AD/BELL 407/31 - Disc Assemblies - Tail Rotor Driveshaft

The AD is organised around a few tightly defined regulatory concepts: applicability, requirements (technical actions), compliance deadlines, and cross-references to manufacturer and foreign authority documents. Each concept has operational consequences for affected operators.

Applicability: The AD lists a precise fleet subset , Bell BHTC Model 407 helicopters with specific serial number ranges (S/N up to 53709, 53711-53716, 53718 and 53720-53722) when fitted with disc assemblies P/N 407-340-340-103. Applicability limits the AD’s reach to a narrow set of airframes and to a particular part number. That is the statutory trigger for the AD’s requirements.

Requirements (technical actions): The AD sets four tasks:

• Requirement 1: Verify disc assemblies P/N 407-340-340-103 for manufacturing date, proper thickness and indexing, in accordance with BHTC Alert Service Bulletin ASB-407-07-76 dated 28 March 2007 or later approved revisions. The AD also instructs that if verification shows no further action is necessary, or if manufacturing date is outside 01 Nov 2005 to 30 Nov 2006, an appropriate log book entry must be made and no further action is required.
• Requirement 2: Remove any disc assembly not within thickness tolerance 0.115-0.127 inch (2.921-3.225 mm).
• Requirement 3: Remove any disc assembly that is not properly indexed.
• Requirement 4: Prohibit installation of disc assembly P/N 407-340-340-103 unless compliant with the ASB.

Compliance deadlines: The AD specifies multiple timing constraints that create sequencing and operational windows:

• Compliance 1 (verification): no later than 25 flight hours or 30 days from the effective date, whichever comes first.
• Compliance 2 (removal where required following verification): within 10 flight hours after completing Requirement 1.
• Compliance 3 (removal for thickness/indexing defects): within 300 flight hours or at next scheduled inspection, whichever comes first, after completion of Requirement 1.
• Compliance 4 (installation prohibition): applies after the effective date.

Cross-references: The AD requires adherence to a particular BHTC ASB as the technical method for verification and remediation (ASB-407-07-76, dated 28 March 2007 or later approved revisions). It also refers to a Transport Canada AD (CF-2007-14 dated 24 August 2007), explicitly acknowledging a foreign authority’s parallel action.

Logbook action: The AD creates an affirmative record-keeping requirement if the inspection discloses no further action or the part falls outside the implicated manufacturing date range: "make an appropriate log book entry to this effect. No further action is required" (Requirement 1).

Signature and authority: The AD is signed by David Villiers, Delegate of the Civil Aviation Safety Authority, with the date 28 September 2007, and states the AD becomes effective on 3 October 2007. The signature binds the directive to CASA’s administrative process and fixes the effective date that starts the compliance clocks.

Collectively, these concepts convert a manufacturing/assembly concern into a short set of verifiable operator actions, time-limited requirements and record-keeping, referencing the manufacturer’s procedural document and acknowledging a Transport Canada AD.

The AD directly applies to operators, owners, maintainers and certificated maintenance organisations responsible for Bell BHTC Model 407 helicopters that meet the Applicability criteria. The Applicability table specifies the affected serial numbers and requires the presence of disc assembly P/N 407-340-340-103. Therefore, the primary affected parties are those owning or operating the listed helicopters equipped with the specified part.

The AD states in plain terms that the obligations fall on entities controlling the aircraft because they are the ones who must carry out verification, removal and logbook entries. Requirement 1 directs an operator to "Verify disc assemblies P/N 407-340-340-103 for manufacturing date, proper thickness and indexing, in accordance with the instructions provided in BHTC Alert Service Bulletin (ASB) ASB-407-07-76 dated 28 March 2007 or later approved revisions." That imposes a technical inspection burden on operators or their maintenance providers. Where removal is required (Requirements 2 and 3), whoever provides maintenance services or parts supply for the helicopter will be tasked with removal and replacement activities.

Maintenance organisations and technicians will be affected because the AD mandates that inspection and removal be done "in accordance with" the BHTC ASB. Those organisations must have access to the ASB and the competence to measure thickness to the tolerance specified (0.115-0.127 inch) and to determine "proper indexing" consistent with the ASB. If operators rely on external maintenance providers, contractual arrangements and scheduling will need to be adjusted to meet the AD’s short deadlines.

Logbook custodians (usually the operator or maintenance organisation) are affected because Requirement 1 requires a logbook entry when no further action is needed or when the manufacturing date is outside the implicated window. That changes documentation practices and creates an auditable record.

Parts suppliers are indirectly affected. Requirement 4 prohibits installing disc assembly P/N 407-340-340-103 into any helicopter unless compliant with the ASB. This prohibition limits the usability of stock parts unless they have been verified and brought into compliance with the ASB; suppliers who hold the specified P/N stock will therefore need to ensure parts are compliant before sale or installation into a CASA-regulated aircraft.

Regulatory actors are implicated: the AD references a Transport Canada AD and is signed by a CASA delegate. While the AD text does not set out enforcement mechanisms or penalties, the presence of a CASA-signed AD confines the obligations within CASA’s regulatory regime and normal aviation oversight. The AD’s effective date sets the timetable for obligation commencement, so operators whose aircraft are within the Applicability must act within the defined compliance windows starting from 3 October 2007.

The AD imposes specific duties on operators and maintenance providers and establishes certain procedural rights by reference to external documents. These duties are expressed as mandatory-sounding "Requirements" with explicit compliance times.

Primary duties:

• Verify: Operators must verify disc assemblies P/N 407-340-340-103 for manufacturing date, proper thickness and indexing, "in accordance with" BHTC ASB-407-07-76 or later approved revisions (Requirement 1). This is a prescriptive duty to follow the manufacturer's procedural guidance for inspection.
• Record: If the verification shows no further action is needed, or the manufacturing date falls outside 1 Nov 2005 to 30 Nov 2006, the operator must "make an appropriate log book entry to this effect" and then no further action is required (Requirement 1). The AD thus creates a duty to document the inspection outcome in the aircraft's logbook.
• Remove: Operators must remove disc assemblies that are outside the specified thickness tolerance (0.115-0.127 inch) (Requirement 2) and must remove assemblies that are not properly indexed (Requirement 3).
• Do not install: Operators and maintenance providers are prohibited from installing disc assembly P/N 407-340-340-103 into any helicopter unless the assembly is compliant with the ASB (Requirement 4). This functionally restricts installation to parts verified and brought into conformance.

Timing duties:

• The verification duty must be completed "no later than 25 flight hours or 30 days from the effective date" (Compliance 1). That is an immediate short-term duty.
• If further action is required after verification, removal must be completed within 10 flight hours following completion of Requirement 1 (Compliance 2). This creates a compressed window for corrective action once an issue is identified.
• Removal for thickness/indexing defects can be delayed to "within 300 flight hours or at next scheduled inspection, whichever comes first, after the completion of Requirement 1" (Compliance 3). This provides some scheduling flexibility for removals not immediately safety-critical, but still limits deferral.
• The installation prohibition applies "after the effective date" (Compliance 4) , meaning that from the AD effective date forward, non-compliant parts may not be installed.

Rights and procedural features:

• The AD delegates the technical method for verification and remediation to the manufacturer's ASB and authorises the use of "later approved revisions" of that ASB. This creates a procedural right for operators to rely on the ASB as the technical standard; it also allows CASA to approve later revisions so operators can adopt updated procedures without separate AD amendments.
• If a disc assembly is outside the implicated manufacturing date range or requires no further action, the AD specifically says "No further action is required" after making the logbook entry. That is a limited substantive right to cease action without further mandatory steps in those circumstances.

Not stated in the AD:

• The AD text supplied does not provide specific rights to request alternative compliance methods or specify the mechanism for getting parts certified as compliant beyond following the ASB. It also does not set out appeals or penalties. Any such rights or administrative processes would exist, if at all, outside this text.

In short, the AD delegates technical procedure to a specified manufacturer ASB, imposes immediate and staged duties to inspect, document, remove and prohibit installation, and sets short operational windows. It implicitly allocates responsibility for performance to aircraft operators and their maintenance providers, while giving them a clear technical standard to apply.

The supplied AD text does not specify penalties, sanctions or the administrative enforcement mechanisms that CASA will employ for non-compliance. The document sets prescriptive "Requirements" and compliance timeframes but contains no express statutory penalty provisions, infringement notices, or criminal sanction language within the text provided. It does, however, bear the imprimatur of CASA by being signed by "David Villiers, Delegate of the Civil Aviation Safety Authority" and carries an effective date, which places it within CASA’s regulatory action stream.

What the document does provide that bears on enforcement mechanics:

• Explicit Requirements and Compliance dates: The AD sets firm deadlines (e.g. "no later than 25 flight hours or 30 days from the effective date" for verification). These create measurable obligations that inspectors or auditors can check against maintenance records and logbook entries.
• Logbook entry requirement: Requirement 1 explicitly mandates making "an appropriate log book entry" where verification shows no further action or where manufacturing date is outside the implicated window. This creates documentary evidence that can be inspected by regulators and used to assess compliance.
• Prohibition on installation: Requirement 4 provides a clear rule - "Do not install any disc assembly P/N 407-340-340-103 into any helicopter unless it is compliant to the ASB-407-07-76 dated 28 March 2007 or later approved revisions." This is a black-letter restriction on conduct that can be verified by examining installed parts and their compliance status.

Absent in the text:

• No fines, demerit regimes, licence suspension procedures or enforcement pathways are stated in the supplied AD text. The AD does not elaborate how CASA will proceed in the event of non-compliance (for example, whether enforcement will be by administrative notice, grounding of aircraft, remedial directions, or referral to enforcement proceedings). The AD similarly does not set out dispute resolution or review avenues.

Cross-references relevant to enforcement:

• The AD references Transport Canada Airworthiness Directive CF-2007-14 dated 24 August 2007. That cross-reference indicates a parallel action by another authority; enforcement practices in that foreign AD may differ but are not provided in this text.

Practical enforcement inference limited to source:

• The AD’s requirements, timelines and logbook duties create a recordable and verifiable compliance regime. Enforcement, penalties or sanctions are not detailed in the text provided; any regime for imposing penalties or other corrective mechanisms would be located in CASA’s broader regulatory framework or enabling legislation, which is not reproduced in this AD text.

Therefore, for legal certainty and risk assessment, affected operators should note that the AD creates concrete obligations and documentation requirements but must consult CASA’s wider regulatory materials or seek direct guidance from CASA to confirm enforcement and penalty exposure for non-compliance, since those elements are not described in the AD itself.

The AD explicitly interacts with manufacturer technical guidance and a foreign authority’s directive, thereby creating a compliance nexus between CASA’s directive, BHTC’s ASB, and Transport Canada’s AD. Within the supplied text, the AD does not assert supremacy over other legislation, nor does it reference domestic aviation statutes or penalty regimes. The interaction points present in the AD are as follows.

Manufacturer technical document dependency: The AD requires inspections and remediation "in accordance with the instructions provided in BHTC Alert Service Bulletin (ASB) ASB-407-07-76 dated 28 March 2007 or later approved revisions" (Requirement 1). This creates an operational dependency where a regulatory obligation under CASA is fulfilled by following the manufacturer’s ASB. That establishes a relationship whereby technical compliance is judged against a private-sector document, with CASA determining that adherence to the ASB satisfies the AD’s substantive requirements.

Cross-jurisdictional reference: The AD notes "Transport Canada Airworthiness Directive CF-2007-14 dated 24 August 2007 refers." The reference acknowledges that another civil aviation authority has taken a parallel safety action. That cross-reference can affect operators with multinational operations, parts supplies, or maintenance chains because Transport Canada’s AD may impose similar or differing technical or timing obligations. The AD’s reference may also indicate that CASA considered foreign regulatory findings in deciding to issue its AD.

Logbook and maintenance records: The AD requires specific logbook entries as proof of inspection outcomes. Logbook requirements commonly interact with broader regulatory frameworks governing continuing airworthiness, maintenance release and airworthiness certification. While the AD does not quote those statutes or regulations, the logbook entry duty will be relevant to demonstrating compliance with wider airworthiness oversight obligations under CASA-administered law.

Parts traceability and installation prohibitions: Requirement 4 prohibits installing P/N 407-340-340-103 unless compliant with the ASB. That prohibition interacts with supply chain, sales and parts certification practices, and potentially with import/export rules for aircraft parts. The AD would operate in practice alongside laws governing commerce in aircraft parts, maintenance release documentation, and approvals for parts of unknown origin.

Absence of explicit statutory enforcement language: The AD does not, within the provided text, invoke a specific enforcement statute or provide details on the legal mechanism by which CASA enforces compliance. As a result, interactions with enforcement laws (administrative penalties, prosecutions for breaches of civil aviation regulations) are not documented in this text. Those interactions will exist in CASA’s broader legal framework but are not described.

Scope limitation and potential overlap: The Applicability provision narrowly identifies serial numbers and a specific P/N. Operators with similar parts on helicopters outside those serial number ranges, or with substitute part numbers, are not captured by the AD as written. That creates potential for regulatory coordination: if other legislation or ADs cover different serial ranges or part numbers, operators must track multiple directives. The AD’s express reference to "later approved revisions" of the ASB allows for dynamic interaction: if the manufacturer updates the ASB and CASA approves that revision, the AD’s technical standard effectively moves with the ASB.

In sum, the AD explicitly ties CASA’s prescriptive duties to a manufacturer ASB and acknowledges a Transport Canada AD. It does not, in the supplied text, cite the enabling legislation for CASA’s authority or specify enforcement statutes; those interactions live outside the AD and should be checked against CASA’s regulatory instruments and the enabling aviation law framework.

The AD text supplied does not record any amendments to the directive itself. It lists the BHTC Alert Service Bulletin (ASB-407-07-76 dated 28 March 2007) as the technical standard and allows use of "later approved revisions" of that ASB, but the AD does not itself include amendments or a revision log. The headings and table rows at the end of the text appear to be duplication for formal identification (AD/BELL 407/31; 12/2007 DM) and include the effective date and signature, but they do not show any subsequent amendments or follow-up notices within the supplied document.

Explicit points from the text relevant to amendment treatment:

• The AD instructs compliance "in accordance with the instructions provided in BHTC Alert Service Bulletin (ASB) ASB-407-07-76 dated 28 March 2007 or later approved revisions." That creates an operational allowance for the ASB to be revised and for those approved revisions to be accepted as satisfying the AD’s technical requirements without the AD itself being formally amended. The AD thus delegates dynamic updating of technical procedure to the ASB approval process rather than requiring amendments to the AD for every technical update.
• The AD is signed and dated (28 September 2007) and given an effective date (3 October 2007). There is no subsequent effective-dated amendment or rescission noted in the text provided.

No explicit amendment record:

• The supplied text contains no "Amendment No." entries, no history table, no superseding AD references, and no rescission or expiry statement. It does, however, incorporate the possibility that the referenced ASB may be amended and that later approved revisions will apply.

Implication for practitioners:

• Because the AD relies on "later approved revisions" of the ASB, practitioners should monitor both CASA communications regarding approved ASB revisions and the manufacturer’s releases. Amendments to the ASB that are "approved" under whatever CASA or approved body process applies will be effective for the technical standard without an AD amendment being printed in this particular document. Practitioners seeking an explicit amendment log should therefore consult CASA’s public AD registry or the BHTC documentation for any updated ASB versions referenced by CASA approvals.

Conclusion for this section:

• Within the supplied text, there is no recorded amendment history for AD/BELL 407/31. The AD includes a mechanism to accept future ASB revisions as meeting the AD’s technical standard, but any actual amendments to the AD or notes of subsequent actions are not present in the document provided.

The supplied AD text contains no litigation history. It does not mention any legal challenges, court proceedings, appeals, or decisions relating to the AD. There are no case names, citations, or references to judicial review processes within the document provided.

What the document does contain that is relevant to potential litigation:

• Prescriptive requirements with measurable deadlines and a logbook documentation obligation, which are the types of regulatory actions that may later form the subject matter of enforcement or judicial review. However, the AD itself contains no record of any such proceedings.
• Cross-references to a Transport Canada AD and to a manufacturer ASB, which could be evidentiary in future disputes over technical compliance standards, but again no litigation is referenced.

If a reader requires litigation history:

• Because the AD text is silent on litigation, any judicial or administrative challenges, enforcement prosecutions, or related proceedings would need to be sought outside this document. That would typically involve searching CASA records, court databases, or legal reporting services for proceedings that mention AD/BELL 407/31 or the subject matter (disc assemblies P/N 407-340-340-103). Nothing in the text authorises the drawing of conclusions about litigation outcomes or the presence of contested matters.

In short, the AD as supplied contains no litigation history. Practitioners seeking to know whether this AD has been litigated or has been the subject of enforcement proceedings must look to external records; no such events are recorded in the AD text itself.

This AD has several operational features that create potential pitfalls for operators, maintainers and parts suppliers; the document’s language and timeframes produce specific compliance risks. The following items are grounded in the AD’s text.

Narrow applicability but part-number dependency: The Applicability combines specific serial numbers with a specific part number P/N 407-340-340-103. Helicopters outside the listed serial numbers or with different part numbers are not covered as written. Operators with mixed fleets must carefully verify serial numbers and installed part numbers; failure to do so risks performing unnecessary removals or, conversely, overlooking affected airframes. The AD’s specificity therefore increases the risk of misclassification if maintenance records or part tagging are incomplete.

Short verification clock: Verification must be completed "no later than 25 flight hours or 30 days from the effective date, whichever comes first" (Compliance 1). That is a short window. Aircraft with continuous operations may hit the 25 flight hours quickly, while others may surpass the 30-day calendar limit. Operators who do not schedule inspections promptly face the risk of being out of compliance within weeks. Practically, the interplay between flight hours and calendar days requires that operators track both metrics precisely.

Staging of corrective action with compressed follow-up: If after verification a disc assembly requires further action, removal must occur "within 10 flight hours, after the completion of requirement 1" (Compliance 2). This creates a compressed corrective window after an adverse finding. Operators that lack immediate spare parts, qualified maintenance availability or slots to take aircraft out of service may find it difficult to meet this requirement.

Two-tier removal timing: The AD provides a more flexible removal deadline for thickness/indexing defects , "within 300 flight hours or at next scheduled inspection, whichever comes first" (Compliance 3) , but it only becomes relevant after Requirement 1 is completed. There is a potential gotcha in sequencing: operators must not conflate the 10 flight hour immediate removal timing for "further action" with the up-to-300 flight hour window , the AD separates these scenarios. Operators need to interpret correctly which defects trigger immediate removal and which can be deferred to the 300-flight-hour window in accordance with the ASB’s guidance.

Reliance on ASB and "later approved revisions": The AD requires actions "in accordance with" BHTC ASB-407-07-76 or later approved revisions (Requirement 1). This delegates technical detail to an external document and allows later revisions to be accepted. Gotchas include ensuring access to the correct ASB version and confirming whether a later revision is "approved" for use under CASA. If an operator follows an unapproved ASB revision, the AD’s requirement might not be satisfied.

Logbook entry phrasing: Requirement 1 instructs operators to "make an appropriate log book entry to this effect" if no further action is required or manufacturing date is outside the implicated window. What constitutes an "appropriate" entry is not defined in the AD. Ambiguity in the content or detail of the logbook entry could create compliance questions during inspection. Operators should ensure the logbook entry includes serial numbers, P/N, inspection date, results, and reference to the ASB version used to avoid ambiguity.

Installation prohibition after effective date: Requirement 4 states "Do not install any disc assembly P/N 407-340-340-103 into any helicopter unless it is compliant to the ASB..." (Compliance 4). This affects inventory management: parts already in stock must be verified for compliance before installation. Suppliers and operators who fit parts without proper verification risk mounting non-compliant parts, even if those parts were purchased before the AD.

Cross-jurisdictional reference: The AD refers to Transport Canada AD CF-2007-14. Operators with international operations must ensure compliance with both directives where applicable. Differences in wording, timing or allowable remedies between the two ADs could create compliance complexities.

Absence of penalty language: The AD does not specify penalties. While this is not itself a compliance exemption, operators cannot rely on the document to understand enforcement exposure or the regulatory consequences of non-compliance. They should assume CASA will enforce the requirements through its broader regulatory powers even though those powers are not detailed here.

Duplication and record clarity: The document contains repeated headings and identifications (e.g. AD/BELL 407/31 repeated). That formatting could cause confusion in record systems if not reconciled to a single AD identifier.

In sum, practical gotchas derive from tight timing windows, sequencing of required actions, delegation to an ASB and the need to make clear logbook entries. Operators should document inspections precisely, confirm ASB versions and approvals, and plan maintenance and parts logistics around the AD’s restricted windows.

Compliance under this AD requires a sequence of verifiable steps, adherence to the specified timeframes and proper documentation. The AD makes the BHTC ASB the technical standard; following the ASB is the method the AD prescribes.

Step 1 , Identify applicability: Cross-check the helicopter serial number against the Applicability list in the AD and confirm whether the helicopter is fitted with disc assembly P/N 407-340-340-103. The AD applies only to the serial numbers explicitly listed and to helicopters fitted with the identified part number. Ensure records and physical part tags corroborate the P/N.

Step 2 , Obtain the ASB and approval confirmation: Acquire BHTC Alert Service Bulletin ASB-407-07-76 dated 28 March 2007 and determine whether any later revisions have been "approved" for use under CASA. The AD requires verification "in accordance with" the ASB or later approved revisions, so ensure you are using an accepted version.

Step 3 , Schedule and perform verification within the AD window: Arrange for the verification in accordance with the ASB to be performed no later than 25 flight hours or 30 days from the AD effective date (Compliance 1). For fleet planning, choose the earlier of the two metrics and schedule maintenance accordingly. The ASB will contain the technical measurement method for manufacturing date, thickness, and indexing; those specific measurement procedures must be followed.

Step 4 , Document the result in the aircraft logbook: If the inspection shows that no further action is required or that the manufacturing date is outside 01 November 2005 to 30 November 2006, enter an "appropriate log book entry" stating the inspection date, serial number, part number, ASB reference (including revision), the outcome (no further action) and the name and signature of the person performing the inspection. Retain copies of inspection records and ASB pages used as reference. The AD’s explicit instruction to make a logbook entry means this is the primary compliance evidence.

Step 5 , Actions when defects are found: If the verification reveals defects that require removal, act according to the AD’s timing split:

• If the verification leads to immediate removal needs (that trigger "further action" under Requirement 1), perform removal within 10 flight hours after completing Requirement 1 (Compliance 2). This may require short-notice scheduling of maintenance and availability of replacement parts.
• For discs outside the thickness tolerance (0.115-0.127 inch) or discs improperly indexed (Requirements 2 and 3), removal must be completed "within 300 flight hours or at next scheduled inspection, whichever comes first" after completion of Requirement 1 (Compliance 3). Apply the ASB’s procedural steps for removal and replacement.

Step 6 , Ensure parts installed are ASB-compliant: Do not install any P/N 407-340-340-103 disc assembly unless it is compliant with the ASB (Requirement 4). Before installation, the part must be inspected and documented as compliant, and relevant traceability (manufacturing date, inspection results, ASB revision used) should be recorded.

Step 7 , Maintain traceability and records: Maintain clear records of the verification, removal (if any), part replacement data, and logbook entries. Include ASB reference and any CASA approvals for ASB revisions. These records will be the primary evidence of compliance.

Step 8 , Coordinate supply and maintenance resources: Given the compressed windows (25 flight hours/30 days for initial verification and 10 flight hours for immediate follow-up), coordinate maintenance slots, qualified personnel and spare compliant parts. If parts are in short supply, prioritise inspections to identify aircraft requiring immediate removal.

Step 9 , Monitor for ASB updates and CASA communications: Because the AD accepts "later approved revisions" of the ASB, practitioners should track manufacturer releases and CASA approvals of ASB revisions. Use approved ASB revisions for future inspections and replacements.

Step 10 , Seek clarification from CASA if needed: The AD contains some terms that require interpretation (for example, what constitutes an "appropriate log book entry" or whether a given ASB revision is "approved"). For regulatory certainty, obtain clarification from CASA where necessary.

Practical record-keeping checklist for inspection outcomes:

• Aircraft serial number and registration.
• Installed disc assembly P/N and serial/manufacturing date markings.
• Date and method of inspection; ASB revision used.
• Measured thickness values and acceptance determination against 0.115-0.127 inch tolerance.
• Indexing assessment and finding.
• Remedial action taken (removed/replaced) or logbook entry if no further action.
• Signatory name, licence or authorisation of inspector/maintenance organisation.

Following these steps will place operators in a position to demonstrate compliance with the AD as it is written. Because the AD references external documents and approvals, operators should maintain contemporaneous evidence linking their actions to the specific ASB revision approved at the time of the work. If in doubt about interpretation of timing or compliance sufficiency, seek formal guidance from CASA.