AD/AT 600/3 - Horizontal Stabiliser Attachment Eyebolts

Scope and objects named in the directive

• Applicability: the AD applies to AT-602 aircraft with serial numbers specified in the text and to any aircraft that have particular eyebolt part numbers installed. The precise applicability language identifies serial numbers up to and including 602-0695, aircraft with serial number 602-0703 and subsequent, and all aircraft that have any 9/16-inch eyebolt (part number 30774-1) installed. That is the textual boundary for who the directive addresses.
• Unsafe condition identified: the Background states the unsafe condition as repeated failures of horizontal stabiliser attachment eyebolts, traced to high-cycle, low-nominal stress and likely loss of torque during service. The operational consequence the AD seeks to prevent is "abrupt change or complete loss of pitch control and/or aircraft departure from controlled flight."

Compliance measures and mechanisms

• Torque action: Requirement 1 mandates tightening the four eyebolts that attach the front and rear spars of the horizontal stabiliser to the respective stabiliser strut, using torque values in Snow Engineering SL No. 129, revised 21 October 2004. The tightening is required within a specified short window and then at fixed intervals.
• Replacement regime: Requirement 2 requires replacement of the eyebolts in accordance with SL No. 129 (issued 26 September 1994, revised 21 October 2004). The directive sets an initial replacement timing , either upon accumulating the hours specified in SL No. 129 or within 50 hours time in service after 1 September 2005, whichever occurs later , and then repetitive replacement at the intervals specified in SL No. 129.
• Modification alternative: Requirement 3 offers an alternative compliance route only for aircraft with serial numbers up to and including 602-0695. That alternative involves replacing the internal steel brace assembly with a new assembly with larger bushings and replacing any 7/16-inch eyebolt with 9/16-inch eyebolt part number 30774-1, in accordance with SL 129A dated 7 August 2004. The directive makes clear that even if the alternative is taken, the repetitive replacement requirement in Requirement 2 still applies.

Parts and installation constraints

• The AD lists specific part numbers that are in scope (5/16-inch AN44-17A or AN44-21A; 7/16-inch AN47-22A or AN-47-30A; 9/16-inch 30774-1 or 30775-1) and explicitly states: "Do not install any 5/16-inch eyebolt ..., 7/16-inch eyebolt ..., or 9/16-inch eyebolt ... that exceeds the corresponding cumulative hours time in service specified in Requirement 2 or 3 of this Directive." That creates a prohibition tied to cumulative hours-in-service limits specified in the referenced SLs and the directive.

Temporal mechanics

• Effective date and initial windows: the AD becomes effective on 1 September 2005. The immediate torque requirement must be done within 100 hours time in service or 12 calendar months after that date, whichever comes first. Initial replacement must follow the applicable hours in SL 129 or be completed within 50 hours after 1 September 2005 if the hours threshold has already been exceeded. The modification alternative may be done "at any time after 1 September 2005" but does not remove the ongoing replacement obligation.

Referential instruments

• The AD depends on external engineering service letters (SL No. 129 and SL 129A) for torque values, replacement intervals and the modification procedure, and it specifically notes an FAA AD (2005-13-12) for reference. Those external documents are incorporated by reference in the sense that the AD requires compliance with the content of those SLs.

Risk mitigation logic

• The directive addresses a recurring mechanical failure mode plausibly linked to loss of torque over service life. The three-pronged approach , immediate torque check, scheduled replacement, and a retrofit option for specific serial numbers to permit longer replacement intervals , implements a combination of inspection, recurring maintenance and a structural modification to reduce risk factors identified in the Background.

Operators and owners

• The directive applies to owners and operators of Airtractor AT-602 aircraft as described in the Applicability block. That includes aircraft with serial numbers up to and including 602-0695, aircraft with serial number 602-0703 and subsequent, and any aircraft that have installed any 9/16-inch eyebolt (part number 30774-1). Those owners and operators are the primary parties who must carry out the AD’s requirements.

Maintenance providers and engineers

• Licensed maintenance organisations, certificated engineers and mechanics who perform the torque tightening, eyebolt replacement and the optional steel brace assembly replacement are directly affected. The AD requires these maintenance actions to be performed using specific torque values and replacement instructions contained in Snow Engineering Co. Service Letters (SL No. 129 and SL 129A), which means technicians must have access to those documents and the specified replacement parts and comply with their procedures.

Parts suppliers and manufacturers

• Suppliers of eyebolt parts and of the steel brace assemblies will be affected by demand for specific part numbers. The AD names particular part numbers: 5/16-inch eyebolts (AN44-17A, AN44-21A), 7/16-inch eyebolts (AN47-22A, AN-47-30A) and 9/16-inch eyebolts (30774-1, 30775-1). For aircraft up to serial number 602-0695, the AD identifies part number 30774-1 as the replacement 9/16-inch eyebolt in the SL 129A modification. Parts suppliers must ensure parts meet the requirements of the referenced SLs and be available to maintenance organisations.

Maintenance planners and fleet managers

• Those responsible for scheduling maintenance and managing airframe hours must factor in the AD’s time windows: tightening within 100 hours or 12 months after 1 September 2005, a 50-hour fallback for initial replacement if service hours already exceeded the SL hours, and ongoing replacement intervals as defined in SL No. 129. For fleets that include aircraft both before and after serial number 602-0695, managers must track which aircraft are eligible for the SL 129A alternative and which are not.

Regulators and certification delegates

• The AD is signed by a CASA delegate, David Villiers, indicating regulator-level issuance. The directive itself references FAA AD 2005-13-12, demonstrating cross-reference to foreign authority work. While the text does not spell out enforcement mechanisms, the CASA delegate’s signature places the AD in the formal instrument category for airworthiness directives.

Safety officers and insurance underwriters

• Airline or operator safety officers will need to monitor compliance to mitigate the safety risk described in the Background. Insurers may be affected indirectly because the AD describes a potential failure mode that can lead to loss of pitch control; insurers typically monitor compliance with airworthiness directives as part of risk assessment even though the AD itself does not state insurance consequences.

Aircraft owners with prior modifications

• The AD treats aircraft that already have any 9/16-inch eyebolt (part number 30774-1) as within the applicability. For those owners, the AD’s replacement or tightening schedules will apply according to the cumulative hours criteria. Owners who have already carried out the SL 129A modification should take note that while the modification is an alternative to permit increased replacement intervals, the AD explicitly states "The repetitive replacement of Requirement 2 is still required," so ongoing replacement obligations remain.

Stakeholders not covered

• The document explicitly refers to AT-301, AT-400 and AT-602 aircraft in the Background as the types associated with reported failures, but the applicability box limits the directive to AT-602 models and the eyebolt-part-number condition specified. Where the text does not include other models or serial numbers, those aircraft are not within the AD’s stated applicability and therefore not directly affected by this instrument as drafted.

Key duties imposed by the AD (textual sources: Requirements and Compliance)

• Tightening duty: Requirement 1 obliges the tightening of the four eyebolts attaching the front and rear spars of the horizontal stabiliser to their stabiliser struts, "using the torque values referenced in Snow Engineering Co. Service Letter (SL) No. 129, revised 21 October 2004." Compliance 1 sets the timing: do this within 100 hours time in service or 12 calendar months after 1 September 2005, whichever occurs first, unless already accomplished, and then at intervals not to exceed 12 calendar months.
• Replacement duty: Requirement 2 requires replacement of these eyebolts "in accordance with SL No. 129, Issued 26 September 1994, Revised 21 October 2004." Compliance 2 specifies initial replacement upon reaching the hours specified in SL No. 129 or within 50 hours time in service after 1 September 2005, whichever occurs later, and then replacement at the intervals specified in SL No. 129.
• Optional modification duty: Requirement 3 lets operators of aircraft up to serial number 602-0695 choose an alternative: replace the steel brace assembly inside the stabiliser with a new assembly with larger bushings and replace any 7/16-inch eyebolt with 9/16-inch eyebolt part number 30774-1, "in accordance with SL 129A, dated 7 August 2004." Compliance 3 allows this to be done "at any time after 1 September 2005," but states that the repetitive replacement obligation of Requirement 2 remains required.

Prohibitions and installation constraints

• Installation prohibition: the AD explicitly states "Do not install any 5/16-inch eyebolt (part number AN44-17A or AN44-21A), 7/16-inch eyebolt (AN47-22A or AN-47-30A), or 9/16-inch eyebolt (part number 30774-1 or 30775-1) that exceeds the corresponding cumulative hours time in service specified in Requirement 2 or 3 of this Directive." This is an express constraint tying permitted installations to cumulative hours-in-service limits established in the directive and the SLs.

Reference and obligation to use SLs

• The AD does not itself provide torque values or specific replacement intervals numerically; rather it mandates compliance with those values and intervals as set out in Snow Engineering Co. Service Letters (SL No. 129 and SL 129A). The duty therefore includes an obligation to consult and follow the content of those SLs. For example, Requirement 1 refers to torque values "referenced in" SL No. 129, and Requirement 2 requires replacement "in accordance with SL No. 129."

Timing obligations and sequencing

• The compliance table creates sequencing rules: the tightening is an immediate action with a defined repetitive interval; replacement has initial trigger points tied to hours specified in the SL or a short fallback window after the AD’s effective date; the SL 129A option is available after the effective date but does not remove ongoing replacement obligations. Those sequencing rules constrain maintenance planning and determine when actions must be documented and executed.

Rights implicit in the instrument

• The AD gives operators a choice (a right) to pursue the SL 129A modification alternative for certain serial-numbered aircraft; it does not require the modification but permits it as a way to take advantage of increased replacement intervals in SL No. 129. The directive also implicitly allows for compliance to be documented and accomplished "unless already accomplished" for the tightening action, which recognises that some operators may have already performed the action prior to the AD effective date.

Reference to other authority

• The text contains a note that "FAA AD 2005-13-12 Amdt 39-14149 refers." That indicates the AD is recognising related FAA regulatory action and signals to operators that the FAA AD is relevant material; the AD does not, however, embed the FAA AD’s text.

Delegation and signature

• The document is signed by David Villiers as "Delegate of the Civil Aviation Safety Authority." That signature identifies the regulatory delegate issuing the directive, which is relevant to questions of authority and provenance of the duty.

Duties not specified in the text

• The AD does not itself specify record-keeping, reporting, or penalty provisions; it imposes maintenance and parts-installation duties but does not set out administrative enforcement or sanctions in the text supplied. Any contractual, insurance or certification consequences of non-compliance are not addressed in the document.

What the directive says about penalties and enforcement

• The text of AD/AT 600/3, as supplied, contains no explicit penalty provisions, enforcement mechanism clauses, or administrative sanctioning language. The instrument states an effective date, the maintenance and replacement requirements and cites supporting SLs and an FAA AD, but does not include sections describing penalties for non-compliance, inspection or audit powers, or the administrative process for showing compliance in records.

Consequences mentioned in the text

• The Background sets out safety consequences of the identified unsafe condition: eyebolt failure "could lead to an abrupt change or complete loss of pitch control and/or aircraft departure from controlled flight." This statement is descriptive of the safety risk rather than prescriptive about enforcement. The AD therefore links the required actions to a specific hazard and consequence, but does not translate that hazard into any stated enforcement mechanism in the document itself.

Inference scope and caution

• Because the AD text supplied does not include enforcement or penalty clauses, readers should not infer additional procedural detail or sanction regimes from the AD alone. Any enforcement or penalty procedures that might apply in practice would come from the broader regulatory framework under which CAS authority issues airworthiness directives, or from operators’ own regulatory obligations, but those instruments and rules are not part of the supplied text and therefore are outside the source for this dive.

Practical implications for operators

• Although the AD does not set out penalties, failure to act in accordance with the AD leaves the aircraft exposed to the safety risk identified in the Background. In operational terms, an aircraft that has not complied with the torque and replacement regime will continue to present the mechanical failure risk described. The AD’s signature by a CASA delegate and its effective date signal regulator-level prescription; the absence of an enforcement clause in the text supplied means that any enforcement questions require reference to the broader regulatory regime not contained in this document.

Evidence of compliance

• The AD mandates compliance with numerical torque values and replacement intervals that are found in SL No. 129 and SL 129A; by requiring operators to follow those documents, the AD creates a compliance target that can be referenced in maintenance records and audits. However, the supplied AD does not itself specify the form, retention period or submission process for such records.

Related foreign regulatory reference

• The AD includes the note "FAA AD 2005-13-12 Amdt 39-14149 refers." That indicates the FAA has issued a related AD; the supplied Australian AD does not articulate whether or how the FAA AD is enforced domestically.

Direct cross-references in the text

• The directive explicitly references Snow Engineering Co. Service Letter No. 129 (issued 26 September 1994, revised 21 October 2004) and SL 129A (dated 7 August 2004) as prescriptive sources for torque values, replacement intervals and modification procedures (Requirements 1 to 3 and Compliance). The AD also includes a note that "FAA AD 2005-13-12 Amdt 39-14149 refers." Those references anchor the AD’s technical requirements in external engineering documentation and a foreign regulatory instrument.

Incorporation-by-reference mechanics implied

• The AD does not reproduce torque numbers or replacement intervals but requires adherence to SL No. 129 and SL 129A. This functionally incorporates those documents into the AD as the authoritative technical standards for compliance. Practically, compliance requires that an operator obtain and follow the content of those SLs. The AD therefore operates by stipulating that specified external technical materials are the operative standards; the AD text itself serves as the legal instruction to follow them.

No other statutory or regulatory cross-reference in the supplied text

• The version of the AD supplied does not cite or quote any domestic statutes, regulations, or penalty provisions. It is silent on interactions with other Australian legislative or regulatory instruments, including any civil aviation acts, regulations, certification standards, maintenance data requirements, or recordkeeping obligations. If interactions with domestic legislative frameworks are relevant for enforcement, certification or penalties, those are not set out in this AD text.

Relation to FAA action

• The AD’s explicit reference to FAA AD 2005-13-12 creates an evidentiary link to the FAA’s assessment of the same unsafe condition. That cross-reference suggests the Australian directive is aligned with, or informed by, the FAA action, but the AD does not specify whether compliance with the FAA AD alone discharges the Australian obligations; the Australian AD itself prescribes actions referencing Snow Engineering SLs and sets Australian compliance windows.

Scope-limiting interaction via technical documents

• Because the AD delegates torque values, replacement intervals and the modification procedure to SL No. 129 and SL 129A, the substantive technical obligations interact tightly with those service letters. Any updates or revisions to those SLs could affect the practical content of the AD’s obligations to the extent that operators rely on the most recent revisions named in the AD: SL No. 129 "revised 21 October 2004" and SL 129A "dated 7 August 2004." The AD’s requirements reference those dated versions specifically.

No administrative process described for deviations or alternative methods of compliance (AMOCs)

• The supplied AD does not include a clause providing for alternative methods of compliance (AMOCs) or a process by which an operator might seek relief, equivalence or approval for alternative procedures. The AD does include a formal alternative (SL 129A modification) for a subset of aircraft, but it does not outline an administrative approval pathway for other alternatives within the text supplied.

Practical consequence for cross-border operations

• For operators who must comply with both FAA and Australian directives, the AD’s explicit referral to FAA AD 2005-13-12 signals overlap but does not create automatic equivalence. The AD requires the Australian-specified actions regardless of foreign compliance status, unless the operator can demonstrate that actions already taken meet the Australian AD’s stated requirements. The supplied text does not elaborate on that interaction, therefore operators should treat this AD as a discrete Australian requirement that references but does not subsume foreign regulatory action.

Dates and revisions referenced in the AD text

• The AD itself is dated 9/2005 and carries a signature line dated 20 July 2005. The directive states "This Airworthiness Directive becomes effective on 1 September 2005," providing a clear effective date (AD text block).
• Snow Engineering Co. Service Letter No. 129 is referenced with two dates: originally issued 26 September 1994 and revised 21 October 2004. The AD requires torque values and replacement intervals "referenced in" or "in accordance with" SL No. 129, as revised 21 October 2004. The AD therefore adopts the 21 October 2004 revision of SL No. 129 as the operative technical document.
• SL 129A is specifically dated 7 August 2004 and is cited as the source for the optional steel brace assembly replacement and the use of larger bushings plus eyebolt replacement to 9/16-inch part number 30774-1 for aircraft up to serial number 602-0695.
• The AD notes the FAA action that relates to the issue, citing "FAA AD 2005-13-12 Amdt 39-14149" as a reference.

Internal sequencing of revisions

• The AD uses the most recent revisions/dates specified in the text for each SL: SL No. 129 (revised 21 October 2004) and SL 129A (dated 7 August 2004). The AD’s referencing of these dates indicates that compliance must be with those versions rather than earlier, unrevised versions; the AD does not, however, say whether later revisions to those SLs would be acceptable or require an amendment to the AD.

No amendment or supersession clauses in the supplied text

• The supplied AD text does not include clauses that amend other ADs, nor does it state that it supersedes previous Australian ADs. It simply prescribes the requirements for the stated applicability. It also does not include language authorising future amendments by reference; any formal amendment history beyond the dates cited must be sought in official amendment records, which are not part of this supplied text.

Record of signature and provenance

• The directive is signed by David Villiers, Delegate of the Civil Aviation Safety Authority, and dated 20 July 2005. That signature and date record the instrument’s issuance and provide a provenance marker for the AD as of that date.

Relation to FAA AD dates

• The FAA AD number is supplied but the text does not reproduce the FAA AD’s date. The supplied AD’s Reference note is limited to the identifier "FAA AD 2005-13-12 Amdt 39-14149 refers." That indicates contemporaneous FAA activity in 2005 relevant to the same safety issue, but the AD does not include a formal cross-amendment statement.

Amendment gaps

• The AD does not list any prior Australian ADs it replaces or any subsequent amendments. The supplied text therefore shows no internal amendment history beyond the incorporation of the dated SLs and the explicit effective date of 1 September 2005.

What the AD states about litigation

• The AD text supplied contains no reference to litigation, court decisions, appeals, petitions for review, or any judicial history. It does not cite any case law, nor does it note any disputes or legal challenges to the directive.

Absence of litigation details in the source

• Because the supplied instrument does not mention litigation, there is no source-grounded litigation history to report. Any information about legal challenges, appeals to administrative bodies, or court proceedings would be outside the scope of the supplied text.

Implication for research

• To discover any litigation connected with AD/AT 600/3, one would need to consult external records, regulatory archives, court databases or CASA release materials beyond the supplied AD text. The AD itself contains only the technical and compliance material and the signature line.

Practical note for compliance-minded parties

• The AD’s lack of litigation history in the text does not affect the obligations it imposes. Entities responsible for compliance should proceed to implement the AD’s requirements as stated; if there are legal questions about the scope, effect or enforceability of the AD, those questions are not addressed in the document itself and would require reference to broader legal materials not provided here.

Precision in applicability

• The directive’s applicability language is precise and segmented: it applies to (a) Model AT-602 aircraft with serial numbers up to and including 602-0695 that have any 7/16-inch eyebolt (AN47-22A) installed; (b) aircraft with serial number 602-0703 and subsequent; and (c) all aircraft that have any 9/16-inch eyebolt (part number 30774-1) installed. Operators must read that sentence carefully: some serial-number ranges are treated differently and the presence of a specified part number on any aircraft immediately brings that aircraft within the AD’s scope regardless of serial number. Misreading the serial-number cutoffs or the part-number triggers is a likely compliance pitfall.

Part-number specificity

• The AD lists multiple part numbers and sizes: 5/16-inch (AN44-17A, AN44-21A), 7/16-inch (AN47-22A, AN-47-30A), and 9/16-inch (30774-1, 30775-1). The installation prohibition binds by part number and cumulative hours in service; an operator who installs or retains a part without confirming its part number or service hours risks non-compliance with the AD’s "Do not install" prohibition.

Dependence on external SLs

• The AD does not provide numeric torque values or numerical replacement intervals within the body of the directive itself. Instead it refers to Snow Engineering Co. SL No. 129 (revised 21 October 2004) and SL 129A (7 August 2004). A potential gotcha is assuming the AD contains all the necessary technical parameters; it does not. Maintenance teams must obtain the referenced SLs to find the exact torque specifications and replacement hours. Failure to consult the SLs would leave implementers without the necessary numeric data to demonstrate correct compliance.

Timing windows and sequencing quirks

• The AD establishes multiple overlapping timing options: tightening within 100 hours or 12 months after 1 September 2005, initial replacement "upon accumulating the applicable number of hours time in service specified in SL No. 129 ... or within 50 hours time in service after 1 September 2005, whichever occurs later." For aircraft that have already exceeded the replacement hours in SL No. 129 by the effective date, the "whichever occurs later" phrasing means there is a 50-hour window to do replacement. Misreading the sequencing or mixing up the tightening and replacement deadlines could produce inadvertent non-compliance.

Alternative that does not remove replacement obligation

• Requirement 3 and Compliance 3 permit the SL 129A modification for aircraft up to serial 602-0695 and allow "use [of] the increased replacement compliance times in Requirement 2." However, the AD explicitly adds: "The repetitive replacement of Requirement 2 is still required." A common misunderstanding would be to assume the modification removes the need for ongoing replacement; it does not. Operators must implement repetitive replacement even after the modification.

Scope of "Do not install" prohibition and cumulative hours tracking

• The prohibition on installing certain eyebolts that "exceeds the corresponding cumulative hours time in service specified in Requirement 2 or 3" creates an administrative task: tracking cumulative hours in service for particular parts. Operators must ensure their records link part numbers to cumulative airframe or part hours. Failing to track those hours accurately could mean unintentionally installing a part that the AD prohibits because it exceeds the cumulative hours threshold.

Part interchange and prior replacements

• Aircraft may have had eyebolt replacements or the SL 129A modification performed prior to 1 September 2005. The AD language "unless already accomplished" covers the immediate tightening action, but operators must still reconcile prior maintenance entries with AD requirements. If prior replacements were carried out under different part numbers or different torque practices, verify whether they meet the SL 129/129A criteria referenced in the AD.

Reference to FAA AD without equivalence statement

• The AD’s note "FAA AD 2005-13-12 Amdt 39-14149 refers" might lead stakeholders to assume that meeting FAA AD requirements satisfies the Australian AD. The supplied text does not state equivalence. Do not assume that compliance with the FAA AD, alone, discharges the obligations of this AD; the Australian AD explicitly prescribes its own measures referencing specific SLs.

Documentation of compliance

• The AD does not describe the form of compliance evidence or reporting, which means operators must ensure their usual maintenance documentation shows the torque checks, part numbers installed, replacement intervals and hours-in-service records tied to each part. A gap in documentation could be a practical compliance fail even if the physical maintenance actions were performed.

Ambiguities about serial-number gaps

• The applicability mentions "serial numbers up to and including 602-0695" and "serial number 602-0703 and subsequent." That leaves a numerical gap between 602-0696 and 602-0702; the AD as supplied appears to intentionally omit those serial numbers or there may be a typographical inconsistency. The AD text must be read literally: it does not, in the supplied text, state that 602-0696 to 602-0702 are covered. This is a potential gotcha. Operators of aircraft with serial numbers in that gap should not assume coverage; they should verify serial-number applicability with the issuing authority or the original AD publication to confirm whether a typographical omission exists in the supplied excerpt.

Obtain the referenced service letters

• The AD makes compliance conditional on procedures and numerical values contained in Snow Engineering Co. Service Letter No. 129 (issued 26 September 1994, revised 21 October 2004) and SL 129A (dated 7 August 2004). Step one for compliance is to secure the current copies of those SLs as referenced in the AD so that torque values, replacement hour thresholds and the SL 129A modification procedure are available to maintenance personnel.

Immediate tightening action

• Requirement 1 requires tightening the four eyebolts attaching the front and rear stabiliser spars to the stabiliser struts, "using the torque values referenced in SL No. 129, revised 21 October 2004." Compliance 1 sets the timing: perform this tightening within 100 hours time in service or 12 calendar months after 1 September 2005, whichever occurs first, unless already accomplished. Thereafter tighten at intervals not to exceed 12 calendar months. Practically, maintenance teams should schedule a torque check within the shorter of the two windows and then place the tightening interval on an annual recurring preventive maintenance schedule.

Eyebolt replacement regime

• Requirement 2 mandates replacement "in accordance with SL No. 129." Compliance 2 clarifies that initial replacement must occur upon reaching the hours-in-service threshold specified by SL No. 129 or within 50 hours time in service after 1 September 2005, whichever is later; subsequent replacements must follow the intervals in SL No. 129. To comply, operators must:
  • Determine the cumulative hours-in-service for each eyebolt on each affected aircraft, as SL No. 129 prescribes.
  • If the eyebolt has already exceeded the SL-specified hours, schedule replacement within the 50-hour window after 1 September 2005.
  • Record the part number, serial or batch identification where available, the hours-in-service at replacement, and the next scheduled replacement interval per SL No. 129.

Optional SL 129A modification for certain serials

• For aircraft with serial numbers up to and including 602-0695, Requirement 3 provides an alternative: replace the steel brace assembly inside the stabiliser with the new assembly having larger bushings and replace any 7/16-inch eyebolt with 9/16-inch eyebolt part number 30774-1, "in accordance with SL 129A, dated 7 August 2004." Compliance 3 allows this work to be done at any time after 1 September 2005 but emphasises that Requirement 2’s repetitive replacement obligation continues. Practically, follow SL 129A’s parts list, fitment and installation steps precisely, document the modification, and then continue to log and replace eyebolts per the intervals allowed by SL No. 129 as modified by SL 129A.

Avoid installing over-life parts

• The AD states: "Do not install any 5/16-inch eyebolt (AN44-17A or AN44-21A), 7/16-inch eyebolt (AN47-22A or AN-47-30A), or 9/16-inch eyebolt (30774-1 or 30775-1) that exceeds the corresponding cumulative hours time in service specified in Requirement 2 or 3." Ensure that maintenance shops check cumulative hours for any eyebolt part before installation, and that parts inventories are not used beyond the AD’s permitted cumulative hours. Mark and segregate parts to prevent inadvertent over-age installation.

Maintenance recordkeeping and scheduling

• Because the AD ties obligations to hours-in-service and calendar intervals, operators must record the hours-at-installation for each eyebolt and the hours remaining until required replacement under SL No. 129 or SL 129A. For annual tightening, schedule and document the action within the aircraft’s maintenance log or the operator’s maintenance management system to demonstrate timing relative to the AD’s deadlines. Use part-number and installation-date entries to create a traceable chain of compliance.

Technical competence and torque accuracy

• The AD requires tightening "using the torque values referenced" in SL No. 129. Ensure maintenance personnel have calibrated torque tools, the precise torque figures from SL No. 129, and training in the proper procedure for achieving and verifying the torque values. Record the torque values applied and who performed the action as part of the compliance record.

Parts sourcing and compatibility

• When replacing eyebolts, procure the exact part numbers named in the SLs and AD where required. For the SL 129A modification, obtain the correct steel brace assembly and 9/16-inch eyebolt part number 30774-1 as specified. Confirm part conformity to the SLs and retain supplier documentation in maintenance records.

Document the alternative modification decision

• If electing the SL 129A modification for eligible aircraft, document the decision, the date of modification, part numbers installed, and follow-up replacement intervals per SL No. 129. Make clear in records that the modification was executed in accordance with SL 129A and that repetitive replacement remains scheduled.

Cross-check serial-number applicability

• Carefully match aircraft serial numbers to the AD’s applicability language. Because the AD has serial-number thresholds and a possible serial-number gap between 602-0695 and 602-0703 in the supplied text, verify the serial number’s status against the AD wording and keep documentation of that verification. If serial numbers fall in a gap or an unclear range, seek authoritative clarification from the issuing authority before assuming coverage or exemption.

Retain evidence for audits

• Keep maintenance entries, parts purchase records, torque check sheets and SLs used for the work as the best evidence of compliance. Although this AD text does not specify the records to produce on demand, preserving clear and contemporaneous records will be necessary to show that the AD’s tightening and replacement requirements were followed.

Monitor for related ADs and SL revisions

• The AD references FAA AD 2005-13-12 and relies on specific dated SLs. Operators should monitor for any later revisions to SLs or further directives that explicitly amend or supersede the AD, and should not assume later SL revisions automatically replace the versions referenced in the AD without formal direction.

Sign-off and authority

• Have the work performed and signed off by appropriately authorised maintenance personnel, following the organisation’s internal approval and release-to-service procedures. The AD is signed by a CASA delegate; ensure that the person releasing the aircraft for flight following maintenance is competent and authorised under the relevant maintenance certification rules applicable to the operator, and that records demonstrate the AD work and timing.

Summary checklist

• Obtain SL No. 129 and SL 129A as referenced.
• Determine applicability for each aircraft by serial number and installed eyebolt part numbers.
• Perform the initial tightening within 100 hours or 12 months after 1 September 2005 and then annually.
• Determine hours-in-service for each eyebolt; replace upon reaching SL No. 129 hours or within 50 hours after 1 September 2005 if overdue; then replace at intervals per SL No. 129.
• For eligible early serials, consider SL 129A modification, document it, and continue repetitive replacements.
• Do not install eyelbolts that exceed cumulative hours allowed by the AD.
• Keep detailed records of parts, hours, torque values applied, and sign-offs.

This sequence implements the directive as written and creates the maintenance record trail necessary to demonstrate conformance to the AD’s stated requirements.