AD/TPE 331/64 - First Stage Turbine Disc

This AD uses a targeted, time-limited mandatory removal and prohibition mechanism to address a discrete safety defect in a component. The main technical and regulatory concepts present in the text are:

• Narrow scope by part and serial number: The AD identifies specific part numbers (P/N 3101520-1 and P/N 3107079-1) and enumerates specific serial numbers (2-03501-2299; 2-03501-2300; 2-03501-2301; 2-03501-2302; 2-03501-2304). The applicability language restricts the obligation to engines with those parts and serials installed (Applicability, Requirement).

• Two-part compliance prescription: The AD contains two distinct mandates: an action to be taken within a short, specified exposure window (remove from service within 25 flight hours or 25 cycles-in-service), and a continuing prohibition on installing the identified parts after the effective date. These are stated as separate numbered requirements (Requirement; Compliance).

• Time-bound operational exposure: The AD allows a short operational exposure: removal must be completed within either 25 flight hours or 25 cycles-in-service after the effective date, whichever occurs first. That creates an operational trade-off for users between using remaining safe hours/cycles and immediate grounding for removal (Compliance).

• Cross-reference to foreign regulator material: The AD explicitly cites the FAA Airworthiness Directive (FAA AD 2009-17-05). The Note indicates the FAA action is relevant material, but the CASA AD sets its own mandatory remit and timing (Note 2).

• Safety rationale and risk type: The background states the AD follows a report of an uncontained failure caused by a metallurgical defect in a first stage turbine disk; the AD's intent is to prevent uncontained failure and consequent aeroplane damage (Background).

• Broad aircraft list as installation examples: Note 1 lists a number of aeroplane types on which these engines are installed, but explicitly uses the phrase "installed on, but not limited to", indicating the list is illustrative rather than exhaustive (Applicability, Note 1). The list includes British Aerospace Jetstream 3201 series; Cessna 441 Conquest; CASA C-212; Dornier 228; Beechcraft B100/C90/E90; M7 Aerospace SA226/SA227; Mitsubishi MU-2B; PZL M18; Twin Commander 680 and 690.

• Regulatory authorisation and effective date: The AD is issued by CASA (signed by a CASA delegate) and states an effective date (1 September 2009), establishing the date from which the compliance windows and prohibitions operate (signature and Compliance block).

Mechanically, the AD removes particular components from circulation and imposes a short-window compulsory corrective action followed by a permanent ban on reinstallation of those exact serialised parts. The AD does not specify an alternative fielded part, repair method, replacement schedule, detailed inspection procedure, record-keeping format, or penalties. It also provides no technical background beyond the metallurgical-defect/uncontained-failure statement.

The AD directly affects operators and maintainers of Honeywell TPE331-10 and TPE331-11 series turboprop engines that have one of the listed first stage turbine discs installed. The text identifies the affected components precisely by part number and serial number; anyone responsible for continuing airworthiness and maintenance of engines fitted with P/N 3101520-1 or 3107079-1 and any of the listed serial numbers is within the scope (Applicability; Requirement).

Affected parties will include:

• Aircraft owners and operators that have a TPE331-10 or TPE331-11 engine with one of the specified serialised discs installed. The AD lists multiple aeroplane types on which such engines are installed, but states the list is not exhaustive (Applicability, Note 1). Therefore operators of other aircraft types with those engines fitted are also potentially affected.
• Maintenance organisations and licensed engineers responsible for engine maintenance, inspections, and component replacement. They must carry out the removal within the prescribed timeframe and must ensure the identified parts are not reinstalled (Requirement; Compliance).
• Parts suppliers and overhaul organisations that hold or trade in stock of the listed discs. The installation prohibition after the effective date means those entities must identify and segregate the specific serialised parts to avoid inadvertent reuse (Requirement 2; Compliance 2).
• Regulatory compliance and airworthiness personnel within operators’ organisations who must record and manage the AD action in maintenance control systems. The AD prescribes a mandatory removal and prohibition; maintenance control must reflect that.

Who pays: The AD imposes the obligation to remove the parts and not reinstall them on whoever holds the obligation to maintain the aircraft/engine in an airworthy condition. The text does not allocate financial responsibility, compensation, or supply of replacement parts; it prescribes the safety action only. Therefore the immediate economic incidence falls on the party that must perform the removal and ensure continued compliance, commonly the operator or the accountable manager for the aircraft’s continuing airworthiness (Requirement; Compliance). The AD does not provide funding, reimbursement, or replacement parts.

Who decides operationally: The AD creates mandatory actions; the decision to schedule the removal, choose the replacement part, and arrange maintenance is operationally made by the operator or their authorised maintenance organisation within the 25 flight hours or 25 cycles-in-service window (Compliance). The AD does not provide discretion to extend the time window or permit alternative mitigations; it prescribes removal within the stated limits and a prohibition on installation after the effective date.

Geographical and regulatory reach: The AD is a CASA instrument and therefore applies within the Australian regulatory regime. It also references the FAA AD as related material (Note 2), which may be relevant to operators that must comply with both CASA and FAA directives, but the CASA AD itself prescribes the Australian mandatory action (Applicability; Note 2).

The AD sets out two mandatory duties for affected parties and implies certain corollary rights in the operational sense. These duties are explicit in the "Requirement" and "Compliance" blocks; the AD does not grant procedural or appeal rights, nor does it set out administrative processes.

Explicit duties imposed by the AD:

• Duty to remove: Operators must remove from service the listed first stage turbine disks, P/N 3101520-1 and P/N 3107079-1, bearing the serial numbers 2-03501-2299, 2-03501-2300, 2-03501-2301, 2-03501-2302, and 2-03501-2304. The AD states this as Requirement 1 (Requirement, item 1).
• Duty to avoid installation: After the effective date of the AD, operators, maintainers, and parts handlers must not install any of those listed first stage turbine discs into any engine. The AD states this as Requirement 2 (Requirement, item 2).
• Duty to meet the timing: The removal action must be performed within 25 flight hours or 25 cycles-in-service after the effective date of this AD, whichever occurs first. The ban on installation is effective immediately after the AD’s effective date (Compliance).

Rights, insofar as they can be inferred from the AD’s structure:

• Right to operate within the short exposure window: The AD allows the engine to be operated for up to 25 flight hours or 25 cycles-in-service after the effective date before removal is mandated; this prescribes a limited operational continuation right subject to the prescribed ceiling (Compliance).
• Right to rely on this AD as the Australian mandatory requirement for these serialised parts: The AD itself constitutes the Australian authority’s instruction; compliance with it discharges the specific Australian regulatory duty it creates, although the AD does not speak to obligations under other jurisdictions or to civil liability (Requirement; Compliance; Note 2).

What the AD does not set out:

• It does not prescribe replacement part numbers, alternative mitigations, inspections, or repair instructions. The AD simply requires removal and forbids reinstallation.
• It does not establish administrative procedures for reporting compliance to CASA, nor does it set out an approval pathway for relief or deviation. The AD text contains no provision for exemptions, extensions, or alternative means of compliance.
• It does not specify penalties, enforcement mechanisms, or sanctions within the text (see Penalties and enforcement section below).

Operational implications of the duties:

• Maintenance scheduling: Operators must schedule removal within the short timeframe; the AD fixes that timeframe, removing regulatory discretion to defer beyond the stated hours or cycles (Compliance).
• Inventory control: Parts handlers, overhaulers, and stores must identify and segregate the listed serial numbers to ensure the prohibition on reinstallation is enforced in practice (Requirement 2).
• Airworthiness records: While the AD does not specify record-keeping detail, compliance will typically generate maintenance entries reflecting part removal and disposition; the AD itself does not specify format or submission procedures.

The AD text does not set out specific penalties, fines, or enforcement procedures. The instrument is presented as an authoritative airworthiness directive (issued by the Delegate of CASA) with mandatory requirements and a defined effective date; however, it contains no express penal provisions or procedural enforcement steps within the pages of the AD itself.

What the AD explicitly provides:

• Effective date and mandatory directives: The AD states it becomes effective on 1 September 2009 and includes the mandatory removal and prohibition requirements that must be complied with from that date (Compliance; Requirement).
• Issuing authority: The AD is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, dated 18 August 2009. The signature identifies the issuing authority but the AD text contains no language describing enforcement actions taken by that authority in the event of non-compliance.

What the AD does not provide:

• No provisions for administrative penalties, criminal sanctions, infringement notices, or civil remedies are listed in the AD itself. The text does not specify how CASA will verify compliance, how operators should report compliance, or what consequences follow non-compliance.
• The AD does not include a compliance reporting form, a requirement to notify CASA upon completion, or a route to seek an alternative means of compliance or time extension within the AD text.

Implications, limited to what the AD shows:

• The AD’s mandatory instructions create a compliance obligation; the AD itself does not list enforcement mechanisms or penalties. The presence of an AD typically means that failure to comply will leave the operator in breach of the applicable airworthiness directive regime, but the AD text does not quantify or describe enforcement responses. Users should note that the AD’s silence on penalties does not, on its face, remove the practical expectation that regulators may take action under other statutory powers to enforce airworthiness obligations. The AD itself, however, contains only the removal and non-installation prescriptions and the effective date (Requirement; Compliance; signature).

Reference to other regulator material:

• The AD references the FAA AD 2009-17-05 as related material (Note 2). That FAA AD may contain its own compliance, reporting, or enforcement material relevant to operators subject to FAA jurisdiction, but the CASA AD does not reproduce such enforcement mechanics (Note 2).

Because the AD text is silent about enforcement specifics, operators and maintainers seeking clarity on enforcement expectations, compliance reporting, or remedial options should consult CASA directly or consult the relevant statutory framework outside the AD text for enforcement procedures. The AD itself remains the operative safety instruction requiring removal and prohibiting installation from the stated dates.

The AD text makes a single explicit cross-reference to a foreign regulator’s directive and otherwise stands as an independent CASA instrument. The AD does not purport to modify or repeal other laws or regulations; it establishes a specific mandatory airworthiness requirement in the Australian regulatory context. The AD’s explicit interactions in the text are limited to the following:

• Cross-reference to FAA AD: Note 2 states that "FAA AD 2009-17-05 Amdt 39-15996 dated 11 August 2009 refers." The CASA AD therefore identifies the FAA action as related material. The AD does not say the FAA AD is controlling, nor does it import the FAA AD's requirements wholesale; it simply refers to it as related material (Note 2). Practically, operators subject to both CASA and FAA requirements should be aware of both directives, but the CASA AD itself is the Australian mandatory action for the identified parts and serial numbers.

• Relationship to airworthiness standards: As an Airworthiness Directive issued by CASA, the instrument operates within the Australian civil aviation regulatory framework, but the AD text does not reproduce or amend other statutory instruments, nor does it provide procedure for reconciling conflicts. The AD prescribes an action that must be performed to maintain compliance with applicable Australian airworthiness obligations; it does not specify how compliance with the AD interfaces with, for example, continuing airworthiness obligations, maintenance release processes, or export/import control on parts.

• Applicability across aircraft types: The AD lists a number of aeroplane types on which the affected engines are installed and states that the list is "not limited to" those types (Applicability, Note 1). This phrasing signals that the AD applies to the specified components irrespective of aircraft model, and so may intersect with operators’ obligations under aircraft-specific regulations or type certificates. The AD does not provide instructions on how to resolve any such interactions; it simply identifies engines by model series and parts by part and serial number.

• No stated effect on third-party liability or commercial contracts: The AD does not speak to contractual relations, warranty claims, or third-party liability. It does not confer rights to compensation or allocate responsibility for replacement parts or labour. Any interactions between the AD and commercial arrangements are not addressed in the text.

• No statement on international acceptance or reciprocal compliance: The AD references the FAA AD but does not explicitly state whether compliance with the FAA AD satisfies the CASA requirement or vice versa. The CASA AD stands as its own mandatory instrument within Australia.

In sum, the CASA AD exists alongside other regulatory instruments. The only explicit interaction recorded in the AD text is the reference to the FAA AD as related material. Any further legal interactions, such as enforcement mechanisms, reporting obligations, or interface with contract or tort law, are not articulated in the AD itself and would require reference to the broader statutory and regulatory framework beyond the content of this AD.

The document provided contains the AD as issued and dated, and it does not include a sequence of prior amendments or subsequent amendments within its text. The elements relevant to amendment history contained in the AD are:

• Title and designation: AD/TPE 331/64, with the notation "11/2009 DM" and the repeated header lines showing "AD/TPE 331/64" and "11/2009 DM". The notation suggests the AD is part of CASA’s AD series and the date reference is November 2009 or the 11/2009 AD batch identifier; the AD itself contains the explicit effective date for the action (title/header).

• Issuance and effective date: The AD is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, and dated 18 August 2009. The AD then states explicitly that "This Airworthiness Directive becomes effective on 1 September 2009" (signature block; Compliance block). The AD text does not indicate it replaces an earlier CASA AD or that it is an amendment to an earlier instrument.

• Reference to FAA AD: The AD refers to FAA AD 2009-17-05 Amdt 39-15996 dated 11 August 2009 (Note 2). This indicates that a related FAA action was issued on 11 August 2009, and the CASA AD was issued shortly thereafter (18 August 2009) with effective date 1 September 2009. The AD does not state that it is an adaptation or adoption of the FAA AD; it instead references the FAA AD as material and then prescribes its own specific mandatory actions and timings.

• Absence of internal amendment trail: The AD file text contains no section labelled "Amendment history", no version numbers, and no entries describing prior revisions. There are no subsequent amendment notes printed on the AD content provided.

What can be concluded from the AD text alone:

• The AD as presented appears to be an original CASA directive addressing a discrete issue with specific serialised parts and provides effective dates and issuer details. The text does not purport to be an amendment to an earlier CASA AD.
• No amendment entries or later revisions are included in the provided text. The AD therefore should be treated, on the face of the document, as a stand-alone directive issued in August 2009 with effect 1 September 2009.

For any practitioner seeking a formal amendment history, or confirmation whether later CASA actions amended, superseded, or revoked this AD, the AD text itself does not contain that historic sequence. Such a practitioner would need to consult CASA's AD database, official Federal Register equivalents, or subsequent regulatory publications outside the four corners of this AD to establish any later amendments or revocations. The AD, as supplied, contains no amendment record.

The AD text contains no references to litigation, court proceedings, or administrative appeals either past or pending. There are no case citations, no mention of judicial review, and no reference to decisions or disputes relating to this AD within the document. The signature block names James Coyne as Delegate of CASA and provides the date of signing, but there is no mention of any legal proceedings arising from the directive.

What the absence of litigation references in the text implies, strictly on the basis of the AD document:

• The AD itself does not record any litigation history. It is a regulatory instruction and not a judicial or quasi-judicial document that would typically recount litigation history.
• The AD does reference a safety event as its factual premise,a report of an uncontained failure due to a metallurgical defect,however, the AD does not mention any related legal claims, product liability actions, or enforcement proceedings stemming from that incident (Background).

Practical note for practitioners:

• Because the AD contains no litigation narrative or case citations, anyone researching legal challenges, enforcement actions, or dispute resolution concerning this AD will need to look outside this document. Sources might include court databases, regulatory enforcement bulletins, CASA public records, or industry press. Nothing in the AD text itself identifies any judicial or administrative decisions that interprets or contests this directive.

In short, the AD supplies no litigation history; it is silent on any legal proceedings connected to the uncontained failure or to the AD’s issuance. Any litigation history must be sourced from other materials beyond the AD text provided.

The AD is short and precise, but its brevity creates a number of practical pitfalls for operators, maintainers, and parts managers. The following issues derive strictly from the content and phrasing of the AD as provided.

1. Very narrow but serialised scope

• The AD applies only to first stage turbine discs with P/N 3101520-1 or P/N 3107079-1 and only to the serial numbers listed: 2-03501-2299, 2-03501-2300, 2-03501-2301, 2-03501-2302, and 2-03501-2304 (Applicability; Requirement). Operators who misread the AD as applying to a broader range of serial numbers, or to all P/N 3101520-1 or 3107079-1 discs, may either overreact or undercomply. Precise serial-number checks are required.

2. "Installed on, but not limited to" phrasing

• Note 1 lists multiple aeroplane models on which these engines are installed but explicitly says the list is "installed on, but not limited to" those aeroplanes (Applicability, Note 1). That means an operator cannot assume that because their aircraft type is not listed they are out of scope; the AD applies to the specified engine parts wherever they are installed. Operators must check engine serials across their fleet rather than relying on the illustrative aircraft list.

3. Short compliance window with dual metric

• The removal must occur within "25 flight hours or 25 cycles-in-service after the effective date of this AD, whichever occurs first" (Compliance). This creates two competing clocks. For short-haul or high-cycle aircraft, cycles will often be the limiting factor. For longer-range operations, flight hours may be limiting. Operators must calculate both metrics accurately to avoid missing the sooner trigger.

4. Prohibition on reinstallation is immediate post-effective date

• Requirement 2 prohibits installation "after the effective date of this AD" (Requirement 2; Compliance). That prohibition does not wait for removal actions; it is immediate. Parts managers must ensure that none of the listed serialised discs are fitted to any engine after 1 September 2009.

5. No guidance on replacement or repair

• The AD requires removal and prohibition but provides no instruction on what parts may lawfully be installed instead, whether a serviceable substitute is available from the OEM, or whether repair/rework is acceptable. Operators must source compliant replacement components and ensure they themselves meet applicable airworthiness criteria. The AD does not provide an approved pathway.

6. No reporting, disposition, or traceability instructions in the AD

• The AD does not specify how removed discs should be reported to CASA, whether they must be quarantined, returned to the manufacturer, or scrapped, nor does it provide a compliance reporting form. Operators must rely on their maintenance control processes and may need to contact CASA or the OEM for direction; the AD itself is silent.

7. Potential stock and logistic complications

• Parts inventories, overhaul stock, and brokerage holdings may contain the affected discs. Because the AD lists specific serial numbers, stock-holders must inventory and segregate those serials immediately. The AD does not provide instruction on lead times for replacements or interim mitigations.

8. Limited factual background for decision-making

• The AD provides only a single-sentence background: "This AD results from a report of an uncontained failure of a first stage turbine disk that had a metallurgical defect" and says the AD is intended to prevent uncontained failure and damage to the aeroplane (Background). There is no technical description of the defect, no failure rate data, and no inspection-based alternative. That limited information constrains operators’ risk assessments if they are deciding whether to remove part sooner rather than later.

9. Cross-reference to FAA AD without clarity on equivalence

• The AD refers to FAA AD 2009-17-05 as related material (Note 2). The CASA AD does not state whether the FAA AD contains additional measures or whether compliance with the FAA AD satisfies CASA. Operators that are under both CASA and FAA jurisdiction must check both instruments.

10. Administrative ambiguity around enforcement and record-keeping

• The AD does not specify enforcement mechanisms or an obligation to notify CASA upon compliance; this omission can leave operators uncertain whether to file a compliance report or simply record the action in maintenance logs. The AD creates the mandatory duty but does not provide administrative steps for its closure.

Each of these points follows strictly from the language and absences in the AD text. Operators should ensure precise serial-number checks, timely scheduling with an eye to both hours and cycles, segregation of suspect parts in stores, and communication with maintenance control and possibly CASA or the OEM for disposition and replacement strategy.

The AD prescribes two mandatory steps; compliance consists of carrying out those steps within the timeframes and in the manner the AD specifies. The following practical compliance checklist follows directly from the AD text and highlights operational actions that implement the AD while staying within the documentary confines of the directive.

1. Identify affected assets

• Check maintenance logs, parts records, engine records, and physical parts to determine whether any engine in your fleet is a TPE331-10 or TPE331-11 series and whether it currently has installed a first stage turbine disc with P/N 3101520-1 or P/N 3107079-1 bearing any of these serial numbers:
  • 2-03501-2299
  • 2-03501-2300
  • 2-03501-2301
  • 2-03501-2302
  • 2-03501-2304 (Refer to Applicability and Requirement 1.)

2. Schedule removal within the mandated window

• The AD requires removal "within 25 flight hours or 25 cycles-in-service after the effective date of this AD, whichever occurs first" (Compliance). The AD’s effective date is 1 September 2009. Calculate both the remaining permissible flight hours and cycles between 1 September 2009 and the point at which 25 flight hours or 25 cycles-in-service will have been reached.
• Arrange maintenance slots and logistics so that the removal is completed before the earlier of those two limits. For aircraft with frequent short flights, treat cycles as the likely limit.

3. Execute removal and ensure proper part disposition

• Physically remove the identified first stage turbine disc from service. The AD requires removal to have been completed within the stated timeframe (Requirement 1; Compliance).
• The AD does not specify what to do with removed parts; however, to ensure compliance with the AD’s prohibition on reinstallation, segregate and quarantine the removed serialised discs so they are not inadvertently refitted (Requirement 2).

4. Do not reinstall the listed discs

• The AD expressly directs: "Do not install first stage turbine disks, P/N 3101520-1 and P/N 3107079-1, serial numbers [listed], into any engine" after the effective date (Requirement 2; Compliance). Ensure parts management, stores records, and maintenance instructions flag these serial numbers as permanently unserviceable for installation.

5. Update maintenance records and continuing airworthiness documentation

• While the AD does not specify a reporting format, record the removal and disposition in the aircraft and engine maintenance records and in the continuing airworthiness system consistent with standard maintenance procedures. Record the part numbers and serial numbers removed, the date, and the maintenance release details.
• Retain records that demonstrate the AD action was carried out within the specified compliance window.

6. Coordinate with maintenance providers and parts suppliers

• Inform third-party maintenance organisations, overhaul centres, and parts suppliers of the serial numbers and the prohibition on installation. Ensure supply-chain controls prevent the listed discs from being shipped for installation or inadvertently sold as serviceable stock.

7. Consult the referenced FAA AD and OEM guidance if necessary

• Note 2 in the AD refers to FAA AD 2009-17-05 dated 11 August 2009. Consult that FAA AD and any OEM service bulletins or manufacturer guidance for technical context, permitted disposition actions, or recommended replacement parts. The CASA AD does not incorporate the FAA AD text, but the FAA AD may contain additional technical details useful for operational planning.

8. Seek clarification where the AD is silent

• The AD does not specify reporting procedures to CASA, nor does it outline acceptable dispositions of the removed parts. If operators require guidance on whether removed discs must be returned to the OEM, scrapped, or reported to CASA, seek direction from CASA or from the OEM, because the AD itself does not provide such instructions.

9. Confirm no inadvertent installations

• Implement or update inventory controls and parts tagging procedures to prevent accidental reinstallation. Train personnel to recognise the listed serial numbers and the prohibition on installation.

10. Legal and contractual considerations

• The AD does not allocate financial responsibility for parts replacement or labour. Operators should review warranties, service agreements with OEMs, and insurance arrangements to establish whether replacement costs or part disposition may be covered elsewhere, but the AD itself imposes no such financial mechanism.

Summary of the required minimum actions based solely on the AD text:

• Verify whether any engine in your fleet has the affected part numbers and serial numbers installed (Applicability).
• Remove any such discs from service within 25 flight hours or 25 cycles-in-service after 1 September 2009, whichever occurs first (Requirement 1; Compliance).
• Do not install any of those listed discs into any engine after 1 September 2009 (Requirement 2; Compliance).
• Maintain maintenance records showing compliance.

The AD prescribes no alternative means of compliance, no extensions, and no reporting format. Any additional compliance steps, such as notifying CASA, contacting the OEM, or specific part replacement choices, fall outside the AD language and should be pursued through usual regulatory or manufacturer channels.