MSB1121-144/3

Page 1 of 11

20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

SERVICE BULLETIN NO. MSB1121-144/3

I. TECHNICAL DETAILS

1.1 Category:

Mandatory

Note: GROB issues Service Bulletins of category Mandatory (MSBs), if the information or 

instructions have a safety intent either related to design or conformity and to 

publish revisions of manuals (AFM, AMM, IPC). However, according to Article 20 

(1) of Regulation (EC) No. 216/2008, only EASA may issue mandatory information, 

in the form of an Airworthiness Directive (AD), in order to react to a given safety 

problem. Service Bulletins classified Mandatory issued by GROB ́s design 

organisation do not have a legally mandatory character equivalent to an AD, 

cannot have enforcement implications and, therefore, serve as information or 

instruction by GROB only. This also applies to cases where a Service Bulletin is 

published in anticipation of an AD.

Note: This Service Bulletin is issued in anticipation of an AD. Issue of an AD will not 

necessarily lead to revision of this Service Bulletin.

1.2 Airplanes affected:

G 120A all S/N

G 120A-I all S/N

1.3 Time of Compliance:

Part A: Before next IFR or VFR Night flight, or within next 50FH, whichever comes first, unless 

already accomplished under MSB 1121-144 at previous issue. 

Part B: Within 100 flight hours.

1.4 Subject:

ATA-Code: 80-00 Starting

Inspection of starter solenoid / Installation of a Starter Relay

1.5 Reason:

GROB received a report about a total loss of electrical power in IMC on a G 115E aircraft. Root 

cause was found to be a defect starter solenoid. The starter solenoid had an internal defect 

causing a short circuit. The defect cannot be detected by visual inspection. The installation is 

similar to the installation on G120 aircraft.

Revision 3 of this Service Bulletin amends the implementation instructions.

This Service Bulletin is intended to prevent an unsafe condition. The configuration of the aircraft 

is affected by Part B of this Service Bulletin.

Note: Implementation of MSB 1121-144/1, Part B prohibits application of RSB1121-128.
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

1.6 Concurrent documents:

Corresponding AMM

1.7 Approval Note:

The technical content of this document is approved under the authority of EASA Design 

Organization Approval No. EASA.21J.030.

These information or instructions relate to change no. MÄM 1121-189 which has been approved 

by the Authority (EASA) under approval no. 10051942.

1.8 Accomplishment/ Instructions

Part A One-time Inspection

1.8.1 Disconnect the aircraft battery, refer to AMM Chapter 24-31.

1.8.2 Remove the Engine Cowlings, refer to AMM Chapter 71-10.

1.8.3 Visually inspect the starter. Make sure that the power connection bolts have the same 

length, refer to Figure 1 for defective item and Figure 2 for correct installation.

Figure 1: Incorrect connection bolts Figure 2: Correct installation

1.8.4 Release the two bolts on the starter solenoid. Carefully pull the solenoid away from the 

starter housing until the dead stop. Make sure that the solenoid plunger is still attached, 

refer to Figure 3. Attach the solenoid to the starter with the two bolts.
MSB1121-144/3

Page 3 of 11

20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

Figure 3: Starter solenoid at dead stop

1.8.5 If the starter is OK, do step 1.8.7.

1.8.6 If the starter is not OK or in case of doubt, replace the Starter.

1.8.7 Install the Engine Cowlings; refer to AMM Chapter 71-10.

1.8.8 Connect the aircraft battery; refer to AMM Chapter 24-31.

1.8.9 Release aircraft into service according to national requirements.

Part B/1 Installation of Starter Relay (Terminating action) with RSB1121-128 

installed

1.8.10 Ensure that the aircraft is safe for parking I.A.W. AMM chapter 10-10.

1.8.11 Disconnect the aircraft battery for maintenance, refer to MM Chapter 24-30.

1.8.12 Remove the Engine Cowlings, refer to MM Chapter 71-10.

1.8.13 Disconnect the spark plug cables from the spark plugs.

1.8.14 Unplug all terminals with cables from relay 5KA. Remove relay 5KA with clamp, bolt, two 

washers and nut from engine mount and discard.

Figure 4: Relay 5KA

1.8.15 Unplug terminal with cables KA 02F20-E and KA 09G20-E from START BOOSTER 3KA 

connector VIN (red housing). Cut terminal as short as possible and discard it.

Relay 5KA
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

Figure 5: STARTER BOOSTER 3KA

1.8.16 Remove cable KA 09G20-E (previous routed from 5KA to 3KA) and Cable KA 07E14-E 

(previous routed from 5KA to 2KA) and discard them.

1.8.17 Drill a 5mm hole in the condenser frame 35mm left of the existing second hole of the top 

condenser frame at the inner border. Attach the new starter relay (7KA) (Item 1 of List 

2.2), so that the terminals point downwards. Use 2xM5 screw (Item 2 of List 2.2), 4xM5 

washers (Item 3 of List 2.2) and 2xM5 nuts (Item 4 of List 2.2). To balance the distance 

between the condenser frame and the relay mounting bracket on the forward side, use 

an additional spacer (Item 5 of List 2.2).

Figure 6: STARTER RELAY 7KA

START BOOSTER

3KA

New hole in condenser frame Spacer

New starter relay 7KA
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

1.8.18 Install and lengthen new cable KA 02H20-E (Item 6 of List 2.2), along existing cable 

loom from START BOOSTER 3KA to new starter relay 7KA with the pre-installed 

terminal at the starter relay 7KA end. Connect to terminal 86+ on relay 7KA.

1.8.19 On the START BOOSTER 3KA end dismantle existing cables KA 02F20-E and new 

cable KA 02H20-E, pair and crimp them to terminal AMP 160773-6 (Item 7 of List 2.2) by 

using crimping tool AMP 654174-1 or equivalent (Item 1 of List 2.3).

1.8.20 Attach red housing AMP 154719-2 (Item 8 of List 2.2) to terminal and plug to START

BOOSTER 3KA connection VIN. Strap new cable to existing cable loom.

1.8.21 Use existing cable KA 08E20N-P (previous located at 5KA) from VN17101 and root to 

new starter relay 7KA. Cut existing terminal as short as possible and discard it. 

Dismantle cable KA 08E20N-P and crimp to terminal MS25036-149 (Item 9 of List 2.2) 

by using crimping tool AMP 169400-0 or equivalent (Item 2 and 3 of List 2.3). Connect to 

terminal 85- on relay 7KA.

1.8.22 Remove cable tie from rubber cap of middle bolt VV17103 on firewall. Push back cover 

to gain access to stop nut. Remove and discard nut and washer, therefore hold up 

counter nut and do not damage black wrapping tape. Remove cable complete KA 

06E14-E from VV17103 to relay 5KA and discard. Remove cable PA 03G06-E from bolt 

VV17103 (leave the rubber cap at the cable!) and route it back along existing wire to 

new starter relay 7KA. Connect to terminal 88a on starter relay 7KA. Secure rubber cap 

strap with cable tie (Item 10 of List 2.2).

1.8.23 Install new cable PA 03L06-E (Item 11 of List 2.2) and connect to terminal 88 on starter 

relay 7KA therefore the cable has to be led through the new rubber cap (Item 12 of List 

2.2). Root along existing loom to middle bolt VV17103 on firewall. Therefore the cable 

has to be led through the new rubber cap (Item 12 of List 2.2). Tighten terminal with new 

washer and stop nut on bolt (Item 13 and 14 of List 2.2), while holding up counter nut. 

Paint with blue NYCOTE 7-11 protective coating (Item 15 of List 2.2).

1.8.24 Let lacquer dry before reinstalling rubber cap. Secure rubber caps (on both end of 

PA 03L06-E) strap with cable tie (Item 10 of List 2.2).

1.8.25 Install the jumper cable 115E-9510.03 (Item 16 of List 2.2) on the starter solenoid, refer 

to wiring diagram. Attach to connector “S” at Starter Motor 2KA using the old washer and 

screw. Paint with blue NYCOTE 7-11 protective coating (Item 15 of List 2.2). Let lacquer 

dry before marking with inspection lacquer (Item 17 of List 2.2). (See Figure 7)

Figure 7: STARTER 2KA
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

1.8.26 Secure the cables with cable ties, where necessary.

1.8.27 Connect the spark plug cables to the spark plugs.

1.8.28 Install the Engine Cowlings, refer to AMM Chapter 71-10.

1.8.29 Connect the aircraft battery, refer to AMM Chapter 24-30.

1.8.30 Do an engine run-up, refer to AMM Chapter 71-00. 

1.8.31 Release aircraft into service according to national requirements.

Part B/2 Installation of Starter Relay (Terminating action) without RSB1121-128 

installed

1.8.32 Ensure that the aircraft is safe for parking I.A.W. AMM chapter 10-10.

1.8.33 Disconnect the aircraft battery for maintenance, refer to MM Chapter 24-30.

1.8.34 Remove the Engine Cowlings, refer to MM Chapter 71-10.

1.8.35 Disconnect the spark plug cables from the spark plugs.

1.8.36 Unplug terminal with cables KA 02G20-E and KA 02F20-E from Starter Booster 3KA 

connector VIN (red housing). Cut terminal as short as possible and discard it. Cap and 

stow cable KA 02G20-E with TC cap (Item 19 of List 2.2) using a heat gun (Item 4 of List 

2.3).

Figure 8: STARTER BOOSTER 3KA

1.8.37 Drill a 5mm hole in the condenser frame 35mm left of the existing second hole of the top 

condenser frame at the inner border. Attach the new starter relay (7KA) (Item 1 of List 

2.2), so that the terminals point downwards. Use 2xM5 screw (Item 2 of List 2.2), 4xM5 

washers (Item 3 of List 2.2) and 2xM5 nuts (Item 4 of List 2.2). To balance the distance 

between the condenser frame and the relay mounting bracket on the forward side, use 

an additional spacer (Item 5 of List 2.2).

START BOOSTER

3KA
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

Figure 9: STARTER RELAY 7KA

1.8.38 Install and lengthen new cable KA 02H20-E (Item 6 of List 2.2), along existing cable 

loom from START BOOSTER 3KA to new starter relay 7KA with the preinstalled terminal 

at the starter relay 7KA end. Connect to terminal 86+ on relay 7KA.

1.8.39 On the START BOOSTER 3KA end dismantle existing cables KA 02F20-E and new 

cable KA 02H20-E, pair and crimp them to terminal AMP 160773-6 (Item 7 of List 2.2) by 

using crimping tool AMP 654174-1 or equivalent (Item 1 of List 2.3).Attach red housing 

AMP 154719-2 (Item 8 of List 2.2) to terminal and plug to START BOOSTER 3KA 

connection VIN. Strap new cable to existing cable loom.

1.8.40 Remove and discard nut and washer from grounding bolt VN 17101, therefore hold up 

counter nut. Remove terminal, turn by 180° and reattach to bolt. Install new cable KA 

08E20N-P (Item 20 of List 2.2) along existing cable loom from starter relay 7KA to 

grounding bolt VN 17101. Tighten terminal with new washer and stop nut on bolt (Item 

21 and 22 of List 2.2) while holding up counter nut. Paint with blue NYCOTE 7-11 

protective coating (Item 15 of List 2.2). Strap in new cable back in cable loom strap with 

cable ties. (See Figure 10)

New starter relay 7KA

New hole in condenser frame Spacer
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

Figure 10 Bolts at Firewall

1.8.41 Remove cable tie from rubber cap of middle bolt VV17103 on firewall. Push back cover 

to gain access to stop nut. Remove and discard nut and washer, therefore hold up 

counter nut and do not damage black wrapping tape. Remove cable KA 06E14-E 

complete from VV17103 to relay 5KA and discard. Remove cable PA 03G06-E from bolt 

VV17103 (leave the rubber cap at the cable!) and route it back along existing wire to 

new starter relay 7KA. Connect to terminal 88a on starter relay 7KA. Secure rubber cap 

strap with cable tie (Item 10 of List 2.2).

1.8.42 Install new cable PA 03L06-E (Item 11 of List 2.2) and connect to terminal 88 on starter 

relay 7KA therefore the cable has to be led through the new rubber cap (Item 12 of List 

2.2). Root along existing loom to middle bolt VV17103 on firewall. Therefore the cable 

has to be led through the new rubber cap (Item 12 of List 2.2). Tighten terminal with new 

washer and stop nut on bolt (Item 13 and 14 of List 2.2), while holding up counter nut. 

Paint with blue NYCOTE 7-11 protective coating (Item 15 of List 2.2).

1.8.43 Let lacquer dry before reinstalling rubber cap. Secure rubber caps (on both end of 

PA 03L06-E) strap with cable tie (Item 10 of List 2.2).

1.8.44 Unplug terminal with cable KA 02G20-E from Engine Starter Motor 2KA connector “S”. 

Keep screw and washer. Cut terminal as short as possible and discard it. Cap and stow 

cable KA 02G20-E with TC cap (Item 19 of List 2.2) using a heat gun (Item 4 of List 2.3).

1.8.45 Install the jumper cable 115E-9510.03 (Item 16 of List 2.2) on the starter solenoid, refer 

to wiring diagram. Attach to connector “S” at Starter Motor 2KA using the old washer and 

screw. Paint with blue NYCOTE 7-11 protective coating (Item 15 of List 2.2). Let lacquer 

dry before marking with inspection lacquer (Item 17 of List 2.2). (See Figure 11)

VN 17101

VV 17103 Grounding Bolt
MSB1121-144/3

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20 February 2015

Replaces Issue: 05 February 2015

1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

Figure 11: STARTER 2KA

1.8.46 Safety the cables with cable ties, where necessary.

1.8.47 Connect the spark plug cables to the spark plugs.

1.8.48 Install the Engine Cowlings, refer to AMM Chapter 71-10.

1.8.49 Connect the aircraft battery, refer to AMM Chapter 24-30.

1.8.50 Do an engine run-up, refer to AMM Chapter 71-00. 

1.8.51 Release aircraft into service according to national requirements.

1.9 Repetitive Actions

none
MSB1121-144/3

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20 February 2015

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1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

II. PLANNING INFORMATION

2.1 Weight and CG

N/A

2.2 Material and Availability

Part B/1:

Item P/N Description Qty. / A/C

1 GS246001-9 Starter Relay 1

2 LN9037-05018 Screw 2

3 LN9025-0510 Washers 4

4 LN9348-05 Nut 2

5 NAS43DD3-6N Spacer 1

6 120A-940010.02A KA 02H20-E 1

7 AMP 160773-6 Terminal 1

8 AMP 154719-2 Housing, Red 1

9 MS25036-149 Terminal, Red 1

10 GS510010-100 Cable Ty, Blue 8

11 115E-9470.01 PA 03L06-E 1

12 MS 25171-3S Rubber Caps 2

13 LN9348-M8 Nut 1

14 LN9025-0815L Washer 1

15 Nycote7-11 BLUE Protective Coating

AR

to be ordered 

separately

16 115E-9510.03 Jumper cable 1

17 GS513010 Inspection Lacquer

AR

to be ordered 

separately

18 GS510010-200 Cable Ty, Blue 4

Part B/2: additional

19 GS247009-2-32 Heatshrinkable Caps 2

20 120A-940010.01A KA 08E20N-P 1

21 LN9348-M10 Nut 1

22 LN9025-1020L Washer 1
MSB1121-144/3

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1121-144_3 MSB, Inspection of starter solenoid G 120A, A-I

Grob Aircraft AG, Lettenbachstrasse 9, D-86874 Tussenhausen-Mattsies

2.3 Special Tools

Part B/1:

Item P/N Description

1 AMP 654174-1 (or equivalent) Crimping tool PEZ 100

2 AMP 169400-0 (or equivalent) Crimping tool CERTI-LOK

3 AMP 169404 (or equivalent) Die Set for AMP 169400-0

Part B/2: additional

4 Commercial Heat Gun

2.4 Labor costs

N/A

2.5 Reference documents

Corresponding AMM and IPC

2.6 Credit

N/A

III. REMARKS

The instructions in paragraph 1.8 have to be accomplished and certified in the logbook by 

authorized staff:

- in EASA countries according to Article 5 VO EG 2042/03 (VO EG 1056/2008) Appendix III –

Part 66

- in non-EASA countries according to national regulations with respect to maintenance.

If you have sold your aircraft in the meantime, we kindly ask you to forward this information to 

the new owner and to provide us with the name and address of the new owner as well as with 

the respective serial number.

For questions and assistance please contact:

Product Support,

phone: +49 8268 998105

fax: +49 8268 998200

e-mail: productsupport@grob-aircraft.com