AD/DAUPHIN/78 - Main Gearbox Bottom Plate

The instrument advances three interlocking technical concepts that determine compliance: the inspection mandate and method, the timing regime for inspections, and the removal requirement on detection of cracks. Each concept is anchored to specific text in the AD.

First, inspection methodology. The AD does not prescribe a bespoke inspection technique in its own text but instead mandates carrying out the inspection “in accordance with paragraph 2.B. of EUROCOPTER SA 360/365 Alert Service Bulletin No. 05.25 or later DGAC approved revisions” (Requirement, para 1). That cross-reference makes the manufacturer’s service bulletin the normative source for inspection procedures, limits, and any illustrative details. The AD also acknowledges the DGAC/EASA approval pathway for that service bulletin (Requirement, Note 1), making the DGAC-approved revision the acceptable standard.

Second, the timing regime. The AD sets four distinct timing categories that apply depending on the MGB’s overhaul/repair history and logged cycles (Compliance, para 1(a)-(d)). They are:

• For MGBs never overhauled or repaired and with less than 26,900 cycles: inspect at the latest at 26,900 cycles, then every 55 flying hours.
• For MGBs never overhauled or repaired and with 26,900 cycles or more: inspect at the latest at the ALF-check from the AD effective date, then every 55 flying hours.
• For newly overhauled or newly repaired MGBs: inspect at the latest at the ALF-check from the effective date, then every 55 flying hours.
• For MGBs held as spares: comply with the relevant timing (1(a), 1(b) or 1(c)) before installation.

The directive therefore mixes a cycle-based threshold (26,900 cycles) with an operational, time-based repetitive interval (55 flying hours) and uses the ALF-check as a required event for certain initial inspections.

Third, the removal requirement. Where inspection reveals any crack in the MGB bottom plate, the AD requires removal of the MGB “before further flight” (Requirement, para 2). The AD also explains a practical complication: the MGB bottom plate is not subject to follow-up in service, so tracking the specific cycles of that component is not possible when the plate may have been replaced on overhaul or repair (Compliance, Note 2). This creates a record-keeping and traceability issue that directly connects to the timing regime described above.

The background statement provides the hazard rationale: detection of a crack in the web of an MGB bottom plate that ran to the inside of the plate and on to the MGB casing, with potential to interrupt rotor torque-to-structure transmission if allowed to grow (Background). The AD therefore links a discrete detected failure mode to a mandated inspection and removal regime.

Normatively, the AD delegates detailed inspection procedures to the manufacturer service bulletin and asserts DGAC/EASA approval as the conformity path (Requirement). It imposes immediate operational constraints through the “before further flight” removal instruction and sets periodic inspection burdens through the 55 flying-hour interval. The AD’s design therefore distributes technical certainty (inspection method) to the manufacturer bulletin, operational cadence to the AD text, and authority confirmation to DGAC/EASA reference.

The AD expressly applies to operators, owners, maintainers and spare-part holders of EUROCOPTER SA 360 C and SA 365 C, C1, C2, and C3 helicopters (Applicability). Those parties include commercial and private helicopter operators that fly the listed types, maintenance organisations that perform inspections and overhauls, and entities that hold MGBs as spare components for installation.

Operationally, the text creates three distinct actor roles:

• Aircraft operators and owners. They must ensure the inspection occurs per the specified intervals and that, if cracks are found, the MGB is removed before further flight (Requirement; Compliance paras 1-2). The operator will therefore bear the operational costs of arranging inspections, scheduling ALF-check inspections, and managing aircraft downtime while inspections and any required removals or repairs occur.

• Maintenance and repair organisations. The AD mandates use of EUROCOPTER Alert Service Bulletin No. 05.25 paragraph 2.B. or later DGAC approved revisions for inspection technique (Requirement, para 1). Maintenance organisations will therefore need access to that service bulletin and any DGAC-approved revisions, and must be competent to carry out the mandated inspections and removals. If the MGB bottom plate is not subject to follow-up in service, maintainers must grapple with potential lack of component-specific cycle-traceability when a plate has been replaced on overhaul or repair (Compliance, Note 2).

• Spare-part holders and resellers. The AD requires that MGBs held as spares be inspected at the intervals specified in paragraphs 1(a)-(c) “before installation in a helicopter” (Compliance, para 1(d)). This places a pre-installation compliance obligation on whoever installs or supplies spares, and it shifts inspection timing from post-installation to pre-installation for spare MGBs.

The AD’s reference to DGAC approval and an EASA reference (Requirement, Note 1) indicates that the directive interacts with approvals issued by foreign aviation authorities and the manufacturer’s service bulletins as incorporated documents. The signature block shows a CASA delegate issued the AD (Delegate of the Civil Aviation Safety Authority; signature date 21 February 2005) and the AD became effective 23 February 2005. Those facts identify the Australian regulator as the issuing authority and the effective date as the regulatory trigger for compliance.

The AD does not create exemptions, appeal procedures, or penalty schedules in its text. Any party that wishes to challenge the AD or seek alternative compliance would need to look beyond the AD text to CASA procedural rules or applicable aviation regulation frameworks; those are not contained in the AD itself. The AD therefore directly binds operators, maintainers and spare holders of the listed helicopter models to the inspection and removal regime that it prescribes.

The AD imposes explicit duties on operators, maintainers and spare holders; it does not articulate statutory rights, remedies, or alternative compliance pathways in the text. The principal duties are as follows.

Inspection duty. Operators must inspect the MGB bottom plate for cracks “in accordance with paragraph 2.B. of EUROCOPTER SA 360/365 Alert Service Bulletin No. 05.25 or later DGAC approved revisions” (Requirement, para 1). That places a substantive duty to follow the manufacturer’s prescribed inspection procedure as the normative method. The AD also links to DGAC/EASA approvals (Requirement, Note 1), which conditions acceptable revisions of the service bulletin on regulatory approval.

Timing duty. The AD specifies inspection timing by four categories (Compliance, para 1(a)-(d)). For MGBs that have never been overhauled or repaired and have logged fewer than 26,900 cycles, the inspection is required "at the latest at 26,900 cycles", then at intervals of no more than 55 flying hours. For MGBs that have never been overhauled or repaired and have logged 26,900 cycles or more, the inspection is required "at the latest at the ALF-check" from the AD effective date, then at intervals not more than 55 flying hours. Newly overhauled or newly repaired MGBs must be inspected at the latest at the ALF-check as from the AD effective date, then at intervals of no more than 55 flying hours. MGBs held as spares must be inspected according to the applicable interval before installation. The AD therefore creates a duty tied to component history and cycle thresholds and imposes a uniform repetitive inspection cadence of 55 flying hours after initial compliance.

Removal duty. Where any crack is found, the AD requires removal of the MGB “before further flight” (Requirement, para 2). That is an immediate operational constraint that compels grounding the helicopter pending a remove-and-repair/replace action.

Documentation and reference duty. The AD requires use of the specific paragraph of the manufacturer’s service bulletin and allows later DGAC-approved revisions; this creates a duty to source and use the approved version of the bulletin. Note 1 explicitly ties the directive to DGAC N° UF-2005-036 approved under EASA reference No 2005-1825 dated 17 February 2005, indicating a duty to acknowledge and follow the approved document trail (Requirement, Note 1).

Rights and omissions. The AD text does not set out any rights such as appeal, temporary exemptions, or permitted deviations. It also does not set out enforcement or penalty provisions. The signatory and effective date are stated, but no process for seeking alternative methods of compliance is included in the AD text itself. Parties seeking to establish rights, exemptions, or alternative compliance measures would need to locate those mechanisms, if any, in CASA’s broader regulatory framework; the AD does not specify them.

Operational consequence. The duties interact to produce predictable operational effects: inspection scheduling, potential removal and replacement of MGBs, and pre-installation inspection obligations for spares. The AD also notes a traceability limitation for the MGB bottom plate because the component is not subject to follow-up in service; this affects how the duties operate in practice when plates have been replaced during overhaul or repair (Compliance, Note 2).

The AD text furnishes limited explicit information about enforcement and contains no express penalty provisions. It does, however, express authority and an effective date that create enforceable obligations under the issuing regulator’s broader powers.

Issuing authority and effective date. The AD carries the signature block of a CASA delegate and states that the AD “becomes effective on 23 February 2005” (effective date; signature block). That indicates the directive is an instrument issued under the regulator’s authority and establishes an operational start date. The AD’s formal issuance and effective date create a compliance trigger for the affected community.

Absence of penalty language. The text does not specify criminal, civil or administrative penalties for non-compliance, nor does it articulate enforcement procedures such as inspections by regulator staff, mandatory reporting of defects, or timelines for correction. The lack of explicit penalty text in the AD means that the AD itself does not state the sanctions that will attach to failure to comply.

Enforcement implication. Even though the AD does not specify penalties, the directive’s status as an airworthiness directive issued by the national regulator typically implies that compliance is mandatory under the regulator’s statutory regime. The AD’s requirement that inspections be performed in accordance with a specified manufacturer service bulletin and that removal occur “before further flight” where cracks are found establishes mandatory operational requirements for the affected aircraft. Parties should therefore treat the AD as creating binding safety obligations from the effective date, even though the AD text does not spell out enforcement mechanisms or penalties.

Reference to other authorities. The AD incorporates DGAC-approved revisions and an EASA reference (Requirement, Note 1). That conditionality situates the AD within a wider web of safety approvals and suggests that enforcement and conformity are likely to be assessed against the AD plus the referenced DGAC/EASA-approved service bulletin. The AD does not itself state how compliance will be audited or enforced, nor does it provide an administrative path for demonstrating alternative compliance.

Practical enforcement risk. Because the AD requires immediate removal prior to further flight where cracks are detected, the practical enforcement consequence of a detected crack is de facto grounding until removal and remedial action occur. The AD therefore imposes an operational enforcement effect through its technical prescription even though it does not specify sanctions.

In short, the AD provides the issuing authority and an effective date but does not set out penalties or enforcement mechanisms within its text. Parties must therefore refer to the broader regulatory regime of the Civil Aviation Safety Authority and associated enforcement procedures to understand sanctions for non-compliance; those procedures are not present in the AD itself.

The AD primarily interacts with technical, regulatory and approval instruments rather than enumerating specific statutes in its text. The explicit cross-references in the AD show the interaction points.

Reference to manufacturer service bulletin. The AD mandates inspections “in accordance with paragraph 2.B. of EUROCOPTER SA 360/365 Alert Service Bulletin No. 05.25 or later DGAC approved revisions” (Requirement, para 1). By making the service bulletin the operative inspection methodology, the AD ties regulatory compliance to a manufacturer’s technical document and to any later revisions that have received DGAC approval. That creates an interaction between regulator-issued ADs and manufacturer-prescribed inspection standards.

DGAC and EASA approvals. The AD notes DGAC N° UF-2005-036 approved under EASA reference No 2005-1825 dated 17 February 2005 (Requirement, Note 1). That reference indicates that the AD is aligned with approvals issued by foreign authorities and the European Aviation Safety Agency. The AD therefore sits in a network of international airworthiness approvals, relying on foreign authority approvals of service bulletin revisions as the measure of acceptability for changes to inspection technique. In practical terms, compliance with the AD requires adherence to documents that may themselves be regulated by or approved under foreign aviation authorities.

Component service-follow-up. The AD expressly states the MGB bottom plate “is a component that is not subject to follow-up in service” and that it is not possible to follow up the specific cycles of this component on MGBs where the plate may have been replaced upon overhaul or repair (Compliance, Note 2). That statement interacts with record-keeping, maintenance release and traceability obligations operators and maintainers may have under civil aviation maintenance regulations. The AD thereby imposes a practical constraint on applying cycle-based compliance rules when component-specific cycle records do not exist.

Operational checks. The AD uses “ALF-check” (the check after the last flight of the day) as a reference event for certain inspections (Compliance paras 1(b)-(c)). ALF-checks are standard maintenance events; the AD therefore links its inspection timing to established maintenance checkpoints.

Absence of express statutory cross-reference. The AD does not itself cite primary legislation or specific domestic regulatory provisions (for example, Civil Aviation Safety Regulations or Acts). The issuing authority is identified as the Civil Aviation Safety Authority delegate, but the AD does not enumerate the statutory powers being exercised in the text. Parties therefore must infer that the AD is issued under CASA’s statutory powers and enforceable under the broader statutory scheme; those powers and enforcement provisions are not included in the AD text.

In summary, the AD interacts with manufacturer service bulletins as the procedural standard, relies on DGAC/EASA approvals for accepted revisions, and introduces practical interactions with component traceability and maintenance record regimes by noting the lack of follow-up applicability for the MGB bottom plate. Any legal questions about authority, enforcement or available remedies would require reference to CASA’s enabling legislation and regulatory framework, which the AD itself does not reproduce.

The AD text provides limited material relevant to amendment history. The document as supplied indicates a single AD issuance with an effective date and an explicit linkage to a DGAC approval; it does not set out prior versions, subsequent amendments, extensions, supersessions or revocations. The concrete items in the text relevant to amendment history are:

• Effective date. The AD “becomes effective on 23 February 2005” and is signed by a CASA delegate dated 21 February 2005. That establishes the start of the AD’s applicability (effective date; signature block).

• Reference to service bulletin revisions. The AD requires compliance “in accordance with paragraph 2.B. of EUROCOPTER SA 360/365 Alert Service Bulletin No. 05.25 or later DGAC approved revisions” (Requirement, para 1). The insertion of “or later DGAC approved revisions” creates an internal mechanism for the AD to accommodate future revisions of the referenced service bulletin that receive DGAC approval, but it does not itself constitute an amendment to the AD text. Instead, it acknowledges that later DGAC-approved revisions of the service bulletin will be acceptable for meeting the AD’s inspection methodology requirement.

• DGAC/EASA approval reference. The AD cites DGAC N° UF-2005-036 approved under EASA reference No 2005-1825 dated 17 February 2005 (Requirement, Note 1). That cross-reference documents the approval basis for the service bulletin at the time of the AD’s issuance.

• Absence of subsequent amendments in the text. The AD document as provided does not contain any marked amendments, revision history entries, corrigenda, or notices of supersession. It presents itself as the operative AD with the effective date stated, without recording any later changes.

Because no amendment history beyond the single issuance and the service bulletin approval reference is included in the text, a reader seeking to know whether the AD has been amended, superseded, or rescinded must consult CASA’s official records or subsequent published ADs outside the text supplied. The AD’s incorporation of later DGAC-approved revisions of the service bulletin does mean compliance can be achieved by following later approved bulletin revisions, but that permissive language addresses inspection methods rather than changing the AD’s own prescriptive requirements or intervals.

Therefore, the AD’s explicit amendment-centric content is limited to its effective date and its openness to later DGAC-approved revisions of the referenced service bulletin; it contains no internal amendment log or subsequent revision statements.

The AD document supplied contains no litigation history, case citations, references to judicial review, or records of legal challenges. The text is a single regulatory instrument: it states applicability, prescribes requirements, specifies compliance intervals, notes DGAC/EASA approval references, and gives an effective date and signing delegate. It does not mention court proceedings, administrative appeals, or disputes arising from the AD’s content or enforcement.

Accordingly, within the four corners of the AD as supplied:

• There are no named cases, judgments, or appeals recorded against the AD.
• There is no mention of parties seeking judicial review, injunctions, or declarations in response to this AD.
• There is no record of contested enforcement action or disciplinary proceedings related to compliance with this AD.

If a practitioner needs to establish whether litigation has occurred in relation to AD/DAUPHIN/78, or whether disputes arose around implementation, enforcement, or interpretation, they will need to consult court records, administrative tribunal records, or CASA archives beyond the AD text itself. The AD as provided does not supply any litigation foothold or precedent to cite.

Given the AD references DGAC and EASA approvals, any cross-border legal interactions that might have produced litigation (for instance, disputes over the content of the EUROCOPTER service bulletin or the scope of DGAC/EASA approvals) are not documented here. The AD also does not purport to summarise any challenged operational consequences, nor to document indemnities, claims or commercial disputes arising from removal and replacement costs.

In short, the supplied AD contains no litigation history. Readers requiring litigation context must seek external legal databases, regulator records or case law repositories for proceedings relating to this directive or the referenced service bulletin.

The AD’s text contains a number of operational and compliance pitfalls that are explicit or follow logically from the AD’s provisions. These are practical areas where confusion or unexpected costs can arise.

Traceability of the MGB bottom plate. The AD explicitly warns that the MGB bottom plate “is a component that is not subject to follow-up in service” and that it may not be possible to track the specific cycles of this component where the plate has been replaced on overhaul or repair (Compliance, Note 2). This creates a gotcha for operators relying on component-level cycle records to determine which compliance timing bucket applies. If plate-specific cycles are not recorded, an operator may have to treat the MGB as if it falls into the more conservative timing category, or otherwise manage uncertainty about when the mandated inspection must occur.

Cycle threshold versus flying hours. The AD mixes cycle-based thresholds (26,900 cycles) with a flying-hours repetitive interval (55 flying hours) and the ALF-check as an inspection event (Compliance, paras 1(a)-(c)). A gotcha is that operators must map cycles to operational records that may separately record running hours, cycles, and daily ALF checks. The operator must ensure accurate reconciliation between cycles and the AD’s thresholds, particularly where component traceability is incomplete.

Spare MGB handling. The AD requires that MGBs held as spares be inspected “at the intervals specified in compliance paragraph 1(a) or 1(b) or 1(c) as is applicable, before installation in a helicopter” (Compliance, para 1(d)). A potential pitfall is supply-chain timing: a spare part stored in inventory may not have a clear cycle or overhaul history, so the party installing the spare must determine which timing category applies and perform required inspections before installation, potentially delaying return-to-service.

Use of alert service bulletin revisions. The AD mandates inspection per paragraph 2.B. of EUROCOPTER Alert Service Bulletin No. 05.25 or later DGAC approved revisions (Requirement, para 1). Operators and maintainers must ensure they are using the version that has DGAC approval. Using an unapproved revision of the service bulletin could fail to meet the AD’s specification. The AD’s Note 1 references DGAC N° UF-2005-036 approved under EASA reference No 2005-1825 (Requirement, Note 1), which provides the approval trail but requires operators to obtain the correct approved revision.

Immediate grounding on detection. The directive requires removal of the MGB “before further flight” where any crack is found (Requirement, para 2). That is an immediate operational constraint; discovery of a crack will effectively ground the aircraft until removal and remedial action are completed. Operators should plan for potential unscheduled downtime.

No penalty or appeal language in the AD. The AD does not set out enforcement procedures or remedies; it simply states the requirements and effective date. Parties must therefore be cautious: the absence of explicit enforcement language does not mean compliance is optional. The issuing authority is a CASA delegate and the AD is effective from a stated date (effective date; signature block). Parties should assume mandatory compliance and consult broader regulatory frameworks for enforcement details.

Ambiguity over ALF-check timing. The AD invokes “the ALF-check (check after the last flight of the day)” for initial inspections in some categories (Compliance, paras 1(b), 1(c)). Operators must ensure their ALF-check procedure is performed on schedule and that the inspection required by the AD is integrated into that event; failure to align ALF-check scheduling with the AD could create inadvertent non-compliance.

In summary, key gotchas emerge around traceability of the MGB bottom plate, reconciling cycles and hours, ensuring the correct DGAC-approved service bulletin revision is used, pre-installation inspection obligations for spares, and the immediate grounding effect of detecting a crack. These are concrete operational risks embedded in the AD text.

The AD sets clear, documentable steps for compliance. Below is a practical compliance checklist derived directly from the AD text, including the mandated inspection method, the timing regimes and the action required on detection of cracks.

1. Confirm applicability. Verify that the helicopter is a EUROCOPTER SA 360 C or SA 365 C, C1, C2 or C3 model (Applicability). If yes, the AD applies.

2. Obtain the mandated inspection procedure. Acquire EUROCOPTER SA 360/365 Alert Service Bulletin No. 05.25 and identify paragraph 2.B. Use that paragraph as the procedural standard for inspecting the MGB bottom plate, or use a later DGAC-approved revision of the same bulletin (Requirement, para 1). Also note DGAC N° UF-2005-036 under EASA reference No 2005-1825 dated 17 February 2005 for the approval trail (Requirement, Note 1).

3. Determine the MGB’s status and history. Classify each MGB as one of the following: (a) never overhauled or repaired and under 26,900 cycles; (b) never overhauled or repaired and 26,900 cycles or more; (c) newly overhauled or newly repaired; or (d) being held as a spare (Compliance, para 1(a)-(d)). If plate-specific cycle records are missing, account for the AD’s Note that the MGB bottom plate is not subject to follow-up in service (Note 2); in such cases adopt a conservative approach consistent with the AD’s timing language.

4. Schedule and perform the initial inspection. For each MGB:

   • If (a): inspect at the latest by 26,900 cycles, then at intervals not more than 55 flying hours.
   • If (b): inspect at the latest at the ALF-check as from the AD effective date, then at intervals not more than 55 flying hours.
   • If (c): inspect at the latest at the ALF-check as from the AD effective date, then at intervals not more than 55 flying hours.
   • If (d) spare: perform the applicable inspection specified in 1(a), 1(b) or 1(c) before installation. (Compliance, para 1(a)-(d))

5. Use correct inspection methodology. Ensure the inspection follows paragraph 2.B. of Eurocopter Alert Service Bulletin No. 05.25 or the later DGAC-approved revision; record which version was used and its approval status (Requirement, para 1; Note 1).

6. Inspect for cracks. Conduct the inspection to detect any cracks in the MGB bottom plate per the referenced service bulletin method (Requirement, para 1).

7. Act on findings. If any crack is found in the MGB bottom plate, remove the MGB before further flight (Requirement, para 2). Arrange for repair, overhaul, or replacement in accordance with approved procedures and the operator’s maintenance programme.

8. For spares and inventory. Before installing an MGB from spares, ensure it has undergone the applicable inspection identified in step 4. Do not install a spare MGB that has not been brought into compliance with the relevant inspection interval (Compliance, para 1(d)).

9. Integrate into maintenance schedule. Incorporate the 55 flying-hour repetitive interval into the aircraft’s maintenance scheduling process so that inspections occur at no more than every 55 flying hours. For categories tied to ALF-checks, include the AD inspection in the ALF-check workflow (Compliance, paras 1(a)-(c)).

10. Record-keeping and traceability. Although the AD does not specify documentary requirements, operators and maintainers should maintain records demonstrating the MGB’s category, inspection dates, the version of the service bulletin used (and its DGAC approval), findings, and corrective actions taken, because the AD’s requirements include event-based obligations (ALF-check) and thresholds tied to cycles and flying hours. The AD warns that the MGB bottom plate is not subject to follow-up in service, which affects traceability where plates have been replaced (Compliance, Note 2). Keeping clear documentation will assist in applying the AD’s timing rules.

11. Respond to uncertainty about cycles. If component-specific cycles for the bottom plate are unavailable, identify the MGB’s overhaul/repair history and use the AD’s categories to determine the applicable inspection timing. If necessary, consult the manufacturer’s documentation and the DGAC-approved bulletin for guidance on conservative application where records are incomplete.

12. Liaise with regulator and manufacturer where necessary. If there is uncertainty about interpretation of the service bulletin paragraph 2.B., version approvals, or how to treat particular component histories, seek clarification from CASA or use the manufacturer’s support channels referenced in the Eurocopter service bulletin. The AD itself allows later DGAC-approved revisions of the bulletin to be used (Requirement, para 1).

Following these steps will place the operator or maintainer in alignment with the AD requirements as stated: performing inspections per the manufacturer service bulletin, applying the AD’s timing regime according to the MGB’s history, removing any MGB with detected cracks before further flight, and ensuring spares are inspected before installation. The AD’s effective date is 23 February 2005, so initial compliance obligations tied to the effective date should be calculated with that date in mind.