AD/A330/84 Flight Control Primary Computer Dispatch Limitations (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 A330 Series Aeroplanes

AD/A330/84 Flight Control Primary Computer Dispatch Limitations 3/2008 TX

Applicability:

A330-200 and -300 series aircraft, all serial numbers.

Requirement:

The following operational limitation is required as indicated:

a.    For all aircraft identified in applicability section except aircraft on which Airbus  modification 44385 has been embodied during production and Airbus modification 44431 has been embodied either during production or whilst in service by Airbus Service Bulletin (SB) A330-24-3011:

Dispatch restriction:

Dispatch with the FCPC “PRIM 1” inoperative (item numbered 27-93-01-A in the associated MMEL) is prohibited.

b.    For aircraft on which Airbus modification 44385 has been embodied during production and Airbus modification 44431 has been embodied either during production or whilst in service by Airbus SB A330-24-3011:

(i)    Dispatch with the FCPC “PRIM 1” inoperative (item numbered 27-93-01-A in the associated MMEL) is allowed provided that the operational test of the FCPC3 second electrical power supply is successfully performed in accordance with instructions of AOT A330-27A3158 or later approved revision, before the first flight of the MMEL interval.

(ii)   If the test is not successful, repair in accordance with instructions of AOT A330-27A3158 or later approved revision, before dispatch with FCPC “PRIM 1” inoperative (item numbered 27-93-01-A in the associated MMEL).

Note 1:  These operational limitations are covered by the following Temporary Revision (TR) of the Master Minimum Equipment List (MMEL):

A330 TR 01-27/01Z Issue 01 for A330-200/-300 aircraft pre-mod 44385 or post-SB A330-27-3040 (NO-GO),

A330 TR 01-27/02Z Issue 01 for A330-200/-300 aircraft with mechanical rudder and post-mod 44385 (GO-IF), and

A330 TR 01-27/03Z Issue 01 for A330-200/-300 aircraft with electrical rudder and post-mod 44385 (GO-IF),

Incorporation of the appropriate MMEL TR or inserting the above dispatch restriction or a copy of this Directive into the Aircraft Operations Manual (AOM) and strict adherence to above dispatch restriction by the flight crew is acceptable to comply with requirements of this Directive.

Later revisions of the above MMEL TRs accepted by the European Joint Aviation Authorities (JAA), or any general JAA approved MMEL revision including the above procedures are also acceptable for compliance with requirements of this Directive.

Note 2:  EASA Emergency AD 2008-0010-E refers.

Compliance:

As of the effective date of this Directive

This Airworthiness Directive becomes effective on 18 January 2008.

Background:

On A330 aircraft, the Flight Control Primary Computer 2 (FCPC2) and FCPC3 are supplied with power from the 2PP bus bar.  Electrical transients on the 2PP bus bar may occur during number 2 engine failures.  Such electrical transients lead to a FCPC2 reset.  FCPC3 reset does not occur due to the introduction of a second electrical power supply to FCPC3 from 1PP bus bar associated to Electrical Contactor Management Unit (ECMU) standard 5.

During evaluation of specific engine failure cases at take-off on Airbus flight Simulators, it has been evidenced that with FCPC1 inoperative, in the worst case, when FCPC2 and FCPC3 resets occur during rotation at take off, a transient loss of elevator control associated with a temporary incorrect flight control law reconfiguration could occur.  It leads to a movement of the elevators to the zero position, which induces a pitch down movement instead of a pitch up movement needed to lift off.  In addition, it leads to a limitation of the pilot authority in pitch axis and limits the capacity to counter the pitch down movement during this flight phase, which constitutes an unsafe condition.

To prevent such situation, this Directive aims to prohibit aircraft dispatch with FCPC1 inoperative (from GO to NO-GO) for certain aircraft configuration.  For the other configurations dispatch is allowed when integrity of the FCPC3 second electrical power supply is ensured.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

16 January 2008