AD/HS 125/178 - Air Conditioning - Fan Venturi Motor

The Directive is structured around a small number of concrete regulatory concepts drawn from the supplied text: applicability, mandatory corrective action, prohibition on installation of an identified spare part, acceptable methods of compliance, relationship to manufacturer service bulletins, and a fixed compliance window.

• Applicability: The Directive applies only to airframes listed in the text, specifically Raytheon Model DH.125, HS.125 and BH.125 series aeroplanes; BAe.125 Series 800A (C-29A and U-125), 800B, 1000A and 1000B aeroplanes; and Model Hawker 800 (including variant U-125A) and 1000 aeroplanes, but limited to those “identified in Raytheon Service Bulletin SB 21-3669, dated December 2004.” The wording requires cross-reference to that service bulletin to determine the precise serial numbers or subfleet affected.

• Dual-choice corrective action: The operator must effect either a modification of the motor within the existing assembly (install P/N 207640-34 into P/N 132322-2-1), or replace the entire fan venturi assembly with P/N 132322-3-1. Both are stated as acceptable compliance routes when accomplished “in accordance with the Accomplishment Instructions” of the Raytheon SB.

• Prohibition on reinstallation: Requirement 2 is a rules-based, retrospective and prospective control on spare parts management: the older fan venturi P/N 132322-2-1 may not be installed as a replacement part on any aeroplane unless it has been modified per Requirement 1(a) or it has the new P/N per Requirement 1(b). The Directive thus affects both in-service hardware and inventory.

• Standards of service information: The Directive nominates Raytheon SB 21-3669 as the operative technical method and explicitly acknowledges that the Raytheon bulletin “includes” Honeywell Service Bulletin 132322-21-4041, Revision 2, dated 20 August 2004, as an additional source. It also sets out that later revisions of the Raytheon SB, when approved by the FAA as an AMOC to FAA AD 2006-01-04, are acceptable for compliance.

• Time-limited compliance: Two timing mechanisms are used: an hours-in-service clock (1,200 hours) and an elapsed-time clock (24 months), with the Directive requiring the earlier of the two to be used. The prohibition on installing the older P/N is effective “as of the effective date of this Directive,” which for this instrument is 11 May 2006.

• Relationship to previous Directive and FAA AD: The Directive supersedes AD/HS 125/141, which had required inspections rather than mandated modification/replacement. It explicitly cites FAA AD 2006-01-04 (Amdt 39-14443) as relevant, both in Note 2 and in the clause that makes FAA-approved AMOCs acceptable.

Each of these concepts carries operational implications for fleet managers, maintenance organisations, logistics and parts procurement. The main mechanics therefore reallocate operator effort from recurring inspections (as required by the superseded AD) to a one-off modification or replacement, and introduce a parts-control rule that removes an older part number from replacement use unless modified or replaced.

The Directive affects multiple roles within the aviation operator and maintenance ecosystem; the text identifies the affected aeroplanes and prescribes actions which create obligations for specific parties:

• Registered operators and owners of the listed aeroplane models who have airframes “identified in Raytheon Service Bulletin SB 21-3669, dated December 2004.” Determining whether a given aircraft is “identified” requires reference to that service bulletin, so the owner/operator must consult the Raytheon SB to confirm applicability.

• Maintenance organisations and licensed maintenance personnel tasked with carrying out the “Accomplishment Instructions” of Raytheon SB 21-3669. The Directive conditions compliance on performing the modification or replacement “in accordance with the Accomplishment Instructions,” so the technical steps and acceptance criteria in that Raytheon SB are binding for compliance under the Directive.

• Parts suppliers, spares managers and logistics teams who hold or source fan venturi P/N 132322-2-1. Requirement 2 forbids installing that P/N as a replacement unless it has been modified in accordance with Requirement 1(a) or has been superseded by P/N 132322-3-1, so inventory policies and procurement plans must reflect this prohibition as of the Directive’s effective date.

• Regulatory compliance staff within airlines, corporate flight departments and third-party maintenance providers who need to schedule and document compliance within the defined window (1,200 hours time in service or 24 months after the effective date, whichever occurs first). Determination of the correct compliance date will depend on each aircraft’s hours-in-service profile.

• Technicians and engineers who will need access to the Raytheon SB and the Honeywell service bulletin referenced within it (Honeywell Service Bulletin 132322-21-4041 Rev 2, dated 20 August 2004), because the Raytheon SB includes the Honeywell SB and instructs that the Accomplishment Instructions are to be followed.

• National and international regulators insofar as the Directive references FAA AD 2006-01-04. Operators who also maintain aircraft under other jurisdictions (particularly US registration) will need to reconcile the CASA Directive with any FAA requirements or AMOCs, and the Directive explicitly allows FAA-approved AMOCs on later Raytheon SB revisions to be used for compliance.

Parties that are not specifically called out but bear indirect effect include aircraft lessors (who must ensure lessees comply with the AD), avionics and adjacent-equipment maintainers (because the stated risk involves heat and fire damage to equipment adjacent to the fan venturi), and aircraft insurers (who may be interested in compliance status given the stated fire risk). The Directive does not itself list enforcement agencies or penalties in the text provided, but the operative duties in Requirements 1 and 2 create direct obligations for the operator/maintenance chain identified above.

The Directive establishes a small set of clear duties for affected operators and maintenance organisations, and it recognises a limited procedural right regarding accepted methods of compliance. The duties and rights as expressed in the source text are:

Key duties

• Duty to perform corrective action (Requirement 1): Operators must, if not previously accomplished, carry out either modification 1(a) or replacement 1(b) in accordance with the Accomplishment Instructions of Raytheon Service Bulletin SB 21-3669. The duty is framed as mandatory where the action has not already been accomplished.

• Duty to meet the compliance window (Compliance): The corrective action under Requirement 1 must be completed within 1,200 hours time in service or 24 months after the Directive’s effective date, whichever occurs first. This creates a dual trigger; operators must calculate the earlier of the two thresholds to determine the deadline.

• Duty on parts control (Requirement 2): As of the Directive’s effective date, fan venturi P/N 132322-2-1 may not be installed on any aeroplane as a replacement part unless it has been modified in accordance with Requirement 1(a) or unless it has a new P/N in accordance with Requirement 1(b). This duty affects procurement and spare-part installation decisions.

• Duty to follow nominated technical instructions: The Directive conditions compliance on using the Accomplishment Instructions of Raytheon SB 21-3669, and notes that the Raytheon SB includes Honeywell Service Bulletin 132322-21-4041 Rev 2 as additional service information. Where a specific SB is nominated, following its Accomplishment Instructions is the required method.

Limited procedural right

• Right to use FAA-approved AMOCs for later revisions of Raytheon SB: The Directive explicitly states that later revisions of the Raytheon SB, approved by the FAA as an Alternate Method of Compliance to FAA AD 2006-01-04, are acceptable for compliance with the equivalent requirements of this Directive. That creates a concrete procedural right to use technically equivalent methods, provided they have FAA AMOC approval relative to the cited FAA AD.

Constraints and boundaries

• The Directive supersedes the earlier AD/HS 125/141, which required inspections. The new requirement to replace or modify changes the regulatory expectation from recurring inspection to hardware change. The Directive does not provide alternative inspection-based compliance as an option.

• The Directive sets an effective date (11 May 2006) and a signature date (signed by a CASA delegate on 28 March 2006). The requirements are tied to those dates; in particular, the prohibition in Requirement 2 is effective as of the effective date.

The Directive does not specify appeals procedures, reporting formats, certification documentation to be returned to the regulator, or explicit penalties in the text supplied. The only express procedural concession granted is the acceptance of FAA-approved AMOCs for later Raytheon SB revisions relative to FAA AD 2006-01-04.

The text of the Directive as supplied does not set out civil or criminal penalties, fine amounts, enforcement processes, or detailed mechanisms by which non-compliance will be policed. What the Directive does provide, which has enforcement implications in practice, are the operative requirements and the effective date:

• Operative prohibitions and mandatory actions: Requirement 1 imposes a mandatory corrective action (modify or replace in accordance with Raytheon SB 21-3669) and Requirement 2 imposes an immediate prohibition on installing fan venturi P/N 132322-2-1 as a replacement part unless it is modified or replaced as required. These are regulatory commands that become effective at the Directive’s effective date (11 May 2006).

• Issuer identification and signature: The Directive is signed by a Delegate of the Civil Aviation Safety Authority (James Coyne), which identifies the issuing authority within the CASA administrative structure. That institutional attribution indicates the domestic regulator responsible for the Directive, but the text supplied does not detail enforcement pathways or sanctioning measures.

• Relationship with FAA AD and AMOCs: The Directive references FAA AD 2006-01-04 and accepts later revisions of Raytheon SB approved by the FAA as AMOCs for the FAA AD as acceptable for compliance. This linkage creates a cross-recognition pathway for alternative compliance methods approved through FAA processes, which may reduce disputes over acceptable technical methods. The text does not explain how CASA will administratively accept evidence of an FAA AMOC in an enforcement context.

What is absent in the supplied text

• No penalty schedule: There is no schedule of fines, suspensions, or administrative penalties contained in the Directive text.

• No surveillance or reporting requirements: The Directive does not identify inspection, reporting, or certification return obligations to CASA within the text supplied.

• No process for CASA verification: The Directive does not set out auditing, verification or record-keeping obligations in the supplied text that an operator must follow to prove compliance to CASA.

Implications for operators

• The Directive’s requirements and the prohibition on using an identified P/N create a clear compliance obligation that operators will need to meet. While the Directive itself does not state enforcement steps, operators should treat the requirements as enforceable regulatory obligations from the issuing authority named in the Directive and plan to document compliance. The Directive’s acceptance of FAA-approved AMOCs for later Raytheon SB revisions offers a pre-agreed technical route for equivalence, but the Directive text does not specify how CASA will accept or verify such AMOCs in practice.

Because the supplied text does not enumerate enforcement mechanisms or penalties, any operational or legal consequences of non-compliance would need to be confirmed from sources other than this Directive if a party requires specifics on sanctioning or enforcement processes.

The Directive references and interacts with prior and parallel regulatory instruments and manufacturer service bulletins. The supplied text makes the following explicit cross-references and supersessions:

• Supersession of a previous CASA directive: The Directive states that it supersedes AD/HS 125/141. The earlier Directive required visual inspections to check clearances between the fan venturi motor casing and adjacent equipment, detect signs of overheating, degradation of insulating material, and ingestion of debris into the motor, and required replacement of discrepant parts with serviceable parts. The present Directive replaces that inspection regime with a mandatory modification or replacement requirement. This is an internal regulatory progression: prior law required continued inspection; the new law requires a hardware change.

• Relationship with FAA AD 2006-01-04: The Directive includes Note 2 stating that FAA AD 2006-01-04 Amendment 39-14443 is referred to, and the Directive states that later revisions of Raytheon SB approved by the FAA as an Alternate Method of Compliance to FAA AD 2006-01-04 are acceptable for compliance. This creates an explicit cross-jurisdictional technical recognition: CASA will accept FAA AMOC approvals relative to the cited FAA AD for later Raytheon SB revisions as meeting the CASA Directive’s equivalent requirements. The directive therefore allows technical harmonisation between CASA and FAA instruments to the extent stated.

• Manufacturer service bulletins as technical norm: The Directive makes Raytheon Service Bulletin SB 21-3669 the operative technical method for implementing the required actions, and notes that the Raytheon SB refers to Honeywell Service Bulletin 132322-21-4041 Rev 2 dated 20 August 2004 as additional service information. In effect, the Directive anchors compliance to industry technical data (Raytheon and Honeywell SBs). The Directive also explicitly allows later Raytheon SB revisions with FAA AMOC approvals to be used.

• Interaction with maintenance practice standards: While not explicitly stated in the supplied text, the Directive’s requirement that the specified actions be accomplished “in accordance with the Accomplishment Instructions” of the Raytheon SB ties operator obligations to the technical and procedural standards found in that SB. The Directive does not detail how that interacts with any existing maintenance manuals or continuing airworthiness management procedures; it simply designates the SB as the compliance source.

What is not stated

• There are no express cross-references to other Australian statutes, civil penalties, or administrative law provisions in the supplied text. The Directive’s text is focused on the prescribed hardware action, the parts control prohibition, and specified relationships with the Raytheon and Honeywell service bulletins and the FAA AD. Any broader legal interaction with Australian aviation law outside the instrument itself is not included in the provided text.

In sum, the Directive replaces a prior CASA AD’s inspection regime with a mandatory hardware modification/replacement regime, anchors compliance to specific manufacturer service bulletins (and the Honeywell SB they include), and permits FAA AMOC-approved later revisions of Raytheon SBs to be used as an acceptable compliance method relative to FAA AD 2006-01-04.

The supplied text contains a compact amendment and issuance history which can be extracted as follows:

• Supersession: The Directive explicitly supersedes AD/HS 125/141. The earlier AD/HS 125/141 required visual inspections for clearance, signs of overheating, insulation degradation, and debris ingestion into the motor, and replacement of discrepant parts. AD/HS 125/178 replaces that inspection-based approach with a mandatory modification or replacement. The source text states that this Directive supersedes the earlier AD.

• Service bulletin references and dates: The Directive relies on Raytheon Service Bulletin SB 21-3669, dated December 2004, as the controlling technical document for the Accomplishment Instructions for both modification and replacement actions. Within Note 1 the Raytheon SB is said to refer to Honeywell Service Bulletin 132322-21-4041, Revision 2, dated 20 August 2004, and the Raytheon SB includes the Honeywell SB. The Directive therefore adopts and incorporates these dated technical documents as part of its compliance regime.

• Relation to FAA documentation: Note 2 explicitly refers to FAA AD 2006-01-04 Amdt 39-14443. The Directive also allows later revisions of Raytheon SB that have FAA AMOC approval relative to the FAA AD to be acceptable for compliance. That clause creates an allowance for subsequent technical amendments to the SB , provided FAA grants the AMOC.

• Delegate signature and effective date: The document shows it was signed by James Coyne, Delegate of the Civil Aviation Safety Authority, on 28 March 2006. The Directive states that it becomes effective on 11 May 2006. The document header lists the directive as AD/HS 125/178, dated 5/2006, which indicates the administrative labelling used by the issuing authority.

• No later amendments recorded in text: The supplied text does not contain any further amendments, revocations or subsequent revisions to AD/HS 125/178 itself. It does, however, provide an explicit mechanism by which later revisions of the Raytheon SB that receive FAA AMOC approvals can be relied upon for compliance, effectively permitting technical methods updated by the manufacturer and accepted by the FAA to be used without needing an immediate CASA amendment to this Directive.

Taken together, the amendment history recorded in the supplied Directive is concise: AD/HS 125/178 supersedes AD/HS 125/141, adopts Raytheon SB 21-3669 (Dec 2004) and the incorporated Honeywell SB (Rev 2, 20 Aug 2004) as the technical compliance source, references FAA AD 2006-01-04, was signed 28 March 2006, and becomes effective on 11 May 2006. The Directive does not include later CASA-issued amendments or a catalogue of subsequent changes within the text provided.

The supplied Directive contains no litigation history, case references, court decisions, or mention of disputes. The text does not cite any administrative appeals, judicial challenges, or enforcement proceedings arising from AD/HS 125/178. The only authoritative references are to manufacturer service bulletins (Raytheon SB 21-3669 and Honeywell SB 132322-21-4041 Rev 2) and to FAA AD 2006-01-04. The Directive does not identify any legal proceedings having been brought against CASA, the delegate, any operator, or manufacturer in relation to this Directive within the supplied material.

Because there is no litigation material in the text, readers who require information about any legal challenges, compliance disputes, or enforcement cases must consult sources beyond the Directive itself. The Directive does not provide procedural or contact details for contesting the directive, nor does it enumerate an administrative review or appeal path in the supplied text.

In short, the document as provided shows no litigation history and contains no reference to legal proceedings that could be relied upon to infer contested legal outcomes or judicial interpretation of the Directive’s terms.

The Directive contains several concrete points that can cause compliance confusion or operational risk if overlooked. These are drawn directly from the document language and the practical implications of the requirements:

• Applicability tied to the Raytheon SB: The Directive applies to the models listed only if the individual aeroplane is “identified in Raytheon Service Bulletin SB 21-3669, dated December 2004.” The SB will typically list serial numbers or configured subfleets; failure to cross-check an aircraft’s serial number against the Raytheon SB can lead to misclassification of applicability. Do not assume all airframes of those types are included; confirm against the SB.

• Two alternative actions are not cumulative: Requirement 1 presents two mutually exclusive routes: modify the existing P/N 132322-2-1 by installing motor P/N 207640-34, or replace the assembly with P/N 132322-3-1. Operators should not interpret the Directive as leaving open inspection-only remedies, because the prior AD that required inspection has been superseded.

• Prohibition on installing the older P/N affects spares and maintenance practices: Requirement 2’s language , “Fan venturi, P/N 132322-2-1, may not be installed on any aeroplane as a replacement part unless the fan venturi has been modified in accordance with Requirement 1.a. or unless the fan venturi has a new P/N in accordance with Requirement 1.b.” , means that spare parts inventory containing the older P/N cannot be used as replacements after the effective date unless they have been modified or replaced. This has implications for parts warehouses, repairs and over-the-counter availability. Operators who consume old spares without confirming modification status may be non-compliant.

• Timing trigger can be the earlier of hours or months: Compliance with Requirement 1 is required “within 1,200 hours time in service or 24 months after the effective date of this Directive, whichever occurs first.” Operators with low utilisation aircraft must be careful: a low-hour aeroplane may reach the 24-month limit before accruing 1,200 hours, and a high-utilisation aircraft may hit 1,200 hours more quickly. Calculate both thresholds and use the earlier.

• Effective date and retrospective prohibition: The effective date is 11 May 2006, and Requirement 2 is “as of the effective date of this Directive.” This means the prohibition on installing the older P/N takes effect immediately on that date; operators replacing parts after that date must ensure those parts comply with Requirements 1(a) or 1(b).

• Raytheon SB includes Honeywell SB but the primary compliance document is Raytheon SB: Note 1 states that Raytheon SB SB 21-3669 refers to Honeywell SB Rev 2 and that the Raytheon SB includes the Honeywell SB. Compliance must be performed “in accordance with the Accomplishment Instructions of Raytheon Service Bulletin SB 21-3669,” and operators must therefore follow the Raytheon SB’s instructions, which include or reference the Honeywell SB. Using the Honeywell SB alone without following the Raytheon SB’s Accomplishment Instructions risks a methodological mismatch.

• AMOC acceptance is tied to FAA approvals and a specific FAA AD: Later revisions of the Raytheon SB are acceptable only if they are “approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2006-01-04.” The acceptance is therefore conditional on FAA action relative to that FAA AD. An AMOC approved by another authority or an amendment to the Raytheon SB without FAA AMOC approval is not automatically acceptable under the Directive’s text.

• Supersession of inspection regime means records of prior inspections may not discharge the Directive: The earlier AD (AD/HS 125/141) required inspections. AD/HS 125/178 supersedes that AD and requires modification/replacement. If an operator performed repeated inspections under the earlier AD, those inspections do not substitute for the mandatory modification/replacement unless the modification or replacement has already been accomplished. The Directive’s text requires the actual modification/replacement if not previously accomplished.

• Part numbers must be exact: The Directive uses precise part numbers (P/N 132322-2-1; motor P/N 207640-34; replacement fan venturi P/N 132322-3-1). Small transcription or cataloguing errors in part numbers can lead to incorrect installations.

• No enforcement details in text: The Directive does not list procedural steps for demonstrating compliance to CASA or any documentation format. While this is not a legal gap in the Directive itself, operators should be aware that the document does not state what proof the regulator expects in an audit or inspection. The supply text does, however, make FAA-approved AMOCs acceptable for later SB revisions.

Pay careful attention to these operational details. Misreading the “identified in Raytheon SB” criterion, mismanaging spares, or missing the earlier of the hours/months deadline are realistic sources of non-compliance emerging directly from the Directive language.

The Directive prescribes specific actions and acceptable reference documents; successful compliance requires following those steps and using the nominated technical information. The following is a source-grounded, step-by-step approach based on the Directive text:

1. Confirm applicability for each airframe: Consult Raytheon Service Bulletin SB 21-3669, dated December 2004. The Directive’s applicability provision restricts the AD to the listed models only insofar as each aeroplane is “identified in Raytheon Service Bulletin SB 21-3669, dated December 2004.” Review the SB to confirm the aircraft serial numbers or configuration status that make a given aeroplane subject to the Directive.

2. Determine whether the corrective action has already been accomplished: The Directive requires the action “if not previously accomplished.” Verify maintenance records to establish whether prior modification or replacement to P/N 132322-3-1 or motor P/N 207640-34 has been performed.

3. Select acceptable compliance path per Requirement 1: If the corrective action has not already been completed, choose one of the two paths specified in the Directive and perform it in accordance with the Raytheon SB’s Accomplishment Instructions:

   • Option A (Modification): Modify the existing fan venturi P/N 132322-2-1 by installing the improved motor P/N 207640-34 into that assembly; or
   • Option B (Replacement): Replace the entire fan venturi P/N 132322-2-1 with a new fan venturi P/N 132322-3-1.

4. Use the specified technical instructions: Execute the selected action “in accordance with the Accomplishment Instructions of Raytheon Service Bulletin SB 21-3669.” Note 1 indicates that the Raytheon SB refers to and includes Honeywell Service Bulletin 132322-21-4041, Revision 2, dated 20 August 2004, as additional service information. Do not rely solely on the Honeywell SB if the Raytheon SB’s Accomplishment Instructions contain specific steps or acceptance criteria.

5. Meet the compliance window: Complete the chosen modification or replacement within 1,200 hours time in service or 24 months after the Directive’s effective date, whichever occurs first. Calculate both clocks for each airframe; the earlier threshold is the deadline for compliance.

6. Implement the replacement-part prohibition: Effective as of the Directive’s effective date (11 May 2006), do not install fan venturi P/N 132322-2-1 on any aeroplane as a replacement part unless that unit has been modified in accordance with Requirement 1(a) or has the new P/N 132322-3-1 as per Requirement 1(b). Update spares-control procedures to ensure no unmodified P/N 132322-2-1 assemblies are fitted post-effective date.

7. Consider AMOC options for updated Raytheon SB revisions: If a later revision of Raytheon SB 21-3669 exists, confirm whether the FAA has approved that later revision as an AMOC to FAA AD 2006-01-04. The Directive states such FAA-approved AMOCs are acceptable for compliance with the equivalent requirements. Where an FAA AMOC exists for a later Raytheon SB revision, that revision’s Accomplishment Instructions can be used.

8. Technical verification: Ensure that the installed motor P/N 207640-34 or the replacement assembly P/N 132322-3-1 is the correct part, and verify installation per the Accomplishment Instructions. The Directive does not provide test criteria in the text; those will be found in the Raytheon SB.

9. Record-keeping (operationally necessary though not specified in the text): While the Directive text does not set out a required return form, maintain contemporaneous maintenance records documenting the accomplishment of Requirement 1 and the change in the part number where replacement occurs, so as to be able to show that the airframe is compliant with the AD’s requirements. Although the Directive does not mandate a specific format, document the SB revision used and, where relevant, any FAA AMOC relied upon.

10. Spare parts and procurement adjustments: Remove or quarantine unmodified P/N 132322-2-1 units from inventory for use as replacement parts, unless they have been modified per Requirement 1(a) or are replaced with P/N 132322-3-1. Coordinate with parts suppliers to obtain P/N 207640-34 motors or P/N 132322-3-1 assemblies as required.

11. Cross-jurisdictional alignment: If operating aircraft under multiple regulatory authorities, reconcile this Directive’s acceptance of FAA-approved AMOCs relative to FAA AD 2006-01-04 with any other regulator’s expectations. The Directive allows FAA AMOC-approved later Raytheon SB revisions to be used, so where such an FAA approval exists, rely on that revised SB and the AMOC for the technical method.

The Directive itself contains the essential compliance blueprint: determine applicability by reference to Raytheon SB 21-3669 (Dec 2004), perform either the modification or replacement per the SB’s Accomplishment Instructions within either 1,200 hours TIS or 24 months (whichever comes first), and enforce the prohibition on installing P/N 132322-2-1 as a replacement part after the effective date unless modified or superseded. The practical compliance tasks derive from those obligations and from inventory and planning consequences that flow directly from Requirement 2.