AD/A320/178 Trimmable Horizontal Stabilizer Actuator (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Airbus Industrie A319, A320 and A321 Series Aeroplanes

AD/A320/178 Trimmable Horizontal Stabilizer Actuator 7/2005

Applicability:

AIRBUS A318, A319, A320 and A321 aircraft.

Requirement:

1.    (a)   Do a check of the clearance between secondary nut trunnion and junction plates at the lower Trimmable Horizontal Stabilizer Actuator (THSA) attachment and apply, if necessary, the corrective actions in accordance with the instructions given in AIRBUS Service Bulletin (SB) A320-27-1164 Revision 2 or later DGAC approved revisions.

(b)   Inspect the upper THSA attachment and apply, if necessary, the corrective actions in accordance with the instructions given in SB A320-27-1164 Revision 2 or later DGAC approved revisions.

(c)   Report the results of these 2 inspections to AIRBUS through page 2 of appendix 01 of SB A320-27-1164 Revision 2 or later DGAC approved revisions “inspection reporting sheet”.

2.    Repeat the inspections as detailed in Requirement 1 of this Directive.

Note:  DGAC AD F-2005-051 EASA approval No. 2005-2572 dated 22 March 2005 refers.

Compliance:

1.    Unless already accomplished, within 20 months since first flight or within 600 flight hours from the effective date of this Directive, whichever occurs later.

2.    At intervals not exceeding 20 months.

This Airworthiness Directive becomes effective on 7 July 2005.

Background:

The THSA has been tested on rig in order to check its behaviour in case of primary load path failure.  In that configuration, the loads are transferred to the secondary nut, which should jam, preventing any THS motion.

Tests have shown that the secondary nut did not jam as expected, preventing the detection of the primary load path failure.

James Coyne
Delegate of the Civil Aviation Safety Authority

19 May 2005