AD/DAUPHIN/46 Amdt 2 - Main Rotor Gearbox Suspension Diagonal Cross-Member

This Civil Aviation Safety Authority Airworthiness Directive (AD/DAUPHIN/46 Amdt 2, dated 7/2007, effective 5 July 2007) requires inspections and mandatory corrective action for the main rotor gearbox suspension diagonal cross-member on specified Eurocopter (Dauphin) helicopters. The directive applies to AS 365 N, N1, and N2 model helicopters that are equipped with main rotor gearbox suspension diagonal cross-members, part numbers 365A38-3023-20, -21, -22, -23 and -24 (Applicability). It directs operators to carry out the action specified in paragraph 2.B of Eurocopter AS 365 N Alert Service Bulletin No. 05.00.37 Revision 2, or any later EASA approved revision (Requirement).

Operationally, the AD mandates an initial non-destructive check of the centre portion of the diagonal cross-member at specified flight-cycle thresholds and within a short flight-hours/flight-cycles grace window for those already beyond the thresholds, and then recurrent checks at fixed short intervals thereafter (Compliance). If a crack is detected during an inspection, the AD requires removal and replacement of the diagonal brace cross-member before further flight in accordance with paragraph 2.B.3.a of the Eurocopter Requirement document. If complete failure of the diagonal cross-member is detected, the AD requires removal and replacement and the performance of additional checks before further flight, as described in paragraph 2.B.3.b (Requirement; note that the AD explicitly refers to EASA AD 2007-0129).

The AD amends earlier directions: Amendment 1 had previously altered compliance times; Amendment 2 (this document) adopts checks prompted by the referenced EASA AD to address requirements when complete failure occurs (Background). The directive is signed by a CASA delegate and dated 16 May 2007, with the stated effective date 5 July 2007 (signed material).

The AD is structured around a set of concrete maintenance-management concepts: applicability by model and part number, a service-bulletin-driven inspection and rectification requirement, defined compliance triggers based on flight cycles and flight hours, recurrence intervals, and specific mandatory corrective actions tied to inspection findings.

Applicability: Only AS 365 N, N1 and N2 helicopters fitted with cross-members with the listed part numbers are covered (Applicability). The AD thus targets specific airframes and specific components installed on those airframes; applicability is not universal across all Dauphin models.

Service-bulletin incorporation: The AD does not itself set out detailed inspection steps in text; rather it mandates action "in accordance with paragraph 2.B of Eurocopter AS 365 N Alert Service Bulletin No. 05.00.37 Revision 2, or later EASA approved revision" (Requirement). That means the detailed technical steps, inspection techniques, acceptance criteria, and replacement instructions are to be taken from the manufacturer's Alert Service Bulletin (ASB) as approved by EASA.

Triggering criteria and timing: The initial inspection is required either upon accumulation of a specified number of flight cycles (15,000 for AS 365 N and N1; 11,000 for AS 365 N2) or, for cross-members that already have exceeded those cycle thresholds, within a short retrospective window: within 50 flight hours or 250 flight cycles after 16 July 2003, whichever occurs first (Compliance 1). After the initial inspection, repeat inspections are required at intervals "not to exceed 50 flight hours or 250 flight cycles, whichever occurs first" (Compliance 2). The AD states that "the compliance times remain unchanged by this issue of the Directive" indicating that Amendment 2 is not altering those stated intervals (Compliance).

Mandatory corrective action: Inspection findings determine immediate mandatory steps. If a crack is detected, the cross-member must be removed and replaced before further flight following the ASB paragraph 2.B.3.a. If a complete failure is detected, removal and replacement together with additional checks per 2.B.3.b are required before further flight (Requirement). The AD therefore creates an obligation to take the aircraft out of service until the required removal/replacement and checks are completed when those defect findings occur.

Reference to other regulatory material: The AD explicitly refers to EASA AD 2007-0129 and makes the ASB effective only in its EASA-approved revision; Amendment 2 was issued "in response to a new EASA AD, which introduces certain check requirements when complete failure of the diagonal cross-member occurs" (Background). The AD therefore functions as a national implementation that follows EASA-prescribed content.

The directive affects the owners, operators, maintenance organisations, maintenance engineers, and airworthiness managers of Eurocopter AS 365 N, N1 and N2 helicopters that have the listed diagonal cross-member part numbers installed. Applicability is explicitly limited to helicopters "equipped with main rotor gearbox suspension diagonal cross-members, part number 365A38-3023-20, -21, -22, -23, and -24" (Applicability). If a particular AS 365 N/N1/N2 airframe does not have one of those part-numbered cross-members installed, the AD does not apply to that airframe under the terms stated.

Who pays: The AD text does not assign funding. Operationally within the aviation maintenance context, the likely budget holders are the operators or aircraft owners who must arrange inspection, removal, replacement and any associated checks. The AD requires physical work and possible part replacement, and contains a "before further flight" obligation if faults are discovered, which creates direct operational costs in the form of part procurement, labour, and aircraft downtime. The AD itself does not specify who pays but it creates obligations that typically fall on the operator as the entity responsible for continuing airworthiness.

Who decides: The AD requires action "in accordance with paragraph 2.B of Eurocopter AS 365 N Alert Service Bulletin No. 05.00.37 Revision 2, or later EASA approved revision" (Requirement). That places decision-making about detailed inspection technique and acceptance criteria in the hands of the manufacturer and EASA through the ASB and any approved revisions, with CASA enforcing compliance domestically. Maintenance organisations and licensed engineers decide when and how to perform the mandated steps in line with the ASB and the AD.

Who enforces: The directive is issued by the Civil Aviation Safety Authority and signed by its delegate (David Punshon). The document itself functions as a regulatory instrument ordering particular maintenance actions; the AD gives operators no discretion to ignore the required inspections and corrective actions for aircraft within applicability.

Operational impacts on flights: The AD creates immediate operational constraints when defects are found. Both a detected crack and a detected complete failure trigger "before further flight" removal and replacement obligations (Requirement), which require the operator to ground the aircraft until compliant action has been completed. The AD therefore has direct effects on availability and scheduling for affected helicopters.

Who must track compliance: Because the compliance schedule depends on elapsed flight cycles and on flight hours for the retrospective window, operators and maintenance record-keepers must track flight cycles and flight hours for the specific cross-member fitted to each aircraft to determine when inspections are due (Compliance).

Mandatory duties

• Inspect per ASB: The central duty is to perform the inspection(s) of the centre portion of the main rotor gearbox diagonal cross-member "in accordance with paragraph 2.B of Eurocopter AS 365 N Alert Service Bulletin No. 05.00.37 Revision 2, or later EASA approved revision" (Requirement). The AD therefore imposes a duty to follow the ASB method and criteria as EASA approved.

• Timing obligations: Operators must perform an initial check at specified flight-cycle thresholds,upon accumulation of 15,000 flight cycles for AS 365 N and N1, and upon accumulation of 11,000 flight cycles for AS 365 N2,or, for cross-members already beyond those thresholds, within 50 flight hours or 250 flight cycles after 16 July 2003, whichever occurs first. After the initial check, inspections must be repeated at intervals not exceeding 50 flight hours or 250 flight cycles, whichever occurs first (Compliance 1 and 2). The AD states that these compliance times are unchanged by this Amendment (Compliance).

• Corrective actions tied to findings: If a crack is detected in the cross-member, the AD imposes a duty to "remove and replace the diagonal brace cross-member" before further flight, following the ASB paragraph 2.B.3.a. If a complete failure is detected, the AD imposes the duty to remove and replace the cross-member and to "perform the checks in accordance with paragraph 2.B.3.b of the Requirement document" before further flight (Requirement). The "before further flight" language creates a strict temporal duty: operations must not resume until the mandated work is completed.

• Use of approved revisions: The AD requires adherence to the specified ASB revision or later EASA-approved revisions, thereby limiting operators to EASA-approved technical content (Requirement).

Implied duties and administrative obligations

• Recordkeeping and tracking: The compliance regime is predicated on accurate tracking of flight cycles and hours for the relevant cross-member. The AD therefore implicitly imposes a duty on operators to maintain or consult airframe/component records to determine when initial and recurrent inspections are due (Compliance).

• Application to specific part numbers: The duty is limited to aircraft with the listed part numbers for the diagonal cross-member. Operators with other part numbers are not required by this AD unless the cross-member installed matches the listed numbers (Applicability).

Textual scope of enforcement information

• The AD itself contains mandatory instructions and an effective date; it is signed by a CASA delegate and made effective on 5 July 2007 (footer and Effective date). The document however does not set out specific monetary penalties, criminal offences, or administrative sanction provisions within its text.

How enforcement is framed by the AD’s wording

• The AD phrases the corrective actions as mandatory requirements (for example, "If a crack is detected, before further flight, remove and replace the diagonal brace cross-member" and similarly for complete failure) and sets out explicit compliance times (Requirement; Compliance). The "before further flight" language operates as a compliance trigger with immediate operational consequences since an aircraft cannot be flown further until the required work is completed.

What the AD implies about regulatory enforcement

• The AD is issued by the Civil Aviation Safety Authority and is presented as an airworthiness directive; within standard aviation regulatory frameworks, ADs are binding on operators for continuing airworthiness. The AD text itself does not narrate enforcement mechanisms, such as administrative fines or certificate action, but being a formal CASA directive implies that regulatory oversight bodies will expect compliance and may take administrative or enforcement steps under their broader regulatory powers where non-compliance is identified. The AD text does not specify those powers.

Operational enforcement mechanics stated or implied by the AD

• Immediate grounding obligation for defective findings: The AD explicitly requires corrective action "before further flight" in the event of finding a crack or complete failure. That requirement implies that an aircraft with such findings cannot be legally flown until the mandated replacement and checks have been carried out.

• Dependence on EASA-approved ASB: The AD binds operators to perform actions consistent with the specified ASB revision or later EASA-approved revisions. Enforcement therefore includes checking whether the appropriate ASB revision was applied.

Limitations in the AD text about penalties

• No express penalty schedule: There is no explicit schedule of penalties, infringement notices, or criminal sanctions set out within the AD. For specific enforcement measures and penalties, operators would need to consult CASA's general regulatory framework and the Civil Aviation Act and associated civil penalty provisions, which are not reproduced in this AD text.

Direct cross-references within the AD

• Reference to EASA AD and ASB: The AD explicitly refers to EASA AD 2007-0129 and requires action in accordance with Eurocopter ASB No. 05.00.37 Revision 2, or later EASA approved revision (Requirement; Background). This creates a legal and operational relationship between the CASA AD and EASA documents, with the AD effectively importing technical content from an ASB and EASA AD into the national regulatory requirement.

Interaction with continuing airworthiness obligations

• The AD prescribes actions that are part of continuing airworthiness obligations for the applicable airframes. Those obligations are typically governed by domestic aviation safety law; although the AD text does not restate the domestic statutes, it functions within that regulatory architecture by issuing a mandatory safety directive to address a specific component defect.

Implications for certification and approvals

• The AD binds operators to comply with EASA-approved revisions of the manufacturer’s ASB. That suggests that certifications and approvals that require compliance with ADs will need to be reconciled with the ASB content as approved by EASA. The AD does not itself alter type certificates or other approvals, but non-compliance with the AD could be material to the airworthiness status of the helicopter under national rules.

Potential interactions not specified in the AD text

• The AD does not specify interaction with insurance, leasing contracts, maintenance agreements, air operator certificates, or export/import controls. However, compliance or non-compliance with an AD commonly intersects with those contractual and administrative regimes. The AD text itself does not describe those interactions.

Temporal interactions and retrospective checks

• The compliance provision treats cross-members that have already logged more than the threshold flight cycles differently by requiring an initial check "within 50 flight hours or 250 flight cycles after 16 July 2003, whichever occurs first" (Compliance 1.b). This establishes a retrospective compliance window tied to a calendar date and suggests that even historical operations are brought within the AD’s regime for initial inspection. That date-based instruction interacts with operators’ historical maintenance/flight records, which must be consulted to determine whether the retrospective window applies.

Amendment numbering and purpose

• The directive is titled "AD/DAUPHIN/46 Amdt 2" indicating it is the second amendment to AD/DAUPHIN/46. The AD text states that "Amendment 1 introduced changes to compliance times" and that "Amendment 2 is issued in response to a new EASA AD, which introduces certain check requirements when complete failure of the diagonal cross-member occurs" (Background). Thus the documented amendment history in the AD is: original AD/DAUPHIN/46, then Amendment 1 (which altered compliance times), and then this Amendment 2 (which implements EASA-driven additional check requirements related to complete failure).

Dates in the document

• The AD as shown is dated 7/2007 and the signature block shows David Punshon, Delegate of the Civil Aviation Safety Authority, dated 16 May 2007. The AD states that "This Amendment becomes effective on 5 July 2007" (Compliance section). The AD also contains a retrospective compliance reference to 16 July 2003 for cross-members already beyond the threshold cycles (Compliance 1.b). The combination of these dates indicates a standing directive with an effective future date and a retrospective inspection window tied to an earlier date.

What the amendment text changes or leaves unchanged

• The AD states that "The compliance times remain unchanged by this issue of the Directive" (Compliance). That sentence indicates that while Amendment 2 makes changes in content (introducing certain check requirements when complete failure occurs), it does not alter the previously established compliance timing intervals. Amendment 1 had previously altered compliance times, but Amendment 2 leaves those times unchanged.

Authority and signature

• The AD is formally issued under the authority of CASA and is signed by its delegate, David Punshon, on 16 May 2007. The signature block and date are part of the amendment record for Amendment 2.

Referenced external materials in the amendment history

• Amendment 2 explicitly refers to EASA AD 2007-0129 as the external regulator-driven source prompting additional check requirements. The AD also refers to Eurocopter AS 365 N Alert Service Bulletin No. 05.00.37 Revision 2, and allows later EASA-approved revisions to be used; those are part of the technical amendment pathway.

Missing historical specifics

• The AD does not publish the text of Amendment 1 or the original AD in full within this document. It notes the effect of Amendment 1 only by reference ("introduced changes to compliance times"). For detailed comparison among original AD, Amendment 1 and Amendment 2, one would need to consult the earlier AD documents and the Eurocopter ASB revisions referenced, which are not reproduced here.

What the AD text records

• The AD does not record any litigation or legal proceedings. The document limitedly provides background about a manufacturer report (report of a cracked main rotor gearbox suspension diagonal cross-member) and procedural amendment reasons (Amendment 1 changed compliance times; Amendment 2 responds to an EASA AD) (Background).

Absence of cases or disputes in the AD

• There are no references to court decisions, administrative hearings, disputes, or litigation in the AD text. The AD does not reference or cite judicial or tribunal matters.

Implications for legal challenge

• The AD itself does not set out a mechanism for appeal or judicial review. Generally, statutory or regulatory instruments can be subject to legal challenge under relevant administrative law, but the AD text does not describe such pathways or any history of challenges. No historical litigation record is provided in this document.

How to find litigation history outside the AD

• The AD’s silence on litigation means any litigation history will not be discoverable from this text alone. To establish the existence of judicial or administrative challenges related to this AD, one would need to consult external sources such as court or tribunal databases, CASA enforcement records, or legal reporting that are not included in the AD text.

Scope limitations based on part numbers and models

• The AD applies only to AS 365 N, N1 and N2 helicopters that are "equipped with main rotor gearbox suspension diagonal cross-members, part number 365A38-3023-20, -21, -22, -23,and -24" (Applicability). Operators of AS 365 variants not fitted with those part-numbered cross-members must not assume applicability; conversely, operators who possess those part-numbered items must ensure they are included even where the component may have been installed as a spare or during a modification. The AD text does not discuss interchangeability or superseded part numbers; care is needed when interpreting parts databases.

Timing rules and the "whichever occurs first" formulation

• The compliance timing employs the "whichever occurs first" construct twice: initial-rectification window ("within 50 flight hours or 250 flight cycles after 16 July 2003, whichever occurs first") and the repeat interval ("at intervals not to exceed 50 flight hours or 250 flight cycles, whichever occurs first"). That phrasing requires operators to track both flight hours and flight cycles, and to schedule inspections based on the earliest reaching of either threshold. Failure to track both metrics could cause an operator to miss the effective inspection due date.

Retrospective window anchored to 16 July 2003

• The AD requires operators with cross-members that have already logged more than 15,000 (or 11,000 for N2) flight cycles to perform the initial check "within 50 flight hours or 250 flight cycles after 16 July 2003, whichever occurs first" (Compliance 1.b). The presence of a past calendar date in the compliance regime may create confusion in record interpretation. The AD does not explain whether replacement parts installed before or after that date are treated differently. Operators must examine maintenance and flight logs going back to that date to determine whether the retrospective window applied and whether any remedial inspections were performed then.

"Before further flight" is absolute

• The AD repeatedly uses "before further flight" in its required remedial steps for both cracks and complete failures (Requirement). That language is absolute: if an inspection uncovers a crack or complete failure, the AD requires removal, replacement and in the case of complete failure, additional checks, before the helicopter may be flown again. Treat "before further flight" as a grounding-order trigger until the specified actions are completed.

Step 1 , Confirm applicability and identify affected airframes and components

• Verify the helicopter model: confirm the helicopter is an AS 365 N, N1 or N2 model. Confirm the part number: verify that the installed main rotor gearbox suspension diagonal cross-member is part number 365A38-3023-20, -21, -22, -23 or -24 (Applicability). If the cross-member in the aircraft is not one of the listed part numbers, the AD’s requirements do not apply as written.

Step 2 , Obtain the governing technical document

• Obtain Eurocopter AS 365 N Alert Service Bulletin No. 05.00.37 Revision 2, and confirm whether any later EASA approved revision exists and is applicable. The AD requires action "in accordance with paragraph 2.B" of that ASB, or the later EASA-approved revision (Requirement). Use only the ASB revision that is EASA approved.

Step 3 , Determine inspection timing

• For cross-members that have not yet reached the threshold flight cycles: plan an initial inspection upon accumulation of the threshold cycle count , 15,000 flight cycles for AS 365 N and N1; 11,000 flight cycles for AS 365 N2 (Compliance 1.a).

• For cross-members that have already logged more than the threshold flight cycles as of the pertinent date: perform the initial inspection within the retrospective window, that is, within 50 flight hours or 250 flight cycles after 16 July 2003, whichever occurs first (Compliance 1.b). Review maintenance and flight logs to determine whether that retrospective inspection was performed; if not, schedule it immediately consistent with the AD.

Step 4 , Carry out the inspection per the ASB

• Perform the inspection of the centre portion of the main rotor gearbox diagonal cross-member as specified in paragraph 2.B of the ASB. The AD does not reproduce the ASB inspection technique and acceptance criteria; therefore, strictly follow the ASB steps and any EASA-approved revisions (Requirement).

Step 5 , Act on inspection findings immediately

• If a crack is detected: remove and replace the diagonal brace cross-member "before further flight" in accordance with paragraph 2.B.3.a of the ASB (Requirement). Do not fly the helicopter until replacement is completed.

• If complete failure of the diagonal cross-member is detected: remove and replace the diagonal cross-member and perform the additional checks required by paragraph 2.B.3.b of the ASB "before further flight" (Requirement). Again, do not operate the helicopter until the required removal, replacement and checks are completed.