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SERVICE BULLETIN 

BAE SYSTEMS (OPERATIONS) LIMITED, 

PRESTWICK INTERNATIONAL AIRPORT, 

AYRSHIRE, KA9 2RW, 

SCOTLAND. 

J41-24-043 

TRANSMITTAL SHEET 

This page transmits revision 3 of service bulletin J41-24-043, pages 1 to 20. 

TITLE: ELECTRICAL POWER - DC GENERATION - OVERHEAT FAILURE OF EARTH POSTS 

(LEFT AND RIGHT}. 

INSPECTION 

Actions 

(1) Remove and discard service bulletin at revision 2. 

(2) Insert Service Bulletin at revision 3. 

Reasons for Revision 

(1) Para.2.B.(2).(e) Accomplishment- Torque value changed to 200 lbf.in. (22.6 Nm.) 

(2) Para.2.C.(1). Recovery - Installation of fairings added. 

INCORPORATION OF THIS REVISION DOES NOT REQUIRE REWORK OF THE 

MODIFICATION(S) EMBODIED BY EARLIER REVISIONS OF THIS SERVICE BULLETIN. 

ORIGINAL ISSUE: SEP 27/11 

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J41-24-043 

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SERVICE BULLETIN 

BAE SYSTEMS (OPERATIONS) LIMITED, 

PRESTWICK INTERNATIONAL AIRPORT, 

AYRSHIRE, KA9 2RW, 

SCOTLAND. 

J41-24-043 

TITLE: ELECTRICAL POWER- DC GENERATION- OVERHEAT FAILURE OF EARTH POSTS 

(LEFT AND RIGHT). 

INSPECTION BULLETIN 

1. PLANNING INFORMATION 

A. Effectivity 

All Jetstream Series 41 00 Aircraft. 

B. Reason 

An operator has reported an incident involving an overheat failure of the bracket on 

which is located the earth post for the generator and propeller de-ice systems. Although 

the earth post and cables were not damaged, the mounting bracket and underlying 

structure was damaged and needed to be replaced or repaired. 

This Service Bulletin is to make sure there are no signs of corrosion or damage to the 

aircraft structure on or around the bracket, that the earth posts are secure and that the 

electrical performance of each earth post is within specified limits. 

C. Description 

This Service Bulletin calls for an inspection of the earth post EP2 (Left) and earth post 

EP4 (Right) on the structure for the Left and Right power plants. 

The tasks are as follows: 

- Fairing panels are removed. 

- Inspect for signs of arcing and lateral movement of the earth post. 

- A high-current millivolts-drop test is done between each earth post and the main wing 

structure. 

- The panels are installed. 

- The aircraft records are amended. 

D. Manpower 

4.0 man-hours. 

Electrical skills are necessary. 

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E. Material -Cost and Availability 

Not applicable. 

F. Tooling- Price and Availability 

Refer to AMM Subtask 20-21-00-760-004. 

ITEM 20-0002 Ammeter, 150 amp. 

ITEM 20-0007 Millivolt meter. 

ITEM 20-0009 Variable power-supply unit, 150 amp. 

Alternatively, use the following commercially available equipment or equivalent. 

Megger MOM2 High current hand held micro-ohmmeter. 

G. Weight and Balance 

None. 

H. Aircraft Noise Levels 

Aircraft noise is not affected. 

I. Electrical Load Data 

Not affected. 

J. Software Accomplishment Summary 

Not applicable. 

K. References 

- Aircraft Maintenance Manual (AMM). Chapters 06, 12, 20 and 71. 

- Structural Repair Manual (SRM). Chapter 51. 

L. Publications Affected 

J41-24-043 

PAGE2 

None. 

ORIGINAL ISSUE: SEP 27/11 

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SERVICE BULLETIN 

M. Family Tree Of Modification Relationships 

Not applicable. 

N. Approval 

BAE SYSTEMS recommends that this service bulletin is accomplished within 12 months 

of the original issue date of this service bulletin. 

The technical content of this service bulletin is the subject of EASA Airworthiness 

Directive consultation. 

The technical content of this service bulletin is approved under the authority of EASA 

PART 21 Approval No. EASA.21J.047. 

Signed 

Date 

EASA Part 21 Approval No. EASA.21J.047. 

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SERVICE BULLETIN 

2. ACCOMPLISHMENT INSTRUCTIONS 

WARNING : MAKE SURE THE AIRCRAFT AND THE AIRCRAFT SYSTEMS ARE MADE 

SAFE AS DETAILED IN THE APPLICABLE CHAPTERS OF THE AIRCRAFT 

MAINTENANCE MANUAL. 

NOTE: Abbreviations used in the accomplishment instructions of this service bulletin 

are: 

AMM - Aircraft Maintenance Manual. 

SRM - Structural Repair Manual. 

A. Preparation 

(1) Refer to AMM, Chapter 12-00-00. Remove all aircraft electrical power. 

(2) Display a warning notice in the flight compartment 'DO NOT APPLY 

POWER TO THE AIRCRAFT'. 

B. Accomplishment - Left and Right - Information in brackets is applicable to the Right 

installation. 

(1) Refer to the AMM Chapters 06 and 71. Remove the inboard fairing panel 

414AR from the left engine and the outboard fairing panel 424AR from the 

right engine. 

(2) Refer to Figure 1 and the SRM Chapter 51. Look for defects and take 

actions as follows: 

(a) Inspect the structure around the earth post EP2 (EP4) and the 

mounting bracket to which it is attached. Look for damage caused by 

arcing or signs that the structure has been overheated. Also look for a 

colour change of the protective treatments on the structure. No lateral 

movement of the earth post is permissible. 

(b) Examine the attachment of the nacelle horizontal support on the same 

mounting bracket. Look for damage caused by arcing or signs that the 

linkage has been overheated. 

(c) If any movement or damage is apparent then this must be repaired 

before further flight. 

Report all findings of damage to:-

Repair Drawing Office, 

BAE Systems (Operations) Limited, 

Prestwick International Airport, 

Ayrshire, KA9 2RW, 

Scotland. 

Give the aircraft tail number, flying hours and details of the damage. 

Request a repair scheme. 

(d) Inspect the earth cables for the generator and propeller de-ice 

systems. Look for signs that the cable insulation has been overheated. 

Look for arcing damage or signs that the terminal tags have been 

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overheated. Replace damaged cables and retest systems affected as 

appropriate. 

(e) Check torque load of the earth post stiff nut to 200 lbt.in. (22.6 Nm.) 

(3) Refer to the procedure in Appendix 3 for the high-current millivolt-drop test. 

Alternatively, use a high current micro-ohmmeter such as a Megger MOM2 

or equivalent and follow the manufacturer's instructions for high current 

measurements. 

(a) Do a high-current millivolts-drop test for the earth bolt EP2 (EP4) 

using a nominal test current of 1 00 amp. 

EITHER 

1 Measure the resistance between the earth bolt and the adjacent 

primary structure. The resistance must not be greater than 200 

micro-ohms. 

OR 

.2 Measure the resistance between the earth bolt and the bracket, 

and measure the resistance between the bracket and the adjacent 

primary structure. The resistance for each measurement must not 

be greater than 100 micro-ohms 

(4) If any resistance measurement is found to be in excess of the quoted limits, 

then steps must be taken to investigate the source of the high resistance 

and to clean all the surfaces to achieve the requisite resistance value before 

further flight. 

(5) Complete the record sheets attached to this bulletin in Appendices 1 and 2, 

and send the results to BAE Systems at the address shown. 

C. Recovery 

( 1) Remove all materials, tools and equipment. Make sure work area is clean. 

(2) Refer to the AMM Chapters 06 and 71. Install the inboard fairing panel 

414AR on the left engine and the outboard fairing panel 424AR on the right 

engine. 

(3) Remove warning notice from the flight compartment. 

(4) Restore electrical power to the aircraft. 

(5) Aircraft records: 

Add service bulletin number 'J41 -24-043' to the aircraft records. 

NOTE: Operators are reminded of the necessity to inform the Business 

Support Team, Technical Publications, BAE SYSTEMS, Regional 

Aircraft, Prestwick International Airport, Ayrshire, KA9 2RW, 

SCOTLAND, of the accomplishment of this SB in order to obtain 

the necessary revisions for the affected manuals, see paragraph 

1.l. Publications Affected, of this SB. 

J41-24-043 ORIGINAL ISSUE: SEP 27/ 11 

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GENERATOR CABLE 

NUT 

NAS509-6 

WASHER 

SP47J 

BRACKET 

14157435-7 LEFT 

14157436-8 RIGHT 

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NUT 

HW14-6 

EARTH BOLT 

PKS1017-6 

FRONT SPAR 

(REF) 

PROPELLER DE-ICE CABLE 

~arth Post Installation EP2 lett and EP4 right. 

ORIGINAL ISSUE: SEP 27/11 

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FIGURE 1 

24-43-10001 

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3. MATERIAL INFORMATION 

Not applicable. 

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4. CONTINUED AIRWORTHINESS 

A. Continued Airworthiness Instructions 

Continued airworthiness instructions applicable to this service bulletin are detailed 

below. 

B. Scheduled Maintenance 

c. 

D. 

E. 

F. 

(1) The instructions within this Inspection Service Bulletin will be the subject of a 

MRB review and, as such, may then provide the basis for repeat inspections, 

with the instructions incorporated in the AMM. 

Removal Procedures 

(1) Not applicable. 

Installation Procedures 

(1) Not applicable. 

Test Procedures 

(1) Not applicable. 

Trouble Shooting 

(1) Not applicable. 

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Appendix 1 - Test Record Sheet. 

(1) Refer to section 2.B.(2).(a) to (c) of the main bulletin and confirm if any damage was 

referred to the Repair Design Office (ROO), BAE Systems (Operations) Limited. 

YES NO 

(2) Refer to Section 2.B.(2).(d) of the main bulletin and confirm if any cables have been 

replaced. 

YES NO 

Details (if applicable) 

(3) Refer to Section 2.B.(3).(a) of the main bulletin and record the final micro-ohm 

measurements obtained. 

Result 

Location Test Number 

Limit 

(micro-ohms) (micro-ohms) 

Left Wing Either 1 (Earth Bolt to Structure) < 200 

Or 2 (Earth Bolt to Bracket) < 100 

And 2 (Bracket to Structure < 100 

Right Wing Either 1 (Earth Bolt to Structure) < 200 

Or 2 (Earth Bolt to Bracket) < 100 

And 2 (Bracket to Structure) < 100 

(4) Also, record here whether any remedial action e.g. cleaning was required to achieve the 

above measurements. 

Left Wing YES NO 

Right Wing YES NO 

(5) Send the results to BAE Systems (Operations) Limited (see Appendix 2). 

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Appendix 2- Inspection Report. 

Complete and return this form and the form in Appendix 1 to:-

Customer Technical Support (Building 37), 

BAE Systems (Operations) Limited, 

Prestwick International Airport, 

Ayrshire, 

KA9 2RW, 

Scotland. 

Fax+ 44 (0) 1292 675432 

E-mail raengliaison@baesystems.com 

Operator 

Aircraft Registration 

Constructor's Number 

Flight Hours 

Landings 

Inspection Date 

Findings 

Brief details of Test Equipment used 

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A. General 

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Appendix 3- Procedure for High-Current Millivolt-Drop Test. 

NOTE: The following procedure is applicable to the left earth post installation EP2 and the 

right earth post installation EP4. 

NOTE: The following procedure is a modified version of the test in AMM 20-21-00 page 

210 Subtask 20-21-00-760-004. 

NOTE: As an alternative to this procedure, operators can use a high current microohmmeter such as a Megger MOM2 or equivalent and follow the manufacturer's 

instructions for high current measurements. 

B. Equipment 

Item Description 

20-0002 Ammeter, 150 amp 

20-0007 Millivolt meter 

20-0009 Variable Power Supply Unit (VPSU), 0 to 150 amp 

C. Test 

WARNING: BECAUSE OF THE CONFINED SPACE IN WHICH THIS TEST MAY NEED 

TO BE PERFORMED, CARE MUST BE TAKEN TO ENSURE THAT THE 

OPERATOR IS REMOTE FROM THE TEST AREA WHEN APPLYING THE 

HIGH CURRENT. 

(1) Make sure the fasteners and the probes are clean. 

(2) Connect the millivolt meter probes as shown in figure 1. 

NOTE: The millivolt meter probes should be bolted in place to ensure the operator 

can remain remote from the test area. 

Caution: The power connections must be bolted onto the structure and onto the 

earth post. 

Caution: Ensure that appropriately sized cables are used for the test. 

(3) Connect the VPSU and the ammeter and bolt in place as shown in figure 1. Make 

sure that the fasteners are near to each side of the electrically bonded joint, but not 

on it. 

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( 4) Attach the test leads for the millivolt meter to positions near to each side of the 

electrically bonded joint, but not on it. 

NOTE: If the use of probes is unavoidable, then apply heavy pressure to the probes 

whilst taking the measurements. 

(5) Adjust the VPSU to provide a test current of 100 amps. 

WARNING: MAKE SURE THE TEMPERATURE OF THE JOINT DOES NOT 

INCREASE TO MORE THAN 40 DEGREES CELSIUS (104 DEGREES 

FARENHEIT) ABOVE THE LOCAL TEMPERATURE. 

(6) After a minimum of one minute, record the millivolt meter reading obtained. 

(7) Adjust the VPSU until no current flows and then disconnect the VPSU, the millivolt 

meter and the ammeter. 

(8) Remove all of the equipment. 

(9) Make sure the resistance is within the following limits:-

J41-24-043 

PAGE 18 

(a) If the resistance measurement is between the earth bolt and the adjacent 

primary structure, then the resistance must not be greater than 200 microohms. 

OR 

(b) If the resistance measurement is between the earth bolt and the bracket, and 

then between the bracket and the adjacent primary structure then the 

resistance for each measurement must not be greater than 100 micro-ohms. 

NOTE: To get the resistance of the electrically bonded joint, in micro-ohms, divide 

the voltage by the current:-

e.g. 7.5 millivolts divided by 100 amps= 75 micro-ohms. 

ORIGINAL ISSUE: SEP 27/11 

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BOLTED 

CONNECTION 

EARTH POST 

PSU 

VARIABLE 

PROBE 

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EARTH RETURN STRUCTURE 

PROBE 

Schematic - High current test 

FIGURE 1 

BOLTED 

CONNECTlON 

24-43-1 0007 

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ACCOMPLISHMENT REPORT 

I SERVICE BULLETIN NUMBER J41-24-043 

TITLE: ELECTRICAL POWER- DC GENERATION - OVERHEAT FAILURE OF EARTH POSTS 

(LEFT AND RIGHT). 

TO: THE BUSINESS SUPPORT TEAM, 

TECHNICAL PUBLICATIONS, 

BAE SYSTEMS (OPERATIONS) LIMITED, 

PRESTWICK INTERNATIONAL AIRPORT, 

AYRSHIRE, KA9 2RW, 

SCOTLAND. 

Telephone: (01292) 675207 

Fax: (01292)675704 

E-mail: RAPublications@baesystems.com 

PLEASE BE ADVISED THAT THE ABOVE SERVICE BULLETIN HAS BEEN EMBODIED ON 

AIRCRAFT CONSTRUCTORS NUMBER(S): 

WE REQUEST THE APPROPRIATE REVISIONS TO APPLICABLE MANUALS. 

NAME: ............................................ ..................................... . 

SIGNED: ................. ............................................................. . 

COMPANY: ...................... ................................................... . 

DATE: ....................................... .......................................... . 

SERVICE BULLETIN COMMENTS/FEEDBACK 

Please report any non-technical comments or inaccuracies regarding this service bulletin to the 

above address.