AD/AS 355/90 - Main Servo-Controls

The AD rests on a small set of technical and regulatory concepts expressed in the source text. Those concepts define the norm of behaviour it imposes, and they are the reference points for compliance.

Technical concepts

• Main servo-control and tapered housing: The affected component is the main servo-control, specifically the tapered housing region where cracking was reported. The AD instructs inspection of these tapered housings for cracks and places significance on crack orientation (vertical versus oblique/horizontal) and length.
• Crack classification and thresholds: The AD uses concrete dimensional thresholds. A vertical crack "along the servo-control axis" that is less than 20 mm long permits an interim action (marking the crack and resuming flights after a prescribed compliance action). A vertical crack of 20 mm or longer, crack growth exceeding 5 mm, oblique or horizontal cracks, or multiple cracks mandate replacement of the servo-control.
• Attachment to non-rotating swashplate: The background links failure modes to the risk of "loss of attachment of the affected servo-control to the non-rotating swashplate," and consequently "loss of control" of the helicopter. The AD therefore treats the tapered housing crack as a direct safety hazard.

Regulatory concepts

• Incorporation by reference and delegation to manufacturer's ASB: The AD requires inspections and replacements "in accordance with" specified paragraphs of Eurocopter ASB No. 05.00.48. Thus the ASB provides the technical procedure; the AD supplies the mandatory legal force and the compliance schedule.
• Applicability carve-outs by modification status and maintenance history: The AD applies only to aircraft that meet a particular maintenance/ modification history test: those that are "not modified per MOD 073343" and on which the nut-tightening torque increase was implemented following either MOD 073191 or compliance with a named MET Work Card since a specific MET revision. That ties legal applicability to prior modifications and maintenance records.
• Time-limited and recurring inspection regimes: The AD establishes an initial short-term inspection window (10 flight hours or 10 days after the effective date) and, for certain cases, recurring inspections "during the check after the last flight of the day" subject to limits (not exceeding 10 flight hours between two inspections) and a deadline for replacement (no later than within 150 flight hours without exceeding 3 months).
• Spare-part handling as regulatory target: The AD explicitly extends rules to main servo-controls held as spares, requiring their inspection before installation or within 10 days after the AD's effective date, and directing return for repair if cracks are evident.

Documentary cross-links

• The AD refers to Eurocopter ASB No. 05.00.48 for procedural detail, and to EASA AD 2006-0055-E as a related authority. It does not reproduce the ASB content beyond paragraph references; therefore compliance requires consulting Eurocopter’s ASB.

Operational thresholds and decision points

• The AD builds a simple decision tree in the Requirement section: inspect; if no crack, comply with a single ASB paragraph and resume flights; if a vertical crack < 20 mm, mark end of crack and resume flights after a single ASB action, while also complying with an additional ASB paragraph; if the crack meets or exceeds certain criteria, replace the servo-control in accordance with the ASB. These are unambiguous operational triggers, with precise timing constraints.

The main concepts therefore combine component-level engineering thresholds with an enforcement mechanism that links those thresholds to a manufacturer's service document and to limited, defined inspection cadences governed by the AD.

The AD identifies who must act and who bears operational consequences through its applicability clause and its requirements.

Primary affected parties

• Operators and owners of Eurocopter AS 355 E helicopters that are equipped with main servo-controls, all part numbers, where the aircraft have not been modified per MOD 073343 and where the tightening torque of the nut securing the upper ball-end was increased following either embodiment of MOD 073191 or compliance with MET Work Card 67.30.00.402 since MET Revision 04-08. These operators are the primary duty-holders because the AD mandates inspections, repairs and replacements that must be carried out on their helicopters within fixed time limits.
• Maintenance organisations and maintenance personnel responsible for carrying out the checks, marking, and replacements in accordance with ASB No. 05.00.48. The AD explicitly requires actions "in accordance with" specified ASB paragraphs, so the maintenance shop must access, interpret and apply those ASB procedures.

Secondary affected parties

• Entities holding main servo-controls as spares. The AD contains a specific paragraph addressing spares: these spare units must be inspected as required by the ASB paragraphs and, if cracking is evident, must be returned for repair rather than being placed into service.
• Manufacturers and repair stations who will receive returned components for repair and will implement paragraph 2.A of the ASB if replacement is required.
• Regulators and inspectors who monitor compliance with ADs: the AD is issued by the Civil Aviation Safety Authority (CASA) delegate and thus becomes part of the compliance universe that operators are required to follow.

Who pays

• The AD does not specify who bears costs. The text, by mandating inspection and replacement, allocates practical compliance costs to the operators/owners and to those holding spare parts: they must pay for inspections, marking, replacements, and any downtime. Repair stations or manufacturers may incur costs in repairing returned spares, but the AD does not shift or assign financial responsibility beyond imposing the mandatory actions.

Who decides

• The AD was issued by David Punshon, Delegate of the Civil Aviation Safety Authority, and therefore CASA (through its delegate) is the issuing authority. While the AD requires specific actions, the detailed procedural steps are delegated to the Eurocopter ASB, which operators and maintenance organisations must follow.

Operational impacts on flight scheduling and asset availability

• Short compliance windows (within 10 flight hours or 10 days after the effective date, last-flight-of-day checks not exceeding 10 flight hours between inspections, and replacement deadlines no later than within 150 flight hours or 3 months in an interim situation) impose immediate maintenance workload and potential grounding or restricted operations where replacement is required "before further flight."

Documentation and record-keeping

• Because applicability depends on prior modifications and a maintenance entry (MOD 073191, MET Work Card 67.30.00.402 compliance since MET Revision 04-08), operators will need to consult maintenance logs and modification records to determine whether each helicopter falls within the AD’s scope.

In short, the AD directly affects operators and maintainers of defined AS 355 E helicopters and those holding spares, imposing inspection, marking, return-for-repair and replacement duties on precise timelines, and indirectly affects manufacturers and repairers who provide the technical procedures or conduct repairs.

The AD prescribes a compact set of duties and leaves no explicit statutory "rights" set out in the text; compliance obligations are precise. The AD also delegates procedural detail to the referenced Eurocopter ASB. The key duties are as follows.

Duties imposed on operators and maintenance organisations

• Conduct the initial inspection of the tapered housings of the main servo-controls for cracks "in accordance with paragraph 2.B.2. of Eurocopter AS 355 Alert Service Bulletin (ASB) No. 05.00.48." This is the AD’s starting obligation (Requirement 1).
• If no crack is evident, comply once with paragraph 2.B.3. of ASB No. 05.00.48 and then "resume flights" (Requirement 1.b). This is a single action requirement with an immediate operational implication: flights may continue following that one-off ASB procedure.
• If a vertical crack (along the servo-control axis) is found and it is less than 20 mm long:
  • Comply once with paragraph 2.B.3. of ASB No. 05.00.48, identify the end of the crack using an indelible ink marker, and resume flights (Requirement 1.b.(i)). The AD therefore requires marking as a condition of continued operation.
  • Also comply with paragraph 2.B.4. of ASB No. 05.00.48 (Requirement 1.b.(ii)). The AD clarifies timing for these inspections: the check after the last flight of the day, without exceeding 10 flight hours between two inspections, pending replacement "no later than within 150 flight hours without exceeding 3 months."
• If the crack meets specified criteria the AD requires replacement:
  • Replace the servo-control "in accordance with paragraph 2.A. of ASB No. 05.00.48" where there is a vertical crack 20 mm or longer, the crack has grown by more than 5 mm, there is an oblique or horizontal crack, or there are several cracks (Requirement 2). Replacement of the servo-control in these circumstances is mandatory, and where the AD states "Before further flight" as the compliance timing for Requirement 2.
• For servo-controls held as spares:
  • Accomplish paragraph 2.B.2.b of ASB No. 05.00.48. If no crack is evident, comply once with paragraph 2.B.3. If a crack is evident, return the servo-control for repair (Requirement 3). The AD also sets the timing: within 10 days after 6 March 2006, or before installing a spare.

Timing obligations

• Initial inspection: "Within 10 flight hours or 10 days after 6 March 2006, whichever occurs first." This creates a short window for operators to act after the AD’s effective date.
• Interim monitoring: For certain small vertical cracks the AD requires checks "during the check after the last flight of the day, without exceeding 10 flight hours between two inspections," pending replacement subject to the replacement deadline.
• Replacement deadline in interim monitoring: Replacement must occur "no later than within 150 flight hours without exceeding 3 months." The AD therefore sets both flight-hour and calendar limits.

Delegation of procedural content

• The AD repeatedly requires actions "in accordance with" specified ASB paragraphs. Those paragraphs contain the procedural detail (inspection technique, limits, and replacement procedure). The duty-bearer therefore must obtain and follow Eurocopter ASB No. 05.00.48 to perform the required actions correctly.

Rights or procedural prerogatives

• The AD itself does not grant discrete "rights" such as appeals or exemptions; it simply prescribes mandatory actions and sets timelines. The AD does, however, incorporate the manufacturer’s ASB as the technical standard to be followed, so an operator’s compliance route is the ASB procedures as referenced.

Record-keeping and traceability duties implied by applicability

• Because applicability depends on modification status and prior maintenance actions, operators implicitly must consult modification and maintenance records (MOD 073343, MOD 073191, MET Work Card 67.30.00.402 and MET Revision 04-08) to determine whether their aircraft are within scope. The AD thus imposes a practical duty to inspect logs and maintenance history to determine applicability.

Summary

• The operator’s duties are concrete: inspect, mark if allowed, continue operations subject to short-term monitoring, replace in specified cases, and inspect spares. The AD requires adherence to Eurocopter ASB No. 05.00.48 paragraphs as the technical standard. The AD sets short compliance windows and explicit replacement triggers, with replacement "before further flight" where required.

The AD prescribes mandatory maintenance, inspection and replacement actions and fixes compliance timelines, but the document itself does not set out monetary penalties or the enforcement mechanics in statutory text. The AD provides the instrument of obligation and records its issuance by a CASA delegate; it is therefore part of the regulated airworthiness framework, but the AD’s text contains no penal provisions, infringement schedules, or enforcement procedures.

What the text does say about enforcement context

• Issuing authority: The AD is signed by David Punshon, who is identified as "Delegate of the Civil Aviation Safety Authority". The AD thereby originates from CASA’s delegated authority.
• Mandatory character: By its form and the language used ("Requirement", "Compliance", "This Airworthiness Directive becomes effective on 6 March 2006"), the AD establishes mandatory actions and deadlines. The AD’s structure prescribes actions to be carried out and when they must be completed.
• Cross-reference to applicable technical standards: The AD incorporates Eurocopter ASB No. 05.00.48 and references EASA AD 2006-0055-E. Non-compliance with the AD therefore means non-compliance with a CASA-mandated maintenance requirement which in ordinary regulatory practice would affect an aircraft’s airworthiness status.

What the AD does not state

• The AD does not specify penalties, enforcement procedures, or sanctions for non-compliance. It does not list fines, licence consequences, administrative penalties, or criminal sanctions in the text provided.
• The AD does not specify the mechanism by which CASA will monitor or audit compliance, nor does it set out the process for seeking relief, exemptions, or extension of compliance times.

Implications that can be drawn from the instrument (on the basis of the text alone)

• Because the AD is issued by CASA’s delegate and sets mandatory maintenance tasks, operators must treat it as a legal requirement for continuing airworthiness of affected helicopters. The AD’s effective date and fixed inspection/replacement deadlines mean that failure to comply will result in the operator being unable to represent the aircraft as airworthy under the AD’s terms.
• The AD’s lack of articulated penalties means that enforcement and penalty detail, if any, will be governed by the broader statutory and regulatory framework under which CASA operates; that framework is not reproduced within the AD text.

Practical note for operators and maintainers

• Treat the AD as a binding maintenance requirement: perform the inspections and replacements as required and keep records demonstrating compliance. The AD’s explicit times and replacement triggers are the operative criteria an inspector or regulator would use to assess compliance. If an operator faces difficulty complying within the stated times, the AD contains no procedure for extensions; operators should therefore seek CASA guidance (not contained in this AD text) rather than assume flexibility.

The AD expressly links to other regulatory and technical instruments, but the text does not set out a legal hierarchy beyond its own status as an AD issued by CASA’s delegate. The AD’s interaction with other instruments must be read from the cross-references present in the document.

Cross-references made in the AD

• Eurocopter ASB No. 05.00.48: The AD repeatedly requires actions "in accordance with" specified paragraphs of Eurocopter Alert Service Bulletin No. 05.00.48. That ties the AD’s technical requirements directly to a manufacturer’s service bulletin, making the ASB the operative technical method for inspection and replacement. The ASB is therefore incorporated by reference into the AD as the procedural standard.
• EASA AD 2006-0055-E: The AD notes "Note: EASA AD 2006-0055-E refers." This records a connection to a European Aviation Safety Agency airworthiness directive that is relevant to the same technical issue. The AD does not reproduce EASA’s text but acknowledges its existence as related material.
• MOD and MET references affecting applicability: The Applicability clause excludes helicopters "modified per MOD 073343" and applies only to helicopters "on which the tightening torque of the nut ... has been increased following embodiment of MOD 073191; or, compliance with MET Work Card 67.30.00.402 since MET Revision 04-08." That means an aircraft’s prior modification and maintenance history, as recorded in modification orders and MET Work Card compliance entries, determine whether the AD applies. The AD therefore interacts with maintenance records and modification documentation as legal markers of scope.

Legal relations and practical consequences

• The AD prescribes actions that operators must follow, and it does so by incorporating manufacturer's procedures and referring to an EASA AD. Operators must therefore coordinate compliance with both CASA’s AD and the detailed ASB actions to be considered compliant.
• The AD does not state how conflicts between the ASB and other regulatory instruments are to be resolved, nor does it indicate a mechanism for reconciling differences between CASA and EASA directives; it simply imposes the CASA-mandated AD that requires compliance with the named ASB paragraphs.

What the AD does not address about other laws

• The AD does not discuss how it interacts with contractual obligations between operators and maintenance providers, warranty arrangements with manufacturers, or insurance provisions. The AD sets a regulatory obligation but does not govern commercial allocation of cost or liability.
• The AD does not set out appeal, exemption or extension procedures, nor the procedural steps to challenge the AD itself. Any such processes would lie in the statutory framework governing CASA actions, which is not set out in this instrument.

Practical reading for operators and maintainers

• To be compliant, an operator must (a) determine applicability by examining modification and MET Work Card records, (b) execute the inspections and replacements in strict accordance with the named ASB paragraphs, and (c) treat the EASA AD as relevant background material. The AD therefore functions as the CASA-enforced requirement that incorporates manufacturer technical methods and recognises corresponding EASA action.

In short, the AD interacts with other regulatory and technical instruments through express incorporation by reference and by tying applicability to modification and maintenance entries; it does not itself resolve legal hierarchy or enforcement mechanics beyond stating its effective date and issuing authority.

The AD as provided contains a compact amendment trail comprised of identifying references and an effective date, but no subsequent amendment entries or revisions appear in the text supplied.

Items recorded in the source

• AD identifier and edition: The document identifies itself as "AD/AS 355/90 Main Servo-Controls 4/2006 TX" and repeats the AD references (multiple line headers in the supplied text show "AD/AS 355/90", "Main Servo-Controls" and "4/2006 TX"). These labels identify the AD number and its issue identifier.
• Effective date: The AD states explicitly, "This Airworthiness Directive becomes effective on 6 March 2006." The Compliance section then expresses deadlines relative to that date (for example, "within 10 flight hours or 10 days after 6 March 2006").
• Related authority reference: The AD notes that "EASA AD 2006-0055-E refers" and that the AD requires compliance with Eurocopter ASB No. 05.00.48. Those are references to contemporaneous materials rather than textual amendments to this AD, but they are elements of the regulatory context at the time of issue.

What is not present in the source

• No revisions, supersessions, or later amendment dates: The AD does not include any subsequent amendment notes, no superseding AD references, and no series of versioned changes within the provided text. There is no "as amended" history recorded in the document supplied.
• No revocation or replacement language: The AD does not indicate that it supersedes or revokes any earlier CASA directive; likewise, it does not itself state any planned future amendment.

Practical implications

• For compliance and record-keeping, the operative version is the one that became effective 6 March 2006. If operators require information about later amendments or whether this AD was superseded, that information is not contained in the text supplied and must be sought from CASA or from subsequent AD publications.
• The AD’s cross-references to ASB No. 05.00.48 and EASA AD 2006-0055-E provide the contemporaneous technical and regulatory context as of the effective date. Any later versions of those ASBs or EASA ADs, or any CASA amendments to this AD, are not recorded in this document.

Summary

• The source provides a single-issue amendment record: issuance with identifier AD/AS 355/90, labeled 4/2006 TX, effective 6 March 2006, incorporating Eurocopter ASB No. 05.00.48 and acknowledging EASA AD 2006-0055-E. No further amendment history is recorded in the supplied text.

The supplied AD text contains no litigation history. It names no court decisions, does not recount any legal challenges to the directive, and does not cite case law. There are therefore no reported judicial decisions, appeals or disputes recorded in the instrument provided.

What the AD does record that could be relevant in litigation contexts

• Issuance by regulator: The AD is signed by David Punshon, Delegate of the Civil Aviation Safety Authority, which identifies the issuing authority should any judicial context require confirmation of source authority or decision-maker.
• Technical and procedural cross-references: The AD’s reliance on Eurocopter ASB No. 05.00.48 and the reference to EASA AD 2006-0055-E would be primary evidentiary documents in any dispute about what the required standard of care or technical procedure was at the relevant time, but the AD text itself does not summarise the ASB content beyond paragraph references.
• Applicability criteria: The AD’s explicit applicability carve-outs (MOD 073343 exclusion; requirement that the tightening torque increase was implemented following MOD 073191 or MET Work Card compliance since MET Revision 04-08) create concrete fact questions that would be relevant in any enforcement or liability proceeding, but the AD contains no litigation narrative.

Absence of litigation record in the document

• No mention of appeals, contested decisions, or regulatory findings that were subject to adjudication appear in the text supplied.
• No direction or summary of dispute resolution routes, appeals to CASA, or judicial review is included.

Practical consequences for researchers or counsel

• If litigation history or challenges to the AD are material, the AD itself does not supply the necessary information. Researchers or counsel must consult external sources , for example, CASA public records, tribunal or court databases, or subsequent AD amendments and notices , to determine whether this AD was contested, amended following challenge, or cited in litigation.

In short, this AD contains no litigation history or case references. All references are administrative and technical.

The AD contains several precise conditions, thresholds and cross-references that can be operational pitfalls if overlooked. These “gotchas” are drawn directly from the wording of the directive and the way it links to external documents.

Applicability trap: modification and maintenance-history dependence

• The AD applies only to helicopters that are "not modified per MOD 073343" and that have had the tightening torque increased "following embodiment of MOD 073191; or, compliance with MET Work Card 67.30.00.402 since MET Revision 04-08." Operators who assume the AD applies or does not apply without checking modification logs and MET Work Card entries risk misclassifying aircraft. The AD ties legal scope to historical maintenance entries; incomplete or inaccurate logs therefore create compliance uncertainty.

Technical threshold precision

• Crack orientation and length matter. The AD treats a "vertical crack (along the servo-control axis) that is less than 20 mm long" differently from a vertical crack "20 mm long or longer", and treats any oblique or horizontal crack as an immediate replacement case. The exactness of the 20 mm measurement and the phrase "along the servo-control axis" mean that measurement technique and crack orientation judgment are material. The AD does not provide measurement tolerances, so operators must rely on the ASB’s measurement technique (the ASB paragraphs being incorporated by reference).

Interim inspection cadence constraints

• Where a vertical crack < 20 mm is marked and flights resume, the AD requires compliance with paragraph 2.B.4 and prescribes that inspections occur "during the check after the last flight of the day, without exceeding 10 flight hours between two inspections." That imposes a daily or close-to-daily inspection cadence in many operational contexts and constrains scheduling. The AD also requires replacement "no later than within 150 flight hours without exceeding 3 months." Operators must track both flight hours and calendar days to remain compliant.

Marking as a limiting measure

• The AD requires identifying the end of a crack "using an indelible ink marker" when a small vertical crack is found. That marking is a mandated action that may determine whether the aircraft can be flown; failure to mark correctly or to record the marking could create regulatory exposure.

Spare parts handling nuance

• Spares are not outside the AD’s reach. A main servo-control held as spares must be inspected under paragraph 2.B.2.b of the ASB and inspected within 10 days after 6 March 2006 or before installing a spare. If a spare with cracks is installed because inspection obligations were overlooked, the aircraft becomes non-compliant. The AD also instructs return-for-repair of cracked spares rather than ad hoc in-field repairs.

Reference-dependence and procedural gaps

• The AD does not reproduce the ASB’s procedural detail. Compliance therefore requires obtaining Eurocopter ASB No. 05.00.48 and following the named paragraphs precisely. If maintenance personnel or organisations do not have immediate access to that ASB, they cannot execute the AD’s requirements correctly.

Confusingly formatted identifiers

• The AD text supplied includes repeated header fragments ("AD/AS 355/90", "Main Servo-Controls", "4/2006 TX") and duplicate headings. While this does not change the substance, it may create transcription or document-filing confusion, particularly when reconciling with maintenance records or later ADs.

Timing conflation risk

• The AD contains several timing instructions with different triggers: "within 10 flight hours or 10 days after 6 March 2006", "during the check after the last flight of the day, without exceeding 10 flight hours between two inspections", "no later than within 150 flight hours without exceeding 3 months", and "within 10 days after 6 March 2006, or before installing a main servo-control held as spares." Operators must map these different periods to individual aircraft status and avoid conflating them.

No penalties stated

• The AD contains no penalty schedule or enforcement steps. That does not mean enforcement is absent; it only means the AD itself does not specify enforcement mechanics. Operators should not interpret silence as flexibility: the AD imposes mandatory tasks and deadlines that affect airworthiness status.

EASA link but no harmonisation text

• The AD notes "EASA AD 2006-0055-E refers." It does not state whether the CASA AD follows, modifies, or narrows EASA’s AD. Operators might assume exact harmonisation with EASA; the AD merely references EASA's directive and incorporates Eurocopter ASB paragraphs as the required procedural standard.

Summary of gotchas

• Applicability depends on specific modification and maintenance history entries; precise crack orientation and length rules drive different outcomes; short inspection windows and a strict replacement deadline create scheduling pressure; spares are in scope; the AD incorporates (but does not reproduce) ASB procedures; and the AD contains no enforcement or penalty language within the text provided. Each of these points requires careful attention to records, access to the ASB, accurate measurement and marking, and tracking of both flight-hour and calendar limits.

The AD’s compliance path is procedural and short-form: obtain the referenced ASB and implement the specified checks, markings and replacements within the AD’s timelines. Below is a practical, source-grounded checklist mapped to the AD’s requirements and timelines.

Step 0 , Confirm applicability

• Consult modification and maintenance records to determine whether each AS 355 E helicopter in your fleet is within scope. The AD applies to "Models AS 355 E helicopters, equipped with main servo-controls, all part numbers, not modified per MOD 073343, and on which the tightening torque of the nut that secures the upper ball-end has been increased following:- embodiment of MOD 073191; or,- compliance with MET Work Card 67.30.00.402 since MET Revision 04-08." If your aircraft are modified per MOD 073343 they are excluded; if they have not had the tightening torque increase per MOD 073191 or the named MET Work Card since the stated revision they are outside the AD’s scope as written.

Step 1 , Obtain the referenced technical documents

• Obtain Eurocopter ASB No. 05.00.48 and locate paragraphs 2.A, 2.B.2, 2.B.2.b, 2.B.3 and 2.B.4 as referenced in the AD. The AD requires actions "in accordance with" those paragraphs; the AD does not contain the procedural steps itself.
• Note the reference to EASA AD 2006-0055-E for situational awareness and for any cross-checking of recommended actions.

Step 2 , Initial inspection timing

• For each affected helicopter (per Step 0), schedule the initial tapered-housing inspection "within 10 flight hours or 10 days after 6 March 2006, whichever occurs first." If you are already beyond those windows, perform the inspection immediately (the AD became effective on 6 March 2006).

Step 3 , Perform the inspection in accordance with ASB paragraph 2.B.2

• Carry out the tapered housing check "in accordance with paragraph 2.B.2. of Eurocopter AS 355 Alert Service Bulletin (ASB) No. 05.00.48." Record the inspection result and any measurements of crack length and orientation. Ensure personnel performing the inspection are competent to interpret crack orientation (vertical along the servo-control axis, oblique, horizontal) and to measure crack length to the precision required by the ASB.

Step 4 , Follow the AD’s prescribed outcomes based on inspection result

• If no crack is evident:
  • Comply once with paragraph 2.B.3 of ASB No. 05.00.48 and then "resume flights" as the AD directs.
• If a vertical crack less than 20 mm long (along the servo-control axis) is found:
  • Comply once with paragraph 2.B.3 of ASB No. 05.00.48.
  • Identify the end of the crack using an indelible ink marker as required by the AD.
  • Resume flights, but also comply with paragraph 2.B.4 of ASB No. 05.00.48 for interim monitoring.
  • Ensure interim monitoring is performed "during the check after the last flight of the day, without exceeding 10 flight hours between two inspections."
  • Plan replacement in accordance with paragraph 2.A of the ASB "no later than within 150 flight hours without exceeding 3 months."
• If a vertical crack is 20 mm or longer, the crack has grown by more than 5 mm, there is an oblique or horizontal crack, or there are multiple cracks:
  • Replace the servo-control "in accordance with paragraph 2.A. of ASB No. 05.00.48."
  • The AD specifies replacement "Before further flight" in Requirement 2, so do not operate the aircraft again until replacement has been completed.

Step 5 , Spares handling

• For main servo-controls held as spares, accomplish paragraph 2.B.2.b of ASB No. 05.00.48.
• If no crack is evident in the spare, comply once with paragraph 2.B.3 and the spare may be placed into service.
• If a crack is evident in the spare, return the servo-control for repair, rather than attempting to place it into service.
• Observe the AD’s timing on spares: inspect spares "within 10 days after 6 March 2006, or before installing a main servo-control held as spares."

Step 6 , Record-keeping

• Make a maintenance record entry for each inspection, marking action, interim inspections and replacements, citing the AD reference "AD/AS 355/90 Main Servo-Controls 4/2006 TX" and the specific ASB paragraph(s) used for the procedure.
• Retain evidence of the indelible ink marking for small vertical cracks and document the flight-hour and calendar tracking for the replacement deadline (150 flight hours or three months maximum).

Step 7 , Operational constraints and scheduling

• Where interim monitoring is permitted, ensure that the "check after the last flight of the day" is scheduled and that no more than 10 flight hours pass between inspections.
• For replacement deadlines set at "no later than within 150 flight hours without exceeding 3 months," track both flight hours and calendar time; replacement must be achieved before either limit is breached.

Step 8 , Coordination with repair stations and parts supply

• If replacement is required, ensure replacement parts conform to the ASB and are either new or repaired in accordance with the repair methods specified in paragraph 2.A of ASB No. 05.00.48.
• If spares are returned for repair, route them to the authorised repair facility designated by Eurocopter or as specified in the ASB.

Step 9 , Regulatory liaison

• Because the AD was issued by CASA and references EASA AD 2006-0055-E, if there is ambiguity about applicability or compliance timing, contact CASA for guidance. The AD itself contains no extension or exemption procedure. If unable to meet the AD timelines due to parts availability or scheduling, seek CASA's direction in writing; do not operate outside the AD’s requirements without explicit regulatory relief.

Step 10 , Training and procedure updates

• Update maintenance procedures and training materials to incorporate the ASB inspection methods referenced in the AD and to ensure technicians can measure cracks and apply the marking and monitoring requirements correctly.
• Ensure the operations department is aware of the inspection cadence and replacement deadlines, since these requirements can affect flight schedules and aircraft availability.

Checklist summary (minimum actions)

• Confirm applicability using MOD and MET records.
• Obtain Eurocopter ASB No. 05.00.48, especially paragraphs 2.A, 2.B.2, 2.B.2.b, 2.B.3 and 2.B.4.
• Inspect tapered housings within the AD’s initial window.
• Follow the AD’s decision steps depending on crack presence, length and orientation.
• For small vertical cracks, mark with indelible ink, inspect daily (as required), and replace within 150 flight hours but not more than 3 months.
• Replace immediately "before further flight" for the higher-risk crack conditions.
• Inspect spares before installation or within 10 days after the AD’s effective date; return cracked spares for repair.
• Record all actions citing the AD and ASB paragraphs.

Following these steps will implement the AD’s mandatory requirements as written, but operators should maintain documentary proof of compliance and liaise with CASA if any procedural or timing difficulties arise.