EASA AD No.: 2013-0154

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EASA AIRWORTHINESS DIRECTIVE

AD No.: 2013-0154

Date: 22 July 2013

Note: This Airworthiness Directive (AD) is issued by EASA, acting in accordance with Regulation 

(EC) No 216/2008 on behalf of the European Community, its Member States and of the 

European third countries that participate in the activities of EASA under Article 66 of that 

Regulation.

This AD is issued in accordance with EU 748/2012, Part 21.A.3B. In accordance with EC 2042/2003 Annex I, Part M.A.301, the 

continuing airworthiness of an aircraft shall be ensured by accomplishing any applicable ADs. Consequently, no person may operate an 

aircraft to which an AD applies, except in accordance with the requirements of that AD, unless otherwise specified by the Agency [EC 

2042/2003 Annex I, Part M.A.303] or agreed with the Authority of the State of Registry [EC 216/2008, Article 14(4) exemption].

Design Approval Holder’s Name:

EUROCOPTER DEUTSCHLAND GmbH

Type/Model designation(s):

MBB-BK117 helicopters

TCDS Number: EASA.R.010

Foreign AD: Not applicable

Supersedure: None

ATA 76 Engine Controls – N2 Control Arm – Inspection / Modification

Manufacturer(s): Eurocopter Deutschland GmbH (formerly Messerschmitt-Bölkow-Blohm GmbH, 

Eurocopter Hubschrauber GmbH), American Eurocopter LLC

Applicability: MBB-BK117 A-1, A-3, A-4, B-1, B-2, C-1 and C-2 helicopters, all serial 

numbers.

Reason: In a recent incident on a MBB-BK117 C-2 helicopter, the aircrew noticed a drop 

of the rotor speed / RPM within the green range, which could not be re-adjusted 

back to the nominal value. An inspection of the engine N2 control system 

revealed a heavily corroded and broken N2 control arm. This broken control 

arm was responsible for the loss of the engine droop compensation. 

Further analysis revealed that, under unfavourable circumstances and 

depending on flight condition and power demand, a broken control arm can 

cause a significant and non-recoverable drop in rotor RPM.

This condition, if not detected and corrected, could lead to a loss of control of 

the helicopter.

To address this potential unsafe condition, Eurocopter (ECD) issued Alert 

Service Bulletin (ASB) MBB-BK117-60A-126 for MBB-BK117 model A-1, A-3, 

A-4, B-1, B-2, and C-1 helicopters, and ASB MBB-BK117 C-2-76A-005 for 

model C-2 helicopters, providing instructions for an initial inspection, followed 

by repetitive inspections, of the N2 control arm.

Effective Date: 05 August 2013
EASA AD No.: 2013-0154

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Required Action(s) 

and Compliance

Time(s):

Required as indicated, unless accomplished previously:

(1) Within the compliance time as identified in Table 1 of this AD and, 

thereafter, at intervals not to exceed 12 months, inspect the N2 control arm 

for corrosion in accordance with the instructions of ECD ASB MBB-BK117 

C-2-76A-005 or ASB MBB-BK117-60A-126, as applicable to helicopter 

Model.

Table 1

Date of Helicopter First Flight Compliance time

More than 2 years before the 

effective date of this AD

Within 4 weeks after the 

effective date of this AD

Less than 2 years before the 

effective date of this AD

Before reaching 2 years after the 

date of first flight, or within 12 

months after the effective date of 

this AD, whichever occurs first

Note: A non-cumulative tolerance of 3 months can be applied for the initial 

inspection on helicopters with less than 2 years from the date of first flight and 

for the repetitive inspections required by paragraph (1) of this AD .

(2) If, during any inspection as required by paragraph (1) of this AD, a part 

shows suspected exfoliation corrosion, before next flight, replace the part 

with a serviceable part.

(3) If, during any inspection as required by paragraph (1) of this AD, damage, 

corrosion and/or scratches of 0.5 mm or more are found, before next flight, 

replace the affected part with a serviceable part.

(4) If, during any inspection as required by paragraph (1) of this AD, damage, 

corrosion and/or scratches of less than 0.5 mm are found, before next 

flight, accomplish corrective action in accordance with the instructions of 

ECD ASB MBB-BK117 C-2-76A-005 or ECD ASB MBB-BK117-60A-126, 

as applicable to helicopter Model.

(5) Replacement of affected parts with serviceable parts as required by 

paragraphs (2) and (3) of this AD or corrective action as required by 

paragraph (4) of this AD do not constitute terminating action for the 

repetitive inspections required by paragraph (1) of this AD.

(6) After the initial inspection as required by paragraph (1) of the AD has been 

accomplished, compliance with the requirements of this AD can be 

demonstrated by

(6.1) Revising, as follows, the approved Aircraft Maintenance Programme 

(AMP) on the basis of which the Operator or the Owner ensures the

continuing airworthiness of each operated aeroplane: 

Incorporate the repetitive 12-months inspection of the N2 control 

arm specified in the Aircraft Maintenance Manual (AMM) MBBBK117 C-2 Revision 14 or AMM MBB-BK117 A-B Revision 43 / 

AMM MBB-BK117 C-1 Revision 26, as applicable to helicopter 

Model, 

and 

(6.2) Complying with the approved AMP described in paragraph (6.1) of 

this AD

Ref. Publications: ECD ASB MBB-BK117 C-2-76A-005, original issue dated 24 June 2013.

ECD ASB MBB-BK117-60A-126, original issue dated 24 June 2013.

The use of later approved revisions of these documents is acceptable for 

compliance with the requirements of this AD.
EASA AD No.: 2013-0154

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Remarks: 1. If requested and appropriately substantiated, EASA can approve 

Alternative Methods of Compliance for this AD.

2. Based on the required actions and the compliance time, EASA have 

decided to issue a Final AD with Request for Comments, postponing the 

public consultation process until after publication.

3. Enquiries regarding this AD should be referred to the Safety Information 

Section, Executive Directorate, EASA. E-mail: ADs@easa.europa.eu.

4. For any question concerning the technical content of the requirements in 

this AD, please contact: Eurocopter Deutschland GmbH, Industriestrasse 4, 

86607 Donauwörth, Germany

Telephone: + 49 (0)151 1422 8976, Fax: + 49 (0)906 71 4111.