Airworthiness Directive (AD): A legally enforceable notice issued by a national aviation authority mandating corrective action on an aircraft or component to ensure continued safe operation. Under CASR Part 39, compliance with an AD is non-negotiable for the aircraft’s airworthiness certificate to remain valid. This AD is a continuing airworthiness directive meaning it imposes recurring actions, not a one‑off fix.

Incorporation by reference of FAA AD 2015-08-04: The Australian AD does not recite the full inspection procedures; it directs the reader to an external document,the FAA AD. That FAA AD in turn references two Piper Mandatory Service Bulletins (MSBs): MSB No. 528D dated 19 October 1990 and MSB 910A dated 10 October 1989. These MSBs contain the detailed instructions for inspection, removal, and replacement. Because the FAA AD is incorporated as in force at the date of the Australian AD, any later changes to the FAA AD are not automatically accepted unless CASA separately updates the Australian AD. This creates a static reference point: 12 December 2016.

State of design vs. foreign state of design: The background explains that the United States is no longer considered the state of design for these aircraft. Under CASR Part 39, foreign state‑of‑design requirements (such as FAA ADs) may not automatically be accepted as equivalent to an Australian AD. Thus Amendment 9 explicitly “accepts and aligns to the requirements” of the FAA AD but removes any suggestion that alternative X‑ray inspections were pre‑approved (as they had been under earlier amendments). Any AMOC must now be specifically approved by CASA, not automatically assumed from FAA approval.

Terminating action: The FAA AD allows replacement of the original struts with new sealed struts (Piper part number unspecified in the AD text) as a one‑time fix that ends the repetitive inspection requirement. The Australian AD incorporates that provision but does not specify a part number or supplier; the operator must refer to the FAA AD and Piper MSBs.

Alternative Method of Compliance (AMOC): A mechanism that allows a different means of achieving the safety outcome, subject to approval. This AD centralises AMOC approval with CASA, removing any prior delegation to industry or automatic recognition of FAA approvals. This adds administrative cost and delay for operators who wish to deviate from the prescribed inspection method.

Applicability range: The serial number range 25-1 to 25-8156024 covers essentially all production PA-25 Pawnee aircraft. This is a large fleet of agricultural and utility aircraft still in service worldwide, including in Australia. The directive is therefore broad in scope but targeted at a specific airframe component.

The AD directly imposes obligations on the registered operator of an affected aircraft, because under CASR the operator holds primary responsibility for maintaining the aircraft in an airworthy condition. In practical terms, compliance falls on:

• Aircraft owners who may not be the operator; they bear financial costs but the legal duty usually rests with the operator (or the holder of the certificate of registration).
• Maintenance organisations (CASA‑approved Part 145 or similar) that physically perform the inspections, removals, and replacements. They must have access to the FAA AD and the referenced Piper MSBs, and must ensure their technicians are properly trained to detect internal corrosion, particularly in the lower bottom area of the struts and at the upper cuff fairing screw attachment.
• CAR 35 Authorised Persons (engineers authorised under Civil Aviation Regulation 35 to certify maintenance) are explicitly mentioned in the background concerning assessment of struts with corrosion indicated by radiographic inspection. Even though Amendment 9 removes X‑ray as an alternative, CAR 35 holders remain involved in certifying any AMOC or condition inspections.
• CASA itself becomes a gatekeeper for AMOC approvals. The AD notes that any AMOC application will be assessed by CASA, meaning CASA personnel must develop or maintain technical expertise on strut corrosion assessment and Piper design standards.
• Piper Aircraft Inc., while not a party to the AD, is indirectly affected because its MSBs become mandatory by reference. Piper may need to support inquiries from owners or maintainers about the correct part numbers and installation procedures for replacement struts.
• Insurance companies and financiers holding security over affected aircraft will care about compliance because non‑compliance can render the aircraft unairworthy and potentially uninsurable or unsaleable.
• Agricultural operators are a particularly affected cohort because the PA-25 Pawnee is a dedicated aerial application aircraft. For them, downtime for strut inspection and possible replacement represents lost revenue, especially if inspections occur during spraying season.

The AD does not distinguish between private, commercial, or aerial‑work operations; it applies uniformly to all aircraft within the serial number range regardless of use.

Duty to comply: The operator must ensure that each affected aircraft on the Australian register is in compliance with FAA AD 2015-08-04 as incorporated by this AD. This includes performing:

• Initial and repetitive inspections of wing lift struts at the intervals specified in the FAA AD and Piper MSBs.
• Inspection after removal of struts (the AD clarifies that struts must be removed to detect corrosion that may be hidden if only external visual checks are performed).
• Inspection of the strut upper end when the upper cuff fairing is attached by a screw (introduced in Amendment 7).
• Replacement with new sealed struts as a terminating action if corrosion is found or if the operator opts to eliminate the repetitive requirement.

Right to previous compliance credit: Inspections carried out in accordance with prior amendments of this AD (Amdt 3 through Amdt 8) are accepted as satisfying past repetitive inspection requirements of the FAA AD. However, future inspections must follow the FAA AD; operators cannot rely on the older, less stringent X‑ray alternative even if that was previously allowed.

Right to apply for an AMOC: An operator may propose an alternative method of compliance, but must apply to CASA for approval. This AD explicitly removes any automatic acceptance of FAA AMOC approvals; the operator must obtain CASA’s own assessment. There is no guaranteed timeline for CASA to decide, creating potential uncertainty.

Duty to maintain records: Compliance with the AD must be documented in the aircraft maintenance records, including evidence that inspections were performed, findings (including any corrosion), and any strut replacements. The FAA AD will prescribe specific recording requirements.

Right to terminate repetitive inspections: By installing new sealed struts with the redesigned fork, the operator ends the recurring inspection obligation for that aircraft. This is a capital cost but may be cost‑effective over the long term if the aircraft will be operated for many years.

No right to opt out: The AD is mandatory. An aircraft not in compliance cannot be flown; the operator faces enforcement action. There is no provision for exemption based on low utilisation or private use,the requirement applies regardless.

Duty of the maintenance organisation: The organisation performing the work must have the current FAA AD and Piper MSBs on hand, must understand the corrosion detection criteria, and must certify the work correctly. Incorrect certification can lead to regulatory action against the organisation and the certifying engineer.

Non‑compliance with an Australian Airworthiness Directive is a breach of the Civil Aviation Safety Regulations. Under CASR Part 39, operating an aircraft that does not meet the requirements of an applicable AD is an offence. Specifically, CASR 39.014 makes it an offence to operate an aircraft unless each applicable AD has been complied with. The penalties include:

• Civil penalties: CASA can issue infringement notices (on‑the‑spot fines) typically in the range of several thousand dollars per breach. For a corporation, fines can be higher.
• Criminal prosecution: Deliberate or reckless non‑compliance may lead to prosecution under the Civil Aviation Act 1988. Penalties can include large fines and, for individuals, imprisonment (though imprisonment is rare in practice for airworthiness offences).
• Enforcement actions short of penalty: CASA can suspend or cancel the aircraft’s certificate of airworthiness, issue a grounded aircraft direction, or impose conditions on the operator’s approval. This stops revenue generation and may affect the operator’s other approvals.
• Liability implications: In the event of an accident where non‑compliance with this AD is a contributing factor, the operator and the certifying engineer could face civil liability, including negligence claims and workers’ compensation consequences. The AD’s background explicitly links a prior fatal accident to undetected strut corrosion that would have been caught by removal and inspection.
• Insurance consequences: An aircraft flown out of compliance may void hull and liability insurance coverage, exposing the operator to massive uninsured loss.
• Rectification costs: CASA may direct the operator to perform inspections at the operator’s expense, and may also require additional oversight such as increased surveillance of the operator’s maintenance procedures.

The AD itself does not specify a dollar penalty; enforcement is under general CASR provisions. The practical penalty for most operators is the forced grounding and rectification cost, which can far exceed any fine.

This AD operates within the broader framework of CASR Part 39, which governs the issuance and acceptance of airworthiness directives. Part 39 distinguishes between domestic ADs (issued by CASA) and foreign ADs (issued by the state of design). For the PA-25, because the USA is no longer the state of design, the FAA AD is not automatically binding in Australia; hence this Australian AD is needed to make the FAA AD mandatory. This interaction creates a cascade:

• The Australian AD references FAA AD 2015-08-04 as a static document; any later revision of that FAA AD (e.g., Amendment 10 by the FAA) does not automatically become binding in Australia unless CASA issues an amendment to this AD. Operators and maintainers must check both the FAA version in effect on 12 December 2016 and any later Australian amendments.
• The FAA AD in turn references Piper MSB 528D and 910A. These MSBs may themselves be updated by Piper, but the AD references specific dates (19 October 1990 and 10 October 1989). If Piper issues later revisions, they are not mandatory unless the FAA AD or this Australian AD explicitly incorporate them. However, an operator may voluntarily use a later MSB if it is equivalent, but that would require an AMOC from CASA.
• CASR Part 42 (continuing airworthiness requirements) obligates the operator to ensure the aircraft is maintained in accordance with the maintenance program. This AD becomes part of that program. Failure to embody the AD could lead to non‑compliance with Part 42 additionally.
• CASR Part 145 (maintenance organisations) requires approved organisations to have appropriate data for the tasks they perform. The AD requires them to hold the FAA AD and MSBs. An organisation that performs the work without having the correct data breaches its own approval.
• Civil Aviation Regulation 35 (CAR 35) is mentioned in the background for assessment of strut corrosion. CAR 35 authorised persons may be involved in evaluating corrosion findings and deciding whether a strut is serviceable. Their authority derives from a different regulation, but the AD specifies the required action.
• Other ADs might exist for the same aircraft type (e.g., AD/PA-25/40 series). This AD supersedes Amendment 8 and earlier amendments for the wing lift struts, but other ADs may cover different components (e.g., engine, propeller, flight controls). Operators must track all applicable ADs independently.
• Work Health and Safety laws are indirectly relevant: maintenance personnel must handle struts safely during removal and inspection. The AD does not address WHS, but operators must comply with state and territory WHS legislation.

There is no interaction with privacy, competition, or consumer law. The AD is purely technical airworthiness regulation.

This document is AD/PA-25/40 Amdt 9. The background summarises key changes from earlier amendments:

• Amendment 3: Clarified that assessment of struts with corrosion indicated by radiographic inspection must be performed by a CAR 35 Authorised Person. This introduced a human‑factors requirement: only specifically authorised engineers could evaluate corrosion found by X‑ray.
• Amendment 4: Updated the reference document (likely the Piper MSB) and introduced replacement with new sealed struts as terminating action. The new strut also incorporated a redesigned strut fork, addressing a potential failure point.
• Amendment 5: Reduced the corrosion inspection interval following two reports of excessive corrosion appearing within the previous 5‑year interval. This amendment also clarified that wing struts must be removed for inspection; prior wording may have allowed visual checks without removal. The background notes that failure to remove struts led directly to at least one fatal accident.
• Amendment 6: Corrected the compliance paragraph to allow 24 months since the last X‑ray inspection. This was a transitional accommodation for operators who had already performed X‑ray inspections under earlier amendments.
• Amendment 7: Introduced inspection of the strut upper end if the upper cuff fairing is attached by a screw. This was in response to reports of severe internal corrosion at the screw attachment hole area, a location previously overlooked.
• Amendment 8: Aligned the Australian AD with the requirements of a new FAA AD (superseding 93-10-06) that had been referenced in Amendment 7. This was a procedural alignment.
• Amendment 9 (this amendment): Accepts and aligns to FAA AD 2015-08-04 because the USA is no longer the state of design. It removes references to alternative X‑ray inspection methods and centralises AMOC approval with CASA. This is the most significant structural change: it ends automatic acceptance of FAA AD revisions and requires CASA assessment for any deviation.

The amendment history shows a progressive tightening of requirements: from allowing X‑ray without removal (Amdt 3), to requiring removal (Amdt 5), to adding upper end inspection (Amdt 7), and finally to removing alternative methods entirely (Amdt 9). Each amendment responded to in‑service evidence of corrosion risk.

The source text contains no reference to any court cases arising from this AD or its predecessors. It is highly likely that no published Australian administrative or appellate decisions exist directly on AD/PA-25/40, because airworthiness directives are generally complied with as a matter of routine rather than litigated. Operators may challenge CASA decisions (e.g., refusal of an AMOC) through the Administrative Appeals Tribunal (AAT) or seek judicial review in the Federal Court, but such challenges are rare and rarely publicised in a way that creates precedential case law. The AD’s background mentions a fatal accident linked to undetected corrosion, but that accident appears to have been operational, not a basis for litigation against CASA or Piper. In the absence of any case name or citation in the source, a deep‑dive cannot fabricate litigation history. The most one can say is that no court has interpreted or invalidated this specific AD, and no common‑law duty of care has been found to modify its requirements. The enforcement of ADs is primarily administrative, not judicial.

• Static incorporation of FAA AD: The AD incorporates FAA AD 2015-08-04 only as in force at the date of the Australian AD. If the FAA later revises its AD to allow longer intervals or a different inspection method, those revisions do not automatically apply in Australia. Operators must continue using the older FAA version unless and until CASA issues an amendment. This can create a trap for the unwary who assume that FAA updates are automatically accepted.
• Removal of X‑ray alternative: Prior amendments allowed radiographic (X‑ray) inspection. Amendment 9 removes that option entirely. An operator who has invested in X‑ray equipment or contracted a radiographic service can no longer use that method to satisfy the inspection requirement unless they obtain a specific AMOC from CASA. This increases cost and disruption.
• Upper cuff fairing screw attachment area: This requirement (from Amendment 7) is easily overlooked. The screw attachment area on the upper end of the strut is a small, inconspicuous location. Maintainers who only inspect the lower bottom area of the strut (as the manufacturer considered critical) could miss corrosion at the upper end and be non‑compliant.
• Removal required: The AD explicitly states that water may enter the struts and corrosion may go undetected if struts are not removed. A mere borescope or visual check through drain holes is insufficient. This imposes significant labour cost because removing and reinstalling a wing strut on a Pawnee requires jacking the aircraft and correctly torquing the attachment bolts, plus re‑rigging if necessary.
• AMOC process is centralised: Any request for alternative compliance must be sent to CASA. There is no pre‑approved list of equivalent inspections; each case is decided individually. This introduces delay (potentially weeks or months) and uncertainty. CASA may require additional engineering justification, increasing costs.
• Serial number range includes all production: The serial numbers 25-1 to 25-8156024 cover virtually every PA-25 ever built. There is no exemption for aircraft that have been modified, stripped of agricultural equipment, or used for other purposes. Even a PA-25 used as a glider tug is subject.
• Terminating action is not mandatory: The AD requires compliance with the FAA AD, which offers terminating action via replacement. However, replacement is not required unless corrosion is found or the operator chooses it. Some operators may inadvertently believe they can continue indefinite inspections,they can, but the AD does not force replacement.
• CASR Part 39 interactions: If an aircraft arrives on the Australian register from overseas with a foreign equivalent of this AD already complied with (e.g., an EASA AD or Brazilian AD), that compliance may not be accepted unless CASA has a bilateral agreement covering that specific AD. The operator must ensure the Australian AD is explicitly satisfied, not just a foreign equivalent.
• Compliance date after issue: The AD commences on 6 January 2017, but it was signed on 12 December 2016. Operators had less than a month to arrange the first inspection if they were not already in compliance with prior amendments. Those who relied on X‑ray under earlier amendments had no grace period to switch to removal‑based inspection.

Practical steps for the operator or maintenance organisation:

1. Determine applicability: Check whether the aircraft is a Piper PA-25, PA-25-235, or PA-25-260 with a serial number within 25-1 to 25-8156024. Obtain a copy of the Australian AD (AD/PA-25/40 Amdt 9) and FAA AD 2015-08-04, plus Piper MSB 528D dated 19 October 1990 and MSB 910A dated 10 October 1989. Ensure the organisation has these documents in its maintenance data system.

2. Review prior compliance history: If the aircraft was previously in compliance with an earlier amendment (Amdt 3-8), those inspections count toward past requirements. However, the next inspection must follow the FAA AD intervals. Calculate the next due date from the last inspection recorded in the maintenance records. If the last inspection was an X‑ray only, that does not satisfy the current requirement for physical removal; a removal inspection is needed.

3. Perform the inspection per the FAA AD and MSBs: Remove both wing lift struts (left and right). Inspect the lower bottom area of each strut thoroughly for internal corrosion. Also inspect the strut upper end where the upper cuff fairing attaches (if attached by screw). The Piper MSBs will specify inspection methods (visual, dye penetrant, etc.). Record all findings, including any corrosion pitting, etching, or scaling. If any corrosion is found that exceeds the limits in the MSBs, the strut must be scrapped and replaced.

4. Consider terminating action: If the inspection reveals corrosion, the strut must be replaced. If no corrosion is found, the operator may choose either to reinstall the same struts and continue with repetitive inspections at the FAA AD intervals, or to purchase and install new sealed struts (which include the redesigned fork). Installing new struts ends the repetitive inspection requirement. However, the new strut part number must be correct for the specific PA-25 model; check with Piper or an approved distributor.

5. Document compliance: Enter the AD reference, the action taken (inspection, findings, replacement), and the date in the aircraft maintenance records. Include a copy of the FAA AD and MSBs as reference. The certifying engineer (CAR 35 or Part 66 authorised) must sign the certificate of release to service.

6. If alternative method is desired: Prepare a detailed engineering justification explaining why the alternative method (e.g., X‑ray without removal, or a different inspection interval) provides an equivalent level of safety. Submit it to CASA’s Airworthiness Directives section. Be prepared for CASA to request additional data or to reject the application. There is no fast track; allow several months for a decision. In the interim, the aircraft must comply with the standard AD.

7. Maintain ongoing surveillance: The repetitive inspection interval is set by the FAA AD (likely 5 years, but check the actual text because Amendment 5 reduced it after excessive corrosion reports). If the aircraft is operated in corrosive environments (coastal, agricultural chemicals), more frequent inspections may be prudent even if not required; however, the AD specifies minimum compliance.

8. Check for subsequent amendments: CASA may issue Amdt 10 or later. Subscribe to the CASA AD mailing list or check the CASA website regularly. If a new amendment references a later FAA AD, the compliance date for that later FAA AD will be specified. Do not rely on the FAA alone to track changes.

9. Consider fleet economics: For an operator with multiple PA-25s, it may be cheaper to replace all struts fleet‑wide rather than manage varied inspection due dates and the risk of in‑service corrosion findings. Also, new sealed struts eliminate the labour cost of repetitive removal and inspection. Run a cost‑benefit analysis factoring in the opportunity cost of grounding during inspections.

By following these steps, the operator can achieve and maintain compliance, minimise enforcement risk, and ensure the aircraft remains airworthy and insurable.