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EMERGENCY

ALERT SERVICE BULLETIN

SUBJECT: TIME LIMITS - MAINTENANCE CHECKS

Rear structure - Check of the rear frame reinforcement angles

ATA: 53

AIRCRAFT

CONCERNED NUMBER Version(s)

Civil Military

AS350 05.00.70 B, BA, BB, B1, B2, B3, D L1

AS355 05.00.62 E, F, F1, F2, N, NP

AS550 05.00.45 A2, C2, C3, U2

AS555 05.00.41 AF, AN, SN, UF, UN

Revision No. Date of issue

Revision 0 2014-03-24

Summary:

The purpose of this ALERT SERVICE BULLETIN is to visually ensure that there are no cracks on the reinforcement 

angles of the tail boom / rear structure junction frame on helicopters with at least one RH reinforcement angle.

Compliance:

Airbus Helicopters renders compliance with this ALERT SERVICE BULLETIN mandatory.

For the attention of
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1. PLANNING INFORMATION

1.A. EFFECTIVITY

1.A.1. Helicopters/installed equipment

Helicopters fitted with a rear structure / tail boom junction frame, repaired or reinforced with at least one 

reinforcement angle on the RH side as per MRM Work Card 53.10.22.772 or AMM Task 53-31-00, 8-5 or 

which embody MOD 073215.

NOTE 1

Helicopters which embody MOD 073232 are not concerned 

by the instructions of this ALERT SERVICE BULLETIN.

The purpose of MOD 073232 is to produce a new machined 

frame.

NOTE 2

The purpose of MOD 073215 is to reinforce the rear 

structure / tail boom junction frame on new helicopters by 

installing 4 reinforcement angles.

CAUTION

HELICOPTERS FITTED WITH AT LEAST ONE

REINFORCEMENT ANGLE ON THE RIGHT HAND SIDE 

OF THE FRAME ARE NO LONGER SUBJECT TO 

COMPLIANCE WITH ASB No. 05.00.43 FOR AS350, 

No. 05.00.21 FOR AS550, No. 05.00.42 FOR AS355 AND 

No. 05.00.22 FOR AS555 BUT ARE NOW SUBJECT TO 

COMPLIANCE WITH THIS ALERT SERVICE BULLETIN.

CAUTION

HELICOPTERS WHICH HAVE NO REINFORCEMENT 

ANGLE(S) ON THE RIGHT HAND SIDE OF THE FRAME 

REMAIN SUBJECT TO COMPLIANCE WITH ASB 

No. 05.00.43 FOR AS350, No. 05.00.21 FOR AS550, 

No. 05.00.42 FOR AS355 AND No. 05.00.22 FOR AS555 

AND ARE NOT SUBJECT TO COMPLIANCE WITH THIS 

ALERT SERVICE BULLETIN.

1.A.2. Non-installed equipment

Not applicable.

1.B. ASSOCIATED REQUIREMENTS

Not applicable.
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1.C. REASON

SIN 2463-S-53, issued in June 2012, informed you of a case of cracks on the upper RH side reinforcement 

angle of the rear structure / tail boom junction frame, discovered during an unscheduled inspection. 

Investigations revealed that the origin of the cracks was that the reinforcement angle attachment holes were 

not de-burred following compliance at the customer's premises with MRM Work Card 53.10.22.772 or AMM 

Task 53-31-00, 8-5.

Following further cases of cracks, analyses have revealed that the cracks initiate on the non-visible surface 

of the angle (surface in contact with the frame).

To date, all the cases of cracks have been encountered on "non compliant" installations (presence of burrs).

For this reason, and because the propagation of these cracks can, in time, lead to failure of the tail boom 

connection and affect the integrity of the helicopter structure, Airbus Helicopters makes compliance with the 

instructions in this ALERT SERVICE BULLETIN mandatory.

Helicopters which embody MOD 073232 (creation of a new machined frame) are not concerned by the 

instructions of this ALERT SERVICE BULLETIN.

Airbus Helicopters is currently studying a solution that will improve this attachment and that will cancel the 

additional maintenance introduced by this ALERT SERVICE BULLETIN.

1.D. DESCRIPTION

1) Carry out a visual inspection for cracks without removing hardware on the attachment 

points (5 to 12) of the RH reinforcement angles of the rear frame.

Then,

2) Carry out a visual inspection for cracks including removal of hardware on the attachment 

points (5 to 12) of the RH reinforcement angles of the rear frame.
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1.E. COMPLIANCE

1.E.1. Compliance at the works

Not applicable.

1.E.2. Compliance in service

Helicopters/installed equipment:

a) For helicopters with angle reinforcements which have logged less than 640 flying hours since 

installation at the date of receipt of the ALERT SERVICE BULLETIN:

1) Comply with paragraph 3. (except 3.B.2.) of this ALERT SERVICE BULLETIN, at the latest when the 

reinforcement reaches 650 flying hours,

Then,

- Comply with paragraph 3.B.1. at intervals not exceeding 10 flying hours until paragraph 1.E.2.a.2.

has been complied with

Then,

2) Compy with paragraph 3. (except paragraph 3.B.1.) of this ALERT SERVICE BULLETIN within 

165 flying hours once the reinforcement has 650 flying hours.

Then,

- Comply with paragraph 3.B.2. at intervals not exceeding 165 flying hours.

b) For helicopters with angle reinforcements which have logged 640 flying hours or more since 

installation at the date of receipt of the ALERT SERVICE BULLETIN:

1) Comply with paragraph 3. (except paragraph 3.B.2.) of this ALERT SERVICE BULLETIN, within 

10 flying hours following receipt of this ALERT SERVICE BULLETIN issued on the date indicated at 

the foot of the page,

Then,

- Comply with paragraph 3.B.1 at intervals not exceeding 10 flying hours until paragraph 1.E.2.b.2.

has been complied with

Then,

2) Within 165 flying hours following receipt of this ALERT SERVICE BULLETIN, issued on the date 

indicated at the bottom of the page, comply with paragraph 3. (except paragraph 3.B.1.) of this ALERT 

SERVICE BULLETIN, 

Then,

- Comply with paragraph 3.B.2. at intervals not exceeding 165 flying hours.

Non-installed equipment:

Not applicable.
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1.F. APPROVAL

Approval of modifications:

Not applicable.

Approval of this document:

The technical information contained in this ALERT SERVICE BULLETIN Revision 0 was approved 

on March 24, 2014 under the authority of EASA Design Organization Approval No. 21J.056 for helicopters of 

civil versions subject to an Airworthiness Certificate.

The technical information contained in this ALERT SERVICE BULLETIN Revision 0 was approved 

on March 24, 2014 under the prerogatives of the recognition of design capability FRA21J-002-DGA for 

French Government helicopters.

The technical information contained in this ALERT SERVICE BULLETIN Revision 0 was approved 

on March 24, 2014 by the Airbus Helicopters Airworthiness Department for export military versions.
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1.G. MANPOWER

For compliance with this ALERT SERVICE BULLETIN, Airbus Helicopters recommends the following 

personnel qualifications: 

- 1 Mechanical Engineering Technician.

Or,

- 1 pilot with appropriate training and certification, in accordance with the local regulation in force.

The time for the operations is given for information purposes, for a standard configuration.

- Approximately 30 minutes for the inspection without removing hardware.

- Approximately 2 hours for the inspection including removal of hardware.

Helicopter downtime: 

Not applicable.

1.H. WEIGHT AND BALANCE

Not applicable.

1.I. EFFECT ON ELECTRICAL LOADS

Not applicable.

1.J. SOFTWARE MODIFICATION EMBODIMENT RECORD

Not applicable.

1.K. REFERENCES

The documents required for compliance with this ALERT SERVICE BULLETIN are as follows:

For AS350 helicopters versions B, BA, BB, B1, D and L1, AS355 helicopters all versions, 

AS550 helicopters versions A2, C2 and U2 and AS555 helicopters all versions:

MET 53.00.00.402: Fuselage - tail-boom: Removal - Installation.

For AS350 helicopter versions B2 and B3 and AS550 helicopters version C3:

AMM 53-31-00, 4-1: Rear fuselage - Removal / Installation.

1.L. DOCUMENTS AFFECTED

Not applicable.

1.M. INTERCHANGEABILITY OR MIXABILITY OF PARTS

Interchangeability: Not applicable.

Mixability: Not applicable.
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2. MATERIAL INFORMATION

2.A. MATERIAL: PRICE - AVAILABILITY - PROCUREMENT

Not applicable.

2.B. INFORMATION CONCERNING INDUSTRIAL SUPPORT

Airbus Helicopters remains at your disposal for any information concerning compliance with this ALERT 

SERVICE BULLETIN.

Contact the Customer Service Technical Support Department:

- Tel.: + 33 (0)4.42.85.97.03

- Fax: + 33 (0)4.42.85.99.66

- E-mail: Airframe.Technical-Support@eurocopter.com.

2.C. MATERIAL REQUIRED FOR EACH HELICOPTER/COMPONENT

Not applicable.
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3. ACCOMPLISHMENT INSTRUCTIONS

3.A. GENERAL

Not applicable.

3.B. OPERATIONAL PROCEDURE

3.B.1. Visual check for cracks on the angle reinforcement(s) on the RH side of the frame without removing 

screws 5 to 12 of the angle reinforcements

NOTE 1

Thoroughly clean the area before checking for cracks.

As per Figures 1 and 2

- Visually inspect the RH angle reinforcement(s) (Z1 and Z2) of the frame for cracks at the areas of 

attachment screws 5 to 12.

. If there are no cracks: Leave as is and resume flights.

. If there is a crack in at least one of the 2 angle reinforcements:

.. Take photos of the cracked areas.

.. Contact Airbus Helicopters according to the conditions described in paragraph 2.B. for technical 

instructions.

3.B.2. Visual check for cracks on the angle reinforcement(s) on the RH side of the frame including removal of 

screws 5 to 12 of the angle reinforcements

NOTE 2

Thoroughly clean the area before checking for cracks.

NOTE 3

The screws must be removed and installed one after 

another.

As per Figures 1 and 2

- Remove the screw (a).

- Visually inspect the reinforcement angle of the frame at the attachment bore for cracks.

- Install the screw (a) (CROSS SECTION B-B) as per MET Work Card 53.00.00.402 or AMM 

Task 53-31-00, 4-1.

- Comply with the same procedure for each of the bores 5 to 12.

. If there are no cracks: Leave as is and resume flights.

. If there is a crack in at least one of the 2 angle reinforcements:

.. Take photos of the cracked areas.

.. Contact Airbus Helicopters according to the conditions described in paragraph 2.B. for technical 

instructions.
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3.C. IDENTIFICATION

Identification of this document:

Record first compliance with this ALERT SERVICE BULLETIN and its revision number in the helicopter 

documents.

Identification of modifications on the documentation:

Not applicable.

Identification of modifications on the equipment:

Not applicable.

3.D. OPERATING AND MAINTENANCE INSTRUCTIONS

Not applicable.
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Area to be 

inspected 

Screws (a) from 

5 to 12

B

B

Figure 1: Check of angle reinforcements

No. 

12

Z2

No. 

5 Z1

a

The screw installation 

order is not important

SECTION

B-B

RH side
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Figure 2: Example of cracks

Example of cracks