SERVICE BULLETIN - BK117

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DATE: 2018-06-08

SERVICE BULLETIN

KSB-117-406B

Kawasaki BK117

TITLE: Inspection and Retrofit of Fasteners for Hydraulic Module Plate Assembly

NOTE: This Service Bulletin revises KSB-117-406A (issued Jun. 12, 2017).

The revised parts are indicated by vertical bars ("｜").

1. EFFECTIVITY

Model Mfg. Serial No.

KAWASAKI-BK117 C-2 ALL

2. PURPOSE

The results of a design reassessment of the hydraulic module installation conducted by AHD

found that in cases where the fasteners are damaged, there is possibility that the flight control

system may be affected due to excessive deformation of the hydraulic module plate assembly.

This Service Bulletin provides the procedures for external visual inspection, tightening torque

checks, and periodic inspections for the corresponding fasteners to prevent the aforementioned

hazard.

This Service Bulletin also prescribes the retrofit procedure for the replacement of conventional

hydraulic plate fasteners with new double locking attachment fasteners as a countermeasure for

the aforementioned issue.

Furthermore, this Service Bulletin prescribes in order to reliably prevent the bottoming of the nut

due to dimensional tolerance of the fastening member with respect to the fastener on the rear side

of the plate, it is necessary to adjust by a washer with different thickness (when necessary),

confirmed tightening torque after fastening instruct. And in order to improve the reliability of

electrical bonding, repositioning the attachment position of the ground strap is instructed.

A relocation of electrical bonding in this Service Bulletin is not mandatory. However, it is advisable

to reposition the electrical bonding for improvement of reliability.

The AHD design reassessment was performed on request from the European Aviation Safety

Agency (EASA) due to a defect (cracking of self-locking nuts) that occurred on aircraft other than

the BK117 C-2. No such malfunction has been reported for the BK117 C-2.

3. CATEGORY

MANDATORY

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4. COMPLIANCE

After receiving this Service Bulletin, the work in the following steps (1) and (2) must be

accomplished in accordance with the flowchart indicated in Figure 1.

However, it is unnecessary to conduct steps (1) and (2) after the retrofit of the attachment

fasteners in step (3).

In addition, the work in the following steps (3) or (4) must be accomplished in accordance with

the flowchart indicated in Figure 1A.

(1) Initial Inspection

After receiving this Service Bulletin, conduct the external visual inspection and tightening

torque check in accordance with Section 9, Part 1 and Part 2 within 100 flight hours. If any

defects are found during either inspection, replace the corresponding fasteners before the

next flight.

If work has already been accomplished in accordance with previous revisions of this

Service Bulletin, this procedure is not necessary.

(2) Repetitive Inspection after Initial Inspection

After accomplishing the work in section 4 (1) above, conduct a repetitive visual inspection

in accordance with section 9, Part 1 every 400 flight hours (a tolerance of +40 hours is

permitted). If any defects are found during this inspection, replace the corresponding

fasteners before the next flight.

For helicopters from which the hydraulic module has been temporarily removed, conduct the

aforementioned inspections after re-installation of the hydraulic module.

(3) Retrofit of the Attachment Fasteners

If work has not been accomplished in accordance with Section 9, Part 3 of this Service

Bulletin Revision A, conduct the installation of the double locking attachment fasteners for

the hydraulic module plate in accordance with section 9, Part 3 of this Service Bulletin

Revision B as a countermeasure within July 3rd

, 2018. If the retrofit in section 4 (3) above

has already been accomplished in accordance with Section 9, Part 3 of revision A, this

procedure is not necessary.

NOTE: If the retrofit in step (3) above has already been accomplished in accordance with Rev.

A of this Service Bulletin, conduct step (4) below.

(4) Tightening torque check (for the Aft Attachment Fasteners)

After receiving this Service Bulletin (Rev.B), tightening torque check for the aft attachment

fasteners in accordance with Section 9, Part 4 within 800 flight hours (a tolerance of +80

hours is permitted). As necessary, replace the washers. And at the same time, it is

advisable to reposition the grounding strap.

5. JCAB APPROVAL

Approved by JCAB.

KSB-117-406B

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6. LOGBOOK ENTRY

Make an entry in the Aircraft Logbook stating that work in accordance with KSB-117-406B has

been done.

7. MAN-HOUR REQUIRED

(1) Approximately 1.0 man-hour (for reference only) will be required for the fastener inspection.

(2) Approximately 2.0 man-hours (for reference only) will be required for the fastener

replacement in accordance with inspection results.

(3) Approximately 3.0 man-hours (for reference only) will be required for the retrofit of the

attachment fasteners.

(4) Approximately 2.0 man-hours (for reference only) will be required for the repositioning of the

grounding strap of the aft attachment fasteners.

8. WEIGHT AND BALANCE CHANGE

Negligible

9. ACCOMPLISHMENT INSTRUCTIONS

(1) Preparation

a. If an external power supply is connected to the helicopter, disconnect the external power

supply in accordance with AMM 24-00-00, 2-1.

b. If the battery is connected, disconnect the battery in accordance with AMM 24-00-00, 2-2.

c. Post a notice in the cockpit stating "DO NOT START THE ENGINES."

d. Post a notice in the cockpit stating "DO NOT MOVE THE FLIGHT CONTROLS."

e. Remove the crest cowling in according with AMM 71-11-00, 4-1.

f. Remove the LH and RH covers (4, Figure 2) in accordance with AMM 29-14-00, 4-1A.

(For 4002 and up. For Part 4, this procedure is not necessary.)

(2) Part 1: External Visual Inspection

a. Conduct the following external visual inspection of the four fasteners on the hydraulic

module plate assembly (refer to Figures 2 and 3).

(a) Inspect the condition of the LH and RH cotter pins (4, Figure 3), and check that the

cotter pins are correctly installed.

(b) Inspect the condition of the LH and RH castellated nuts (2, Figure 3) and the hexagon

bolts (3), and check that the nuts and bolts are correctly installed.

(c) Use a mirror and flashlight to inspect the LH and RH nuts (3, Figure 2) for cracks in

the installed state.

(d) Use a mirror and flashlight to inspect the condition of the LH and RH hexagon bolts (2,

Figure 2) in the installed state.

KSB-117-406B

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b. If cracks or other abnormalities are found during the aforementioned external visual

inspection, replace the corresponding fasteners (hexagon bolts, nuts, and cotter pins if

installed) before the next flight (refer to Figures 2 and 3). In addition, contact the KHI civil

helicopter product support business section regarding the aforementioned abnormalities.

When replacing the fasteners, remove the center fairing in accordance with AMM

71-11-00, 4-2 as necessary.

(3) Part 2: Tightening Torque Check

a. Conduct a tightening torque check of the forward fasteners (2 places) on the hydraulic

module plate assembly (1, Figure 2).

(a) Apply the required tightening torque of 9 to 10 Nm to the LH and RH nuts (3, Figure 2),

and check that the nuts are tight.

(b) If the nuts are found to be loose in the aforementioned check, replace the

corresponding hexagon bolts and nuts (refer to Figure 2). In addition, contact the KHI

civil helicopter product support business section regarding the aforementioned parts.

(4) Part 3: Retrofit of the Attachment Fasteners

a. Retrofit of the forward attachment fasteners (2 places)

NOTE: The following describes the procedure for the LH side. The procedure for the RH

side is identical.

(a) Remove the nut (4, Figure 4), the washer (3), and the hexagon bolt (2). Discard the

removed parts.

(b) Install the new hexagon bolt (5, Figure 4) and the new nut (6A). Tighten the nut (6A)

with a tightening torque of 13 to 14 Nm.

(c) Determine the self-locking torque of the nut (6B, Figure 4) as follows.

NOTE: The self-locking torque must be determined separately for the LH and RH side.

( i ) Tighten the nut (6B) on the hexagon bolt (5).

( i i ) Adjust a torque wrench initially to 1.0 Nm.

(iii) Gradually increase the adjustment of the torque wrench from the initial torque

(1.0 Nm) until the nut (6B) can be turned without a clicking sound of the

torque wrench. The value on the torque wrench at this time is the self-locking

torque of the nut (6B).

NOTE: A thread protrusion down to 0 mm (nut flush with the bolt thread) is allowed as

long as the self‐locking torque can be applied.

(d) Tighten the nut (6B, Figure 4) with the self‐locking torque +1 Nm determined in (c)

until the nut contacts the nut (6A).

KSB-117-406B

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b. Retrofit of the aft attachment fasteners (2 places)

NOTE: The following describes the procedure for the LH side. The procedure for the RH

side is identical.

NOTE: Remove the center fairing in accordance with AMM 71-11-00, 4-2 as necessary.

(a) Remove the installed cotter pin (5, Figure 5), the old castellated nut (3), the grounding

strap (6), the washer (2), and the old hexagon bolt (4). Discard the cotter pin,

castellated nut and hexagon bolt.

NOTE: During the reinstallation, the grounding strap must be installed to the opposite side

(bolt head side) of the attachment point.

(b) Install the new hexagon bolt (4, Figure 5), the grounding strap (6), the washer (2), and

the new castellated nut (3). The grounding strap must be installed to the opposite

side (bolt head side). Tighten the castellated nut (3) with a tightening torque of 11 to

13 Nm.

(c) Set a torque wrench to 8 Nm, and then turn the nut in the tightening direction without

using counter torque. At this time, make sure that the fastener joint cannot be turned.

If the fastener joint cannot be turned, proceed to step (e).

(d) If the fastener joint can be turned in work step (c) above, conduct the steps that

follow:

( i ) Remove the castellated nut (3, Figure 5).

(ii ) Replace the washer (2) with a thick washer (2A).

NOTE: If one side fastener joint is turned, it is recommended to replace the thick

washer on both sides of the aft attachment fasteners.

NOTE: A thread protrusion down to 0 mm (nut flush with the bolt thread) is

allowed while using the thick washer (2A).

(iii) Tighten the castellated nut (3) with a tightening torque of 11 to 13 Nm.

(e) Secure the castellated nut (3, Figure 5) with a new cotter pin (5).

(f) Inspect the grounding strip in accordance with AMM 20-00-00, 2-11.

(5) Part 4: Tightening torque check (for the Aft Attachment Fasteners)

NOTE: Only conduct the following steps if the retrofit in Part 3 of KSB-117-406A has been

accomplished.

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NOTE: The following describes the procedure for the LH side. The procedure for the RH side

is identical. In addition, remove the center fairing in accordance with AMM 71-11-00,

4-2 as necessary.

a. Remove the installed cotter pin (5, Figure 6), the castellated nut (4), the grounding strap (7),

the washer (2), and the hexagon bolt (6). Discard the cotter pin and the castellated nut.

NOTE: During the reinstallation, the grounding strap must be installed to the opposite side

(bolt head side) of the attachment point. In addition, inspect the removed hexagon

bolt, and replace it with a new one as necessary.

b. Install the hexagon bolt (6, Figure 6), grounding strap (7), washer (2), and the new

castellated nut (4). The grounding strap (7) must be installed to the opposite side (bolt

head side). Tighten the castellated nut (4) with a tightening torque of 11 to 13 Nm.

c. Set a torque wrench to 8 Nm, and then turn the nut in the tightening direction without using

counter torque. At this time, make sure that the fastener joint cannot be turned. If the

fastener joint cannot be turned, proceed to step e.

d. If the fastener joint can be turned in work step c above, conduct the steps that follow:

(a) Remove the castellated nut (4, Figure 6).

(b) Replace the washer (2) with the thick washer (3).

NOTE: If one side fastener joint is turned, it is recommended to replace the thick washer

on both sides of the aft attachment fasteners.

NOTE: A thread protrusion down to 0 mm (nut flush with the bolt thread) is allowed while

using the thick washer (3).

(c) Tighten the castellated nut (4, Figure 6) with a tightening torque of 11 to 13 Nm.

e. Secure the castellated nut (4, Figure 6) with a new cotter pin (5).

f. Inspect the grounding strip in accordance with AMM 20-00-00, 2-11.

(6) Close Up

a. Reinstall both covers (4, Figure 2) in accordance with AMM 29-14-00, 4-1A.

As necessary, replace any damaged covers (for 4002 and up. For Part 4, this procedure is

not necessary).

b. If the center fairing was removed, reinstall the center fairing in accordance with AMM

71-11-00, 4-2.

c. Install the crest cowling in accordance with AMM 71-11-00, 4-1.

d. Remove the "DO NOT MOVE THE FLIGHT CONTROLS" notice from the cockpit.

e. Remove the "DO NOT START THE ENGINES" notice from the cockpit.

KSB-117-406B

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f. As necessary, connect the battery in accordance with AMM24-00-00, 2-2.

g. As necessary, connect the external power supply in accordance with AMM24-00-00, 2-1.

h. Complete this Service Bulletin by making an entry in the Aircraft Logbook stating that work

has been accomplished in accordance with KSB-117-406B.

10. PARTS AND MATERIAL INFORMATION

(1) Required Parts for One Helicopter

Part Number Part Name Qty Remarks

LN29522S08019 Hexagon Bolt 2 2, Figure 2 In accordance with inspection results.

LN9338-08 Nut 2 3, Figure 2 In accordance with inspection results.

LN9345-08 Castellated Nut 2 2, Figure 3 In accordance with inspection results.

LN29522S08014 Hexagon Bolt 2 3, Figure 3 In accordance with inspection results.

LN94-20020 Cotter Pin

2 4, Figure 3 In accordance with inspection results.

2 5, Figure 5

2 5, Figure 6

D290M0001201 Hexagon Bolt 2 5, Figure 4

EN2883-080 Nut 4 6A and 6B, Figure 4

DIN65246-08E Castellated Nut 2 3, Figure 5

2 4, Figure 6

EN2549D080016F Hexagon Bolt

2 4, Figure 5


EN2914-08025

(or LN29952-0825M) Washer

2 2A, Figure 5 Replace as necessary.

2 3, Figure 6 Replace as necessary.

GPN910-2179 Cover 2 4, Figure 2 Replace as necessary.

(2) Required Materials for One Helicopter

Specification Material Name Qty Remarks

FED O-A-51 TL6810-003

Acetone AR Use for cover re-installation. CM203 (NOTE)

SAE-AMS-S-8802 CL.B-2

Sealing Compound AR Use for cover re-installation. CM662 (NOTE) PR1422, B-2

WL 5.7006 Clear Lacquer AR Use for aft side fastener replacement. CM421 (NOTE)

NOTE: CM numbers indicate the consumable material CM numbers listed in the

MAINTENANCE MANUAL.

KSB-117-406B

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(3) Parts to be Removed

Part Number Part Name Qty Remarks

LN29522S08019 Hexagon Bolt 2

2, Figure 2 In accordance with inspection results.

2 2, Figure 4

LN9338-08 Nut 2


2 4, Figure 4

LN9016-08L Washer 2 3, Figure 4

LN9345-08 Castellated Nut 2


2 3, Figure 5

LN29522S08014 Hexagon Bolt 2


2 4, Figure 5

LN94-20020 Cotter Pin


2 5, Figure 5

2 5, Figure 6

LN29952-0815M Washer 2 2, Figure 5 Replace as necessary.

2 2, Figure 6 Replace as necessary.

DIN65246-08E Castellated Nut 2 4, Figure 6

EN2549D080016F Hexagon Bolt 2 6, Figure 6 In accordance with inspection results.

GPN910-2179 Cover 2 4, Figure 2 Replace as necessary.

11. SPECIAL TOOL REQUIRED

None

12. REFERENCE TECHNICAL DATA

KAWASAKI BK117C-2 AIRCRAFT MAINTENANCE MANUAL (AMM)

13. AVAILABILITY OF KIT

Information on availability of the parts and materials required for the accomplishment of this

Service Bulletin is provided on request by the KHI helicopter product support business

section.

Prepared by: KAWASAKI HEAVY INDUSTRIES, LTD.

AEROSPACE SYSTEMS COMPANY

1, Kawasaki-cho, Kakamigahara City,

Gifu Prefecture, 504-8710, Japan

KSB-117-406B

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NOTE: The flowchart below is valid until Section 4.(3) has been accomplished.

Figure 1 KSB Flowchart (Part 1 and Part 2)

NO

YES

NO

YES

NO

Receipt of KSB

Part 1 External Visual Inspection

(Refer to Sec. 9. (2))

Nuts and

bolts OK?

Replace the affected parts before

the next flight, and inform KHI

BK117 helicopter product support

business section.

Part 2 Tightening Torque Check


Torque

OK?

Repeat Part 1 every

400 F/H.

100 F/H

400 F/H

Nuts and

bolts OK?

YES

Confirm This KSB

Replace the affected parts before

the next flight, and inform KHI

BK117 helicopter product support

business section.

KSB-117-406B

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NOTE: The flowchart below prescribes the work flow of Section 4. (3) and 4. (4).

Figure 1A KSB Flowchart (Part 3 and Part 4)

Part 3 Retrofit of the

Attachment Fasteners


Part 4 Tightening torque

check (for the Aft

Attachment Fasteners)


Within

July 3rd

2018

Accomplish 4.

(3) i.a.w Rev. A?

NO

800 F/H

YES

Confirm

accomplishment of

this KSB

Receipt of this

KSB Revision B

Receipt of this

KSB Revision B

Confirm

accomplishment of

this KSB

KSB-117-406B

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VIEW A (RH Shown, LH Opposite)

1. Hydraulic module and hydraulic module plate

2. Hexagon bolt (P/N: LN29522S08019)

3. Nut (P/N: LN9338-08) Tightening torque: 9 ~ 10 Nm (79.65 ~ 88.50 in-lb)

4. Cover (P/N: GPN910-2179, For 4002 & UP)

1 Use a mirror and a flashlight to inspect the condition of the nuts and the hexagon bolts.

2 Check the nut tightening torque.

Figure 2 Inspection of Hydraulic Module Plate Fasteners (Fwd Side)

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VIEW A (LH Side) VIEW B (RH Side)


2. Castellated nut (P/N: LN9345-08)

3. Hexagon bolt (P/N: LN29522S08014)

4. Cotter pin (P/N: LN94-20020)

1 Inspect the condition of the cotter pins, the castellated nuts, and the hexagon bolts, and

check that the aforementioned are correctly installed.

2 Apply the protective coating to the bonding points in accordance with AMM 20-00-00, 2-11.

(Images show work by AHD. The actual color of the protective coating is different.)

Figure 3 Inspection of Hydraulic Module Plate Fasteners (Aft Side)

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VIEW A (LH Shown, RH Opposite)

1 Determine the self‐locking torque of the nut. Tighten the nut with self-locking torque +1 Nm

until the nut contacts the nut (6A).

2 A thread protrusion down to 0 mm (the nut flush with the bolt thread) is allowed as long as

the self-locking torque can be applied.

Figure 4 Retrofit of Hydraulic Module Plate Fasteners (Fwd Side)

BEFORE RETROFIT AFTER RETROFIT

FWD

13-14 Nm

6A

Self-locking Torque +1 Nm


2. Hexagon bolt (P/N: LN29522S08019): Discard

3. Washer (P/N: LN9016-08L): Discard

4. Nut (P/N :LN9338-08): Discard

5. Hexagon bolt (P/N: D290M0001201)

6A. Nut (P/N: EN2883-080)

6B. Nut (P/N: EN2883-080)

Cover Cover 6B

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VIEW A (LH INBD Shown, RH Opposite)


2 The grounding strap must be installed to the opposite side (bolt head side) of the attachment

point.

3 A thread protrusion down to 0 mm (nut flush with the bolt thread) is allowed while using the

thick washer (2A).

Figure 5 Retrofit of Hydraulic Module Plate Fasteners (Aft Side)

FWD

BEFORE RETROFIT AFTER RETROFIT

2

2

2A

3

3

4 4 5 5

11-13 Nm

6

6


2. Washer (P/N: LN29952-0815M)

2A. Washer (P/N: EN2914-08025

or LN29952-0825M): For adjustment

3. Castellated nut (P/N: DIN65246-08E)

(P/N: LN9345-08, Discard)

4. Hexagon bolt (P/N: EN2549D080016F)

(P/N: LN29522S08014, Discard)


6. Grounding strap

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VIEW A (LH INBD Shown, RH Opposite)


2 The grounding strap must be installed to the opposite side (bolt head side) of the attachment

point.

3 A thread protrusion down to 0 mm (nut flush with the bolt thread) is allowed while using the

thick washer (3).

4 Replace the castellated nut with a new one.

Figure 6 Repositioning of the Grounding Strap (for the Aft Attachment Fasteners)

2

3


2. Washer (P/N: LN29952-0815M)

3. Washer (P/N: EN2914-08025

or LN29952-0825M) For adjustment

4. Castellated nut (P/N: DIN65246-08E)


6. Hexagon bolt (P/N: EN2549D080016F)

7. Grounding strap

7

4

6 5

PRE KSB-117-406B

POST KSB-117-406B

FWD

11-13 Nm

SERVICE BULLETIN - BK117

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