AD/ENST 28/39 - Main Rotor Blade Retention Pin

The Directive is framed around four core operational concepts: applicability by model and serial number, serial-number verification, time-in-service based replacement thresholds, and documentary certification of compliance.

Applicability: The Directive applies to a defined set of Enstrom helicopter models (listed verbatim in the Applicability cell: Model F-28, F-28A, F-28C, F-28C-2, F-28C-2R, F-28F, F-28F-R, 280, 280C, 280F, 280FX, TH-28, 480, and 480B) where the main rotor blade retention pin has a serial number that appears in the long serial-number list included in the table. The serial numbers are enumerated in ranges and discrete values; operators must compare each pin head against that list. The Directive explicitly instructs where the serial number is located ("See Figure 1 for the location of the serial number"), so the serial-number check is a physical verification on the retention-pin head.

Serial-number verification as terminating action: If the retention-pin head contains no serial number (the head is blank), the Directive states "the retention pin does not need to be replaced and this determination constitutes a terminating action for the requirements of this Directive for that retention pin." That is an unusual but explicit rule: absence of a marking excludes that pin from replacement under this Directive.

Time-in-service thresholds: The Directive splits required action by TIS. Affected pins with 545 hours or more TIS fall into an accelerated replacement bucket (remove and replace with a serviceable, non-listed-serial-number pin within the next 5 hours TIS or within 30 days). Affected pins with less than 545 hours TIS must be replaced before reaching 550 hours TIS or within 30 days. The two thresholds create overlapping compliance triggers: 545 hours fixes an immediate short-window replacement obligation and less-than-545 allows a slightly wider window up to 550 hours.

Replacement specification: Replacement pins must be "serviceable" and have serial numbers that are not contained in the Applicability list. The Directive does not specify approved sources, part numbers, or new serial-number ranges; it only sets the constraint that the replacement serial number must not be one of those listed.

Certification and recordkeeping: The Directive requires that it "shall be entered on the Maintenance Release as maintenance required." It also permits the serial-number check to be performed and certified by the Pilot in Command if the pilot "has been trained by an appropriately qualified person," and in that case a copy of the Directive must be carried in the aircraft. The Directive further references Enstrom Service Directive Bulletins No. T-029 and 0102 (original issues or later FAA-approved revisions) and FAA AD 2007-16-01 Amdt 39-15140, signalling related material to consult.

Background safety rationale: The document states the manufacturer reported some retention pins "were not manufactured in accordance with specifications cited on the engineering drawing," and that "Failure of a retention pin would result in separation of a main rotor blade from the helicopter, and subsequent loss of control." The Directive is therefore targeted to address a specific manufacturing deviation reported by the manufacturer.

Aircraft operators: The Directive affects operators of the listed Enstrom models when those airframes have main rotor blade retention pins bearing any of the serial numbers listed in the Applicability table. Every operator of a listed model must physically verify serial numbers on the retention pin heads, determine TIS for each affected pin, and if required remove and replace affected pins within the Directive’s specified windows. The operational burden attaches to the operator that holds regulatory responsibility for maintenance and airworthiness of the aircraft.

Maintenance organisations and personnel: Licensed maintenance organisations and technicians will carry out the removals and replacements when pins meet the Directive’s replacement criteria. The Directive requires the action to be entered on the Maintenance Release as "maintenance required," so maintenance organisations must complete the associated documentation. The Directive also permits a Pilot in Command to perform and certify the serial-number check provided that the pilot has been trained by an appropriately qualified person; that establishes a procedural option that transfers the initial inspection task to the flight crew in some circumstances but leaves replacement work to maintenance organisations unless otherwise permitted by maintenance regulations.

Pilots: The Directive explicitly contemplates pilot involvement for the serial-number check. The pilot may perform and certify Requirement 1 if trained by an appropriately qualified person, but must carry a copy of the Directive in the aircraft when doing so. That creates an administrative duty for pilots who are authorised to make the check.

Parts suppliers and manufacturers: The requirement to replace affected retention pins with serviceable pins whose serial numbers are not listed places obligations on parts suppliers to provide compliant pins. Suppliers must ensure the serial numbers on replacement parts do not appear in the list. The Directive does not on its face instruct who pays for new parts, but the immediate economic effect is likely to fall on operators to procure serviceable replacement pins, unless otherwise borne by manufacturer warranty or commercial arrangement (no such arrangement appears in the Directive).

Regulator and delegated officials: The Directive is an instrument signed by a CASA delegate (David Villiers) and becomes effective on 15 August 2007. The delegate’s role is to issue the safety requirement; ongoing oversight of compliance would rest with the regulator under the usual statutory framework for airworthiness directives, but the Directive itself specifies recordkeeping (Maintenance Release entry) and the conditions under which pilots may certify certain checks.

Aircraft owners with unmarked pins: Owners whose retention pins have blank heads are affected differently: the Directive provides that a blank head means the pin "does not need to be replaced" and that this determination is "a terminating action" for that specific pin under the Directive. That establishes an exemption pathway tied to the physical marking status.

Entities not named: The Directive does not extend to helicopters of other models or to pins with serial numbers not listed. It also does not create criminal or civil penalty provisions within its text; any enforcement, penalties or oversight would arise from the broader regulatory framework external to the text as issued.

Duties to inspect and document: Operators must check the serial number on the head of each main rotor blade retention pin against the list provided in the Applicability section. The Directive requires this serial-number check as Requirement 1 and instructs the location is shown in Figure 1. The Directive further requires the action to be entered on the Maintenance Release as maintenance required. These duties create a clear, documentable inspection obligation and an associated maintenance-record entry.

Duties to replace affected pins by TIS threshold: Where a retention pin’s serial number is listed and the pin is within the relevant time-in-service threshold, the operator must remove the pin and replace it with a serviceable retention pin whose serial number is not on the Applicability list. For pins with 545 hours or more TIS, the replacement timeframe is the next 5 hours TIS or 30 days, whichever occurs first. For pins with less than 545 hours TIS, replacement is required before the pin reaches 550 hours TIS or within 30 days. Those removal and replacement duties are affirmative obligations in the Directive.

Right to use pilot inspection as terminating action for a pin: The Directive allows the serial-number check (Requirement 1) to be performed and certified by the Pilot in Command if the pilot "has been trained by an appropriately qualified person." If the pilot performs the check and finds the head is blank, the Directive says the blank-head determination constitutes a terminating action for that retention pin. The pilot must carry a copy of the Directive in the aircraft when performing and certifying this check. Thus, some limited duties may be devolved to pilots, reducing immediate maintenance loads when appropriate training and conditions exist.

Duty to use serviceable, non-listed replacement pins: The Directive specifies that replaced retention pins must be "serviceable" and bear serial numbers not listed in the Applicability table. The Directive does not define "serviceable" within its own text, so implementers will rely on normal maintenance standards and the referenced Enstrom Service Directives for detail. Nonetheless, the duty creates a constraint on acceptable replacement parts.

Recordkeeping duty: The Directive requires the action to be recorded on the Maintenance Release as maintenance required. That imposes an administrative duty on whoever performs the maintenance or certifies compliance, to make the prescribed record entry.

Right to consult referenced bulletins and FAA AD: The Directive notes "Enstrom Service Directive Bulletin No. T-029, original issue, and Enstrom Service Directive Bulletin No.0102, original issue, or later FAA approved revisions, refer." It also notes "FAA AD 2007-16-01 Amdt 39-15140 refers." These are references rather than mandatory incorporations in the text; the Directive treats them as documents to consult. Operators have the right to refer to those documents for guidance, but the Directive’s mandatory actions are those expressly stated.

Absence of internal sanction language: The Directive does not itself state penalties or enforcement mechanisms or provide explicit rights of appeal in the text provided. Compliance is required by virtue of the Directive’s airworthiness status and the regulator’s authority, but any sanction or enforcement mechanism must be sourced to the wider regulatory framework rather than the text of this Directive itself.

No penalty provisions included in text: The Directive as provided contains no express penalty, fine or sanction text. There is no clause in the table that specifies monetary fines, licence sanctions or criminal offences for non-compliance. The document is framed as a safety directive with recordkeeping requirements and timelines. Any punitive measures for non-compliance would arise from the broader civil aviation regulatory framework under which this Directive was issued; the Directive itself does not set those penalties.

Enforcement mechanism signalled by maintenance-record requirement: The Directive requires that the Directive "shall be entered on the Maintenance Release as maintenance required." This recordkeeping obligation supplies an enforcement pivot. In practice, regulators enforce airworthiness directives by inspection, audit of maintenance releases and records, and surveillance of operators. The Directive’s explicit Maintenance Release instruction makes non-entry detectable in a records audit. The Directive itself does not say how CASA will enforce the recordkeeping entry.

Delegation and authority: The instrument is signed by a delegate of the Civil Aviation Safety Authority (David Villiers). The existence of a delegate signature indicates an administrative enforcement mechanism under CASA’s regulatory powers, but the text provides no procedural detail about follow-up inspections, notices to comply, directions to ground aircraft, or prosecutions. Those enforcement paths must be sourced to the regulator’s statutory toolkit, not to this Directive’s text.

Operator responsibility for safety actions: The Directive imposes operational duties (inspection, replacement and record entry) that, if not carried out, would leave the airworthiness status of affected aircraft non-compliant. A regulator may, under separate statutory powers, ground or restrict aircraft that do not meet airworthiness directives, but the Directive does not itself set out grounding processes or immediate on-the-spot enforcement steps.

Certification and pilot role as compliance evidence: The Directive allows a Pilot in Command who has been trained to perform and certify the serial-number check, and requires that the pilot carry a copy of the Directive if acting in this capacity. That creates a form of documented certification that an enforcement officer could inspect in the aircraft. The Directive does not specify the format of the pilot’s certification entry or who is authorised to carry out further enforcement checks.

Reference to external documents: It refers to Enstrom Service Directive Bulletins (T-029 and 0102) and FAA AD 2007-16-01. Those documents may contain procedural detail or compliance instructions that enforcement bodies and operators will use in practice. The Directive does not incorporate them by reference as regulatory text beyond stating that they "refer," so any enforcement reliance on them would be procedural rather than founded on wording within this Directive.

References to manufacturer bulletins and FAA AD: The Directive explicitly refers to Enstrom Service Directive Bulletin No. T-029 and No.0102 (original issues or later FAA-approved revisions), and to FAA AD 2007-16-01 Amdt 39-15140. These references indicate the Directive sits alongside manufacturer service documentation and a parallel FAA airworthiness directive. The Directive treats those documents as relevant references; operators are instructed to consult them for related details. The Directive itself does not purport to amend or supersede those documents; it imposes independent mandatory actions for aircraft within CASA’s jurisdiction.

Maintenance Release and maintenance-law interaction: The Directive requires the action to be entered on the Maintenance Release as maintenance required. That connects the Directive to maintenance recordkeeping obligations that exist in airworthiness and maintenance regulations. While the Directive does not recite those statutory recordkeeping requirements, the Maintenance Release entry acts as the compliance record that will be reviewed under whatever maintenance-law framework applies to the operator.

Interaction with airworthiness regulatory regime (implicit): The Directive is an airworthiness instrument issued by a CASA delegate. It therefore functions as part of the broader airworthiness regulatory regime. The document itself is silent on appeal routes, suspension, or revocation proceedings; these procedural elements would be found in the enabling statutes and regulations that empower CASA to issue and enforce ADs. The Directive does not attempt to reproduce or explain those legal relationships; it only specifies the technical requirements to be met.

Parts and import/export controls (implied): By requiring replacement with "serviceable" retention pins whose serial numbers are not on the Applicability list, the Directive affects parts procurement and inventory control. It does not itself regulate manufacturing or importation, but operators and suppliers must ensure parts provided meet the Directive’s constraint. If those parts are sourced internationally, the FAA AD reference and Enstrom bulletins may provide supplier guidance. The Directive does not, however, state customs, import or supplier obligations.

Relationship to pilot privileges and limitations: The Directive permits the pilot in command to perform and certify the serial-number check if trained by an appropriately qualified person, and requires the pilot to carry a copy of the Directive while doing so. That is a procedural interaction with standards for pilot privileges and training. The Directive does not change the pilot’s licencing conditions or training standards; it merely authorises a specified, limited inspection and certification when certain training has been provided. Any legal implications for pilot competence or liability would come from licensing and operational rules outside the Directive itself.

No stated interaction with civil liability or insurance regimes: The Directive does not mention civil liability, insurance, warranty or indemnity matters. While a failure to comply with an airworthiness directive will have downstream consequences for liability or insurance coverage, the Directive text does not address or alter those legal regimes.

Document identifiers and effective date: The Directive appears under the heading AD/ENST 28/39 and is annotated "10/2007 DM" in the table header. It states "This Airworthiness Directive becomes effective on 15 August 2007." The signature block gives the date of signing as 8 August 2007 and names David Villiers as "Delegate of the Civil Aviation Safety Authority." No further amendments, supersessions or revocations are contained within the text provided.

No amendment track recorded in document: The provided material does not include any later amendments, corrigenda, or revocation notices. The notes in the Requirement section say that Enstrom Service Directive Bulletins No. T-029 and No.0102 "original issue, or later FAA approved revisions, refer"; that is a cross-reference to potentially updated manufacturer material but is not an amendment to the Directive itself.

Document numbering suggests single-issue status: The AD identifier (AD/ENST 28/39) and date code (10/2007 DM) suggest an individual issuance in 2007. The document does not include an "amendment history" table or list of version changes. Based on the text supplied, readers must treat this instrument as a single-issue Directive effective 15 August 2007.

References to FAA AD as contemporaneous material: The Directive notes "FAA AD 2007-16-01 Amdt 39-15140 refers." That indicates the FAA AD was a contemporaneous or antecedent regulatory action informing this Directive; however, the Directive does not itself say it amends or adopts the FAA AD. The reference is advisory as presented.

No reissue or cancellation indicated: The signature block contains no language reissuing or cancelling prior directives. The text does not say this AD supersedes any previous Australian AD. Operators should therefore assume it was a new requirement at that effective date unless later FAA/CASA notices amended it; those later actions are not included in this text.

No litigation history in the text: The Directive includes no mention of legal challenges, judicial review, appeals, or litigation arising from its issuance. There are no court citations, case references, or notes of contested enforcement or disputes in the provided material.

No administrative appeals recorded: The Directive does not set out or reference an administrative appeals process in the text. It is silent on whether and how an operator could seek review of the Directive or a variation. Any available remedies or appeals would therefore need to be identified from the wider statutory regime under which CASA operates; the Directive itself contains no litigation or dispute-resolution history.

Implied enforcement but no reported disputes: The background provides a safety rationale (manufacturer reported manufacturing deviations) and the Directive prescribes remedial actions. The document does not report disputes with the manufacturer, parts suppliers, or operators, nor does it document any subsequent litigation. From the text supplied, no legal proceedings are recorded.

Operators should treat absence of reported litigation as absence of recorded litigation in the Directive text, not as evidence that no disputes or enforcement actions occurred after issuance. Any post-issuance litigation, compliance notices, or prosecutions would be recorded elsewhere; the Directive contains no litigation history.

Blank-headed retention pins are exempt: The Directive explicitly states that if "there is no serial number marked on the head of the retention pin (ie. The retention pin head is blank), the retention pin does not need to be replaced and this determination constitutes a terminating action for the requirements of this Directive for that retention pin." Practically, this means a blank-headed pin is treated as outside the replacement mandate. Operators must be precise and careful when making this determination: the Directive also says "See Figure 1 for the location of the serial number",if the location is misread, a pilot or technician might erroneously characterise a pin as blank. The Directive does not provide tolerances or tests for faint or worn markings; the literal reading is that absence of any marked serial number is the relevant condition.

Careful reading of serial-number list is required: The Applicability table contains a long enumerated list of serial numbers and ranges, presented as concatenated sequences (for example "04098-01 through 04098-56 05018-01 through 05018-36" etc.). Operators must ensure accurate transcription and comparison. The way the serial numbers are printed in the table is compact; transcription errors could result in incorrect compliance decisions. The Directive references Figure 1 for head location, but the figure is not included in the text provided here, so users must obtain the official AD package to verify the figure.

TIS thresholds create narrow operational windows: The Directive establishes two thresholds, 545 hours and 550 hours, with different time windows for replacement (5 hours or 30 days for pins at 545+ hours; before reaching 550 hours or within 30 days for pins under 545 hours). For an operator whose pin is at, say, 544 hours, replacement must occur before 550 hours or within 30 days. For a pin at 545 hours, replacement must occur within 5 hours or 30 days. That small numerical band requires attention to the exact current TIS. Misreading could lead to late replacement.

Pilot-performed inspections require training and documentation: While the Directive allows the Pilot in Command to perform and certify Requirement 1, the pilot "has been trained by an appropriately qualified person" and "a copy of this Directive is to be carried in the aircraft." Failing to carry the Directive when a pilot performs the check, or lacking proper training, means the operator cannot rely on the pilot certification. The Directive does not define "appropriately qualified person" in the text, so operators must determine who meets that standard under their maintenance/operational rules.

Replacement pins must have serial numbers not listed: The replacement must be a "serviceable retention pin with a serial number that is not listed in the Applicability section." Operators must ensure that replacement parts have compliant serial numbers. The Directive does not provide permitted serial-number ranges or approved suppliers; sourcing errors could result in replacement with another affected pin, which would not satisfy the Directive.

Maintenance Release entry is mandatory: The Directive requires that it "shall be entered on the Maintenance Release as maintenance required." Failure to make the entry will leave the operator without the documentary evidence of compliance. The Directive does not specify the format of the entry, so the operator must follow the usual Maintenance Release practice to show compliance.

Figure 1 is required but not included here: The Directive references Figure 1 for serial-number location. Users relying solely on the text supplied here must obtain the official AD documentation to see the figure and avoid location misidentification.

Note references to other documents are not self-incorporating: The Directive "refers" to Enstrom Service Directive Bulletins and FAA AD 2007-16-01 but does not itself adopt their text. Operators must review those external documents for technical procedures and possibly for clarification of "serviceable" criteria, but must treat the Directive’s requirements as binding regardless of what the external documents say.

No internal guidance on "serviceable": The term "serviceable" is used but not defined in the Directive text provided. Operators must rely on maintenance standards, manufacturer documentation, or other airworthiness rules to determine serviceability.

Time-limited effective date: The Directive became effective on 15 August 2007 and was signed 8 August 2007. If operators are reading residual documentation many years later, they must verify whether subsequent amendments, superseding directives, or continuing obligations have altered requirements. The text given contains no amendment history.

Step 1 , obtain complete AD package and figures: Before starting work, obtain the complete official AD with Figure 1 and any referenced Enstrom Service Directive Bulletins (No. T-029 and No.0102) and the FAA AD 2007-16-01 Amdt 39-15140. The Directive explicitly refers to the figure for serial-number location and to the Enstrom bulletins for reference; compliance requires access to that material.

Step 2 , identify affected airframes: Confirm that your helicopter model is within the list in the Applicability (Model F-28, F-28A, F-28C, F-28C-2, F-28C-2R, F-28F, F-28F-R, 280, 280C, 280F, 280FX, TH-28, 480, and 480B). Only aircraft of those models are potentially affected under this Directive.

Step 3 , inspect each main rotor blade retention pin for serial number: Per Requirement 1, check the serial number marked on the head of each main rotor blade retention pin and compare it to the serial numbers listed in the Directive’s Applicability section. Use Figure 1 for locating the number. If the head is blank (no serial number present), record that finding; the Directive says such a finding "constitutes a terminating action for the requirements of this Directive for that retention pin" so no replacement is required for that pin under this AD. The serial-number check may be performed and certified by the Pilot in Command only if that pilot "has been trained by an appropriately qualified person," and the pilot must carry a copy of the Directive in the aircraft when performing certification.

Step 4 , determine time in service (TIS) for any retention pin whose serial number is listed: For any retention pin whose serial number is one of those enumerated in the Applicability table, determine the pin’s current hours TIS.

Step 5 , apply replacement timing rules:

• If the retention pin has 545 or more hours TIS, remove and replace it with a serviceable retention pin whose serial number is not listed in the Applicability section. Replacement must occur within the next 5 hours TIS or within 30 days, whichever occurs first.
• If the retention pin has less than 545 hours TIS, remove and replace it with a serviceable retention pin whose serial number is not listed in the Applicability section. Replacement must occur before the pin reaches 550 hours TIS or within 30 days, whichever occurs first.

Step 6 , source compliant replacement parts: Obtain a "serviceable" replacement retention pin with a serial number that does not appear in the Applicability list. The Directive does not define serviceable or provide supplier approvals; therefore, apply standard maintenance standards, and consult the referenced Enstrom Service Directive Bulletins for technical guidance and accepted part numbers or installation procedures.

Step 7 , perform removal and replacement under authorised maintenance procedures: Ensure removal and replacement are performed by appropriately authorised maintenance personnel and in accordance with the manufacturer’s service instructions and applicable maintenance standards. If a pilot performed and certified the serial-number check, ensure maintenance records show that replacement work was performed by authorised maintenance personnel where applicable.

Step 8 , make the Maintenance Release entry: The Directive requires that "This Directive shall be entered on the Maintenance Release as maintenance required." Record the action taken, including serial numbers inspected, TIS at time of replacement, replacement part serial number(s), and certification signature(s) in the Maintenance Release entry consistent with local maintenance recordkeeping practice.

Step 9 , retain documentary evidence: Keep copies of the Directive, any pilot certification of the serial-number check (if applicable), maintenance release entries, and invoices or part supply documentation showing the serial numbers of replacement pins, so that an audit of compliance is supported.

Step 10 , consult referenced documents for technical detail: Use Enstrom Service Directive Bulletins No. T-029 and No.0102 and FAA AD 2007-16-01 Amdt 39-15140 for any additional technical instructions, measurement criteria or torque settings that the Directive does not specify. Treat those documents as supplemental guidance; the Directive’s mandatory timeframes and replacement constraints are binding irrespective of any differing manufacturer advice.

Step 11 , verify training and carriage requirements if pilot certifies check: If the pilot in command will perform the serial-number check and certify compliance for Requirement 1, verify the pilot has received the required training from an "appropriately qualified person" and ensure a copy of the Directive is carried in the aircraft at the time of certification.

Step 12 , plan inventory and operational scheduling: Because the Directive imposes short replacement windows for pins at or above 545 hours TIS (5 hours or 30 days), plan procurement and maintenance scheduling to avoid unplanned grounding. Ensure parts inventory or supplier lead-times are sufficient to meet the Directive’s short-term replacement windows.

Step 13 , monitor for subsequent directives: After completing the above, operators should monitor CASA communications for any subsequent amendments, supersessions or related directives. The text provided shows the Directive was effective 15 August 2007; the Directive itself contains no amendment history, so later regulatory actions could alter compliance obligations.