EASA AD No.: 2012-0175

CAP.00110-001 © European Aviation Safety Agency. All rights reserved. 1/3

Proprietary document. Copies are not controlled. Confirm revision status through the EASA-Internet/Intranet.

EASA AIRWORTHINESS DIRECTIVE

AD No.: 2012-0175

Date: 07 September 2012

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 EC 1702/2003, Part 21A.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].

Type Approval Holder’s Name :

AIRBUS

Type/Model designation(s) :

A318, A319, A320 and A321 aeroplanes

TCDS Number: EASA.A.064

Foreign AD: Not applicable

Supersedure: None

ATA 27 Flight Controls – Trimmable Horizontal Stabilizer Actuator Ballscrew 

Lower Splines – Inspection / Replacement

Manufacturer(s): Airbus (formerly Airbus Industrie)

Applicability: Airbus A318-111, A318-112, A318-121, A318-122, A319-111, A319-112, A319-113, 

A319-114, A319-115, A319-131, A319-132, A319-133, A320-111, A320-211, A320-

212, A320-214, A320-215, A320-216, A320-231, A320-232, A320-233, A321-111, 

A321-112, A321-131, A321-211, A321-212, A321-213, A321-231 and A321-232 

aeroplanes, all manufacturer serial numbers.

Reason: Some Trimmable Horizontal Stabilizer Actuators (THSA), Part Number (P/N) 47147-

500 fitted on A330/A340 aeroplanes have been found with corrosion, affecting the 

ballscrew lower splines between the tie bar and the screw-jack. The affected 

ballscrew is made of steel and anti-corrosion protection is ensured, except on both 

extremities (upper and lower splines) where Molykote is applied.

The results of the technical investigations have identified that the corrosion was 

caused by a combination of:

- contact/friction between the tie bar and the inner surface of the ballscrew leading 

to the removal of Molykote (corrosion protection) at the level of the tie bar splines,

- humidity ingress initiating surface oxidation starting from areas where Molykote is 

removed, and

- water retention in THSA lower part leading to corrosion spread out and to the 

creation of a brown deposit (iron oxide).

The results of the technical investigations have also concluded that A320 family 

THSA P/N 47145-XXX (where XXX stands for any numerical value) ballscrews 

might be affected by this corrosion issue.

This condition, if not detected and corrected, may lead, in case of ballscrew rupture, 
EASA AD No.: 2012-0175

CAP.00110-001 © European Aviation Safety Agency. All rights reserved. 2/3

Proprietary document. Copies are not controlled. Confirm revision status through the EASA-Internet/Intranet.

to loss of transmission of THSA torque loads from the ballscrew to the tie-bar, 

prompting THSA blowback, possibly resulting in loss of control of the aeroplane.

For the reasons described above, this AD requires repetitive detailed inspections of 

the ballscrew lower splines of THSA having P/N 47145-XXX to detect corrosion and, 

depending on findings, the accomplishment of applicable corrective actions.

Effective Date: 21 September 2012

Required Action(s) 

and Compliance 

Time(s):

Required as indicated, unless accomplished previously:

(1) Initially, within the compliance time indicated in Table 1 of this AD, and 

thereafter at intervals not to exceed 24 months, perform a detailed inspection of 

the THSA ballscrew having a P/N 47145-XXX in accordance with the 

instructions of Airbus Service Bulletin (SB) A320-27-1214.

Table 1 – Initial THSA inspection

Compliance time, whichever occurs later, A or B

A Before accumulating 22 years, but not before 20 years 

since THSA first flight (see Note)

B Within 3 months after the effective date of this AD

Note: For the purpose of this AD, the definition of THSA first flight is the THSA 

“entry into service date” as listed in Goodrich SB 47145-27-16. If the THSA P/N is 

not listed in Goodrich SB 47145-27-16, the THSA first flight is the manufacturing 

date engraved on the THSA identification plate.

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

found, within the applicable compliance time as defined in Paragraph 1.E.(2) of 

Airbus SB A320-27-1214, accomplish the applicable corrective actions 

(additional inspections of the affected THSA ballscrew, followed by replacement 

of the affected THSA) in accordance with the instructions of Airbus SB A320-

27-1214. Within 90 days after an inspection where corrosion is found, report the 

results to Airbus.

(3) Replacement of a THSA as required by paragraph (2) of this AD does not 

constitute terminating action for the repetitive inspections as required by 

paragraph (1) of this AD.

(4) From the effective date of this AD, do not install a THSA having P/N 47145-

XXX on an aeroplane, unless the THSA has not yet accumulated 20 years 

since its first flight, or unless it has been determined that the THSA is classified 

as Type 1 (no corrosion) at the time of installation, in accordance with criteria 

defined in Airbus SB A320-27-1214, and on the conditions that the THSA is 

thereafter inspected and, depending on findings, corrected, in compliance with 

the requirements of this AD.

Ref. Publications: Airbus SB A320-27-1214 original issue dated 23 February 2012.

Goodrich SB 47145-27-16 original issue dated 07 November 2011.

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

compliance with the requirements of this AD.

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

Methods of Compliance for this AD.

2. This AD was posted on 04 June 2012 as PAD 12-057 for consultation until

18 June 2012. The Comment Response Document can be found at 

http://ad.easa.europa.eu.

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 
EASA AD No.: 2012-0175

CAP.00110-001 © European Aviation Safety Agency. All rights reserved. 3/3

Proprietary document. Copies are not controlled. Confirm revision status through the EASA-Internet/Intranet.

AD, please contact: AIRBUS – Airworthiness Office – EIAS,

Fax +33 5 61 93 44 51, E-mail: account.airworth-eas@airbus.com.