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1/15
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
KSB-117-406B
2 / 15
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
3 / 15
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
4 / 15
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
5 / 15
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.
KSB-117-406B
6 / 15
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
7 / 15
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
2 6, Figure 6 In accordance with inspection results.
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
8 / 15
(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
3, Figure 2 In accordance with inspection results.
2 4, Figure 4
LN9016-08L Washer 2 3, Figure 4
LN9345-08 Castellated Nut 2
2, Figure 3 In accordance with inspection results.
2 3, Figure 5
LN29522S08014 Hexagon Bolt 2
3, Figure 3 In accordance with inspection results.
2 4, Figure 5
LN94-20020 Cotter Pin
2 4, Figure 3 In accordance with inspection results.
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
9 / 15
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
(Refer to Sec. 9. (3))
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
10 / 15
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
(Refer to Sec. 9. (4))
Part 4 Tightening torque
check (for the Aft
Attachment Fasteners)
(Refer to Sec. 9. (5))
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
11 / 15
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)
KSB-117-406B
12 / 15
VIEW A (LH Side) VIEW B (RH Side)
1. Hydraulic module and hydraulic module plate
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)
KSB-117-406B
13 / 15
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
1. Hydraulic module and hydraulic module plate
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
KSB-117-406B
14 / 15
VIEW A (LH INBD Shown, RH Opposite)
1 Apply the protective coating to the bonding points in accordance with AMM 20-00-00, 2-11.
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
1. Hydraulic module and hydraulic module plate
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)
5. Cotter pin (P/N: LN94-20020)
6. Grounding strap
KSB-117-406B
15 / 15
VIEW A (LH INBD Shown, RH Opposite)
1 Apply the protective coating to the bonding points in accordance with AMM 20-00-00, 2-11.
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
1. Hydraulic module and hydraulic module plate
2. Washer (P/N: LN29952-0815M)
3. Washer (P/N: EN2914-08025
or LN29952-0825M) For adjustment
4. Castellated nut (P/N: DIN65246-08E)
5. Cotter pin (P/N: LN94-20020)
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