AD/PA-24/36 Amdt 1 - Fin Forward Spar Attachment - Inspection

The AD's central technical concept is focused inspection of the fin forward spar attachment where three components are riveted together: a channel (Part No. 20749-0) and two straps (Part Nos. 20749-5 and -6). The two inspection objectives are: (a) detect and remove rough edges in the channel’s bend relief holes and (b) detect cracks in the channel and the two straps at and around those bend relief holes. The directive requires that inspection for cracks be carried out using visual methods aided by a magnifying glass of at least five power (Requirement: 1-2).

The amendment introduces a once-only preventative action for the bend relief holes, namely polishing any rough edges found, and clarifies compliance timing by reference to scheduled maintenance-release inspections rather than hours in service (Amendment 1; Compliance). The AD therefore embeds two temporal regimes: a single immediate/one-off rectification step if rough edges are found at the first applicable maintenance inspection after the effective date, and a continuing requirement to inspect for cracks at every scheduled inspection for issue of a maintenance release (Compliance: 1-2).

The AD also draws attention to documentation and identification issues: the individual part numbers named are not listed separately in the Parts Catalogue because they form components of a complete fin front spar assembly that has its own part number (Note 1). This affects traceability and the ability of maintenance personnel to order replacement components by the part numbers cited in the AD; the AD flags this to avoid confusion.

Another noteworthy concept is legal source-mapping. The Background records that the original 1975 AD derived from FAA AD 75-12-06 (amendment 39-2227), and that the original Australian AD omitted mention of polishing rough edges and a once-only dye-penetrant inspection (Background). The current amendment explicitly adds the once-only inspection/rectification for rough edges and rephrases timing in maintenance-release terms (Amendment 1).

Operationally, the AD prescribes the required inspection technique (visual with at least 5x magnification) and a specific remedial action when a defect type (rough edge) is present (polish to remove roughness). It does not specify acceptance criteria for cracks or a required follow-on repair method if cracks are found. The AD therefore sets mandatory detection and basic rectification obligations while leaving unspecified procedural details that may be covered in maintenance manuals or by maintenance organisations’ standard practices.

The AD applies to all owners and operators of Piper PA-24, PA-24-250, PA-24-260, and PA-24-400 aeroplanes that are certificated in any category, as stated in the Applicability section. Practically, that means any certificated operator, private owner, maintenance organisation or certificated maintenance engineer responsible for the airworthiness of an affected aircraft must ensure compliance because the compliance triggers are scheduled inspections for issue of a maintenance release (Applicability; Compliance).

Maintenance organisations and individuals authorised to perform inspections and to issue maintenance releases will be the decision-makers responsible for scheduling and executing the required inspections and any polishing of rough edges. The AD ties compliance to the maintenance-release process, so maintenance certifiers who sign the release must have inspected, or ensured inspection, for the specified items at the applicable maintenance event (Compliance). The AD does not itself allocate a monetary obligation explicitly, but the practical effect is that owners/operators bear direct costs through labour time and any materials used for polishing, plus any follow-up work required if cracks are detected (Requirement; Compliance). The AD does not contain cost estimates or an explicit funding mechanism.

Parts custodians and logistics personnel are affected because the AD cites part numbers (20749-0; 20749-5; 20749-6) and warns that those numbers are not listed separately in the Parts Catalogue (Note 1). This affects how maintenance teams identify the relevant components in parts documentation and may require cross-reference to the complete fin front spar assembly part number in the Parts Catalogue.

Regulators and inspectors within CASA have an oversight and enforcement interest. The AD is issued under CASA authority and is dated and signed by a CASA delegate, indicating that CASA will rely on the AD to set mandatory maintenance expectations for the affected fleet (signature block; effective date). The AD also references FAA AD 75-12-06; operators that conduct maintenance under international standards or coordinate with FAA-derived service guidance will need to reconcile this AD’s requirements with any FAA or manufacturer service bulletins.

Aircraft lessors, insurers and safety management personnel are indirectly affected because the AD modifies the baseline airworthiness expectations for the listed models. Compliance at the specified maintenance-release points will need to be evidenced in maintenance records. The AD notes that compliance with the original 1975 issue constitutes compliance with Requirement 2 of the amendment (Note 3), which affects operators who complied earlier: such operators do not need to repeat Requirement 2 as a consequence of the amendment.

The AD creates mandatory duties in the form of inspection and rectification tasks. The primary duties are:

• Inspect the fin forward spar to fuselage attachment assembly at the channel and straps where they are riveted together (Requirement: 1). The specific elements to inspect are the bend relief holes in the channel and the areas of the channel and the two straps in the region of the bend relief holes.
• If the bend relief holes have rough edges, polish the edges to remove the roughness (Requirement: 1).
• Using a magnifying glass of at least five power, visually inspect for cracks in the channel and the two straps in the area of the channel bend relief holes (Requirement: 2).

Timing duties are explicit: inspections are to be carried out at the next scheduled inspection for issue of a maintenance release after the amendment’s effectivity date, and thereafter at each scheduled inspection for issue of a maintenance release (Compliance: 1-2). Requirement 2 in the amendment is satisfied by compliance with the original 1975 AD (Note 3).

Rights, as such, are not detailed in the AD’s text. The instrument does not state appeal or variation mechanisms directly in the supplied text. It does, however, provide clarifying Notes: Note 1 informs maintainers that the part numbers mentioned may not appear separately in the Parts Catalogue because they are components listed under a separate complete assembly part number; Note 2 references the FAA AD for further context; Note 3 clarifies that prior compliance with the original AD satisfies the amendment’s ongoing inspection requirement. These notes function as interpretive guidance embedded in the AD itself and therefore confer an informational right to rely on them when determining compliance.

The AD does not prescribe specific repair or replacement procedures beyond polishing rough edges where found. It therefore places an evidential duty on the maintenance organisation or certifying engineer to determine acceptability of detected cracks and to apply the appropriate repair practices under their regulatory and organisational maintenance processes. The AD leaves to maintenance practice decisions about what constitutes an acceptable crack-free condition and, if cracks are found, what repair or component replacement is necessary. The AD does not include technical acceptance criteria or a mandated repair method for any cracks detected.

Finally, the AD’s applicability language makes the duty universal for the listed models certificated in any category. The obligation to inspect at scheduled maintenance-release inspections means that the maintenance, inspection and release processes of operators and maintenance organisations must integrate these inspection steps into their scheduled inspection checklists and maintenance-release documentation.

The supplied AD text does not specify penalties or enforcement procedures. The instrument is presented as a mandatory airworthiness directive issued by CASA (signed by a CASA delegate), which imposes inspection and rectification requirements, but the text provided contains no explicit penalty clauses, infringement schedules or administrative fine provisions (signature; effective date; Requirement; Compliance).

Because the AD is issued by the Civil Aviation Safety Authority, it functions as an instrument of regulatory airworthiness control. The text identifies the obligations and timing for compliance but leaves enforcement mechanics unstated in the document itself. The AD does not describe investigation processes, record-keeping requirements, sanctions for non-compliance, or a pathway for requesting alternative methods of compliance within the text provided. It likewise does not reference any specific enforcement provisions under other statutory instruments.

From the text alone, an operator or maintenance organisation must therefore treat the AD’s requirements as mandatory for continued airworthiness of the affected aeroplanes, but the AD does not itself set out the formal enforcement regime or administrative consequences in the content supplied. Any enforcement action, audits, or sanctions would be exercised under the broader regulatory and statutory powers available to CASA and related civil aviation law, which are not stated in this AD excerpt.

Because the AD ties compliance to maintenance-release inspections, a practical enforcement vector is likely to be the maintenance-release certification process: a maintenance certifier signing for an inspection that did not include the items mandated by the AD would be in a position of non-conformity. The AD does not, however, itself specify corrective pathways such as grounding until remediation, conditional release, or the need to file corrective action reports; those operational details are outside the text supplied.

If operators require authoritative guidance on penalties or alternative compliance procedures, they must consult CASA’s broader regulatory framework or seek direct clarification from CASA, as the AD text provided contains no fines, enforcement schedules, or appeals mechanism.

The AD explicitly references FAA AD 75-12-06 (amendment 39-2227) as the origin for the original 1975 Australian directive (Background; Note 2). The AD therefore situates itself in a cross-jurisdictional regulatory context: CASA’s AD mirrors or follows the FAA action in this instance. The AD does not set out any other statutory cross-references in the text provided.

There is a documented interaction with parts and maintenance documentation. Note 1 states that the part numbers cited (20749-0, 20749-5, 20749-6) do not appear in the Parts Catalogue because they are components of the fin front spar, which is listed as a complete assembly under a separate part number (Note 1). That statement informs the interaction between the AD and the aircraft Parts Catalogue and parts ordering systems: the AD’s component references must be reconciled with the Parts Catalogue’s assembly-level numbering.

The AD reinstates or clarifies the compliance timing approach compared with prior requirements. Amendment 1 changes compliance timing from hours in service to inspection at scheduled maintenance-release events (Amendment 1; Compliance). That alters how the AD interacts with an operator’s maintenance schedule and the legal regime for issuing maintenance releases. Operators and maintenance certifiers must align this AD’s inspection timing with their maintenance-release cycles rather than rely on an hours-based trigger that may have appeared in prior FAA-derived directives.

The AD’s notes and background material indicate a relationship with manufacturer and FAA guidance; however, the AD stops short of mandating specific manufacturer repair procedures. It does require polishing rough edges and visual inspection using 5x magnification, but it does not reference a particular manufacturer service bulletin or technical instructions beyond the FAA AD reference. Therefore, the AD interacts with but does not subsume manufacturer technical documents; maintenance organisations will need to use those documents in conjunction with this AD when determining appropriate repair actions if cracks are found.

The AD does not reference the broader legislative enforcement framework or identify specific sections of the Civil Aviation Act or associated regulations as the legal basis for this AD. It neither cites provisions on penalties, alternative compliance approvals, nor appeals in the text provided. For all formal legal interactions beyond the AD’s stated obligations,such as enforcement steps, alternative method approvals, or appeals,operators must look to the wider CASA regulatory framework and enabling legislation, which are not included in this AD extract.

The document supplies a short amendment history limited to two points. First, it records an original Australian AD issued in 1975 based on FAA AD 75-12-06 (amendment 39-2227), and it notes that the original 1975 issue omitted two items: polishing rough edges of bend relief holes in the channel and a once-only dye-penetrant inspection (Background). Second, it records the 2008 Amendment 1 (this instrument), which introduces a once-only inspection for, and rectification of, rough edges in the bend relief holes and specifies the compliance period in terms of the maintenance-release inspection rather than hours in service (Amendment 1; Compliance).

The effective date of this Amendment 1 is stated as 23 October 2008, with the instrument signed by David Villiers, Delegate of CASA, on 8 September 2008 (signature block; effective date). The AD’s header identifies it as AD/PA-24/36 Amendment 1 with the title "Fin Forward Spar Attachment - Inspection" and a date marker 11/2008 (AD/PA-24/36 Amdt 1; Fin Forward Spar Attachment - Inspection; 11/2008).

A further administrative detail in the Compliance notes is that compliance with the original 1975 AD constitutes compliance with Requirement 2 of this amendment (Note 3). This preserves the earlier compliance actions taken under the original AD in respect of ongoing crack inspections while adding the new once-only polishing requirement and changing the compliance timing reference.

No other amendments, revocations, supersessions, or later effective changes appear in the text provided. The AD therefore shows a narrow amendment history: original AD in 1975 influenced by FAA AD 75-12-06 and a single 2008 amendment that added the once-only polishing requirement and changed timing from hours in service to maintenance-release events.

For practitioners tracing obligations over time, the AD documents which prior compliance actions remain effective (Note 3) and which new requirements have been introduced (Amendment 1). It also flags a discrepancy between component part numbers cited and the Parts Catalogue, which has persisted across the original and amended versions (Note 1).

The supplied text contains no litigation history. The AD does not mention any judicial decisions, disputes, appeals, or litigation arising from either the original 1975 directive or this 2008 Amendment 1. There are no citations of case law, no record of contested enforcement actions, nor any reference to litigation channels or outcomes in the text provided.

Because the AD is an administrative instrument issued by CASA, any litigation arising from it would be processed through the civil or administrative courts in Australia, but no examples or references are included in this document. Practitioners seeking litigation precedent or challenges to this AD must therefore search external legal databases, court records, or CASA correspondence; none of those sources are present in the supplied text.

The AD’s Notes and Background do refer to the FAA AD from which the original Australian directive was derived (Background; Note 2), but that reference is to regulatory history rather than litigation. The absence of litigation references in the AD’s text should not be taken as evidence that none exists; it only confirms that no litigation history is recorded within this instrument itself.

There are several operational and interpretive points in the AD text that require attention because they can lead to compliance errors or confusion if overlooked.

• Part numbers not listed separately: Note 1 states that the quoted part numbers (channel 20749-0 and straps 20749-5 and -6) do not appear in the Parts Catalogue, because they are components of the fin front spar listed under a separate complete assembly part number. Maintenance teams that attempt to order or log parts using the numbers cited in the AD may be unable to find them in the Parts Catalogue and must therefore cross-reference to the assembly part number. Failure to recognise this could delay remedial action or generate incorrect ordering actions (Note 1).

• Two distinct obligations with different temporal characters: The AD introduces a once-only requirement (inspection and polishing of bend relief holes with rough edges) and a continuing inspection requirement for cracks at every scheduled maintenance-release inspection (Amendment 1; Requirement; Compliance). Confusing these can lead to missed obligations. Note 3 clarifies that compliance with the original 1975 AD satisfies Requirement 2 of the amendment, which may matter for operators who can show they met the original AD’s ongoing inspection obligations prior to the amendment.

• Limited prescriptive repair guidance: The AD prescribes polishing rough edges but does not specify acceptance limits for polishing, nor does it state what to do if a crack is found beyond "inspect for cracks." If a crack is detected, the AD gives no repair standard or mandatory replacement instruction in the text provided. Operators must therefore rely on manufacturer guidance, maintenance organisation procedures, or other technical sources to determine corrective actions. The AD’s silence on corrective thresholds means that maintenance engineers must exercise judgement, or consult CASA or the aircraft manufacturer, to determine airworthiness actions.

• Inspection method specified but testing options not: Requirement 2 mandates a visual inspection aided by at least five-power magnification. The Background notes the original AD omitted mention of a once-only dye-penetrant inspection. The current amendment does not prescribe dye-penetrant testing, only visual/magnified inspection; operators who previously relied on dye-penetrant methods must note that the amendment introduces polishing and maintains a magnified visual inspection requirement,if operators elect to perform more sensitive non-destructive testing (NDT), that is not mandated by this AD but could be used as an additional precaution.

• Timing linked to maintenance-release inspections: The compliance schedule is tied to the next scheduled inspection for issue of a maintenance release after the effective date and subsequently at each scheduled inspection for issue of a maintenance release. For operators with non-standard maintenance-release cadences or extended time between maintenance releases, this timing approach can affect the interval between required inspections and hence the window during which a defect might remain undetected. The AD replaces an hours-in-service metric with maintenance-release timing, which may extend or shorten intervals depending on operator practice (Compliance).

• Discrepancy between signing and effectivity dates: The AD is signed by the CASA delegate on 8 September 2008 but becomes effective on 23 October 2008. Operators must ensure they schedule the first applicable inspection after the effective date, not the signature date (signature block; effective date). Misreading the dates could result in premature or delayed compliance.

• Scope limited to specific PA-24 variants: Applicability is limited to listed PA-24 variants certificated in all categories. Operators of other Piper models or PA-24 variants not listed should not assume this AD applies to their aircraft; conversely, they must not assume absence of this AD implies absence of other applicable ADs.

The AD sets out a concise, practical compliance pathway; compliance steps in order are:

1. Determine applicability: Confirm that the aircraft is a Piper PA-24, PA-24-250, PA-24-260 or PA-24-400 certificated in any category (Applicability). If the aircraft is not one of these models, the AD’s requirements do not apply.

2. Schedule inspections: The AD requires action at the next scheduled inspection for the issue of a maintenance release after the effective date of the amendment (effective 23 October 2008), and thereafter at each scheduled inspection for issue of a maintenance release (Compliance: 1-2). Insert the AD tasks into the checklist for the next maintenance-release event.

3. Identify inspection area and parts: Locate the fin forward spar to fuselage attachment assembly where the channel Part No. 20749-0 and the straps Part Nos. 20749-5 and -6 are riveted together (Requirement: 1). Note that these part numbers may not be separately listed in the Parts Catalogue because they form components of a complete fin front spar assembly listed under a separate part number (Note 1). Cross-reference accordingly.

4. Once-only inspection and rectification for bend relief holes: Inspect the bend relief holes in the channel for rough edges. If rough edges are found, polish the edges to remove roughness (Requirement: 1). Keep a record of the inspection and any polishing performed; the AD states this is a once-only rectification for rough edges introduced by Amendment 1 (Amendment 1).

5. Visual inspection for cracks: Using a magnifying glass of at least five power, perform a visual inspection for cracks in the channel and the two straps in the area of the bend relief holes (Requirement: 2). Log the inspection result and the magnification used.

6. If cracks are found: The AD text supplied does not set out mandatory repair criteria or replacement instructions for a detected crack. Therefore, if a crack is detected, the maintenance organisation must follow established airworthiness procedures, manufacturer repair instructions, or other accepted maintenance practices to determine and implement the appropriate corrective action. Where necessary, consult CASA or the manufacturer for guidance on acceptable repairs or parts replacement, and document the corrective action. Note 3 indicates that compliance with the original 1975 AD satisfies Requirement 2, so prior documented inspections under the original AD can be relied upon for ongoing crack-inspection compliance.

7. Documentation and maintenance release: Record the inspection and any rectification in the aircraft’s maintenance logbook and in the maintenance-release paperwork. The AD ties compliance to the maintenance-release event, so the certifier issuing the maintenance release must ensure the inspections specified by the AD have been completed and recorded (Compliance).

8. Parts and ordering considerations: Because the components are listed as part of a complete fin front spar assembly in the Parts Catalogue, order replacement parts using the assembly part number from the Parts Catalogue rather than the component numbers cited in the AD (Note 1).

9. Evidence of prior compliance: If the operator or maintenance organisation complied with the original 1975 AD before this amendment, that compliance constitutes compliance with Requirement 2 of this amendment (Note 3). Retain records that demonstrate such prior compliance to avoid redundant inspections.

10. Follow organisational procedures for NDT and acceptance criteria: Although the AD mandates visual inspection with at least 5x magnification and polishing of rough edges, it does not prescribe acceptance limits or NDT thresholds. Maintenance organisations should apply their standard inspection acceptance criteria and, if they choose to use additional NDT methods (e.g., dye-penetrant), document their rationale and findings.

These steps are drawn directly from the AD’s Requirement and Compliance sections and the Notes. The AD does not include repair specifications for detected cracks; compliance therefore requires integrating the AD’s inspection and polishing mandates with the operator’s and maintenance organisation’s existing structural repair procedures and with any manufacturer guidance.

Record-keeping is implicit: because compliance is measured at maintenance-release events, the certifier must be able to produce records that the AD tasks were completed at those events. Operators should ensure that their maintenance records identify the AD reference (AD/PA-24/36 Amdt 1), the date of inspection, the items inspected, magnification used, any polishing performed, and any further actions taken if defects were found.

If uncertainty arises in interpreting the AD,e.g., acceptable limits for polishing, when a crack triggers mandatory replacement, or how to reference parts in the Parts Catalogue,operators should consult CASA or the aircraft manufacturer. The AD itself provides limited technical repair detail beyond inspection and polishing requirements.