2009-11-13

CORRECTION

EC135

SERVICE BULLETIN

EC135-53-023

A correction had been made in the english issue of the Service Bulletin EC13553023. The word

four" in the sentence of section 3.B.(14)(f) must be replaced by all". Therefore the right sentence is

the following:

(f) Using a drill bit dia. 5.03 mm, drill out all rivet holes and debur.

Page 6 has been corrected. The date on the changed page has been underlined but remains

unchanged.

SERVICE BULLETIN

EC135

EC135-53-023

PAGE 1 of 12

2009-08-19

Fuselage – Rear Structure – Attach frame reinforcement to ring frame

X9227 between rear structure tube and Fenestron box

1. Planning Information

A. Effectivity

(1) Helicopters affected: EC135/EC635, all models with rear structure up to 

including Rear Structure S/N 832*, excluding rear 

structures where one of the following RDAS were 

accomplished: AIRF 118/2009, 193/2009, 194/2009, 

205/2009, 206/2009, 207/2009, 208/2009 or 209/2009.

*The S/N of the rear structure (see figure 5) can be determined after removal of the Tail Rotor Drive Shaft Panelling (AMM,

53-50-01, 4-1).

(2) Components affected: Aft ring frame L535A3501230**.

**The aft ring frame L535A3501230 (countersunk rivet, surface sealed) was installed as standard equipment up to rear

structure S/N 832. Starting with rear structure S/N 833 the ring frame is riveted with universal head rivets (L535H2120301).

With accomplishment of this Service Bulletin reinforcement L535H2100201 is installed and the ring frame is re–identified

from L535A3501230 to L535H2120302.

(3) Spare parts affected: Not applicable.

B. Concurrent Requirements

Not applicable.

C. Reason

The rear structure tube is connected to the Fenestron housing by means of a ring frame

attached by two rivet rows each. During preflight checks, cracks were detected on some ring

frames and therefore a scheduled inspection of the ring frame was prescribed with ASB

EC135-53A-022. 

With this Service Bulletin a reinforcement of the ring frame is offered, whereby ASB

EC135-53A-022 is no longer applicable.

D. Description

Attach frame reinforcement and re–identify ring frame.

E. Compliance

Accomplishment of this Service Bulletin is recommended by ECD and can be accomplished

by operator if he has the appropriate tooling and experience in standard repair procedures.

F. Approval

The information or instructions contained in this document refer to change no. 1656. The

technical content of this document is approved under the authority of DOA No.

EASA.21J.034.

This document is available on the internet: www.eurocopter.com/techpub
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 2 of 12

2009-08-19

G. Manpower

Approx. 17 man–hours.

H. Weight and Balance

Weight: 0,434 kg

Moment: 4005 kgmm

I. Electrical Load Data

Not applicable.

J. Software Accomplishment Summary

Not applicable.

K. References

Not applicable.

L. Other publications affected

Not applicable.

M. Interchangeability of Parts

Not applicable.

2. Material Information

A. Material – Price and Availability

Information on cost and availability of required retrofit kits SB-EC135-53-023-2C1 and

SB-EC135-53-023-2C2 will be provided by ECD, Dept. Spares Order Administration on

request.

B. Support Information

Not applicable.

C. Material Necessary for Each Helicopter

Retrofit kit SB-135-53-023-2C1 contains the reinforcement and the consumable material

similar to design document L008H0535883.

No. New P/N Keyword Old P/N Qty Disposition

1 L535H2100201 Frame at X9227 reinforcement − 1 A

2 − Adhesive paste

(CM 6041)

− *a.r. B
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 3 of 12

2009-08-19

No. New P/N Keyword Old P/N Qty Disposition

3 − Primer

(CM 472)

− *a.r. B

4 − Hardener

(CM 459)

− *a.r. B

5 − Thinner

(CM 436)

− *a.r. B

6 − Sealing compound (CM 6068)

PR1771B2

− *a.r. B

*a.r. = as required

Retrofit kit SB-135-53-023-2C2 contains the rivets similar to design document

L008H0535883.

No. New P/N Keyword Old P/N Qty Disposition

1 ASNA0363T0604

or CR7773S0604W

Blind rivet − 8 A, D

2 ASNA0363T0605

or CR7773S0605W

Blind rivet − 35 A, D

− ASNA0026SB0503 18 C

3 ASNA0363T0606

or CR7773S0606W

Blind rivet − 18 A, D

4 ASNA0363T0607

or CR7773S0607W

Blind rivet − 35 A, D

− ASNA0341T0503 18 C

5 ASNA0363T0608

or CR7773S0608W

Blind rivet − 15 A, D

6 ASNA0363T0609

or CR7773S0609W

Blind rivet − 3 A, D

Disposition:

A = New, included in kit.

B = Consumable material, to be ordered from the Interturbine company as needed.

CM item number as per list of consumable materials in the AMM.

C = Part with old P/N is discarded.

Discarded parts are not taken back by ECD.

D = As the length of the blind rivets can only be determined during the installation, additional

blind rivets are supplied.
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 4 of 12

2009-08-19

D. Material Necessary for Each Spare

Not applicable.

E. Reidentified Parts

With accomplishment of this Service Bulletin the ring frame is re–identified from

L535A3501230 to L535H2120302.

F. Special Tooling

Riveting tool: Cherry G83

Drift: H83B–6MB

3. Accomplishment instructions

A. Provide access:

(1) Remove tail rotor drive shaft panelling i.a.w. AMM, 53-50-01, 4-1.

(2) Remove horizontal stabilizer i.a.w. AMM, 53-50-03, 4-2.

(3) Remove tail skid i.a.w. AMM, 53-50-02, 4-2.

B. Attach frame reinforcement:

(1) Position frame reinforcement to rear structure i.a.w. Figure 1. The given dimensions are

for the approximate positioning, actual position is determined by the contour fit between

the reinforcement and the structure. Mark contours of the frame reinforcement on the

rear structure and mask with adhesive tape , Figure 2.

(2) Remove paint, filler and primer in affected area by sanding to the bare metal of ring

frame and composite of the rear structure (1), (2), Figure 2. Use caution to not damage

the composite material of the rear structure .

(3) Position frame reinforcement to the repair area. While doing so, look for the best fit with

the smallest gap between frame reinforcement and ring frame.

CAUTION THE DISTANCE BETWEEN FRAME REINFORCEMENT AND REAR

STRUCTURE MUST NOT BE MORE THAN 1.0 MM. IF THIS VALUE

CANNOT BE REACHED, INFORM ECD OF THE DEVIATION VALUE.

(4) Using a feeler gauge (4), Figure 2 measure the clearance between the frame

reinforcement and the rear structure. The distance must not exceed 1mm at any point

on the periphery. Reposition frame reinforcement in the given area until the tightest

clearance has been reached at all places.

(5) Transfer holes of frame reinforcement onto rear structure (drill bit dia. 2.5 mm). While

doing so, fix frame reinforcement by means of clamping grippers ((1), Figure 3).
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 5 of 12

2009-08-19

(6) Detach frame reinforcement.

CAUTION WHEN DRILLING OUT THE RIVETS, ENSURE THAT THE RIVET

HOLES ARE NOT DAMAGED OR BECOME OVAL–SHAPED.

(7) Drill out countersunk rivets from below the frame reinforcement (2), Figure 3. Remove

only the countersunk rivets from the (upper and lower) edge area for which the edge

distance in the frame reinforcement of 2 x rivet diameter can be maintained, see ,

Figure 3.

(8) Using a magnifying glass (at least 10–fold magnification), inspect ring frame ( ,

Figure 3) for cracks. If cracks are detected in this area, ECD must be informed before

work is resumed.

(9) Attach frame reinforcement to rear structure by means of clamping grippers.

(10) Transfer rivet pattern in ring frame (drilled–out countersunk rivets) from rear structure

to frame reinforcement. To do so, first drill from inside to the outside using drill bit dia.

4.1 mm.

(11) Drill out the remaining rivet holes in the frame reinforcement using drill bit dia. 4.1 mm.

(12) Remeasure distance between frame reinforcement and rear structure. The gap must

not be more than 1 mm.

CAUTION THE GAP BETWEEN THE FRAME REINFORCEMENT AND THE REAR

STRUCTURE MUST BE OFFSET WITH ADHESIVE PASTE (CM 6041).

THE FRAME REINFORCEMENT CAN BE DIRECTLY INSTALLED

WHEN THE GAP IS SMALLER THAN 0.2 MM. IF THE GAP IS BETWEEN

0.2 MM AND 1.0 MM THE ADHESIVE PASTE MUST BE COMPLETELY

DRY BEFORE THE RIVETING IS ACCOMPLISHED.

(13) If the gap between frame reinforcement and rear structure tube is less than 0.2 mm

proceed as follows:

NOTE If the distance is smaller than 0.2 mm the frame reinforcement is

positioned with adhesive paste and immediately riveted before

adhesive dries.

(a) Drill out all boreholes using drill bit dia. 5.03 mm.

(b) Determine rivet lengths by means of a suitable tool.

(c) Detach frame reinforcement and debur boreholes.

(d) Clean repair area using acetone (CM 203).

(e) Protect repair area and all worked surfaces using surface protection (CM 472,

CM 459, CM 436) ((2), Figure 4). Let surface protection dry i.a.w. the

manufacturer’s instructions.
SERVICE BULLETIN

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EC135-53-023

PAGE 6 of 12

2009-08-19

(f) Clean frame reinforcement using acetone (CM 203).

(g) Apply adhesive paste (CM 6041) onto inner side of frame reinforcement.

(h) Position frame reinforcement with adhesive paste (CM 6041) wet onto repair area

and fix it by means of clamping grippers.

(i) Rivet frame reinforcement to the rear structure ((3), Figure 4). While doing so, set

all rivets with sealing compound (CM 6068).

(j) proceed with 3.A.(15).

(14) If the gap between frame reinforcement and rear structure tube is between 0.2 mm and

1.0 mm proceed as follows:

NOTE If the distance is between 0.2 mm and 1.0 mm the frame

reinforcement is positioned with adhesive paste too. However, before

the riveting is accomplished, the drying time of the adhesive paste

must be obeyed.

(a) Detach frame reinforcement and clean repair area and frame reinforcement using

acetone (CM 203).

(b) Protect repair area and all worked surfaces using surface protection (CM 472,

CM 459, CM 436). Let surface protection dry i.a.w. the manufacturer’s instructions.

(c) Position frame reinforcement with adhesive paste (CM 6041) wet onto repair area.

(d) Attach frame reinforcement to at least 50% of the rivet holes by means of clamping

grippers.

(e) Leave adhesive paste to dry i.a.w. the manufacturer’s instructions.

(f) Using drill bit dia. 5.03 mm, drill out all rivet holes and debur.

(g) Determine rivet lengths by means of a suitable tool.

(h) Protect boreholes with surface protection (CM 472, CM 459, CM 436). Let surface

protection dry i.a.w. the manufacturer’s instructions.

(i) Rivet frame reinforcement to the rear structure ((3), Figure 4). While doing so, set

all rivets with sealing compound (CM 6068).

(15) Accomplish a visual inspection of frame reinforcement for gaps. Ensure that there is no

gap between frame reinforcement and rear structure.

(16) Seal the entire periphery of the frame reinforcement using sealing compound

(CM 6068) ( , Figure 4).

(17) Using a permanent pen, mark ring frame with the new part number L535H2120302

(access through horizontal stabilizer).
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EC135

EC135-53-023

PAGE 7 of 12

2009-08-19

(18) Re–establish helicopter’s paint in the affected area.

C. Conclusive work:

(1) Accomplish inspection for foreign objects and for foreign matter.

(2) Install tail skid i.a.w. AMM, 53-50-02, 4-2.

(3) Install horizontal stabilizer i.a.w. AMM, 53-50-03, 4-2.

(4) Install tail rotor drive shaft panelling i.a.w. AMM, 53-50-01, 4-1.

D. Confirm accomplishment of this Service Bulletin by an entry in the historical record of the

helicopter.

4. Appendix

Not applicable.
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 8 of 12

2009-08-19

Positioning of Frame Reinforcement

Figure 1

1 Frame reinforcement L535H2100201

1

1

approx. 10 mm

approx. 5 mm

approx. 5 mm

approx. 10 mm

1
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 9 of 12

2009-08-19

Sand Repair Area and Position Frame Reinforcement

Figure 2

Mask with adhesive tape.

Using a feeler gauge, measure gap around the entire periphery.

(1) Sanding of the repair area. (2) Sanded repair area.

(3) Position frame reinforcement onto 

repair area.

(4) Measure gap with feeler gauge.
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 10 of 12

2009-08-19

Visual Inspection of Ring Frame for Cracks

Figure 3

(1) Copy boreholes from frame 

reinforcement onto rear structure. (2) Drill out countersunk rivets. 

While doing so, obey edge 

distance.

Check ring frame for cracks.

Obey edge distance of frame reinforcement. Remove only the countersunk rivets from the

(upper and lower) edge area for which the edge distance in the frame reinforcement of 2 x

rivet diameter can be maintained.
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 11 of 12

2009-08-19

Frame Reinforcement

Figure 4

(1) Drill rivet holes.

(3) Frame reinforcement riveted and sealed.

(2) All rivet holes drilled and surface 

protection re–established.

Seal the entire periphery of the frame reinforcement using sealing

compound (CM 6068).
SERVICE BULLETIN

EC135

EC135-53-023

PAGE 12 of 12

2009-08-19

S/N – Rear Structure

Figure 5

Label with S/N of the rear structure.