AD/OH-58/7 - Swashplate Support Assembly

The Directive is organised around a small set of operational concepts that determine its effect. Applicability defines the affected airframes and parts: Model OH-58A (Bell 206A-1) series helicopters, including all certificated versions, equipped with swashplate support assembly P/N 206-010-452-001, -005, or -109 (Applicability). The identified assemblies are the locus of concern; the Directive does not extend to other swashplate support assembly part numbers except to say that installation of P/N 206-010-452-113 ends the Directive’s inspection obligations (Requirement, Note).

Inspection protocol is central. The Directive requires a visual inspection in the fillet radius area for cracks using 10x magnification or more (Requirement). The Directive directs operators to follow the Accomplishment Instructions of BHTI Alert Service Bulletin No. 206-93-74 Revision B, or later FAA approved revision, to carry out those inspections (Requirement). Where a crack is suspected on visual inspection, a dye penetrant inspection must be performed before further flight (Requirement). If a crack is confirmed, replacement of the swashplate support assembly with a serviceable assembly is mandatory before the helicopter flies again (Requirement).

Timing and recurrence are explicit. Two pathways are set out based on the assembly’s time in service: for assemblies with 1,500 hours or more total time in service, the visual inspections are required as specified in the Accomplishment Instructions; for assemblies with less than 1,500 hours total time in service, the same inspection technique is required and a specific compliance threshold is imposed before 1,525 hours are reached (Requirement). Compliance timing gives an initial window (within 25 hours time in service after the Directive’s effective date unless already done) and fixed recurrent intervals not to exceed 50 hours time in service until the terminating part is installed (Compliance, paras 1-2).

Corrective action and terminating action are separate concepts. Corrective action: any cracked swashplate support assembly must be replaced with a serviceable assembly before further flight (Requirement). Terminating action: installation of swashplate support assembly P/N 206-010-452-113 constitutes terminating action to the requirements of the Directive, meaning once that part is installed the inspection and re-inspection schedule imposed by this Directive is no longer required for that airframe/assembly (Requirement, Note).

Reference instruments: the Directive expressly ties procedural execution to a manufacturer alert service bulletin (BHTI Alert Service Bulletin No. 206-93-74 Revision B, or later FAA approved revision) and signals a relation to a prior FAA airworthiness directive (FAA AD 94-19-02 Amendment 39-9023) (Requirement; Note). The Directive identifies the relevant procedural and regulatory anchors without reproducing the technical details of the service bulletin in full.

Safety objective: the Background identifies the hazard that motivates the Directive: reports of cracks in the fillet radius area near the base of the swashplate support assembly and the consequent risk of swashplate support failure, main rotor system control loss, and loss of helicopter control (Background). The Directive’s measures are targeted at detecting cracking early and removing cracked assemblies, or replacing them with a specified part that removes the need for continued inspections (Requirement; Note).

Control and authority: the instrument is presented as an Airworthiness Directive with an effective date (28 August 2008) and the signature of a CASA delegate (David Villiers, 14 July 2008), which locates it within the administrative processes of the Civil Aviation Safety Authority (signature; effective date).

The Directive explicitly targets operators and maintainers of Bell OH-58A (Bell 206A-1) series helicopters fitted with specific swashplate support assemblies. Applicability restricts the universe to Model OH-58A (Bell 206A-1) series helicopters, including all certificated versions, that are equipped with swashplate support assembly part numbers 206-010-452-001, -005, or -109 (Applicability). That description identifies the helicopters by model and the parts by part number; no other models or part numbers are included in the text of the Directive.

Subject parties therefore include the holder of the aircraft’s certificate of airworthiness, the operator in charge of maintenance scheduling, licensed maintenance organisations and mechanics who perform inspections and replacements, and those responsible for parts procurement and record keeping. The Directive does not name individuals or companies; the applicability language places the obligation on those who operate or maintain the listed model helicopters with the listed parts installed.

Maintenance organisations will have to follow the Accomplishment Instructions of BHTI Alert Service Bulletin No. 206-93-74 Revision B, or a later FAA approved revision, to satisfy the visual inspection requirement (Requirement). That ties the technical method and acceptance criteria to the referenced service bulletin, so the parties who can legitimately carry out the inspections are those with access to and authority to act under that bulletin. The Directive requires use of at least 10x magnification for the visual inspections, meaning the inspection personnel must have equipment and training sufficient to detect cracks at that magnification (Requirement).

Operators whose swashplate support assemblies have accumulated 1,500 hours or more total time in service must follow the same inspection procedure as those with assemblies under that threshold, but the timing of compliance is arranged so that assemblies approaching 1,525 hours must receive inspection before that accumulation (Requirement; Compliance). Those who have not yet performed an initial inspection must do so within 25 hours time in service after the Directive’s effective date and then at 50 hour intervals, unless they remove the assemblies by installing the terminating part number (Compliance, para 1). Therefore, operators planning flight time accumulation close to these thresholds must integrate the inspections into their maintenance scheduling.

Parts suppliers and manufacturers are affected in the sense that the Directive identifies a terminating part number, P/N 206-010-452-113. Where operators choose to install that part to terminate the inspection cycle, the supplier or manufacturer’s ability to provide that specific assembly becomes operationally relevant (Requirement, Note). The Directive does not state availability, pricing, or lead times for the terminating part; it only identifies it by part number as an accepted terminating action.

Regulatory actors are implicated: the document is issued under the authority of the Civil Aviation Safety Authority as indicated by the delegate’s signature, and it cross-refers to an FAA airworthiness directive (FAA AD 94-19-02 Amendment 39-9023), which may be relevant for operators or maintainers who rely on FAA-approved revisions of the service bulletin (Note). The Directive does not assign penalties or describe enforcement procedures within its text, so affected parties must treat the requirements as mandatory airworthiness actions to be integrated into regulatory compliance processes (see Penalties and enforcement).

Key duties derive directly from the AD text. Duty 1: Perform visual inspection of the swashplate support assembly fillet radius area for cracks using 10x magnification or more in accordance with the Accomplishment Instructions of BHTI Alert Service Bulletin No. 206-93-74 Revision B, or a later FAA approved revision (Requirement). Duty 2: If a crack is suspected on visual inspection, perform a dye penetrant inspection in accordance with the Requirement document before further flight (Requirement). Duty 3: Replace any cracked swashplate support assembly with a serviceable assembly before further flight (Requirement). Duty 4: Comply with the timing rules: unless the initial inspection has already been carried out, perform the first inspection within 25 hours time in service after the effective date of this Directive and thereafter at intervals not to exceed 50 hours time in service until P/N 206-010-452-113 is installed; additionally, perform inspection before accumulating 1,525 hours time in service for assemblies with less than 1,500 hours TIS, and thereafter at intervals not to exceed 50 hours, until P/N 206-010-452-113 is installed (Compliance paras 1-2).

Rights and procedural allowances available under the Directive are limited but identifiable. The Directive permits the use of a later FAA approved revision of the referenced BHTI Alert Service Bulletin in place of Revision B (Requirement). This creates an avenue to rely on updated procedural details if the FAA approves a later revision. The Directive also identifies an explicit terminating action: installation of swashplate support assembly P/N 206-010-452-113 constitutes terminating action to the Directive’s inspection requirements (Requirement, Note). That gives operators a clear, authorised option to end the inspection cycle by fitting the specified part.

The Directive does not provide in-text exemptions, extensions, alternative methods of compliance (AMOCs), or deferred compliance clauses. It does not set out a mechanism for seeking permission to deviate from the stated inspection intervals or replacement-before-flight requirement. The text does allow reliance on a later FAA approved revision of the service bulletin as the method to accomplish the inspections (Requirement). No other procedural flexibility is stated.

Duties to act before further flight are strict in language: suspected cracking triggers an immediate dye penetrant inspection before further flight, and any confirmed crack must be remedied by replacement before further flight (Requirement). Those phrases impose an operational constraint: aircraft with suspected or confirmed cracks in the specified area cannot be flown until the inspection or replacement tasks are complete.

The Directive assigns responsibility implicitly to those who operate and maintain the affected helicopter models. It does not allocate costs or state which party bears replacement parts costs, but by prescribing mandatory maintenance and replacement actions it places the practical responsibility for compliance on aircraft owners/operators and their maintenance providers. The Directive does not set appeals or dispute-resolution procedures; any such processes would need to be sought through the issuing authority’s administrative frameworks, which are not described in the Directive text.

The Directive itself specifies mandatory inspection and replacement actions and an effective date (28 August 2008), but it does not include a section that sets out penalties, fines, or enforcement mechanisms within its text. The document is signed by a delegate of the Civil Aviation Safety Authority (David Villiers) and identifies the Directive as an airworthiness directive, which by its nature establishes mandatory maintenance and inspection obligations for the applicability group (signature; effective date; Applicability; Requirement). The Directive does not, however, state in its text what sanctions will follow non‑compliance, nor does it detail enforcement processes such as the issuance of notices, suspension of certificates, or civil penalties.

Because the Directive prescribes actions that must be carried out before further flight where cracking is suspected or confirmed, operators have an immediate operational imperative: a helicopter with a cracked swashplate support assembly must not fly until the assembly is replaced with a serviceable unit (Requirement). That limits operators’ ability to use affected aircraft and imposes practical enforcement by grounding until compliance actions are completed. The Directive’s language , replace before further flight and perform dye penetrant before further flight where a crack is suspected , functions as an operational enforcement mechanism insofar as adherence is necessary for the aircraft to be legally airworthy.

The Directive references compliance with the BHTI Alert Service Bulletin No. 206-93-74 Revision B, or later FAA approved revision, to carry out inspections (Requirement). Compliance auditing by regulatory authorities typically examines maintenance records and whether service bulletins and airworthiness directives have been followed; the Directive itself does not specify the audit process, but the requisite documentation trail (inspection records, dye penetrant reports, parts replacement records) is implied by the tasks the Directive mandates.

The Directive does not identify any approved alternative methods of compliance, nor does it provide instructions on applying for deviations, nor does it prescribe timelines for regulatory verification. The absence of any explicit penalty text in the Directive means that details of enforcement, sanctions, or remedial notices would exist in other regulatory documents or administrative procedures outside the text provided here. The Directive does, however, create unequivocal obligations regarding inspections and replacement that will be central to any enforcement action based on airworthiness non-compliance: failure to carry out the mandated inspections, to perform required dye penetrant inspection where a crack is suspected, or to replace cracked assemblies before flight would be factual grounds for a regulatory finding that an aircraft is not maintained in accordance with its airworthiness directives.

Finally, the Note referencing FAA AD 94-19-02 Amendment 39-9023 signals a related instrument in another jurisdiction; the Directive does not translate that FAA AD into a penalty regime here, but it flags a regulatory context that may inform how compliance and enforcement are viewed in cross‑jurisdictional maintenance and inspection regimes (Note).

The Directive references and integrates with other technical and regulatory texts rather than setting out an interaction with broader statutory law in its own text. The principal technical cross-reference is the Accomplishment Instructions of BHTI Alert Service Bulletin No. 206-93-74 Revision B, or later FAA approved revision. The Directive makes compliance with the inspection requirement conditional on performing those Accomplishment Instructions, effectively delegating the inspection method and acceptance criteria to that referenced service bulletin (Requirement). Thus, the Directive’s requirements are framed as implementation through an industry technical document approved by the FAA.

A regulatory cross-reference appears in the Note: FAA AD 94-19-02 Amendment 39-9023 is cited. The Directive does not reproduce FAA AD 94-19-02 or explain how it modifies or complements the present Directive; it simply signals that the FAA AD is relevant to the same or related safety concern (Note). The Directive explicitly allows the use of a later FAA approved revision of the BHTI service bulletin, indicating that subsequent FAA approvals of the service bulletin would be acceptable means of compliance with this Directive’s inspection requirement (Requirement).

The Directive is presented as an Airworthiness Directive with an effective date and a CASA delegate’s signature. Those elements place it within the administrative domain of the issuing authority; the Directive itself does not set out how it integrates with other Australian legislation, such as aviation safety statutes, civil aviation regulations, or enforcement frameworks. Therefore, any statutory enforcement mechanisms, penalty regimes, or procedural rules found in broader aviation legislation and regulations are external to the text of the Directive and are not described herein. The Directive imposes operational obligations that would be enforced through the usual application of national aviation safety law and regulation, but the Directive does not itself cite or reproduce those statutory enforcement mechanisms.

Practically, the Directive’s reliance on an FAA-approved service bulletin and its reference to an FAA AD mean operators or maintainers who operate in multiple jurisdictions may need to coordinate compliance actions with both Australian regulatory expectations and FAA-approved procedures. The Directive’s explicit acceptance of later FAA approved revisions of the referenced service bulletin provides a mechanism for harmonising the technical method of compliance with FAA developments; it does not, however, specify whether an FAA AD or FAA approvals automatically confer compliance with this Directive beyond the service bulletin acceptance. The Directive’s Note that FAA AD 94-19-02 refers suggests that the FAA has previously addressed related issues; the Directive does not otherwise map the relationship between that FAA AD and the present Directive.

There is no mention in the Directive of interactions with contractual obligations, insurance requirements, or commercial regulatory instruments beyond the immediate references to the service bulletin and the FAA AD. For owners and operators, the Directive’s inspection and replacement obligations will need to be reconciled with any contractual maintenance programmes and with the maintenance and continuing airworthiness obligations arising under national aviation rules, but such reconciliation procedures are not specified in the Directive text.

The Directive identifies the versioning and cross-references that form its immediate documentary history but does not include a multi-step amendment log within the text provided. The AD is identified as AD/OH-58/7 with date indicators showing 9/2008 and an effective date of 28 August 2008 (heading; Compliance). The delegate’s signature is dated 14 July 2008 (signature line). The AD cites BHTI Alert Service Bulletin No. 206-93-74 Revision B as the required Accomplishment Instructions for carrying out inspections, and allows later FAA approved revisions of that service bulletin to be used (Requirement). That indicates the AD’s procedural implementation is tied to at least Revision B of the bulletin.

The Note in the Requirement section states: "Note: FAA AD 94-19-02 Amendment 39-9023 refers." That cross-reference suggests a prior FAA airworthiness directive addressing related matters exists and is relevant for the historical context of the safety concern; the AD text does not enumerate changes between that FAA AD and the present Directive, nor does it set out a revision history of this Directive itself beyond its label and dates.

The Directive as presented contains repeated headings and formatting that list “AD/OH-58/7” and “Swashplate Support Assembly” along with “9/2008,” which functions as the identifying tag for this issuance (header). The text does not supply earlier Australian AD numbers or an explicit amendment trail for previous ADs in Australia addressing the same part. The primary external revision history element the Directive relies upon is the manufacturer’s alert service bulletin and its potential later FAA approved revisions. The AD therefore ties future amendment of the inspection content to the FAA’s approval of later revisions of the BHTI service bulletin.

Any amendment to the Directive itself (for example rescission, supersession, or extension) is not recorded in the text provided. The AD gives an effective date (28 August 2008), and that is the operative datum contained in the document. Operators and maintainers seeking to track changes or later amendments would need to check subsequent issuances from the Civil Aviation Safety Authority or technical updates to the referenced service bulletin; those later documents are not part of the text here.

In sum, the explicit documentary history in this Directive is limited to: the AD identification (AD/OH-58/7, 9/2008), the signature date of the CASA delegate (14 July 2008), the effective date (28 August 2008), reliance on BHTI Alert Service Bulletin No. 206-93-74 Revision B (or later FAA approved revision), and a note referring to FAA AD 94-19-02 Amendment 39-9023. No further amendment chronology is included in the Directive text provided.

The Directive text contains no references to litigation, court decisions, administrative appeals, or legal challenges. There are no case citations, no references to prior adjudication, and no indication of legal proceedings related to the issuance, content, or enforcement of this Directive within the text provided. The document consists of the safety background, applicability, the inspection and replacement requirements, compliance times, reference to a manufacturer’s service bulletin and an FAA AD, and the signature of a CASA delegate; it does not report disputes or judicial review outcomes.

Where litigation or administrative challenge might be relevant, the Directive does not describe procedures for contesting the directive’s terms or seeking relief from strict compliance within its own text. The absence of litigation history in the document means that any party seeking to explore precedents, appeals, or enforcement litigation must look outside this Directive to regulatory records, tribunal or court filings, or later administrative documents. None of those materials are reproduced or summarised here.

Given the Directive’s date and the factual background stated (reports of cracks), the document functions as a technical and regulatory response rather than a litigation record. If litigation or adjudication had followed this issuance and affected the interpretation or application of the Directive, such developments are not reflected in the text before you.

1. Dual timing rules with tight thresholds. The Directive sets two related timing tracks. If the swashplate support assembly has 1,500 hours or more total time in service, the operator must perform the visual inspection in the fillet radius area using 10x magnification per the Accomplishment Instructions (Requirement). If the assembly has less than 1,500 hours TIS, the operator must carry out the same visual inspection and must do so before the assembly accumulates 1,525 hours TIS (Requirement; Compliance para 2). Separately, unless an initial inspection has already been performed, there is an “within 25 hours TIS after the effective date” initial window and then recurrent inspections every 50 hours TIS (Compliance para 1). The proximity of 1,500 and 1,525 hours to typical maintenance cycles can create scheduling pressure; operators must monitor time in service closely to ensure they do not cross the 1,525 hour point without the required inspection.

2. “Before further flight” phrasing is operationally binding. The Directive requires dye penetrant inspection before further flight if a crack is suspected and mandates replacement before further flight if a crack is found (Requirement). Operators that interpret “before further flight” liberally risk non‑compliance. The phrase indicates an immediate grounding requirement until the specified inspection or replacement action is complete.

3. Magnification and method are prescribed. The Directive insists on visual inspection using 10x magnification or greater and directs that the inspection be carried out in accordance with the Accomplishment Instructions of the referenced service bulletin (Requirement). Using lesser magnification, or deviating from the service bulletin’s inspection steps, is not authorised by the Directive’s text unless the operator adopts a later FAA approved revision of the service bulletin. That means the inspection technique and acceptance criteria are not fully freeform; they must follow specified technical guidance.

4. Terminating action is part-number specific. Installation of P/N 206-010-452-113 is explicitly the terminating action to the requirements of this Directive (Requirement, Note). Installing a different part number, even if similar, is not described as terminating action in the text. Operators contemplating parts substitutions must not assume an alternate part will have the same regulatory effect unless the Directive or the issuing authority states so in a separate amendment.

5. Reliance on a separate service bulletin. The Directive does not reproduce the full procedural details; it refers to BHTI Alert Service Bulletin No. 206-93-74 Revision B (or later FAA approved revision) for the Accomplishment Instructions (Requirement). Access to that service bulletin, and to any later FAA-approved revisions, is necessary to implement the Directive correctly. Failure to follow the service bulletin’s Accomplishment Instructions could render an inspection non-compliant even if a visual check was performed.

6. No penalties or enforcement procedures are set out. The AD does not state sanctions or enforcement mechanics (Penalties and enforcement). That absence can be a procedural surprise for parties expecting an explicit enforcement clause; instead, compliance must be treated as a mandatory airworthiness action with operational constraints tied to flight permissibility.

7. Cross-reference to FAA AD without detail. The Note that FAA AD 94-19-02 Amendment 39-9023 refers provides context but does not explain the relation between that FAA AD and this Directive. Operators who maintain aircraft across jurisdictions should not assume identical procedural or legal effects without examining the FAA AD and any national regulatory bridges.

8. Effective date and initial inspection window. The AD’s effective date is 28 August 2008, and the secretary’s delegate signed the document on 14 July 2008 (effective date; signature). The initial inspection window is tied to that effective date (first inspection within 25 hours TIS after the effective date unless already done), which can require retrospective checking of logbooks if the Directive is adopted after flight hours have accumulated.

9. Replacement before further flight creates logistics demands. The requirement to fit a serviceable assembly before further flight where a crack is found places an immediate parts-supply and maintenance-resourcing demand on operators. Although the Directive identifies a terminating part number, it does not address availability or lead times, so operators must plan for potential grounding until parts and maintenance resources are arranged.

10. Records and traceability implicit but not specified. The AD mandates actions but does not set out record-keeping requirements in the text provided. Operators must nonetheless maintain inspection and replacement records to demonstrate compliance if audited; the Directive’s wording implies that such records will be critical but does not prescribe their form or retention period.

1. Confirm applicability. Verify whether your helicopter is a Model OH-58A (Bell 206A-1) series, in any certificated version, and whether it is fitted with a swashplate support assembly P/N 206-010-452-001, -005, or -109 (Applicability). Cross-check logbooks and parts serial numbers to ensure the correct assemblies are identified.

2. Obtain the procedural document. Acquire BHTI Alert Service Bulletin No. 206-93-74 Revision B, and check whether there is a later FAA approved revision. The AD requires the inspections to be carried out in accordance with the Accomplishment Instructions of that service bulletin or a later FAA approved revision (Requirement). Ensure you have the current FAA-approved revision if one exists.

3. Schedule the initial inspection. If the initial inspection has not already been performed, carry it out within 25 hours time in service after the Directive’s effective date (28 August 2008), per the Compliance paragraph 1. If the assembly currently has less than 1,500 hours TIS, ensure the inspection is performed before accumulating 1,525 hours TIS (Requirement; Compliance para 2). If the assembly has 1,500 hours or more, commence inspections as required by the service bulletin and the AD (Requirement).

4. Perform the visual inspection with the specified magnification. Inspect the swashplate support assembly fillet radius area for cracks using at least 10x magnification as required (Requirement). Follow the Accomplishment Instructions’ prescribed procedures for lighting, surface preparation, viewing angles, and acceptance criteria.

5. Undertake dye penetrant inspection where necessary. If any crack is suspected on visual inspection, perform a dye penetrant inspection before further flight, as required by the Directive (Requirement). Ensure the dye penetrant process and interpretation align with the referenced service bulletin’s Accomplishment Instructions.

6. Replace confirmed cracked assemblies before flight. If the dye penetrant inspection or other confirmation reveals a crack, remove the cracked swashplate support assembly and replace it with a serviceable assembly before further flight (Requirement). The term “serviceable assembly” should be interpreted in line with your organisation’s standards and parts traceability; the Directive recognises P/N 206-010-452-113 as an acceptable terminating serviceable assembly (Requirement, Note).

7. Consider terminating action where operationally appropriate. Installing swashplate support assembly P/N 206-010-452-113 constitutes terminating action to the Directive’s inspection requirements. If your operational and commercial circumstances make repeated 50 hour inspections burdensome, evaluate installing P/N 206-010-452-113 to remove the inspection obligation established by this Directive (Requirement, Note). Verify part provenance and compatibility before installation.

8. Maintain inspection intervals. After the initial inspection, unless you have installed the terminating part, continue inspections at intervals not to exceed 50 hours time in service (Compliance). If your assembly had less than 1,500 hours and you inspected before 1,525 hours, continue 50 hour intervals thereafter until the terminating part is installed.

9. Record inspections and corrective actions. Although the Directive does not specify record-keeping form, document the date and time-in-service for each inspection, the magnification used, any dye penetrant tests performed, and the serial numbers and part numbers of assemblies removed or installed. Keep evidence of compliance with the Accomplishment Instructions of the referenced service bulletin.

10. Coordinate maintenance and flight scheduling. Because suspected or confirmed cracks require inspection and replacement before further flight, coordinate maintenance windows and parts procurement to minimise grounding time. Plan inspections into routine maintenance where possible to avoid unexpected operational interruptions, and monitor time-in-service counters to ensure compliance with the narrow 1,500/1,525 hour thresholds and the 25-hour initial window.

11. Use later FAA approved revisions if available. If the FAA approves a later revision of the BHTI service bulletin, that later revision may be used to accomplish the inspections (Requirement). Confirm FAA approval status and the content of any revised accomplishment instructions before relying on them.

12. Be prepared to show compliance. In an audit or inspection by the regulatory authority, you will need to demonstrate that inspections were done using the specified magnification and the referenced Accomplishment Instructions, that dye penetrant testing was performed where required, and that cracked assemblies were replaced before further flight or that the terminating part was installed. Keep parts and maintenance records accessible.

13. Watch for updates from the issuing authority. Although the Directive’s text here is self-contained, check for any later amendments, superseding directives, or further guidance from the Civil Aviation Safety Authority that might change the inspection interval, introduce alternative methods of compliance, or adjust the terminating action. The Directive allows later FAA approved revisions of the service bulletin to be used, but it does not itself update beyond Revision B in its text.

14. If in doubt, seek regulatory guidance. The Directive does not include alternative methods of compliance or an appeals procedure in its text. If you require an alternative approach, clarification, or an extension based on operational constraints, raise the matter with the issuing authority or authorised representatives and secure written acceptance before deviating from the Directive’s explicit requirements.

Following these steps aligns operational practice with the Directive’s prescriptive requirements: visual inspections at 10x magnification, dye penetrant inspection where a crack is suspected, replacement of cracked assemblies before further flight, recurrent inspections at up to 50 hour intervals unless the terminating part P/N 206-010-452-113 is fitted, and performance of all inspections in accordance with BHTI Alert Service Bulletin No. 206-93-74 Revision B or a later FAA approved revision.