AD/ARRIEL/29 - Low Fuel Pressure Switch

This AD deploys a small set of interlocking technical and compliance concepts that determine the scope and effect of the instrument.

• Applicability by engine model. The AD identifies the affected models as "Turboméca S.A. ARRIEL 2B, 2B1 and 2B1A turboshaft engines." That is the primary inclusion rule. The text also includes a Note that these engines are known to be installed on, but not limited to, Eurocopter AS 350 B3 and EC 130 B4 helicopters, which signals that operators must check fitted engine models to determine applicability.

• Diagnostic inspection tied to a manufacturer's service bulletin. The AD requires "a one-time inspection of the Hydro Mechanical Unit (HMU) in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826." The MSB paragraph is adopted by reference as the procedural mechanism to identify the installed low fuel pressure switch and to inspect the HMU chamber.

• Part-number specific remediation. The AD pivotally distinguishes between a Hydra-Electric low fuel pressure switch, P/N 9 550 17 956 0, and two IN-LHC switches, P/N 9 550 17 199 0 and P/N 9 550 17 913 0. The required action depends on which P/N is present and on the inspection findings:

  • If Hydra-Electric P/N 9 550 17 956 0 is installed, the operator must inspect the switch and the HMU chamber. If any parts of the switch are missing or found in the HMU chamber, the HMU must be replaced by "a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch." If no parts are missing and nothing is found in the chamber, the operator may replace only the low fuel pressure switch with an IN-LHC switch.
  • If an IN-LHC switch P/N 9 550 17 199 0 or P/N 9 550 17 913 0 is installed, two sub-scenarios apply: (a) where the IN-LHC switch has been installed since new, repair or overhaul, the AD states "no further action is required"; (b) where a Hydra-Electric switch P/N 9 550 17 956 0 "has been or may have been previously installed," the operator must inspect the HMU chamber and, if any parts are found in the chamber, replace the HMU with a new or overhauled HMU equipped with an IN-LHC switch.

• Single-time action. The AD requires a one-time inspection. It does not, in the text provided, require ongoing periodic inspections or recurring actions once the corrective path has been completed.

• Safety pathway. The background describes a specific failure mechanism: loss of internal components from the Hydra-Electric low fuel pressure switch into the fuel system, which "may lead to a rupture of the HP-LP pumps drive shaft shear pin, and thus to a possible uncommanded In-Flight Shut-Down (IFSD)." The AD frames the intervention as preventing that chain of events, and specifically notes the safety consequence on single-engine helicopters, where an IFSD "results in an emergency autorotation landing and in certain conditions may lead to an accident."

• Inter-jurisdictional reference. The AD explicitly refers to "EASA AD 2008-0077 dated 28 April 2008," indicating that the Australian AD aligns with or follows the European Aviation Safety Agency directive dated earlier in April 2008.

• Timing. Two dates structure compliance: the AD is "effective on 3 July 2008" and establishes "No later than 30 September 2009" as the compliance deadline for the one-time inspection and any required replacements.

These concepts together create a narrow, technically defined compliance obligation: inspect an HMU per a named MSB, identify the exact switch part number, and apply the stated remedial pathways with a hard deadline. The AD does not expand the scope beyond these steps, nor does it include continuing monitoring obligations or specific enforcement mechanisms within the text provided.

The AD plainly targets a narrow set of operational actors and technical components; the distribution of responsibilities and likely costs can be read from the Requirement and Applicability sections.

Primary affected parties, as identified in the AD text:

• Engine operators and aircraft operators who have Turboméca S.A. Arriel 2B, 2B1 or 2B1A engines installed on their aircraft. The AD’s Applicability statement makes these engines the trigger for the obligation. The Note specifying that these engines are "known to be installed on, but not limited to Eurocopter AS 350 B3 and EC 130 B4 helicopters" indicates that owners or operators of those helicopter types should as a starting matter check whether they have the affected engine models fitted. The phrase "but not limited to" means the instrument could apply to these Arriel 2 variants installed in other airframes as well.

• Maintenance organisations and licensed engineers. The AD requires an inspection "in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826." That action implicates maintenance providers with the competency, tooling and authority to disassemble or inspect the HMU to the level required by the referenced MSB paragraph. The action options include replacement of either the low fuel pressure switch or an entire HMU, tasks commonly within the scope of certified maintenance organisations.

• Parts suppliers and overhaul shops. The remedial options include replacing the Hydra-Electric switch with an "IN-LHC low fuel pressure switch" or replacing the entire HMU "by a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch." Procuring IN-LHC parts or overhauled HMUs therefore engages suppliers and overhaul providers, which has scheduling and availability implications for operators planning compliance.

• Single-engine helicopter operators as a specifically highlighted risk cohort. The Background explicitates that on a single-engine helicopter, an uncommanded IFSD leads to an emergency autorotation and may result in an accident, which explains the safety urgency for operators of single-engine types. The text does not create different legal obligations by single- versus multi-engine configuration, but it signals that the operational consequence of non-compliance is particularly severe for single-engine operations.

Parties not explicitly enumerated but implied:

• Regulatory staff within the Civil Aviation Safety Authority, as the AD is issued under the authority and signed by the Delegate of CASA. They are the issuing authority and therefore the decision-maker on effectivity and publication, as evidenced by the signature block "James Coyne, Delegate of the Civil Aviation Safety Authority 22 May 2008."

Who pays:

• The text does not state a funding mechanism. Practically, the Requirement imposes inspection time and potential parts and overhaul costs upon the operators or their maintenance suppliers. Replacement of switches, or replacement of HMUs with new or overhauled units, will generate material and labour costs for the operator or the entity contracted to perform maintenance.

Who decides:

• The AD prescribes fixed technical decisions contingent on inspection findings: whether to replace only the switch or to replace the entire HMU depends on whether parts are missing or found in the HMU chamber. The operator or maintenance provider performs the inspection per the MSB and then applies the mandated decision tree under the AD.

What changes for those affected:

• Operators must schedule and complete a one-time inspection by 30 September 2009. If a Hydra-Electric P/N 9 550 17 956 0 switch is present, they must either replace the switch or, if parts are loose in the chamber, replace the HMU. If an IN-LHC switch P/N 9 550 17 199 0 or P/N 9 550 17 913 0 is present and has been installed since new, repair or overhaul, no further action is required; otherwise inspection of the chamber is required, with HMU replacement if parts are found. The AD thus alters maintenance scheduling and parts inventory requirements for affected operators.

The AD text does not specify exemptions, alternative procedures, record keeping obligations, or a mechanism for seeking relief. It does, however, cross-reference the manufacturer's MSB and an EASA AD which may contain further procedural detail not reproduced in this AD.

The AD establishes a compact set of duties that bind operators of the specified engine models, and it leaves minimal explicit statements about rights or procedural relief within the instrument itself.

Primary duties as stated in the AD:

• Duty to inspect: "Accomplish a one-time inspection of the Hydro Mechanical Unit (HMU) in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826 to identify the low fuel pressure switch installed on adjusted HMU." This is the foundational duty and prescribes the inspection method through the referenced MSB paragraph.

• Duty to remedy based on specific findings and part numbers:

  • If Hydra-Electric switch P/N 9 550 17 956 0 is installed, the operator must "Inspect low fuel pressure switch and chamber of the HMU body." Then:
    • "If any parts from the low fuel pressure switch are missing or found in the HMU chamber, replace the HMU with a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch."
    • "If not, replace only the low fuel pressure switch with an IN-LHC low fuel pressure switch."
  • If an IN-LHC low fuel pressure switch P/N 9 550 17 199 0 or P/N 9 550 17 913 0 is installed, the AD draws a distinction:
    • "If an IN-LHC low fuel pressure switch has been installed since new, repair or overhaul, no further action is required."
    • "If a Hydra-Electric switch P/N 9 550 17 956 0 has been or may have been previously installed: (i) Inspect the chamber of the HMU body. (ii) If any parts are found in the HMU chamber, replace the HMU by a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch."

• Duty to comply by the specified deadline: The AD sets a compliance date "No later than 30 September 2009." The instrument also notes its effectivity date as 3 July 2008, and is dated 22 May 2008 by the CASA Delegate.

Rights and absence of explicit relief in the AD:

• The AD text does not set out rights, appeals, or administrative relief options, nor does it specify any alternative compliance procedures or authorised deviations within this instrument. It also does not include explicit recordkeeping instructions or prescribe how proof of compliance must be lodged. Therefore, any procedural rights or mechanisms for seeking variation, accepting alternative methods of compliance, or deferring action would need to be sought or derived outside the AD text, for example under broader CASA regulatory processes not contained within the provided text.

Decision rule and operator discretion:

• The AD contains a conditional decision tree driven by physical inspection findings and part numbers. The inspector/operator has the responsibility and technical discretion to identify the installed part number and to determine whether parts are missing or present in the HMU chamber. Once those findings are established, the AD then prescribes specific remedial steps; the operator's discretion is thus limited to the factual determination derived from the MSB-guided inspection and to contracting or executing maintenance to carry out the prescribed replacements.

Reference and procedural duty:

• The inspection duty is to be performed "in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826." That effectively delegates the procedural specifics of the inspection to the manufacturer's MSB paragraph referenced. Operators must therefore obtain and follow that manufacturer-supplied procedure, as the AD does not spell out the inspection steps itself.

In sum, the AD establishes clear duties to inspect and to apply one of a small set of remedial options, tied to identified part numbers and concrete inspection findings, with a fixed compliance deadline. The AD text does not enumerate administrative remedies, appeals, or explicit records obligations within the instrument.

The AD text supplied does not specify civil or criminal penalties, nor does it set out an enforcement mechanism or administrative process for non-compliance. The document provides the following enforcement-relevant statements and indicators, which together define what the AD itself contributes to enforcement architecture:

• Effectivity and signature. The AD states "This Airworthiness Directive becomes effective on 3 July 2008" and is signed "James Coyne, Delegate of the Civil Aviation Safety Authority 22 May 2008." That identifies the issuing authority and the date on which the instrument takes effect.

• Compliance deadline. The AD prescribes a clear deadline: "No later than 30 September 2009." The presence of a firm deadline is the AD’s primary enforcement lever: it converts the inspection and remedial measures into time-bound obligations.

What the AD does not contain:

• No penalties, sanctions or enforcement process are specified in the text provided. There are no specified fines, licence consequences, administrative directions, suspension powers, or criminal provisions set out in the instrument itself.
• No specified process for seeking relief, alternative methods of compliance or special flight permits is set out in this AD text.
• No recordkeeping or reporting obligations are stated within the AD text, for example no instruction to file a compliance report with CASA or to retain maintenance records for a set period.

Practical enforcement implications inferable from the AD text:

• The AD is presented as a directive from the Civil Aviation Safety Authority, signed by its delegate. That identifies the instrument as an authoritative regulatory requirement. In practice, operators typically interpret ADs as mandatory obligations that must be complied with to maintain airworthiness of the affected engine or aircraft type. The AD’s effective and compliance dates are concrete scheduling constraints that operators must accommodate.

• Because the AD cross-references a Turboméca Mandatory Service Bulletin and an EASA AD, it situates the action within an international and manufacturer-led airworthiness remediation context. This often implies that aviation regulators and aviation safety inspectors will expect evidence of compliance during oversight or certification inspections, but such inspection and evidence requirements are not laid out in this document.

Where to look for enforcement detail beyond this AD:

• The AD itself does not set enforcement penalties or a reporting channel. Any enforcement measures, compliance verification, or consequences for non-compliance would arise from the wider regulatory framework administered by CASA and other applicable aviation safety regulations and instruments not reproduced in this text. Those specifics lie outside the four corners of this AD.

In short, the AD sets binding technical requirements and a compliance timetable, but within the text provided it does not articulate penalties, the mechanics of enforcement, or post-compliance reporting obligations. Those enforcement mechanisms would need to be identified in the broader regulatory instruments administered by the Civil Aviation Safety Authority and are not contained in the supplied AD text.

The AD itself makes explicit references to two external, instrument-level sources and thereby creates a bridge between the AD’s requirements and other regulatory or manufacturer procedures. The text provides the following cross-references:

• Turboméca Mandatory Service Bulletin (MSB) 292 73 2826. The AD requires the inspection "in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826." This means the AD adopts that specific MSB paragraph as the procedural standard for how the one-time inspection of the HMU must be performed. The MSB therefore functions as a technical attachment to the AD; operators must follow it to fulfil the AD’s inspection duty.

• EASA AD 2008-0077 dated 28 April 2008. The AD includes "Note 2: EASA AD 2008-0077 dated 28 April 2008 refers." That explicit reference signals that the Australian AD was issued with cognisance of an earlier European Aviation Safety Agency AD on the same technical issue. It indicates coordination or parity between regulatory jurisdictions concerning the safety concern.

What the AD does not do, within its own text:

• It does not reproduce the content of the referenced MSB paragraph or the EASA AD, nor does it purport to replace or amend those instruments. The AD’s operative instructions are limited to their own text plus the procedural instruction to use paragraph 2 of the MSB for the inspection methodology.

• It does not claim to override or modify other regulatory instruments, nor does it cite statutory provisions or enforcement sanctions from other laws in this text. It is presented as a self-contained directive prescribing inspection and remedial steps for the specific engine models.

Consequences of those interactions for operators:

• The requirement to use the manufacturer MSB paragraph means operators will need access to, and compliance with, the manufacturer’s specific procedural guidance. In practice that typically requires following the MSB exactly, including any part identification and disassembly guidance it contains. The AD thereby folds manufacturer-specified technical detail into a regulatory obligation.

• The reference to EASA AD 2008-0077 indicates that there is a parallel or prior regulatory action in another jurisdiction on this technical issue, which may contain additional explanatory material, rationale or procedural guidance. The Australian AD’s referral to the EASA AD situates it within a broader international safety dialogue, and operators may look to the EASA text for context or supplemental requirements, but this AD does not itself reproduce or restate EASA’s enforcement procedures.

Implicit interactional consequences not stated but suggested by structure:

• Because ADs are instruments aimed at maintaining airworthiness, complying with this AD will necessarily intersect with maintenance approvals, component traceability and airworthiness records held by operators and approved maintenance organisations. The AD does not specify recordkeeping or reporting steps but the practical interaction with maintenance standards is implied by the MSB reference.

• If an operator has already performed the MSB paragraph 2 inspection or installed an IN-LHC switch "since new, repair or overhaul" as described in the AD, the AD provides a direct statement that "no further action is required" under those fact patterns. That creates a clear interaction between past maintenance history and the AD’s obligations.

In summary, within the four corners of this document the AD interacts directly with a manufacturer MSB paragraph and an EASA AD, importing the MSB’s procedural content by reference and aligning the Australian action with an EASA directive. The AD does not, in this text, specify how it modifies or is prioritised against other domestic statutory instruments, nor does it contain comprehensive cross-references to broader CASA enforcement rules.

The AD text supplied contains explicit dates relevant to its issuance and compliance timeline, but it does not include any internal amendment history beyond those dates and the cross-references. The document provides the following chronological markers:

• Signature and date of issuance: "James Coyne, Delegate of the Civil Aviation Safety Authority 22 May 2008." That is the date on which the Delegate appears to have signed the AD.

• Effective date: "This Airworthiness Directive becomes effective on 3 July 2008." The AD therefore sets a future effectivity date approximately six weeks after the signing date.

• Compliance date: "No later than 30 September 2009." The AD sets the compliance window for completing the one-time inspection and any prescribed remedial work to that single deadline.

References to other instruments with their own dates:

• The AD refers to "EASA AD 2008-0077 dated 28 April 2008." That shows that the EASA action predated the Australian AD and likely informed it.

What the AD does not include in the supplied text:

• There is no text of any amendment, revision or superseding action included. The AD does not state that it amends, replaces, or supersedes any prior Australian AD on the same subject. It also does not contain an explicit "Amendment" or "History" section listing version numbers, modifications, or revocations.

• No later amendment or extension of deadlines is recorded within this instrument. The AD sets a single compliance deadline and does not provide any follow-up modifications.

Administrative artefacts in the supplied text:

• The supplied text contains some repeated header lines , for example, several lines repeating "AD/ARRIEL/29" and "Low Fuel Pressure Switch" and "7/2008" , but these appear to be duplication or formatting reiteration rather than formal amendments. They do not themselves record changes to the substantive requirements.

Implication for users searching for amendments:

• Because this AD text does not list any amendments, a reader must treat the AD as issued with the dates above and, where necessary, consult CASA’s public AD index or subsequent publications for any later amendments, superseding ADs, or revocation notices. That external search is not reflected in the supplied text.

In sum, the AD as supplied has a clear issuance date, an effectivity date, and a compliance deadline, but contains no internal record of amendments, revisions, or subsequent regulatory changes within the document itself.

The supplied AD does not contain or reference any litigation history. It does not cite any court decisions, administrative appeals, or legal challenges against the AD or its underlying measures. The text includes only:

• The technical requirement detailing inspection and replacement actions.
• The effective and compliance dates.
• The background factual explanation of the safety hazard.
• References to the Turboméca MSB and the EASA AD.

Absence of litigation material in the AD:

• There are no references to appeals, petitions for review, stays, injunctions, contested enforcement actions, or adjudications in the text provided.

How to interpret this absence:

• The AD is a technical regulatory instrument; the supplied text confines itself to technical requirements and dates. The absence of litigation history in the text does not mean litigation did or did not occur elsewhere, only that no litigation or adjudicative narrative is recorded in this AD document.

What readers who require litigation context must do:

• To locate any litigation, administrative appeals, or judicial review actions arising from this AD, one must search external sources such as case law databases, administrative tribunal records, CASA publications or legal reports. Those searches fall outside the content of the supplied AD text.

Therefore, for the purposes of this analysis grounded exclusively in the provided material, there is no litigation history recorded or referenced in the AD text.

This AD contains several detail-sensitive points that can lead to misapplication or operational oversights if not attended to precisely. The following are concrete pitfalls drawn from the AD text and how they operate mechanically.

1. Applicability uses engine model descriptors, not airframe lists. The AD applies to "Turboméca S.A. ARRIEL 2B, 2B1 and 2B1A turboshaft engines." The Note states these engines are "known to be installed on, but not limited to Eurocopter AS 350 B3 and EC 130 B4 helicopters." The gotcha is assuming the AD only covers those helicopter types. Operators must check the actual engine model fitted to their airframe; applicability is engine-focused. If an Arriel 2B family engine is fitted on another helicopter type, the AD still applies.

2. Part-number specificity drives different outcomes. The AD distinguishes three P/Ns:

   • Hydra-Electric P/N 9 550 17 956 0 (the problematic switch)
   • IN-LHC P/N 9 550 17 199 0
   • IN-LHC P/N 9 550 17 913 0 Confusing or misreading these part numbers could produce the wrong remedial action. The operator must positively identify the installed P/N before deciding whether an HMU replacement is required.

3. Historical installations matter. For IN-LHC switches, the AD states "If an IN-LHC low fuel pressure switch has been installed since new, repair or overhaul, no further action is required." But if the IN-LHC is present now and a Hydra-Electric switch "has been or may have been previously installed," the HMU chamber must be inspected and HMU replaced if any parts are found. That introduces a record-tracing element: maintenance history matters, and lack of clear historical traceability ("may have been previously installed") triggers a physical inspection obligation.

4. The remedy for loose parts is HMU replacement, not just switch replacement. If any parts from a Hydra-Electric switch are found in the HMU chamber, the AD mandates replacement of the entire HMU "by a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch." Replacing only the switch is not authorised in that fact pattern. Operators must therefore be prepared for the higher cost and longer downtime associated with HMU replacement when foreign parts are detected.

5. Single-time inspection only. The AD mandates a one-time inspection. That could mislead operators into thinking no further surveillance is ever required. The AD does not require recurring checks within its text. If an operator’s maintenance philosophy or safety management system wants ongoing monitoring, that obligation must be derived separately; it is not imposed here.

6. Reference to MSB paragraph 2 is essential. The AD requires inspection "in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826." Failure to follow the exact MSB procedure could be considered non-compliance with the AD. The AD does not reproduce the MSB steps, so operators must obtain and apply paragraph 2 precisely.

7. Timing window stretches over a year but effectivity precedes compliance. The AD becomes effective on 3 July 2008 and sets compliance "No later than 30 September 2009." Operators have months to schedule inspections, but the AD is effective before the compliance deadline. That combination creates scheduling pressures: operators may elect to fly until they can schedule maintenance before the deadline, but the AD does not address whether continued operation after the effective date but before the compliance deadline is authorised or restricted. The AD does not state interim operating limits.

8. No enforcement or reporting mechanics specified. The AD does not instruct where to file proof of compliance or whether compliance must be recorded in any particular way. That absence may lead to uncertainty when inspectors request evidence of compliance. Operators must therefore be deliberate in maintaining maintenance records that show the inspection was conducted per MSB paragraph 2 and any parts or HMU replacements undertaken by the 30 September 2009 deadline.

9. Ambiguities about "may have been previously installed." The AD’s language for the IN-LHC-installed case uses "has been or may have been previously installed" to trigger an HMU chamber inspection. That phrasing can create conservative decisions by maintenance personnel, because uncertainty in past installation history forces an inspection and possibly HMU replacement if parts are found. Clear documentation of past switch installations avoids unnecessary inspections.

10. Dependency on parts availability and overhaul capacity. The AD’s remedial path contemplates either fitting an IN-LHC switch or replacing the HMU with a new or overhauled HMU equipped with an IN-LHC switch. Operators who cannot obtain the required IN-LHC unit or an overhauled HMU within the compliance window may face logistical constraints. The AD does not provide an alternative mitigant or extension mechanism within its text.

These concrete attention points are grounded in the AD’s specific phrasing. Avoiding these gotchas depends on strict part-number verification, adherence to the referenced MSB procedure, maintenance history traceability, and planning for potential HMU replacement logistics.

The AD’s own requirement section provides the compliance steps. For clarity and operational use, the compliance pathway can be restated as a stepwise checklist that mirrors the AD’s conditional structure and timing. All steps must be performed "in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826" as the AD prescribes.

Timing checkpoint:

• The AD is effective from 3 July 2008 and requires completion "No later than 30 September 2009." Schedule the inspection and any required remedial action so completion is certified by that date.

Stepwise compliance actions (follow MSB paragraph 2 procedure for inspection):

1. Confirm applicability.

   • Verify the engine model installed is Turboméca S.A. ARRIEL 2B, 2B1 or 2B1A. If so, the AD applies. Note that the AD comments these engines are "known to be installed on, but not limited to Eurocopter AS 350 B3 and EC 130 B4 helicopters," so check actual engine fitment.

2. Conduct the one-time inspection.

   • "Accomplish a one-time inspection of the Hydro Mechanical Unit (HMU) in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826 to identify the low fuel pressure switch installed on adjusted HMU." Obtain MSB 292 73 2826 and execute paragraph 2 procedures to identify the installed low fuel pressure switch and to inspect the HMU chamber as required by the MSB.

3. Identify the installed low fuel pressure switch part number and proceed accordingly.

   A. If Hydra-Electric low fuel pressure switch P/N 9 550 17 956 0 is installed:

   • Inspect the low fuel pressure switch and the chamber of the HMU body as specified.
   • If any parts from the low fuel pressure switch are missing or found in the HMU chamber:
     • Replace the HMU with a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch. The AD states replacement must be with an HMU equipped with an IN-LHC switch, not merely with any HMU.
   • If no parts are missing and none are found in the HMU chamber:
     • Replace only the low fuel pressure switch with an IN-LHC low fuel pressure switch.

   B. If an IN-LHC low fuel pressure switch P/N 9 550 17 199 0 or P/N 9 550 17 913 0 is installed:

   • If the IN-LHC switch "has been installed since new, repair or overhaul," then "no further action is required."
   • If a Hydra-Electric switch P/N 9 550 17 956 0 "has been or may have been previously installed," perform an inspection of the HMU chamber:
     • If any parts are found in the HMU chamber, replace the HMU by a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch.

4. Procurement and logistics.

   • Where replacement of the switch is required, procure and fit an IN-LHC low fuel pressure switch of P/N 9 550 17 199 0 or P/N 9 550 17 913 0.
   • Where HMU replacement is required, obtain a new or overhauled HMU "equipped with an IN-LHC low fuel pressure switch" per the AD.

5. Completion by deadline.

   • Ensure the inspection and any resulting replacements are completed "No later than 30 September 2009."

6. Documentation and traceability.

   • Although the AD itself does not prescribe a specific reporting route, best practice dictated by the AD’s reliance on the MSB and the regulatory context is to:
     • Record the inspection results, including part numbers identified, findings about any parts located in the HMU chamber, and the remedial action taken (switch replacement or HMU replacement).
     • Retain invoices, parts traceability, and maintenance records to demonstrate the work was performed in accordance with the referenced MSB paragraph 2 and completed by the compliance date.

7. Consider maintenance history verification.

   • For units with an IN-LHC switch currently installed, verify maintenance history to determine whether that switch has been installed "since new, repair or overhaul." If the history is unclear or indicates prior installation of a Hydra-Electric switch, inspect the HMU chamber as required.

8. Coordinate with overhaul and parts suppliers.

   • If HMU replacement is required, coordinate early with overhaul shops or parts suppliers to ensure availability of a new or overhauled HMU equipped with an IN-LHC switch in time to meet the compliance deadline.

9. Follow referenced procedural detail.

   • Execute the inspection strictly "in accordance with paragraph 2" of MSB 292 73 2826. The MSB paragraph defines the technical steps; the AD makes following that paragraph the mandatory method of inspection.

10. Cross-reference the EASA AD where helpful.

• The AD notes "EASA AD 2008-0077 dated 28 April 2008 refers." Operators may consult that EASA AD for additional context or for comparative instructions; however, compliance with the Australian AD is achieved by meeting the obligations stated herein and following MSB paragraph 2 as referenced.

In summary, compliance requires obtaining and following the Turboméca MSB paragraph 2 inspection procedure, identifying the exact part number of the low fuel pressure switch, applying the AD’s remedial decision tree rigorously, and completing all work by 30 September 2009. Maintain contemporaneous maintenance records that demonstrate the inspection methodology and the part-number-driven remedy that was followed. The AD does not specify reporting mechanics within the document, so operators should ensure their internal records can support any external verification requests from the regulator.