Early detection of transmission failures through oil system debris assessment

Important information

The purpose of this document is to assist line maintenance personnel with oil system trouble-shootingfor the following engine/airframe types:

RB211-22B Lockheed L1011 RB211-524 Boeing 747 and 767, Lockheed L1011 RB211-535 Boeing 757, Tupolev Tu-204 Trent 500 Airbus Industries A340-500/600 Electric MCD (E)MCD Trent 700 Airbus Industries A330-200/300 Trent 800 Boeing 777 BRR 710 Gulfstream GV

Bombardier Global ExpressBAe Nimrod 2000

BRR 715 Boeing 717 Tay Gulfstream GIV, Fokker 70, Fokker 100, Boeing 727 V2500 Airbus Industries A319, A320, A321, Boeing MD-90

This document does not amend, replace or supersede any information contained in the respective AircraftMaintenance Manuals.

All maintenance must be carried out in accordance with the relevant Aircraft Maintenance Manual.

1Contents

Summary 2

Regular MCD inspection benefits 3

MCD standard and configuration 4

Diagnostic MCDs 7

Bayonet MCD practices 9

Screw-in MCDs practices 11

Maintenance schedules and practices 12

Multiple engine inspection 12

MCD inspection intervals 12

MCD inspection practices 13

Method for MCD inspection 15

Removal and examination 15

Method for scavenge (fine) filter inspection 25

Storage of debris 35

Debris identification 36

Bearing lapping failure producing fines 37

Gear wear producing fines 38

Bearing fatigue failure producing flakes 39

Gear tooth fragments 40

Chips 41

Cage rivet failure 42

Roller bearing cage tang failure 43

Build debris or swarf 44

Interpreting the results 45

Actions to take when debris is discovered 46

2Summary

The early detection of transmissions failures can be achieved through

regular inspection of the oil system Magnetic Chip Detectors (MCDs). This

brochure has been developed to describe the best practices for Magnetic

Chip Detector (MCD) inspection and debris assessment. Occasionally it may

be necessary to confirm the debris findings on an MCD by inspection of the

oil scavenge and pressure filters, which is also described. This brochure is

intended for use by line maintenance and laboratory personnel. While this

document does not replace or supersede the relevant Airframe or

Rolls-Royce Maintenance Manual, it has been designed to allow easy

reference to possible sources of engine wear.

At several locations in the

brochure, Top Tips are given in a

blue tinted panel

Top Tips

These tips are based on

previous Rolls-Royce experience.

3Regular MCD inspection benefits

1 Earlier failure detection

2 Scheduled removal of the engine, reducing airline disruption costs

3 Lower secondary damage, reducing shop visit costs and turn

around times

4 Reduction of in-flight shutdowns and delays

This brochure describes a recommended method of monitoring the oil

system by regular inspection of magnetic debris found primarily on both

MCD and Electric MCDs (EMCDs) and also in the oil pressure and scavenge

filters. Photographs are provided to allow the identification of the small

quantities of debris generated early in a component failure sequence,

enabling the sentencing of engines in conjunction with the relevant

Aircraft Maintenance Manuals.

Although it is possible to detect bearing failures from filter blockage

warning or high vibration, these flight deck indications occur late in the

failure sequence when significant secondary damage may have already

taken place.

4MCD standard and configuration

Ensure the MCDs are of the latest standard. The table overleaf showsthe latest version of MCD that should be fitted to the corresponding

engine type.

Also refer to the latest service bulletin which may have updatedrecommended positions.

Top Tips

Current modern engines only

tend to incorporate a single

MCD or EMCD at the master

position.

Bayonet style MCDs have

tended to be replaced by

screw-in MCDs over last

20 years. Bayonet MCDs

remain a customer option but

Rolls-Royce recommends the

screw-in type since it offers a

positive wire locking

mechanism.

5Engine Type Recommended MCD Standard Recommended positions

RB211-22B and -524 SB72-7911 (Bayonet) Master

Improved strength magnet and Internal Gearbox

Balking feature for O-ring High Speed Gearbox

RB211-535 SB72-7911 (Bayonet) Master

Improved strength magnet and Internal Gearbox

Balking feature for O-ring High Speed Gearbox

Trent 500 Screw-in electric MCD Master Only

Trent 700/800 Screw-in Master Only

BR710 SB-BR700-73-100225 (Screw-in) High Speed (Accessory) Gearbox

Front Bearing Housing

Rear Bearing Housing

BR715 SB-BR700-73-101104 (Bayonet) Master Only

V2500 SB 79-0042 All 7 positions

Tay Bayonet Master, High Speed Gearbox

6Sealing plugs andscrew-in MCDs ona Trent 800 engine

7Diagnostic MCDs

Diagnostic MCD's, when installed should be inspected at the same timeas the Master (E) MCD. See MCD Standard and Configuration table for

location of other MCDs installed during normal running.

Sealing plugs (blanking plates) should be fitted when diagnostic MCDsare not installed.

8Excessive pin wearon a bayonet MCD

Alignment check

9Bayonet MCD practices

On examination of the MCD for debris, also inspect bayonet pins forwear. Significant wear may result in MCD mis-alignment during

installation, which may lead to oil loss.

Rolls-Royce recommends that O-ring seals for the MCDs are replacedfollowing each inspection. Debris or damage present on the O-ring may

result in oil leakage.

When refitting the MCD probe check that the bayonet lock is engagedby ensuring the probe will not turn counter-clockwise and that the

locked holes in the probe end face and housing are aligned.

Top Tips

The latest standard of bayonet

MCDs for the RB211

incorporates a balking feature

that prevents fitting of the MCD

in the housing if the O-rings are

not present.

Do not leave diagnostic MCDs

fitted. Pin wear may allow MCDs

to release in flight with

subsequent loss of oil.

10

Wire lockingof a screw-inMCD forsecurity

11Screw-in MCDs practices

Ensure the O-ring is fitted after inspection. Failure to fit the O-ring willincrease the chance of an oil leakage.

Ensure MCD is wire locked for security during flight. Lack of the securitywire may lead to MCD loss.

Tops Tips

Screw-in MCDs suffer from

O-ring wear when removed for

inspection. Rolls-Royce therefore

recommends that O-rings are

replaced following each visual

inspection of the MCD.

12Maintenance schedules and practices

Multiple engine inspection

In order to reduce the potential for multiple-engine in-flight shutdown, power loss, or other anomaly due to

maintenance error, Rolls-Royce recommends that Operators avoid performing maintenance on multiple engines

installed on the same aircraft at the same time. If this is not possible, Rolls-Royce plc recommends that additional

controls are applied, these might be:

Independant inspection of work Separate crews Ground run leak testMaintenance guidelines should be revised, where possible, to promote this recommendation.

MCD inspection intervals

MCD scheduled inspection intervals for each engine type are recommended in line with service experience:

Shorter intervals benefit early detection However too short an inspection interval will not allow debris to accumulate and give a noticeable catch.

Rolls-Royce plc may occasionally issue a Non-Modification Service Bulletin (NMSB) with recommended inspections

to cover a specific problem.

13

The Maintenance Planning Document (MPD) produced by the Airframer contains information regarding the

maximum recommended inspection interval for MCDs. This is particularly important for ETOPS (Extended Twin

Engine Operations).

Engines fitted with an Electric MCD at the master position will not have a scheduled maintenance inspection.

Visual inspection will be carried out when a maintenance message is generated, however this inspection can be

deferred to main base to allow inspection by trained personnel.

Note: Tay NTO48 recommends the deletion of the routine MCD check, but MCDs should remain fitted for

trouble-shooting purposes.

MCD inspection practices

It is advised to use main base trained inspection personnel to avoid variation in the interpretation of results andmaintain a consistent inspection technique

If it is not possible to always inspect at main base, limit stations involved and coordinate findings. Return alldebris back to main base to enable a complete assessment.

Avoid non-scheduled inspections by untrained personnel.

14

MCD and EMCD as removed from engine

15Method for MCD inspection

Removal and examination

At the prescribed interval carefully remove the MCDs from the engine and,

if desired, fit a clean one. Refer to the Aircraft Maintenance Manual for

details.

Top Tips

Most Line Engineers make an

initial assessment of the debris

caught on the probe at the

engine a 5x magnifying glass

and good light source is

recommended for MCD viewing.

However the oil film on the tip of

the MCD probe sometimes

makes fine debris difficult to see.

Washing of the probe tip in

kerosene or another suitable

solvent to remove oil is

recommended if there is any

uncertainty (see page 18).

16

Individualplastic bagsto hold eachMCD whileout on theflightline andfor transportback to thelaboratory

17

If the debris assessment is not to be made immediately, place the

contaminated MCD into a clean, new, heavy duty polythene bag (one MCD

per bag). This will avoid the possibility of cross-contamination of debris

from one MCD to another, or from a dirty container that has been re-used.

Do not worry about debris clinging to the MCD being disturbed this can

be collected from the inside of the bag in the laboratory.

Attach a label to each MCD indicating the engine details and engine MCD

position it was removed from (the label shown on page 34 is appropriate)

Top Tips

Contamination of MCD debris

must be avoided at all stages in

the preparation and inspection

process. Failure to do so can lead

to an incorrect diagnosis of an

engine problem. Ensure that

containers, working media, tools

and preparation surfaces are

clean prior to use.

18

Washing of MCD insolvent

Prior to washing After washing

19

Rinse the magnetic part of the MCD in a beaker (non-metallic container) of

kerosene as stated in the Aircraft Maintenance Manual to wash off the

residue of oil and any non-magnetic material adhering to the magnetic

debris or MCD. For EMCDs, take care not to contaminate the electrical

contacts with kerosene.

Alternatively, wash the MCD in a more volatile solvent such as alcohol or

white spirit, which allows the MCD debris to dry more quickly.

20

Photos showing debris transfer toScotchTM Magic Tape

21

Procedure for MCDs

Ensure all the debris is at the tip of the MCD if necessary, use a clean

wooden spatula or toothpick to achieve this.

Take a piece of 25mm (1 inch) wide transparent adhesive tape, preferably

Scotch Magic Tape (OMat 1269) approximately 50mm (2 inches) long

and apply the centre of the gummed side over the magnetic tip of the MCD.

Wipe off the magnetic debris onto the tape. It may require several attempts

to remove all of the debris with the same piece of tape.

Procedure for EMCDs

Take a piece of 25mm (1 inch) wide transparent self adhesive tape

preferably Scotch Magic Tape (OMat 1269) approximately 50mm

(2 inches) long and apply the centre of the gummed side over the recessed

insulated debris gap. It may require several attempts to remove all of the

debris with the same piece of tape.

Debris transfer/collection

Top TipsBefore refitting an (E)MCD to anengine it is essential that the(E)MCD is free of damage andclean. Check the magnetic tip byconfirming it will lift theappropriate number and size ofsteel balls specified for the MCDtype. Cleaning can be done bypressing the MCD magnet areaand seal ring grooves into aclean lump of plasticine(OMat 249). This should berepeated at least once, and anyplasticine residue removed witha solvent wetted wipe. The cleanMCD should be stored in a cleanpolythene bag, in accordancewith the vendor ComponentMaintenance Manual.

22

Transferringdebris ontorecording card

23

Stick the tape onto the approximate space on the record card taking care

not to lose any debris.

Seal the debris between the tape and the record cards by pressing the tape

to the card all round the sample. Enter details of the sample in the spaces

provided on the card.

Top Tips

Rolls-Royce plc recommends

that debris samples be retained

using Scotch Magic Tape

(OMat 1269) rather than

Sellotape. It is easier to remove

debris from Scotch Magic Tape

during subsequent Scanning

Electron Microscope (SEM)

analysis, and does not

contaminate the SEM reading.

24

25

Occasionally it may be necessary to confirm the debris findings on an MCD by inspection of the oil scavenge and

pressure filters.

The oil scavenge filter on most Rolls-Royce engines is the finest of the two oil system filters. The fine scavenge filter

can capture more debris than the MCDs. Examination of the scavenge filter can more accurately indicate the

quantity and type of debris that has been released from an impending component failure, for example bearing

lapping debris. In addition, the scavenge filter will also collect non-ferrous materials, such as bronze and silver (cage

plating). This evidence may help to determine how soon the engine should be removed.

Note: The scavenge filter cut-up and inspection procedure should be carried out in a clean, laboratory

environment.

The pressure (feed) filter on most Rolls-Royce engines is the coarse filter. Unless the scavenge filter bypass valve has

opened, it is unlikely that significant quantities of debris will have accumulated in the pressure filter. Debris is easily

removed from the pressure filter by washing it in a bucket (made of nonmagnetic material), filled with kerosene.

Alternatively the pressure filter can be immersed in a clean container filled with kerosene (or other suitable solvent)

and agitated in a laboratory ultrasonic bath. Allow the debris to settle to the bottom of the bucket, then use an

MCD to pick up magnetic debris from the bottom of the bucket.

Method for scavenge (fine) filter inspection

26

Cutting through, and removing a section ofthe fine oil filter pleats

27

Find the double joining pleat, containing a metal strip,

and make this position bottom dead centre in the vice

(to avoid cutting through it)

Cut through the filter element close to and parallel to

the filter end caps, around the upper half of the

circumference.

In order to minimise contamination of the engine oil

system filter debris, ensure that the hacksaw is cleaned

prior to use, and cover the main body of the filter with

a plastic bag as shown.

Pull out a section of the pleats over 20cm (8 inches)

long, and cut it free of the filter using snips.

28

Flatten the pleats, separate the gauze andmembrane, and collect gauze debris

29

Extend pleats to form a flat sheet.

Disconnect inner and outer gauze from filter

membrane.

Use an MCD to collect magnetic oil system debris from

the surface of the gauze.

Store debris for assessment.

30

Cut out a segment of filter membrane andagitate to remove debris

31

Cut out a segment of filter membrane 5cm (2 inches)

wide, and 20cm (8 inches) along its circumference. Cut

out the centre section if possible, because the edges

may be contaminated.

Put membrane fully into kerosene and use a laboratory

ultrasonic agitator for approximately five minutes to

release any debris trapped in the membrane.

32

Collection and quantity assessment ofmagnetic debris from the bottom of thebeaker following agitation of the filtermembrane

33

Following ultrasonic agitation, remove the filter

membrane from the beaker. Allow ten minutes for the

debris to settle to the bottom of the beaker. Use a

clean MCD to remove the magnetic material from the

bottom of the beaker. If the debris is to be kept

separate from the MCD, wrap the MCD in a Kimwipe

tissue before removing the debris from the bottom of

the beaker.

Combine with any debris collected from the gauze

(see page 29). Examine and record the debris in the

same way as detailed for the engine MCDs.

Place the magnetic fines debris on a sheet of paper

and spread into a thin layer. Consult relevant Aircraft

Maintenance Manual for engine rejection criteria.

34

Engine monitoring data cardMagnetic Chip Detectors (MCDs)

Master

Ref No

Internal gearbox External orhigh-speed gearbox

MCD locationEnsure MCD debris fits in corresponding column

Operator

Date of sample

Engine type

Engine serial number

Aircraft registration number

Flying hours since last inspection

Total flying hours

Signature of inspector

35

A typical engine monitoring data card is shown above. Either use this

format, or if preferred, create your own similar design which holds the same

information.

By storing the debris on cards, an increasing debris generation trend can

easily be seen, giving a clear indication of of impending failure of bearings

and gears in a high proportion of cases.

Storage of debris

36A Scanning Electron Microscope (SEM) is a useful tool to help with material

analysis and can supplement the visual inspection

To allow prompt identification of debris material once a catch has been

made, it is suggested that the operator arrange an analysis facility with one

of the following:

A local university close to its main operating base A specialist analysis facility

If this is not possible, treat all catches with caution and remove the engine

if in doubt.

Note

It is unusual for engines to be removed with No Fault Found (NFF)

subsequent to an MCD catch.

Debris identification

37

Fines appear on an oily MCD as a black sludge. After being degreasedthey can, with the naked eye, be mistaken for very small metallic flakes.

Bearing lapping failure producing fines

MCD wet

EMCD wet

MCD dry

EMCD dry

MCD picture Hardware failure

38

The gear scuffing shown produces relatively coarse fines.

Note: normal wear fines are similar in size to those produced by bearinglapping failures.

Gear wear producing fines

MCD picture Hardware failure

39

These can be sub-divided into ball bearing, roller bearing, bearing track andgear teeth flakes. Ball bearing and ball bearing track flakes are usually roughly circular

with radial splits Roller bearing and roller bearing track flakes can be roughly rectangular in

shape with criss-cross scratches, but are usually similar to ball bearing flakes Fatigue flakes are typically 0.5-1.0mm (0.020-0.040 inch) in diameter,

and very thin

Bearing fatigue failure producing flakes

MCD picture Hardware failure

MCD

EMCD

Ball

Race

40

Gear teeth fragments corner pieces of gear teeth may be evidence ofincorrect gear alignment or bedding, or handling damage duringoverhaul.

Gear tooth fragments

MCD picture Hardware failure

41

Chips these are very thick flakes or definite lumps of metal usually withone ground (smooth) surface.Bearing race spalling can produce chips in addition to flakes.

Chips

MCD picture Hardware failure

Chip, rough surface

Chip, ground surface

42

Note: there may be acceptance criteria for the number of rivets found.Refer to Aircraft Maintenance Manual.

Cage rivet failure

MCD picture Hardware failure

43Roller bearing cage tang failure

MCD picture Hardware failure

If cage tangs are found, refer to the Aircraft Maintenance Manual or alocal Rolls-Royce Service representative.

44

While every effort is made to remove manufacturing or

build debris (swarf ), unfortunately small amounts may

be present within the engine on build. This debris will

be washed down by the oil system to the MCDs.

Pieces of turning are easily identifiable but milling

debris, when broken up, could possibly be confused

with gear or steel rubbings and must be carefully

examined.

In addition there may be some running-in or

bedding-in of the engine which may produce a small

amount of additional debris. Both will reduce after a

short period of time.

Seal lining material is sometimes released from the

bearing chamber oil seals into the oil system after

engine surges.

Build debris or swarf

MCD picture Explanation

Hairs of seal lining material

Chunks of seal lining material

45

Please refer to the relevant engine Aircraft Maintenance Manual, or consult

a Rolls-Royce Service Representative.

Although every effort is made to ensure cleanliness of the engines during

new production and overhaul, some debris may be released on entry into

service.

It is vital the (E)MCDs are inspected in accordance with the Aircraft

Maintenance Manual to ensure potential failures are not overlooked.

Interpreting the results

46

Actions to take when debris is discovered

(E)MCDdebris

discovered

Analyse debris usingvisual and (optional)

SEM processes

Remove engine fromservice immediately for

investigation

Fit diagnostic MCDs in all positions. Carry out aground run or two, 90 second dry motor cycles

Resume normalmonitoring procedure

Does debris rate reduce?

Compare analysis against AircraftMaintenance Manual acceptance criteria.

Acceptable?

Inspect all MCDs fitted, scavenge screens and oilfilters. Compare against Aircraft

Maintenance Manual acceptance criteria.

Acceptable?

No

No

No

Yes

Yes

Yes

Indicate an alert status on accumulated records andrequest MCD inspections to be taken at more

frequent intervals

47Notes

48Notes

2001 Rolls-Royce plc

The information and instructions in this booklet are prepared for general information purposes only.

The data contained herein shall be considered in no way as replacing or superseding the information

contained in the relevant Aircraft Maintenance Manual.

VCOM 4838 Issue 1 December 2001

Printed in England

Compiled by Nick Harrop and Dave Montagu

Service Engineering

Rolls-Royce plc

PO Box 31,

Derby DE24 8BJ

www.rolls-royce.com