AD/BELL 206/173 - Disc Assemblies - Tail Rotor Driveshaft

The primary legal subjects identified by the AD are operators and maintainers of Bell Helicopter Textron Canada Model 206 and Model 206L series helicopters that fall within the serial-number caps given , S/N up to 4618 for Model 206 and S/N up to 52340 for Model 206L , and that are fitted with disc assemblies P/N 32721-1 (Applicability). That population includes aircraft owners, commercial operators, private owners and any maintenance organisations responsible for those helicopters’ airworthiness.

Maintenance personnel and certifying staff are directly affected because the AD mandates inspections and removals "in accordance with" the specified Alert Service Bulletins (Requirement 1). The AD creates documentation duties for whoever completes the verification: if a disc assembly does not require action, "make an appropriate log book entry to this effect" (Requirement 1). Parts suppliers and installers are affected by the installation prohibition: the AD states "Do not install any disc assembly P/N 32721-1 into any helicopter unless it is compliant to the applicable Alert Service Bulletins" (Requirement 4), which places a gate on onward sale, stock use and installation of that P/N in the affected fleet.

Regulatory or oversight entities are implicated indirectly: the AD is issued under the authority of the Civil Aviation Safety Authority (signed by a delegate), and it cross-references Transport Canada AD CF-2007-16 (Note). Where multiple jurisdictions have parallel ADs, operators who fly between jurisdictions or use parts sourced internationally must track both instruments. Finally, because compliance windows are expressed in flight hours and scheduled inspections, flight departments, schedulers and commercial operators will face operational choices about when to ground aircraft to meet the time-limited requirements (Compliance).

The AD sets out precise duties for affected operators and maintainers. First duty: verify disc assemblies P/N 32721-1 for manufacturing date, thickness and correct indexing following the procedures in the applicable ASBs (Requirement 1). If verification shows the part is outside the manufacturing-date window or requires no further action, the duty is to make an appropriate log-book entry and take no further action (Requirement 1). Second duty: remove any disc assembly not within the thickness tolerance 0.115-0.127 inch (2.921-3.225 mm) (Requirement 2). Third duty: remove any disc assembly that is not properly indexed (Requirement 3). Fourth duty: do not install any P/N 32721-1 unless compliant with the ASBs or later approved revisions (Requirement 4).

Timing duties are explicit and binding within the AD: initial verification must be performed "no later than 25 flight hours or 30 days from the effective date" (Compliance, item 1). Removal for thickness non-conformance must occur within 10 flight hours after completing the initial verification (Compliance, item 2). Indexing-related removals must occur within 300 flight hours or at the next scheduled inspection, whichever comes first, after completing the initial verification (Compliance, item 3). The prohibition on installs applies "after the effective date of this Airworthiness Directive" (Compliance, item 4).

The document does not state affirmative rights such as a right to compensation, a right to seek relief, or a right to appeal set out inside the text. It does, however, specify procedural rights implicitly by allowing compliance "in accordance with" the listed ASBs or "later approved revisions" (Requirement 1 and 4), which gives operators the option to follow updated ASB revisions once approved. The AD also provides a no-action outcome where verification shows the manufacturing date is outside the specified window, thereby avoiding unnecessary removals; this is a conditional relief mechanism contained within the duty structure (Requirement 1).

The text of the AD sets out mandatory inspection, removal and installation prohibitions and gives precise compliance timeframes, but it does not itself include express penalty clauses, sanctioning language, or description of enforcement procedures. The document records that it is issued by the Civil Aviation Safety Authority (delegate David Villiers) and provides an effective date (3 October 2007), but it does not articulate criminal, civil or administrative penalties for non-compliance within the AD text provided.

Enforcement mechanisms, monitoring, certification consequences or sanctioning approaches are not described. The AD does, however, create clear compliance milestones expressed in flight hours and calendar days; this generates an evidentiary record that operators will need to create and retain (for example, the required log-book entry where no further action is necessary). That record will likely be the practical instrument for any oversight enquiries, but the AD as supplied does not state who will audit, how audits will be conducted, or what enforcement body will impose sanctions.

The AD cross-references Transport Canada AD CF-2007-16 (Note), which indicates parallel regulatory action in another jurisdiction; however, the provided AD text does not detail inter-jurisdictional enforcement arrangements. Practically, operators facing this AD will have to meet the specified duties and maintain documentation of verification, removals and compliance windows to demonstrate compliance, because the AD sets mandatory technical actions and explicit timeframes even though it omits an internal penalty schedule.

Within the text, the AD explicitly interacts with manufacturer-origin materials and with a foreign regulator’s directive. The AD mandates that verifications and actions be carried out "in accordance with" the applicable Alert Service Bulletins ASB‑206‑07‑114 (206 series) and ASB‑206L‑07‑145 (206L series), both dated 28 March 2007, or "later approved revisions" (Requirement 1, Requirement 4). That creates an operational dependency: compliance with this AD requires following the methods and steps in those ASBs. Consequently, any changes or approved revisions to those ASBs may change the practical compliance pathway under this AD, because the AD expressly permits later approved revisions to govern.

The AD also references Transport Canada Airworthiness Directive CF‑2007‑16 dated 24 August 2007 (Note). This cross-reference indicates that there is at least one corresponding instrument from Transport Canada on the same technical issue. The AD does not describe whether compliance with one directive satisfies the other, or how conflicts between the instruments would be resolved; it simply records the reference. The AD therefore sits in a multi-source regulatory environment where manufacturers’ ASBs and other national ADs inform how the obligations are met.

The AD contains internal procedural interaction in its recordkeeping requirement: where a disc assembly does not require further action, the AD requires making an appropriate log-book entry (Requirement 1). That log-book entry may be relevant under other regulatory obligations (for example, maintenance records), but the AD does not itself state how those other systems operate. No other statutes, regulations, or penalty provisions are cited inside the text provided. The AD therefore imposes a set of techno-procedural duties that must be executed alongside any existing maintenance and recordkeeping legal regimes, but the precise legal interplay with other laws is not detailed in this document.

The instrument contains an explicit effective date and references certain documents and dates, but the AD text supplied does not record any amendments or revisions to the AD itself. It became effective on 3 October 2007 (Compliance; Effective date), and it cites the ASBs and a Transport Canada AD by date, but there is no section labelled "amendments" and no later dates or revision notes appear in the provided text. The ASBs referenced are specified as "or later approved revisions" (Requirement 1 and Requirement 4), which creates built-in scope for those ASBs to be updated and for an operator to rely on later approved revisions for compliance; however, the AD itself as provided has no recorded amendments.

Procedurally, that phrasing means the AD incorporates by reference those ASBs and any subsequently approved revisions of them, without requiring the AD to be reissued each time the ASB is revised. This is a mechanism for updating technical compliance procedures through the manufacturer’s ASB process and subsequent approval, while keeping the AD stable on its face. The AD therefore leaves open future technical changes via ASB revision, but the AD text does not indicate any retroactive amendment history; it only establishes the initial AD effective 3 October 2007 and identifies the ASBs dated 28 March 2007 as the controlling procedures at issuance.

Because no amendments to this AD are recorded in the supplied text, practitioners relying on this document should check the issuing authority’s records and the listed ASBs for subsequent approved revisions or later ADs that may modify obligations. The AD’s allowance for "later approved revisions" to the ASBs is the principal mechanism for future technical change reflected in compliance practice.

The supplied text contains no information about litigation. There are no references to court proceedings, appeals, administrative reviews or disputes concerning the AD in the document. The AD is signed by a delegate of the Civil Aviation Safety Authority (David Villiers) and dated 28 September 2007, with an effective date of 3 October 2007, but no litigation outcomes, challenge histories, or case citations appear in the AD text provided.

Because the instrument is silent on litigation, the document does not record whether affected parties contested the AD, whether there were enforcement actions that led to judicial review, or whether there were precedential decisions interpreting the AD’s scope, compliance obligations or recordkeeping requirements. Users of this AD should therefore treat the provided text as a primary compliance source and, if litigation history matters for risk assessment, search court and administrative records beyond this document to see if any legal challenges arose after issuance. The AD itself contains no litigation material to analyse.

The AD contains several particulars that create practical risks if overlooked. First, applicability is narrow in technical identifiers: it applies only to helicopters within explicit serial-number caps and fitted with disc assemblies P/N 32721-1. Owners who assume the risk applies generally may over- or under-comply; operators must confirm both serial number and installed P/N before taking action (Applicability). Second, the manufacturing-date window is specific: only discs manufactured between 1 November 2005 and 30 November 2006 are the flagged population. The AD instructs that if the manufacturing date is not in that window and verification shows no further action is required, a log-book entry suffices; failing to check the date could force unnecessary removals or missed removals (Requirement 1).

Third, there are two separate technical criteria that independently require removal: thickness and indexing. A disc could meet the thickness tolerance but be improperly indexed and still require removal (Requirements 2-3). The thickness tolerance is tight and given in both imperial and metric units: 0.115-0.127 inch (2.921-3.225 mm). Maintenance shops must measure against those exact tolerances; rounding or unit-conversion errors are a practical risk. Fourth, the AD delegates inspection methodology to two separate ASBs , one for 206 and another for 206L , and allows later approved revisions; failing to use the correct ASB for the model or an approved revision could misdirect verification (Requirement 1).

Fifth, timing is staged and expressed in flight hours, calendar days and scheduled inspection windows: initial verification "no later than 25 flight hours or 30 days" from effective date; removal for thickness within 10 flight hours after verification; indexing-related removal within 300 flight hours or at the next scheduled inspection (Compliance). Mis-calculating flight hours or missing the scheduled inspection cut-off can create non-compliance. Sixth, the AD prohibits installation of P/N 32721-1 unless compliant with the ASBs; inventory management and parts procurement must track compliance status to avoid wrongful installs (Requirement 4). Finally, the AD cross-references Transport Canada AD CF-2007-16; where international operations or imports are involved, operators must account for parallel regulatory instruments rather than assuming a single document is determinative (Note).

Follow these concrete steps derived from the AD text. Step 1 , identify affected helicopters: confirm the helicopter is a BHTC Model 206 with S/N up to 4618 or a Model 206L with S/N up to 52340 and that the tail rotor driveshaft disc assembly installed is P/N 32721-1 (Applicability). Step 2 , check manufacturing date: determine the manufacturing date of each P/N 32721-1 installed. If the date is outside 1 November 2005 to 30 November 2006, proceed to Step 4 for recordkeeping; if inside that window, proceed to Step 3 (Background; Requirement 1).

Step 3 , verify thickness and indexing per ASB: perform verification of thickness and indexing "in accordance with the instructions provided in the applicable Alert Service Bulletins" ASB‑206‑07‑114 (206 series) or ASB‑206L‑07‑145 (206L series), or their later approved revisions (Requirement 1). Measure thickness with instruments calibrated to allow determination against the specified tolerance 0.115-0.127 inch (2.921-3.225 mm) (Requirement 2). Verify indexing per the ASB procedures (Requirement 3). Timing: complete the initial verification no later than 25 flight hours or 30 days from the AD effective date (Compliance, item 1).

Step 4 , act on verification results: if a disc assembly is outside thickness tolerance, remove it within 10 flight hours after completing the verification (Requirement 2; Compliance, item 2). If a disc assembly is improperly indexed, remove it within 300 flight hours or at the next scheduled inspection, whichever comes first, after verification (Requirement 3; Compliance, item 3). If verification shows no further action and the manufacturing date is not within the flagged window, make an appropriate log-book entry noting that no action is required (Requirement 1).

Step 5 , installation controls: after the AD’s effective date, do not install any disc assembly P/N 32721-1 into any helicopter unless it is compliant with the applicable ASB or later approved revision (Requirement 4; Compliance, item 4). This requires parts control and documentation from suppliers or maintenance providers that the assembly has been verified and is compliant.

Step 6 , document and retain records: make the required log-book entries as specified; retain records of measurements, ASB procedures followed and any removals performed. The AD expressly requires a log-book entry where no further action is necessary, and all other actions will be evidenced by removal tags, work orders and parts records consistent with the ASB procedures. Finally, note the AD’s effective date (3 October 2007) and the cross-reference to Transport Canada AD CF‑2007‑16 (24 August 2007) for concurrent regulatory context (Compliance; Note).