can be dispensed

with.

Complex components

The automation of the repair of more

complex parts, such as blisks and

impellers, calls for a bit more effort.

Figure 1: Welded blade.

EYB2005_3 7/9/04 2:15 pm Page 80

ENGINE YEARBOOK 2005

Without a PBS installed …

it’s just another test cell.

Without a PBS installed …

it’s just another test cell.

Install the world’s best vibration testing and calibration equipment

in your test cell. The PBS product line leads the industry

in features, innovation and performance.

• Vibration Monitoring

• Trim Balancing

• Digital Interfacing

• Charge Amplifiers

• Portable Calibrators

www.mtiinstruments.com/aviation

These engine components require

sophisticated 5-axis NC processes.

Therefore, the CAD data for the

nominal geometry (reverse engineered

or from the OEM) and the CAM-

generated NC programs referring to the

nominal geometry constitute an

additional input to the adaptive

processes.

The different types of damage

encountered on the tip, edges, corners

and airfoils have to be taken into

account. In particular, front-end blisks,

which are used mainly in military

engines, can be heavily damaged. On

impellers and high pressure compressor

blisks, however, it usually suffices to

restore the worn-out areas. This results

in the following repairs:

● the welding of tip, edges, corners

and airfoil sections;

● patches (corners, edges, tip area);

and

● the replacement of entire blades

using linear-friction welding.

In the following, we will describe the

automated repair processes:

● inspection (identification and

localising of the repairs);

● cleaning (cleaning/milling of the

repair areas);

● welding (material addition by laser-

welding); and

● re-profiling (reshaping of the

welded/patched areas).

There is no need to automate the

processes all at once. However, the

installation of a data-handling system

improves efficiency by promoting data

flow and factory automation

throughout the MRO chain.

The aim of inspection is to assess the

general ‘repairability’ of the parts as

well as to identify and locate the

damage. Usually, the automated

dimensional incoming and final

inspection are carried out on a

coordinate measuring machine or on a

‘robot arm’. Various proven measuring

methods are available such as: touch

trigger probes, continuously measuring

probes, spot lasers, line scanners and

range image systems. The suppliers of

dimensional metrology can provide a

broad range of solutions for the

inspection tasks. The results of the

incoming inspection can be of great

value for the subsequent NC repair

processes, especially for adaptive

cleaning and laser-welding. For this

purpose, the inspection systems must

be linked to the other processes via a

data management system.

The cleaning process prepares the

damaged areas for the subsequent

welding process. It is advantageous to

use only a limited number of

geometrically-defined smooth blends.

For example, the length of the cleaned

area for leading-edge repairs may be

permissible with a step width of X mm

and a step width of Y mm. With this

stepwise parameterisation of the

dimensions of the cleaned areas, the

EYB2005_3 9/9/04 12:24 pm Page 81

following repair processes can be

automated more easily and kept

simpler. The main cleaning techniques

used are: milling, grinding and laser

cutting. The cleaning process is the

simplest process in the repair process

chain and there are proven machining

techniques available for cleaning. The

procedure of geometrical adaptation of

the NC paths is restricted to best-fit and

can make use of the measuring data

from the incoming inspection.

More and more, NC-driven laser

welding equipment is replacing manual

welding in the repair and overhaul of

worn-out aero-engine components. The

background to this growing trend is

that laser-welding technologies allow

for more economical and accurate

welding and cladding of higher quality.

In some cases where existing methods

cannot be applied, certain blades can

now be overhauled with laser-welding

techniques. Furthermore, near-net-

shape laser welding can reduce the

effort required for final reprofiling and

finishing to a minimum.

The geometries of worn-out blades of

blisks, impellers and other aero-engine

components differ significantly from

the nominal (CAD) geometry of the new

part. As precision laser-welding and

cladding systems offer high accuracy

and repeatability of some 0.1 mm, the

CNC paths must be generated based on

the actual geometry of the part to be

welded. If the inspection processes are

set up in an integrated manner and the

inspection strategies are reasonably

selected, the measuring data from the

incoming inspection can be used for the

adaptive tasks carried out as part of the

welding process. Otherwise, the

measurement of the blades must be

carried out on the welding machinery

using vision systems, line-scanners or

touch trigger probes.

The laser welding process can be

automated using an adaptive approach.

Because the welding process generates a

material addition that is near net shape

but with a certain amount of

overmeasure, the geometrical adaptation

does not need to be as refined here as

for reprofiling (see below).

The quality of the material addition is

contingent to a high degree upon the

quality of the laser-welding process.

And since the quality of the welding is

pivotal for defining the quality and

safety aspects of the entire repair

process, special attention should be

given to several issues related to

welding technology. Therefore, the

selection of a reasonable welding

method and an experienced equipment

provider are of crucial importance. In

recent years, several laser-welding

processes for material addition have

been developed to a proven state.

However, any welding method can be

automated by adding adaptive

application software to the NC laser

equipment.

From a mathematical, measuring and

machining perspective, the reprofiling

of the repaired areas is the most difficult

repair task; this is because the

machining tolerances are in the range of

some few 1/100mm. Currently, the repair

of blisks is a central issue whenever

consideration is given to replacing

bladed stages with blisks; the feasibility

of such a step hinges on the available

capabilities for the automated repair of

these high-value engine components.

ENGINE YEARBOOK 2005

Figure 2: Four blades in a fixture.

Figure 3: Blisk.

Figure 4: Impeller.

EYB2005_3 7/9/04 2:16 pm Page 82

ENGINE YEARBOOK 2005

Forced by these circumstances, BCT has,

over the past several years, developed

all the software modules and tactile-

measuring strategies necessary for the

adaptive reprofiling of the blisks for the

EJ200 military engine of the

Eurofighter/Typhoon.

The adaptive milling strategies are

applied to different repair methods: weld

repair (tip and edges), patch repair

(different types of patches) and blade

replacement by linear-friction welding.

The nominal part geometry (CAD), the

NC milling strategies (CAM) and the

description of the repair process are in

the hands of the user. This user know-

how is supplied to the software system

for adaptive machining via a standardised

data interface, e. g. the international IGES

format used for CAD data. With this

system layout, the user is able to keep all

repair-technology-related know-how in

house. A further advantage of this

division of responsibilities is that all the

user’s know-how regarding new-part

geometry and new-part milling

technology can be applied to the blisk

repair tasks.

Practicable measuring strategies are of

great importance for the high-precision

adaptation needed for reprofiling. It is

necessary to obtain a detailed overview

of the overall deformation of the blade.

For this purpose a number of points

spread over the entire airfoil have to be

measured using a touch probe. In

addition, detailed measurements have to

be made around the repair areas to

ensure a minimal step between the

parent blade and the repair area and

provide for a smooth transition between

the former and the latter.

The automation of the reprofiling

process requires the application of

sophisticated best-fit and shape

adaptation methods. Since the reprofiling

process generates the final shape of the

blade to be repaired, adaptation

technique requirements are very

demanding in this process. The

experience gained with this technique so

far indicates that larger repair areas

exceeding a certain size, as well as

restrictions in the deviation between

nominal and actual geometry and

aerodynamic demands, necessitate the use

of special adaptation algorithms capable

of meeting requirements and boundary

conditions. In general, the geometrical

adaptation is carried out in two steps:

● best-fit to determine the correlation

between the nominal position of the

“CAD” blade and the actual position

of the repair blade

● adaptation to determine the

correlation between the nominal

ME ET ING

THE CHALLENGE

Huffman Grinder, Laser and Waterjet

Technologies deliver exceptional

technical & commercial results for

manufacture and repair of a wide

variety of ﬂ ight and industrial gas

turbine components.

www.huffmancorp.com

1-888-HUFFMAN

shape of the “CAD” blade and the

actual shape of the repair blade.

With state-of-the-art technology, it

is possible to automate MRO processes

currently performed manually and to

reduce costs and throughput times

while boosting quality and precision.

Adaptive machining technologies such

as welding, milling and polishing can

be applied to a broad range of repair

methods and aero-engine components

from compressor blades and turbine

blades to impellers and blisks. On the

basis of BCT’s many years of

experience in the automation of

engine-component MRO as well as the

experience gained during several

research and development projects, it

is evident that the integration of the

different repair processes using a

common data handling system can

achieve even more efficiency than the

addition of the single processes. ■

Figure 5: Data handling system.

EYB2005_3 9/9/04 12:28 pm Page 83

ENGINE YEARBOOK 2005

Third-generation high-

speed grinders

Airline operating costs are

influenced by many factors,

some of which are directly

associated with engines:

these include fuel

consumption, engine

durability/reliability and the

costs of engine overhaul and

maintenance. Many of these

factors will, in turn, depend

on the quality of engine

manufacture and any

subsequent maintenance. As

REFORM Maschinenfabrik

explains, even the tip

clearances between rotors

and vanes can be critical in

this regard and much

development work has been

accomplished to come up

with machines which can

reliably create such

clearances.

ne of the objectives in engine

overhaul is to optimise blade and

vane tip clearances between

rotating and non-rotating parts. Prior to

1982, the gaps between rotating and

static components were controlled

through the use of low-speed grinders

and shimming was used to stabilise the

blades in their slots. In the mid-eighties,

however, the first high-speed blade tip

grinders were introduced to the industry.

These used centrifugal force to stabilise

the blade during the grinding process.

The HSG 1400 series machines

produced by REFORM Maschinenfabrik

of Fulda, Germany are considered a

third-generation high-speed grinder.

REFORM’s high-speed grinding

experience dates back almost 20 years

when a machine called ‘HSG 1’ was

installed in Hamburg. Lufthansa

Technik (LHT) Hamburg was one of the

first users of high-speed blade tip

grinding technology. Since 1985 more

than 4,000 rotors (CF6-50/80, CFM56,

PW4000, V2500) have been processed at

its facilities on these specially-built

machines.

In the early 1980s LHT was, in fact,

contributory to the design of high-speed

tip grinders, working in conjunction with

another German company (no longer in

existence) to find solutions to the high-

speed grinding process. An interesting

development was that a balancing process

was incorporated into the machine, which

used a tangential blade tip measurement

system. In 1985 this was considered a

novel approach since until then almost

everyone had used a radial laser

measurement system. But it was soon

discovered that the tangential system had

some significant advantages over the

radial system. It was found to be superior

in terms of its speed and accuracy and

today, all new blade tip grinders use the

tangential measurement system.

There are two other major differences

between the high-speed grinding

machines on the market today and those

of the past. The first high-speed grinding

machine used components that came from

rotor balancing machines, such as

balancing pedestals. Subsequently, LHT

developed the tooling required to

integrate the balancing function into the

grinding machine, which was no simple

task. The machine was designed to

operate using a ‘travelling head’ concept,

which means the rotor remained

"The key is to reduce the risk by

retaining well-proven

components which have been

functioning for more than a

decade and combining them

with modern technology and

improvements."

– Holger Winter, HSG project

team, Lufthansa Technik.

EYB2005_4 7/9/04 3:13 pm Page 84

ENGINE YEARBOOK 2005

stationary while the grinding head and

the measuring system moved. HSG 1 was

the prototype of this concept and even

had some components which were made

of concrete (refer to Figure no. 1).

Nevertheless, HSG 1 was in service until

2002 and it performed its job very well.

After the success with the HSG 1, LHT

installed HSG 2 in Hamburg. This was an

improved model with no concrete

components. The advantages of the

travelling-head concept were quite clear

— not only was the system more rigid

than the oscillating-table concept used on

smaller cylindrical grinders, but it could

also be used on heavy work-pieces such as

printing rollers. Another advantage of this

design is that significant floor-space

savings can be made as compared with the

traditional solutions. For many years these

two machines were used at LHT for large

rotors and another smaller machine from

the same manufacturer was used for CF34

rotors.

At almost the same time, two stator-

processing machines were commissioned

to grind, brush and measure stator vanes.

These machines were similar to vertical

turning lathes and were not capable of

performing automatically at the time.

Subsequently, LHT decided that these

machines should be replaced and after

extensive market research it selected

REFORM as its supplier. In 1999,

REFORM supplied its first stator-

processing machine and this was capable

of fully automatic vane grinding,

brushing, measuring and turning

applications. This machine substituted

both of the former manual stator machines

and has worked very well since. Even

today it is the only machine on the market

which can perform these tasks in a fully

automatic manner without an operator.

In view of this experience, LHT

requested REFORM to participate in the

evaluation process for a new HSG

machine during the 2000-2001 timeframe.

This process was quite a challenge since

most recognised HSG manufacturers of

that time had not produced any

travelling-head machines. But, in view of

its desire to clear floor space, LHT sought

to retain this system of working. At the

end of the evaluation process, REFORM

was selected for its willingness to be

flexible in accommodating LHT’s wishes

and providing an economical and

technological solution for the HSG

process. Experience gained on HSG1 and

HSG2 was subsequently shared and

formed the basis of REFORM’s plans to

create a third generation of HSG

technology.

LHT’s Holger Winter, who worked on

the HSG project team in 1983 (when the

first ideas were arrived at during the

evaluation and realisation process) said:

“The key is to reduce the risk by

retaining well-proven components which

have been functioning for more than a

decade and combining them with modern

technology and improvements.” The HSG

1400 followed this recommendation and

was put into operation very soon after

delivery and this was only possible

because customer experience was

incorporated. Nevertheless, even though

it is technically possible to integrate

balancing into grinding machines, many

customers will still prefer to accomplish

balancing on a separate machine.

Apart from the kinematic travelling

head, there is another major difference

between the old machine and the new.

While the 1985 machines had specially

developed hardware and software for the

blade tip measurement system, some

EYB2005_4 7/9/04 3:15 pm Page 85

ENGINE YEARBOOK 2005

disadvantages have become apparent over

the years. Since the electronic

development cycle is rapid, spare parts

redundancy comes about very quickly

and this has meant that it is often difficult

to obtain spare parts. As with a computer,

what is new today is old in one year’s

time; and when one is seeking a life of 10

years or more for a machine tool, this

creates a major problem, especially since

the blade tip measurement gauge is the

heart of the machine.

The measuring of blades at a tip velocity

speed of 40-50m/s is quite a challenge. In

view of problems previously experienced

with spare parts, it was necessary to

consider different solutions to go about

things differently. The solution eventually

arrived at used standard, commonly

available hardware together with dedicated

software. Also, in order to allow for future

development, the possibility of higher tip

speeds was catered for.

The 1985 machine’s tangential system

was specially developed using an ‘optical

transducer’ concept with unique software

and hardware. However, the new approach

is based on software that was originally

developed by MTU in Munich which

REFORM bought and integrated into the

REFORM HSG. The major advantage of

doing so was that it became possible to use

standard components such as: transputer

cards; a laser micrometer; and a PC with a

Microsoft Windows operating system.

The use of the transputer in conjunction

with the laser allows the system to operate

at a much higher tip speed — up to 130

m/s. In the future it might even be

possible to introduce higher tip speeds if

required. The operator-friendly menu

screen makes operation of the machine

quite easy — it is multi-lingual, permitting

the desired language to be selected.

Calibration measurements between the

old and the new systems have indicated

that the performance of the new system is

totally acceptable and as at July 2004 more

than 500 rotors had been processed using

the new machine. The performance of the

machine led LHT to order an additional

HSG 1400 for its facility in Ireland, to

replace the old machines previously used

for CF34 rotors. Each machine is equipped

with a remote diagnosis system and some

have a video-conference system. A 24-

hour hotline service between the

manufacturer and the machine ensures the

minimum possible downtime.

Good cooperation between the end-

user and the machine tool manufacturer

formed the basis of REFORM’s success,

enabling it to deliver advanced

products within a short time period,

even though it was a ‘newcomer’ to the

business. Innovative technology

introduced by REFORM supported by

LHT’s experience in overhauling high-

bypass jet engines has enabled engine-

shop manual blade tip gap

specifications to be accurately and

repetitively achieved, resulting in the

highest possible core-engine

performance levels.

According to LHT’s Winter,

expectations for the new HSG have

been completely satisfied and REFORM

can now be considered a major player

in the aeronautical machine tool

supplier business. In order to

concentrate on the aeronautical machine

tool market, REFORM has established a

subsidiary in the UK; and many engine

overhaul shops around the world that

are planning to replace their HSG

machines have shown interest in

purchasing this latest machine tool

technology. ■

Good cooperation between the

end-user and the machine tool

manufacturer formed the basis

of REFORM’s success,enabling it

to deliver advanced products

within a short time period,even

though it was a ‘newcomer’to

the business.

EYB2005_4 7/9/04 3:17 pm Page 86

framecheck69 25/3/04 11:06 am Page 3

ENGINE YEARBOOK 2005

Adding capabilities to

suit customer need

In today’s airline operating

environment, engineering

and maintenance managers

are under constant pressure

to increase fleet reliability

and to decrease

maintenance costs. Savings

are being sought regardless

of whether they are large or

small. Barbara Mead,

product-line manager for

Praxair Aviation Services,

Kansas City, MO explains how

it has developed capabilities

to assist airlines in this

regard.

EMs are now recommending

that eddy-current inspection is

performed on all engine hub

assemblies, and airline operators have

to consider where they should source

such inspections. Traditionally, such

services have only been available

from OEMs and airline MROs, but

now Praxair Surface Technologies can

offer automated eddy-current hub

inspection capabilities in conjunction

with complete repair and overhaul of

JT8D fan blades and hubs. This

makes the company the only repair

station, other than the OEM, to have

the ability to provide all services at a

single location.

In order to offer this service, Praxair

purchased an ETC-2000 automated

eddy-current inspection system,

together with all associated hardware

and software needed to perform the

recently required blade slot inspection

on the JT8D-200 first-stage hub. Setup

is now complete and FAA approval to

provide complete hub overhaul services

for the JT8D-200 has been obtained.

This includes the automated eddy-

current inspection of the blade slots,

tie-rods and counterweights. In

addition, complete overhaul of standard

JT8D C1/C2 hubs can be supplied. This

capability puts the company in a

position to supply not only this specific

inspection requirement but also to meet

similar automated eddy current

inspection requirements on other

engines later this year.

Eddy current — automated versus

manual

This initial JT8D-200 automated

eddy current inspection requirement

is intended to detect cracks in the

blade attachment slots of the first

stage fan hub. The fan hub must be

disassembled, cleaned and stripped of

anti-gallant in blade attachment slots.

An eddy current probe is then passed

through the blade-attachment slots,

using an automated inspection system

and a defined scan plan. Whilst the

inspection is automated to provide

smoother scanning than can be

accomplished manually, the

inspection must be performed and the

results evaluated by a suitably

trained and qualified inspector.

Pratt & Whitney, which originally

developed the automated inspection

This initial JT8D-200 automated

eddy current inspection

requirement is intended to detect

cracks in the blade attachment

slots of the first stage fan hub.

EYB2005_4 7/9/04 3:17 pm Page 88