AD/AT 800/6 - Horizontal Stabiliser Attachment Eyebolts

The AD is structured around a small set of technical and compliance concepts, each of which governs operator action.

Applicability. The AD is limited to "Model AT-802 and AT-802A aircraft," and then identifies affected serial-number and part-number combinations: aircraft with serial numbers up to and including 802A-0188 that have any 7/16-inch eyebolt (part AN47-30A) installed; aircraft with serial number 802A-0189 and subsequent; and all aircraft that have any 9/16-inch eyebolt (part 30775-1) installed (Applicability). The AD therefore applies to specific model/serial/part combinations; an operator must cross-check airframe serial numbers and installed eyebolt part numbers against this text to establish whether the AD applies to that aeroplane.

Torque retention and loss. The AD signals that loss of torque during service is a core failure mechanism (Background). Accordingly the AD requires an initial torque action and then a scheduled re-torque at intervals not exceeding 12 calendar months (Compliance 1). Torque values are not reproduced in the AD; the AD mandates use of the torque values in Snow Engineering Co. SL No. 129, revised 21 October 2004 (Requirement 1).

Life-limited parts and hour-based replacement. The AD treats eyebolts as components with cumulative hours time in service limits. Replacement intervals and initial replacement triggers are defined by hours TIS referenced in SL No. 129 (Requirement 2). The AD explicitly forbids installing certain eyebolt part numbers that have exceeded the cumulative hours specified in Requirement 2 or 3, embedding a parts life management constraint into maintenance practices (Requirement note).

Retrofit alternative with changed replacement times. For a subset of serial-numbered aeroplanes (up to and including 802A-0188), the AD offers a retrofit alternative that involves installing a new steel brace assembly with larger bushings and replacing 7/16-inch eyebolts with the 9/16-inch eyebolt part number 30775-1 (Requirement 3). That retrofit allows the operator to "use the increased replacement compliance times in Requirement 2," pursuant to SL 129A dated 7 August 2004 (Requirement 3; Compliance 3). The AD clarifies that even where the retrofit is performed, the repetitive replacement obligation of Requirement 2 still applies, albeit using the SL 129A timings (Compliance 3).

Reference to external technical documents and a foreign AD. The AD does not itself contain the detailed torque values, the hours-to-replacement values, nor the installations procedures. Instead it delegates these technical specifications to Snow Engineering Co. Service Letters SL No. 129 (revised 21 October 2004) and SL 129A (7 August 2004), and it refers to FAA AD 2005-13-12 (Amdt 39-14149) as related material. Therefore the AD functions as a compliance umbrella that points operators to those documents for technical execution (Requirement text; Requirement note).

Safety rationale. The background supplies the stated hazard: numerous FAA reports of eyebolt failures on related Airtractor models, with engineering analysis concluding high-cycle, low-nominal stress and probable loss of torque as causative factors, and the consequence risk being abrupt change or complete loss of pitch control and/or departure from controlled flight (Background).

Record-tracking and maintenance rhythm. Because the AD's replacement and installation prohibitions are keyed to cumulative hours TIS and the tightening schedule is time-based, the AD implicitly requires recordkeeping sufficient to demonstrate hours TIS for each eyebolt and to demonstrate that torque and replacement tasks were completed within the prescribed windows. The AD itself does not specify record formats; it establishes the need by attaching compliance to hours and dates (Compliance 1-3; Requirement note).

Delegation and issuance. The AD is signed by a CASA delegate, David Villiers, and dated 20 July 2005, with an effective date of 1 September 2005. The AD is therefore an instrument issued under CASA authority and made effective on an explicitly stated date (signature and effective-date line).

Operators and owners of Airtractor Model AT-802 and AT-802A aeroplanes are the directly affected parties. The AD's applicability clause identifies which aeroplanes within those models are in scope: those with serial numbers up to and including 802A-0188 that have any 7/16-inch eyebolt (AN47-30A) installed; aircraft with serial number 802A-0189 and subsequent; and all aircraft that have any 9/16-inch eyebolt (30775-1) installed (Applicability). That means individual aeroplane applicability depends on both airframe serial number and the eyebolt part numbers presently fitted.

Maintenance organisations, engineers and mechanics who perform stabiliser maintenance are operationally affected because they must perform the specified torque and replacement tasks to the technical specifications in Snow Engineering Co. SL No. 129 (revised 21 October 2004) and, where applicable, SL 129A (7 August 2004) (Requirement 1-3; Compliance 1-3). They must also ensure proper part sourcing and provenance so that installed eyebolts have not exceeded the cumulative hours limits set out in the AD (Requirement note).

Parts suppliers and inventory managers are affected by the AD's parts-installation prohibition and retrofit pathway. The AD forbids installation of certain part numbers that have exceeded specified cumulative hours and requires particular part numbers for retrofit (for example, 9/16-inch eyebolt part number 30775-1 for the SL129A retrofit) (Requirement 3; Requirement note). Suppliers must therefore be able to show parts TIS or provide new parts, and owners must manage stock so that life-limited items are traceable.

For aircraft with serials up to 802A-0188, there is a discrete decision node for owners/operators: accept the baseline replacement schedule in SL No. 129, or perform the steel brace assembly replacement and eyebolt upsize per SL 129A to qualify for increased replacement intervals (Requirement 3; Compliance 3). This creates a choice for affected owners about capital outlay now (parts and labour to retrofit) versus recurring replacement frequency and associated costs.

Regulatory actors are affected in the sense that the AD refers to and aligns with FAA analysis and an FAA AD (FAA AD 2005-13-12). The AD does not themselves list enforcement bodies or penalties in the text provided, but the instrument is issued by a CASA delegate (David Villiers) and given an effective date, so the regulatory regime that issued the AD will be the authoritative point for compliance and any subsequent action (signature; effective date).

Indirectly, operators of aircraft that are not AT-802 or AT-802A, but that may use the same eyebolt parts or share maintenance resources, will need to be aware of parts controls and life-limits if they source components from common suppliers. The AD’s broad prohibition on installing any of the listed eyebolt part numbers that have exceeded their hours TIS has implications for parts interchangeability and inventory practices (Requirement note).

Finally, because the AD relies on service letters produced by Snow Engineering Co., the manufacturer or engineering supplier of the eyebolts and brace assemblies is an affected stakeholder, since its SLs set the torque values and the hours-to-replacement metrics that operators must follow (Requirement 1-3).

Duties

• Initial and recurrent torque action: Operators must "tighten the four eyebolts that attach the front and rear spar of the horizontal stabiliser to the respective stabiliser strut" using torque values in Snow Engineering Co. SL No. 129, revised 21 October 2004. The initial retorque must occur within 100 hours TIS or 12 calendar months after 1 September 2005, whichever occurs first, unless already accomplished, and then at intervals not to exceed 12 calendar months (Requirement 1; Compliance 1).

• Eyebolt replacement: Operators must replace the eyebolts that secure the stabiliser spars to the struts "in accordance with SL No. 129, Issued 26 September 1994, Revised 21 October 2004." The initial replacement must occur either upon reaching the hours TIS specified in SL No. 129 or within 50 hours TIS after 1 September 2005, whichever occurs later. Subsequent replacements must occur at the intervals specified in SL No. 129 (Requirement 2; Compliance 2).

• Retrofit option for certain serials: For aeroplanes with serial numbers up to and including 802A-0188, operators may elect the alternative set out in Requirement 3: replace the internal steel brace assembly with one having larger bushings, and replace any 7/16-inch eyebolt with 9/16-inch eyebolt part number 30775-1, in accordance with SL 129A (7 August 2004). This permits the use of the increased replacement compliance times in Requirement 2, as given in SL 129A, but the repetitive replacement duty under Requirement 2 remains in force (Requirement 3; Compliance 3).

• Parts-installation prohibition: Operators must 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 TIS specified in Requirement 2 or 3 (Requirement note).

Rights and delegated actions

• Reliance on service letter technical detail: The AD authorises compliance by following Snow Engineering Co. SL No. 129 and SL 129A for the technical torque values, replacement intervals, and retrofit procedures. Operators have the right to rely on those specified documents for the technical execution of the duties mandated by this AD (Requirement 1-3).

• Choice between baseline and retrofit pathways (where eligible): For aircraft up to serial 802A-0188, owners may choose either to comply with the baseline replacement intervals in SL No. 129 or to perform the SL 129A retrofit and then comply with the modified replacement intervals provided in SL 129A. The AD frames this as an alternative route to achieve extended replacement times (Requirement 3).

• Time-window coordination: The AD sets two different initial timing triggers for replacement: the hours specified in the service letter, or a short fallback window (within 50 hours TIS after the effective date) if the hours threshold has already been reached; that gives operators a bounded choice in how to schedule the initial replacements depending on the current hours TIS of their parts (Compliance 2).

Operational implications of the duties

• Recordkeeping and traceability. Because the AD’s obligations are expressed in terms of cumulative hours TIS per eyebolt and calendar intervals for torque checks, operators must be able to demonstrate hours accumulation and completion of the tasks to meet the AD. The AD itself does not define record formats, but the duties imply a need for parts-level TIS records and a maintenance schedule to track the periodic 12‑month torque rechecks and the hours-driven replacements (Compliance 1-3; Requirement note).

• Supply and parts procurement. The prohibition on installing over‑hours eyebolts means operators must source either new parts or parts with verifiable TIS below the specified limits. The AD designates particular part numbers for the retrofit path and identifies specific part numbers limited by cumulative hours, so procurement decisions are constrained by the AD’s parts-listing (Requirement 3; Requirement note).

• Safety rationale as the decision driver. The AD’s Background identifies the hazard and causal mechanism (eyebolt failure due to high cycle stress and loss of torque), so the duties are aimed at reducing the particular failure mode via torque routine, parts replacement schedule, and a structural-hardware retrofit that modifies the bushings and eyebolt geometry (Background; Requirement 1-3).

The AD text does not specify penalties, remediation procedures for non-compliance, or administrative appeal rights; the duties and rights above are those expressed within the AD itself (effective date; requirement clauses).

The text of this AD does not set out statutory penalties, enforcement procedures, or inspection regimes within its body. The document records an effective date (1 September 2005) and is signed by a CASA delegate, David Villiers (signature; effective date), but it contains no express provision describing how non-compliance will be enforced or what administrative or civil penalties attach to contravention of the AD's directions.

Consequently, the AD imposes technical and scheduling obligations without specifying in-text enforcement mechanisms. The absence of explicit penalty clauses in the AD text means two consequences follow strictly from the source:

• Compliance evidence will be founded on maintenance execution and time-in-service records. The AD ties compliance obligations to hours TIS thresholds and calendar intervals (for example, tighten within 100 hours TIS or 12 calendar months after the effective date, and replacement upon accumulation of hours specified in SL No. 129 or within 50 hours after the effective date). To demonstrate compliance, operators must therefore produce records that show the actions were performed within the stated times and in accordance with the referenced Snow Engineering Co. service letters (Compliance 1-3; Requirement 1-3). Because the AD conditions installation and replacement on cumulative hours TIS, recordkeeping is an operational necessity.

• Enforcement, oversight and penalties (if any) are not described in this instrument. The AD is an instrument issued by the Civil Aviation Safety Authority (CASA) delegate, but the AD as published does not include the procedural steps that CASA might take to verify compliance, or penalties for non-compliance. The text does cite FAA AD 2005-13-12 (Amdt 39-14149) as a related authority, but does not describe cross‑jurisdictional enforcement mechanisms (Requirement note).

Practical enforcement risks and expectations that follow from the AD’s substantive content, based on the AD’s compliance mechanics, are:

• Proof of compliance will require parts traceability. Because the AD forbids installing listed eyebolt part numbers that have exceeded cumulative hours, enforcement or audit would logically examine parts records, serialisation where present, and maintenance logbooks showing hours TIS and replacement dates (Requirement note).

• Verification of torque checks. The AD’s repeated-torque schedule implies that maintenance records should reflect torque values used (the AD refers operators to SL No. 129 for torque values) and the dates and hours when torque was checked and re-torqued (Requirement 1; Compliance 1). Absent an explicit enforcement section, any regulatory audit would likely base scrutiny on those records.

• Retrofit certification evidence. For aeroplanes taking the retrofit option under SL 129A, evidence of the new steel brace assembly installation, the larger bushings, and the change to part number 30775-1 for 9/16-inch eyebolts will be required to support reliance on the increased replacement intervals (Requirement 3; Compliance 3).

Because the AD text itself does not enumerate enforcement tools or penalties, readers should note the AD defines substantive maintenance duties and timelines whose observance will be demonstrable through maintenance records, but the AD does not itself describe sanctions for non‑observance. Any application of penalties or specific enforcement actions would be governed by the broader regulatory framework under which the AD was issued, but that framework is not contained in the AD text provided.

Within the text of the AD, explicit external references are limited to Snow Engineering Co. service documents and to a related FAA AD. The AD interacts with these external instruments and documents in these ways:

• Delegation to Snow Engineering Co. Service Letters for technical standards. The AD requires compliance with torque values, replacement intervals and retrofit procedures set out in Snow Engineering Co. SL No. 129 (revised 21 October 2004) and SL 129A (dated 7 August 2004) (Requirement 1-3; Compliance 1-3). The AD therefore does not replicate technical specifications itself but incorporates them by reference. This creates an operational dependency: compliance with the AD is achieved by following those service letters.

• Cross-reference to FAA AD. The AD states "Note: FAA AD 2005-13-12 Amdt 39-14149 refers." (Requirement note). That reference ties the CASA AD to the FAA’s airworthiness actions on similar equipment and indicates that the underlying safety concern and remedial measures have a corresponding FAA document. The AD does not reproduce the FAA AD text, but it signals that the AD’s technical rationale and requirements are consistent with FAA action on related Airtractor models.

• Parts life and interchange constraints. By prohibiting the installation of certain eyebolt part numbers that have exceeded cumulative hours TIS specified in Requirement 2 or 3, the AD imposes constraints that affect parts supply, inventory management and maintenance interchange. Those constraints will interact with any national or international rules governing life-limited parts, traceability and parts certification, because the AD sets operational caps on parts based on hours TIS (Requirement note). The AD text, however, does not itself cite the legal regime controlling life-limited parts documentation.

• Effective-date timing and scheduling. The AD specifies an effective date of 1 September 2005 and gives triggered actions keyed to that date (for example, replacement "within 50 hours TIS after 1 September 2005" or tighten "within 100 hours TIS or 12 calendar months after 1 September 2005 whichever occurs first") (Compliance 1-3). Those timing constraints mean that the AD interacts with operators’ ongoing maintenance schedules and any other regulatory scheduling obligations on the affected aeroplanes.

• Relationship to manufacturer service instructions and maintenance approvals. The AD requires operators to use Snow Engineering Co. service letters for execution. In practice, this creates an intersection between the AD and manufacturer or parts-supplier service documentation. The AD thereby elevates the service letters to compliance documents, but does not itself state how conflicts between the service letter and any airframe manufacturer instructions should be resolved.

• No in-text mention of appeals, exemptions or alternate means of compliance. The AD provides an alternative (the SL 129A retrofit) but does not set out a process for obtaining exemptions, alternate means of compliance, or variations. Therefore, within the AD text itself, interaction with any statutory processes for obtaining relief from regulatory obligations is not specified.

Because the AD is compact and technical, its explicit legal interactions are narrowly described: it incorporates Snow Engineering Co. service letters for the operational technicalities, and it references an FAA AD as related material. Any further interactions with broader aviation law, certification or enforcement regimes would be mediated by the regulatory authority that issued the AD and by the wider body of aviation regulatory instruments, none of which are reproduced in this AD text.

The AD text itself records a short paper trail of dates and document editions that constitute its immediate amendment history in the sense of the documents it incorporates.

• AD signatory and date: The AD is signed by David Villiers, Delegate of the Civil Aviation Safety Authority, on 20 July 2005 (signature line). The AD declares an effective date of 1 September 2005 (effective-date line).

• Service letter editions incorporated: The AD mandates compliance with Snow Engineering Co. SL No. 129, originally issued 26 September 1994 and revised 21 October 2004. The AD also references SL 129A dated 7 August 2004 for the retrofit alternative and for the modified replacement times (Requirement 1-3). The AD therefore depends on the 21 October 2004 revision of SL No. 129 and on SL 129A, dated 7 August 2004, as the operative technical documents.

• Reference to FAA AD: The AD notes that FAA AD 2005-13-12 (Amdt 39-14149) is relevant (Requirement note). The AD does not state whether it amends or supersedes any prior CASA instrument; the AD’s text gives no earlier CASA AD numbers for this specific directive.

• No subsequent amendments listed: The AD document furnished contains no later amendments, revocations, or superseding directives within its text. The AD presents the requirements, the effective date, and the incorporated service letters and related FAA AD reference, but it does not include any record of amendment after its signature on 20 July 2005.

• Version control is via incorporated document dates: Because the AD delegates technical detail to SL No. 129 (revised 21 October 2004) and SL 129A (7 August 2004), and it references FAA AD 2005-13-12, the AD’s operative content is linked to the version dates of those external documents. Any amendment to the AD in future would likely need to reference revised editions of those service letters or new ADs, but no such amendments appear in the AD text provided.

In short, the AD’s internal amendment history is limited: it was signed 20 July 2005, is made effective 1 September 2005, and incorporates Snow Engineering Co. documents with specified revision dates; the AD text shows no further amendments or subsequent versions.

The AD text contains no litigation history, case citations, or references to judicial or administrative decisions. It makes reference to FAA reports and an FAA AD (FAA AD 2005-13-12 Amdt 39-14149 refers), and it recites engineering analysis and incident reports as the factual basis for the directive (Background). However, the document does not mention any challenges to the AD, any litigation arising from enforcement, or any judicial interpretations. Therefore, based strictly on this source, there is no recorded litigation history associated with AD/AT 800/6 in the document provided.

Because the AD does not specify any enforcement or penalty mechanisms within its text, and because it does not cite subsequent administrative or judicial action, readers should treat the litigation history as nil in the document. If regulatory or court action occurred later, those events are not captured in the AD text supplied.

Several operational, interpretive and recordkeeping pitfalls arise directly from the AD's wording.

Applicability parsing. The applicability clause lists several categories and mixes serial-number ranges with installed part numbers: "Model AT-802 and AT-802A aircraft, with serial numbers up to and including 802A-0188 that have any 7/16-inch eyebolt (part number AN47-30A) installed; aircraft with serial number 802A-0189 and subsequent; and all aircraft that have any 9/16-inch eyebolt (part number 30775-1) installed." Operators must be careful in parsing this sentence: it ties applicability to both serial number ranges and to specific eyebolt part numbers. An aircraft may be in scope by serial number alone (802A-0189 and subsequent) or by having a specified part (30775-1) installed even if serial number is different. Failure to cross-check both serial number and installed part numbers could lead to mistaken in- or out-of-scope conclusions (Applicability).

Dual-timing triggers and the "later/earlier" rules. Replacement and tightening obligations use mixed triggers that operators must execute correctly. For example, the initial tightening must be within 100 hours TIS or 12 calendar months after 1 September 2005, whichever occurs first (Compliance 1). By contrast, the initial replacement must be upon accumulating the hours specified in SL No. 129 or within 50 hours after 1 September 2005, whichever occurs later (Compliance 2). These "whichever first/whichever later" constructions can produce counterintuitive schedules depending on the current hours TIS. Operators must calculate for each individual eyebolt whether the SL No. 129 hours threshold has already been exceeded and then apply the correct initial replacement window; mistakes here can result in missed replacement deadlines.

Parts-installation prohibition tied to cumulative hours. The AD forbids installation of certain part numbers that have exceeded the corresponding cumulative hours TIS specified in Requirement 2 or 3. That creates a requirement to track hours per part, not just per aeroplane. If parts are swapped between aircraft or held in stock, purchasers and maintainers must be able to demonstrate the cumulative hours for that particular eyebolt. Failure to maintain such part-level TIS records is a compliance risk (Requirement note).

Retrofit does not eliminate replacement duty. Requirement 3 offers a retrofit to allow "increased replacement compliance times in Requirement 2," but the AD explicitly states "The repetitive replacement of Requirement 2 is still required" (Compliance 3). That is a common point of confusion: operators might expect that the retrofit eliminates the need for repetitive replacement; instead it alters the replacement schedule to the timings in SL 129A, but replacement remains a continuing obligation.

Reference dependence on external service letters. The AD mandates compliance with SL No. 129 (revised 21 October 2004) and SL 129A (7 August 2004) for detailed torque values, hours-to-replacement and the retrofit method. The AD itself does not provide the technical numbers. Operators must obtain and use those service letters. Misalignment between the service letter edition used and the edition specified in the AD could produce non-compliance if the wrong revision is applied (Requirement 1-3).

Ambiguity on part-number listings. The AD lists multiple part numbers for eyebolts of different nominal sizes (5/16, 7/16, 9/16). The prohibition clause lists part numbers that must not be installed if they exceed cumulative hours, and the retrofit requires specific part number 30775-1 for the 9/16-inch eyebolt. Operators must ensure they distinguish between part numbers that are similar in appearance or marking to avoid incorrect installations (Requirement note; Requirement 3).

Interplay with FAA AD. The AD notes that FAA AD 2005-13-12 refers. Operators who move aircraft or components between jurisdictions should be aware that corresponding foreign ADs may have different wording, timing or compliance paths. The AD does not describe how divergent requirements would be reconciled; cross-jurisdictional operations therefore require careful attention (Requirement note).

Implicit records and proofs. Because compliance is framed in hours TIS and specific calendar windows, maintenance records must show both the hours and the dates of torque and replacement actions. The AD does not set out recordkeeping format or retention periods, so operators must be careful to preserve contemporaneous evidence that the AD actions were performed in the required windows and "in accordance with" the specified service letters (Compliance 1-3).

No enforcement detail in text. The AD contains no in-text enforcement or penalty provisions. That absence is itself a gotcha: operators cannot rely on the AD for guidance on consequences of non-compliance; any enforcement or penalty regime would have to be found in other regulatory instruments not included in the AD text provided (effective-date; signature; lack of enforcement language).

In summary, the principal operational pitfalls are in parsing applicability, calculating mixed timing triggers, maintaining part-level cumulative hours records, ensuring correct service-letter editions are used, and treating the retrofit as only altering, not eliminating, replacement duties.

This section sets out actionable, source-grounded steps that follow the AD’s text. The AD requires operators to work to the Snow Engineering Co. service letters it references, and to meet the timing windows expressed in the AD. The AD’s internal numbering and timing items are the compliance framework.

1. Determine applicability

• For each AT-802 or AT-802A aeroplane in your fleet, confirm the airframe serial number and the part numbers of all horizontal-stabiliser attachment eyebolts. The AD applies to: (a) AT-802/AT-802A with serial numbers up to and including 802A-0188 that have any 7/16-inch eyebolt AN47-30A installed; (b) aircraft with serial number 802A-0189 and subsequent; and (c) all aircraft that have any 9/16-inch eyebolt part number 30775-1 installed (Applicability). Document the serial numbers and installed part numbers.

2. Obtain the referenced service letters

• Acquire Snow Engineering Co. SL No. 129, revised 21 October 2004 (this contains the torque values and hours-to-replacement schedules), and SL 129A dated 7 August 2004 (this contains the retrofit instructions and modified replacement intervals for eligible serials). The AD requires actions "in accordance with" these documents, so they are the source of the technical torque values and replacement-hours tables (Requirement 1-3).

3. Perform initial tightening

• For aeroplanes in scope, tighten the four eyebolts attaching the front and rear spar of the horizontal stabiliser to the respective stabiliser strut using the torque values specified in SL No. 129 (Requirement 1). Do this within 100 hours TIS or 12 calendar months after 1 September 2005, whichever occurs first, unless already accomplished (Compliance 1).

• After the initial tightening, schedule and perform subsequent torque checks at intervals not exceeding 12 calendar months (Compliance 1). Record the date, hours TIS at the time of the torque action, the torque value applied (as taken from SL No. 129), the technician’s name/signature, and any torque-tool calibration reference used.

4. Implement eyebolt replacements per hours schedule

• For required eyebolt replacements, follow the hours-to-replacement tables and procedures in SL No. 129 (issued 26 September 1994, revised 21 October 2004) (Requirement 2). The initial replacement must occur either upon the accumulation of the hours specified in SL No. 129 for the eyebolts, or within 50 hours TIS after 1 September 2005, whichever occurs later (Compliance 2). Thereafter, conduct replacements at the intervals specified in SL No. 129 (Compliance 2).

• Maintain part-level records showing the cumulative hours TIS for each eyebolt, the dates and flight hours when each replacement occurred, the source and part number of the replacement eyebolt, and any serial numbers or batch identifiers if available.

5. Consider the retrofit for eligible serial numbers

• For aeroplanes with serial numbers up to and including 802A-0188 that wish to use the "increased replacement compliance times" allowed in Requirement 2, perform the retrofit in accordance with SL 129A dated 7 August 2004. The retrofit requires replacing the steel brace assembly inside the stabiliser with a new assembly having larger bushings and replacing any 7/16-inch eyebolt with 9/16-inch eyebolt part number 30775-1 (Requirement 3).

• The AD notes that the retrofit may be done "at any time after 1 September 2005" and that the applicable times in SL 129A should be used once the retrofit is completed (Compliance 3). Record the retrofit work, including part numbers installed, serials of new assemblies (if provided), and the date/hours TIS at which the retrofit was completed.

• Note that even after the retrofit, the repetitive replacement requirement of Requirement 2 remains in force, albeit using the replacement intervals set out in SL 129A; do not assume the retrofit eliminates replacement duties (Compliance 3).

6. Enforce parts-installation restrictions

• Do not install any specified eyebolt part number that has exceeded its cumulative hours TIS as specified in Requirement 2 or 3. The AD specifically references the following part numbers as subject to this prohibition: AN44-17A or AN44-21A (5/16-inch); AN47-22A or AN-47-30A (7/16-inch); and 30774-1 or 30775-1 (9/16-inch) (Requirement note).

• Ensure your parts inventory and procurement process can show the hours TIS for each eyebolt part before installation. If an operator transfers eyebolts between airframes, the part-level hours must be tracked and confirmed not to exceed the AD limits before installation.

7. Recordkeeping and compliance evidence

• For each torque, replacement and retrofit action, log the task date, the hours TIS at the time, the exact service-letter edition used (e.g., SL No. 129, revised 21 October 2004), the part numbers and serial numbers installed, the technician’s identification, and any test or inspection results.

• Because initial replacement windows mix both hours-based triggers and short post-effective-date windows (for example, replacement "within 50 hours TIS after 1 September 2005" or when hours threshold reached), ensure records show the decision logic used to schedule the work.

8. Audit readiness

• Prepare to present maintenance logs showing the torque, replacement and retrofit actions in accordance with the AD and with SL No. 129/SL 129A. Maintain cross-references between aircraft serial numbers, installed part numbers, part hours TIS and the dates of actions carried out to satisfy the AD.

9. Use correct service-letter editions

• Verify that the SL No. 129 edition you are using is the one revised 21 October 2004, and that SL 129A is dated 7 August 2004, as these specific dates are the editions referenced in the AD (Requirement 1-3). Do not rely on earlier or later editions unless the AD is subsequently amended to reference different editions.

10. Document decision on retrofit vs. baseline schedule

• For each aircraft eligible for the SL 129A retrofit (serial ≤ 802A-0188), document the cost-benefit decision to retrofit or not, and record the retrofit completion if taken. Remember that retrofit alters replacement intervals, but does not remove the need to replace eyebolts periodically (Compliance 3).

By following the AD’s explicit words and the procedural steps in the referenced Snow Engineering Co. service letters, an operator will meet the AD’s technical obligations. The AD itself supplies the timing triggers and parts lists; adherence requires disciplined parts-level TIS tracking, use of the specified service-letter editions, annual torque schedules and the replacement programme keyed to the hours tables in SL No. 129 or SL 129A as applicable.