AD/A320/174 Amdt 1 Air Data/Inertial Reference Unit (Cth)
AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/A320/174 and issues the following 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/A320/174 Amdt 1 | Air Data/Inertial Reference Unit | 10/2007 |
Applicability: | Model A318, A319, A320 and A321 series aeroplanes, all serial numbers, equipped with at least one Northrop-Grumman (previously Litton) Air Data/Inertial Reference Unit (ADIRU) with part numbers (P/N) listed in Table 1, except aeroplanes equipped with three ADIRUs P/N 465020-0303-0316 (installed by Airbus modification 35517 or Airbus Service Bulletin (SB) A320-34-1350 dated 20 March 2006) and that have modified the shelf as per Airbus modification 30650 or 30872 or SB A320-25-1248 dated 16 February 2001 (AD/A320/138). | ||
| Table 1 - List of Affected ADIRU P/N | |||
| 465020-0303-0307 | 465020-0303-0312 | 465020-0303-0316 | |
| Note 1. These P/N ADIRUs were introduced during production by Airbus modification 24852 or 25108 or 25336 or 26002 or 28218 or 31070 or 31742 or 35517. | |||
Requirement: | 1. For all aircraft - Operational dispatch of the aircraft with one ADIRU inoperative will be authorised under the following conditions: | ||
| • Stand-by compass operative, and • Stand-by attitude indicator operative. | |||
| For aircraft equipped with conventional standard instruments, compliance with A318/319/320/321 Master Minimum Equipment List (MMEL) Temporary Revision (TR) No 01-34/02Z issue 04 is an acceptable means of compliance with this Requirement. | |||
| For aircraft equipped with Integrated Standby Instruments System (ISIS) (Airbus modification 27620/Airbus SB A320-34-1261), compliance with A318/319/320/321 MMEL TR No 01-34/07Z issue 03 is an acceptable means of compliance with this Requirement. | |||
| 2. For aircraft that have not embodied Airbus modification 30650 or 30872 during production or SB A320-25-1248 whilst in service - Modify the ADIRU shelf supports in accordance with SB A320-25-1248 Revision 1 dated 16 April 2003 or later EASA approved revision. | |
| 3. For all aircraft - Install three Northrop-Grumman (previously Litton) ADIRU | |
| Compliance with Requirements 2 and 3 terminate the Requirement 1 despatch restrictions and no further action is required by this Amendment. | |
| Note 2: EASA 2007-0217 refers. | |
Compliance: | For Requirement 1 - As of the effective date of this Amendment. |
| For Requirement 2 - Within six months after the effective date of this Amendment. | |
| For Requirement 3 - Before 31 May 2010. | |
| This Amendment becomes effective on 27 September 2007. | |
Background: | Initially, the French Direction Générale de l’Aviation Civile (DGAC) advised that some instances of loss of inertial references have been reported which could reduce the control of the aircraft due to the non-availability of some parameters (attitude, vertical speed, ground speed, etc). Subsequent investigation identified the loss of the parameters as being caused by the ADIRU striking the bottom of the upper shelf. |
| AD/A320/138 mandated the modification of the ADIRU shelf supports in an attempt to prevent contact between the ADIRUs and the upper shelf. This measure alone did not prove sufficient and the original issue of this Directive introduced revised despatch limitations for the MMEL. | |
| Again theses measures were found to be insufficient and the European Aviation Safety Agency (EASA) has advised that replacement of the three ADIRUs together with modification of the shelf will provide terminating action for the despatch limitations. Consequently, this Amendment continues the despatch limitations, reiterates the shelf modification and requires replacement of the three ADIRUs. |
| The original issue of this Directive became effective on 4 May 2005. |
Charles Lenarcic
Delegate of the Civil Aviation Safety Authority
14 August 2007
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