AD/A330/46 - Nose Landing Gear Hydraulic Control Block

This Directive combines a small number of interlocking technical and regulatory concepts. The primary technical object is the Hydraulic Control Block, HCB, for the nose landing gear. Two HCB part numbers are named as affected: C24856000-9 and C24856001-7. The modification required is installation of a check valve located between the selector valve and the servo valve within the HCB. The declared mechanical function of that check valve is to limit back pressure that can be generated when torque is applied to the nose gear during ground movement in a free-castoring condition. By limiting that back pressure, the modification is intended to permit a nominal bypass-valve function and avoid a transient hydraulic lock.

The operational failure sequence the Directive records is specific. The Background states that an aircraft experienced a sudden veering during take-off roll at 47 kts. Flight-data analysis showed a "Braking and Steering Control Unit (BSCU) Channel 1 Fault" followed by a loss of Nose Wheel Steering. A brief hydraulic lock in the HCB prevented the transfer from steering to castoring mode and prevented the nose gear returning to straight-ahead. The Background links the presence of a hydraulic lock plus environmental factors, airport geometry and speed to the potential for a hazardous event. The Directive’s stated aim is to require the installation of the check valve on affected HCBs to avoid that situation.

Regulatorily, the Directive is an Airworthiness Directive (AD) published as AD/A330/46, with an internal title "Nose Landing Gear Hydraulic Control Block" and a publication code of 3/2005. The Requirement is implemented by reference to a manufacturer service bulletin, AIRBUS SB A330-32-3156, which provides the technical instructions for the modification. The document also notes that AIRBUS modification 50650 embodied in production, or AIRBUS SB A330-32-3156 embodied in service, are alternative bases on which an aircraft is outside the AD's applicability. The Directive further references foreign regulatory action: DGAC AD F-2005-016 and "EASA approval 2005-499 dated 12 January 2005."

Important administrative facts that shape compliance are included: the AD "becomes effective on 17 March 2005" and requires compliance "Not later than 30 September 2007." The Requirement section contains two labelled notes (Note 1 and Note 2) which explain the part-number result of the modification and state the DGAC/EASA cross-reference respectively. The combined concepts are therefore: an identified flight-safety hazard linked to a hydraulic lock mechanism within an HCB; a targeted engineering change (add a check valve) described in a manufacturer service bulletin; a regulatory instrument mandating embodiment of that SB within a fixed compliance window; and exemptions where the production modification or prior embodiment of the SB already exists.

The scope of who is affected is defined narrowly by aircraft type and by specific HCB part numbers. The Applicability clause states the Directive applies to "AIRBUS A330-200 and A330-300 aircraft series, all serial numbers," except for aircraft on which AIRBUS modification 50650 has been embodied in production or AIRBUS Service Bulletin (SB) A330-32-3156 has been embodied in service. Therefore, operators, owners and lessees of A330-200 and A330-300 aircraft that still have HCBs with part numbers C24856000-9 or C24856001-7 are the primary parties who must act. Maintenance organisations and approved maintenance engineers who are responsible for modifying HCBs will also be directly affected because the Requirement is to "Modify the Hydraulic Control Block (HCB) Part Number (PN) C24856000-9 and PN C24856001-7 in accordance with instructions given in AIRBUS SB A330-32-3156."

Manufacturers and suppliers are affected indirectly because the Requirement references and depends on a design change introduced by AIRBUS and its suppliers, specifically the installation of a check valve between the selector valve and the servo valve. The suppliers that manufacture or retrofit HCBs will need to supply parts or perform the modification in accordance with the SB to meet operator demand prior to the "Not later than 30 September 2007" compliance date.

Regulators and airworthiness authorities are also stakeholders because the Directive cites and aligns itself with foreign actions: "DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005 refers." The Civil Aviation Safety Authority is the issuer within this document, evidenced by the signature block: "James Coyne, Delegate of the Civil Aviation Safety Authority" dated 4 February 2005; the AD also "becomes effective on 17 March 2005."

Aircraft on which AIRBUS modification 50650 has been embodied in production or where AIRBUS SB A330-32-3156 has already been embodied in service are explicitly excluded from the pool of affected aircraft. For those parties, the Directive makes clear that no further action under this AD is required. Finally, as a practical matter, safety managers, continuing-airworthiness personnel and records-keeping staff in affected operators must track the part-number change produced by the modification (the Requirement states the old PNs will become new PNs post-modification) and document compliance within the operator’s maintenance records.

The Directive creates a single, concrete duty: to modify the specified Hydraulic Control Blocks in accordance with AIRBUS SB A330-32-3156. The Requirement text unambiguously states: "Modify the Hydraulic Control Block (HCB) Part Number (PN) C24856000-9 and PN C24856001-7 in accordance with instructions given in AIRBUS SB A330-32-3156." That instruction carries two operational corollaries specified in Note 1: upon completion of the modification, "the HCB PN C24856000-9 will become PN C24856000-11" and "the HCB PN C24856001-7 will become PN C24856001-9." Those PN changes are part of the Directive’s mandatory mechanics and therefore must be reflected in maintenance records and parts inventories.

The compliance duty is time-limited. The Compliance field requires the modification "Not later than 30 September 2007." The AD is effective from "17 March 2005." Those two dates define the enforcement window and the period during which operators must plan and execute the modification. There is an additional duty embedded in the Applicability clause: operators must confirm whether a given aircraft is excluded because "AIRBUS modification 50650 has been embodied in production" or because "AIRBUS Service Bulletin (SB) A330-32-3156 has been embodied in service." In practice that creates an obligation to check production/modification history and maintenance records; the Directive’s textual mechanics make prior embodiment a basis for non-application.

The Directive identifies the method by which the duty is to be discharged: AIRBUS SB A330-32-3156, which is explicitly referenced. The SB is the technical roadmap; the AD does not set out the modification steps itself but requires operators to perform the modification "in accordance with instructions given in AIRBUS SB A330-32-3156." Thus, compliance means executing the SB’s prescribed work scope and any specified parts changes such that the HCB PN is updated as stated.

The source text does not specify any affirmative rights of appeal, review, or extensions within the AD itself. The document does, however, reference an external regulatory family by noting "DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005 refers." The Directive’s structure creates implied operational rights relevant to technical compliance: if an aircraft already embodies AIRBUS modification 50650 in production or has already had SB A330-32-3156 embodied in service, the aircraft is not within the Directive’s applicability and therefore no further action under this AD is required. The AD itself does not specify processes for verifying those conditions, nor does it provide a mechanism for exemption beyond those two stated bases.

Finally, the Directive records who has the authority to issue it and its effective date. It is signed by "James Coyne, Delegate of the Civil Aviation Safety Authority" and dated 4 February 2005, with the AD "becoming effective on 17 March 2005." Those facts place the duty within the administrative process used by the issuer but the AD text does not include procedural details for enforcement, extensions, or dispute resolution.

The source text does not specify penalties, sanctions, or enforcement mechanisms. The Directive states that it "becomes effective on 17 March 2005" and sets a hard compliance deadline: "Not later than 30 September 2007." Those dates create firm temporal obligations for affected aircraft and operators. However, the AD text contains no express provisions describing the consequences of non-compliance, such as administrative fines, grounding, suspension of certificates, or other enforcement steps.

Given the absence of explicit enforcement text in this document, the Directive does not itself provide a schedule of penalties or an enforcement process. The factual record included in the source does establish the issuer and signatory: "James Coyne, Delegate of the Civil Aviation Safety Authority" dated 4 February 2005. The AD also references parallel foreign regulatory action: "DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005 refers." The presence of those references suggests alignment with other authorities, but the AD does not articulate how cross-border approvals translate into enforcement actions domestically.

Where an AD sets a compliance obligation without specifying penalties, enforcement and consequences typically derive from the broader regulatory framework that empowers the issuing authority. That broader framework is not contained in the supplied text. Consequently, this document leaves the specific means by which the issuer will ensure or compel compliance unspecified. The AD imposes an obligation to act by a specified date; the text itself does not outline inspection, reporting, certification, or punitive steps associated with failure to comply.

Practically, affected operators and maintenance organisations must treat the AD as a mandatory direction to complete the specified modification per AIRBUS SB A330-32-3156 by 30 September 2007. The absence of stated penalties in the AD means any enforcement mechanisms, reporting requirements or disciplinary consequences, if they exist, are set out elsewhere and are not part of this document. The AD does not include an explicit right of reply, appeal or process for seeking relief within its text, nor does it offer guidance on record submission or audit modalities.

The Directive explicitly cross-references foreign regulatory instruments and manufacturer actions; it embeds those external steps as part of its applicability and compliance logic. The Requirement Note 2 states: "DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005 refers." That citation connects this AD to a French Directorate General for Civil Aviation action and to an EASA approval document by number and date. The AD thereby situates itself within a network of manufacturer and foreign authority directives, signalling that the technical remedy and regulatory evaluation have counterparts outside this jurisdiction.

The Applicability clause also establishes the conditions under which the AD does not apply: specifically, aircraft "on which AIRBUS modification 50650 has been embodied in production or AIRBUS Service Bulletin (SB) A330-32-3156 has been embodied in service" are excluded from the AD’s requirements. In regulatory terms, that means prior compliance with certain manufacturer-issued modifications or service bulletins is recognised as satisfying the safety objective of this AD. The AD does not, however, set out rules for how that prior embodiment is to be evidenced, certified or documented; the document simply states the condition.

The AD references AIRBUS SB A330-32-3156 as the mandated technical instruction. The SB operates as a delegated source of technical detail for the AD. The AD does not re-state the SB content but makes compliance explicitly dependent on following the SB. Therefore, interactions with other legal instruments include the manufacturer's technical documentation and any regulatory approvals that apply to that SB. The AD also implies that an operator’s maintenance records and parts inventories must reflect the stated part-number changes resulting from the modification.

The Directive contains no express reference to more general domestic statutes, regulations or instrument provisions that would govern the AD’s issuance, enforcement, or appeal. It likewise does not specify reporting obligations or interaction with certification documents. The only direct cross-references in the source are to AIRBUS modification 50650, AIRBUS SB A330-32-3156, DGAC AD F-2005-016 and "EASA approval 2005-499 dated 12 January 2005." The AD therefore interacts with those named instruments by treating prior embodiment of the SB or the production modification as an exclusion, and by relying on the manufacturer’s SB as the authoritative technical means of compliance.

Where the AD identifies a safety deficiency based on a recorded operational event, it situates the remedy within both manufacturer engineering (the check valve design change) and international regulatory alignment (DGAC and EASA references). The AD does not state how its requirements might affect other airworthiness approvals, type certificates or continuing-airworthiness obligations beyond the explicit modification duty. Any further interaction with domestic law or certification processes is not contained in the supplied text.

The source document provides limited material that functions as an amendment history. The AD is published under the designation "AD/A330/46 Nose Landing Gear Hydraulic Control Block 3/2005." The Requirement Note 2 states that "DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005 refers," which records a prior foreign regulatory action and an associated approval number and date. The AD is dated and signed by "James Coyne, Delegate of the Civil Aviation Safety Authority" with the signature date of 4 February 2005 and an effective date recorded as 17 March 2005.

The AD does not include prior versions of itself, rescissions, superseding text, or explicit amendments to earlier domestic ADs within the source text. It records its identification code and issue month/year (3/2005), and the DGAC/EASA references constitute the only historical linkage to prior regulatory decisions noted in the text. The tableed header repeats the AD identification several times, reinforcing its formal identification as AD/A330/46 and the subject "Nose Landing Gear Hydraulic Control Block."

Note 1 within the Requirement sets out what is effectively an irreversible parts amendment: the HCB part numbers will be redesignated following the modification, with PN C24856000-9 becoming PN C24856000-11 and PN C24856001-7 becoming PN C24856001-9. That part-number change is part of the AD’s mechanical amendment to the affected components and therefore functions as a permanent engineering amendment for those parts once the SB work is embodied.

Beyond those items, the AD includes no explicit record of iterative changes, amendments, or versions issued by the Civil Aviation Safety Authority. It provides no schedule of future revisions, nor does it document any earlier domestic AD that it replaces. The only amendment-like data present concerns the engineering change to the HCB part numbers and the cross-reference to DGAC/EASA documents dated January 2005. Any further amendment history, if it exists, is not contained in the supplied text.

The source text contains no litigation history. It records the administrative facts of issuance and effective date, and it cites a foreign AD and EASA approval, but it does not reference any legal challenges, court decisions, or judicial proceedings relating to this AD or to the underlying design change. There are no claims, case names, citations to judicial review, nor any procedural history suggesting that the AD has been subject to litigation.

Because the document does not include any legal challenges or references to court actions, there is no litigation narrative available in the source to summarise. Any lawsuits, appeals, or adjudications that may involve this AD are not recorded in the text provided. The AD therefore stands in the supplied record as an administrative safety requirement with no litigation history included.

Practitioners reviewing this AD should note the absence of litigation information in the Directive itself. If litigation history is required for risk assessment, compliance strategy, or to inform operational decisions, that information would need to be sought from external legal or administrative records not contained in this document. The AD does, however, provide identifiers and dates that would facilitate searching other records: the AD designation AD/A330/46, the service bulletin number AIRBUS SB A330-32-3156, the DGAC AD F-2005-016 reference, and the EASA approval number 2005-499 dated 12 January 2005, plus issuer and signature information ("James Coyne, Delegate of the Civil Aviation Safety Authority" dated 4 February 2005).

The Directive’s brevity hides several operational details that could trip up implementers if not carefully tracked. First, applicability is phrased inclusively ("AIRBUS A330-200 and A330-300 aircraft series, all serial numbers") but immediately carves out two specific exemptions: aircraft on which AIRBUS modification 50650 has been embodied in production, and aircraft on which AIRBUS SB A330-32-3156 has already been embodied in service. The practical effect is that an operator must verify aircraft production/modification history and maintenance records to determine whether the AD applies to a particular airframe. An operator who assumes all A330-200/-300s are in scope without checking for prior embodiment risks unnecessary work or misreporting.

Second, the AD names two precise HCB part numbers to be modified, and it also states the resulting part numbers after modification. The Requirement Note 1 establishes that PN C24856000-9 will become PN C24856000-11 and PN C24856001-7 will become PN C24856001-9. Maintenance and logistics teams must be prepared to update traceability, spares inventories, and records to reflect those PN changes. Failure to update parts records may complicate future airworthiness submissions or parts-replacement operations.

Third, compliance is required "Not later than 30 September 2007," while the AD "becomes effective on 17 March 2005" and was signed on 4 February 2005. The compliance window spans more than two years. That creates a planning consideration: operators may defer the modification to a later maintenance opportunity within the compliance window, but must ensure the work is complete by the deadline. Miscalculation of maintenance scheduling, or supply-chain delays for the check valves or associated hardware, could lead to missed deadlines.

Fourth, the AD requires that the modification be performed "in accordance with instructions given in AIRBUS SB A330-32-3156." The AD itself does not reproduce the SB. Therefore, the precise scope of work, parts, testing, possible operational limitations during the modification, or required test procedures are not in the AD text and must be obtained from AIRBUS SB A330-32-3156. Practical compliance therefore depends on obtaining and following that manufacturer documentation precisely.

Fifth, the AD references a technical failure sequence involving a "BSCU Channel 1 Fault" and a "hydraulic lock" that prevented transfer from steering to castoring mode and the nose gear returning to straight ahead. The AD’s Background describes an operational scenario at 47 kts where environmental effects, airport geometry and speed combined with the hydraulic lock to create a hazardous event. Implementers should note that the AD does not quantify the frequency of the hazard, nor does it provide operational mitigations; it mandates the engineering fix. Any interim operational risk-management measures are not described in the AD.

Sixth, the AD cross-references "DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005." Practically, affected operators operating across jurisdictions should be alert to parallel foreign airworthiness directives and approvals, but the AD does not describe how to reconcile differences or provide detailed cross-border compliance guidance. Finally, the AD contains no explicit penalty or enforcement provisions in its text; implementers should not assume enforcement mechanics or remedial processes are detailed here.

The Directive prescribes a single method of compliance: perform the modification of the specified Hydraulic Control Blocks in accordance with AIRBUS Service Bulletin A330-32-3156. The practical compliance steps, as can be extracted from the AD text, are these.

1. Identify applicability. For each A330-200 or A330-300 airframe in your fleet, determine whether it is within the AD’s scope. Check whether the HCB installed is PN C24856000-9 or PN C24856001-7. Also check whether the aircraft already embodies AIRBUS modification 50650 in production, or whether AIRBUS SB A330-32-3156 has already been embodied in service. If either of those conditions is met, the aircraft is excluded from the AD per the Applicability clause.

2. Obtain the technical instructions. The AD mandates compliance "in accordance with instructions given in AIRBUS SB A330-32-3156." Obtain a current copy of that Service Bulletin from AIRBUS and confirm any referenced parts lists, procedures, and testing steps. The AD does not reproduce the SB content. Ensure that the SB revision you use is the one accepted by your authority or as directed by the Service Bulletin itself.

3. Schedule and resource the modification. Plan to perform the modification before the compliance deadline of "Not later than 30 September 2007." Allocate maintenance man-hours, parts (including the check valve to be installed between the selector valve and the servo valve), tooling and certified personnel required to carry out the SB work. The AD does not provide an estimated labour or parts requirement; those details will be found in the SB.

4. Execute the modification per the SB. Perform the work strictly according to the SB instructions, ensuring the check valve is installed in the specified location (between selector valve and servo valve) and any associated functional checks or tests are completed. The AD indicates that the design change is to limit back pressure from torque applied to the gear during free castor ground movement and to permit the bypass valve to function nominally; carry out any SB-specified validation tests to confirm that functionality.

5. Record the change and update part numbers. After successful completion of the modification, update the aircraft’s maintenance records to reflect that PN C24856000-9 has become PN C24856000-11, and that PN C24856001-7 has become PN C24856001-9, as set out in Note 1 of the Requirement. Update spares inventory records so that the new PN designations are used for future parts procurement and traceability.

6. Evidence compliance. Keep the SB implementation records as the evidence that the AD has been complied with for each aircraft. Although the AD does not specify the format for compliance evidence or to whom proof must be submitted, retain detailed records of the work order, parts used (with serial numbers where applicable), sign-off by the authorised maintenance staff, and test results that confirm the modification’s correct operation.

7. Consider coordination with other regulators and documentation. The AD references DGAC AD F-2005-016 and "EASA approval 2005-499 dated 12 January 2005." If the operator manages aircraft across jurisdictions, ensure that the SB embodiment and AD compliance are recorded in the aircraft’s continuing airworthiness records in a way acceptable to each regulator. The AD itself does not prescribe cross-jurisdictional administrative steps.

8. Monitor for manufacturer or regulator follow-ups. Although this AD does not contain a stated mechanism for amendments, stay alert to any subsequent AIRBUS service bulletins, DGAC or EASA communications (the AD cites those instruments) that might change the method of compliance or identify related corrections. Any additional modifications that become necessary would likely be published through the manufacturer or airworthiness authority channels.

9. Verify no further action where SB already embodied. If an aircraft already has AIRBUS SB A330-32-3156 embodied in service, or was produced with AIRBUS modification 50650, document that fact and record it as the basis for declaring the AD not applicable to that particular aircraft. Maintain clear documentary proof demonstrating that the SB was embodied prior to the AD’s compliance date if relying on that condition.

10. Timetable compliance to avoid deadline exposure. Although the AD sets a generous compliance window extending to 30 September 2007, supply constraints, maintenance booking backlogs, or parts lead times could impede timely completion. Plan early enough to complete the work well before the deadline and avoid last-minute operational disruption.

The above steps are constrained to the content of the AD. The AD does not set out precise test procedures, man-hour estimates, parts lists, or reporting formats; those belong in AIRBUS SB A330-32-3156. The AD requires adherence to that SB and to the compliance timetable and requires updating of part numbers in maintenance records as specified.