AD/TFE 731/13 - Turbine Interstage Transition Duct Re-Inspection

This airworthiness directive (AD/TFE731/13) instructs that certain turbine interstage transition ducts fitted to AlliedSignal (Garrett/AiResearch) TFE/TPE 731 series engines be re‑inspected. The instrument is published under the Civil Aviation Regulations 1998, Part 39 schedule of airworthiness directives administered by the Civil Aviation Safety Authority; the heading on the instrument reads, "COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES". The directive is dated "6/86" and carries the title "Turbine Interstage Transition Duct Re‑Inspection".

Mechanically, the directive does three things. First, it specifies the engines to which it applies by model: the body of the instrument reads, "Applicability: TPE 731-2, -3, -3A, -3AR, -3B, -3BR, -3R engines." Second, it prescribes the substantive requirement by reference, stating: "Requirement: In accordance with requirements of FAA AD 86-03-01 Amdt 39-5212." Third, it provides the compliance timing: "At next major periodic inspection or at next access of affected part, whichever occurs first after 30 June 1986." The directive also lists the reference documents that carry the technical procedures and the serial‑numbered list of affected parts: "Reference Documents: FAA AD 86-03-01 Amdt 39-5212 Garrett SB TFE 731-72-3309 R1 Garrett SB TFE 731-72-3159 R5."

The stated background explains the reason for the re‑inspection: ducts previously inspected under an earlier service bulletin (Garrett SB TFE 731-72-3159) and AD/TFE731/7 are "considered suspect following advice of an error in the inspection procedure carried out on the affected ducts during compliance with Garrett SB TFE 731-72-3159 (AD/TFE731/7)." The current AD therefore directs re‑inspection of the ducts listed by serial number in Garrett SB TFE 731-72-3309 R1. The AD does not reproduce inspection procedures or acceptance criteria itself; rather it imports and makes mandatory the content of the FAA AD and the listed Garrett service bulletins by reference.

In short, the instrument is a directive of mandatory re‑inspection targeted at specified engine models and serial‑numbered ducts, implemented by reference to an FAA airworthiness directive and two Garrett service bulletins, and to be carried out at the next scheduled major inspection or on next part access after 30 June 1986.

This directive rests on a small set of interconnected legal and technical concepts. Applicability is the threshold notion: the AD expressly identifies engine models which bring an aircraft within scope, the text reading "Applicability: TPE 731-2, -3, -3A, -3AR, -3B, -3BR, -3R engines." The AD then operates by reference to external technical instruments, rather than reproducing step‑by‑step procedures. The Requirement clause is concise: "In accordance with requirements of FAA AD 86-03-01 Amdt 39-5212." The AD also supplies explicit reference documents: "Garrett SB TFE 731-72-3309 R1" and "Garrett SB TFE 731-72-3159 R5." Those external documents carry the technical content, including the serial‑number listing and the inspection procedure.

A further core concept is temporal compliance. The AD does not require immediate off‑wing action irrespective of maintenance schedule; it sets a conditional timing rule: carry out re‑inspection "At next major periodic inspection or at next access of affected part, whichever occurs first after 30 June 1986." That timing rule creates a choice point for operators and maintainers: the mandated action is triggered by either the scheduled major periodic inspection milestone or by the earlier physical access to the affected part. The AD thereby links regulatory obligation to the routine maintenance cadence and to any unplanned access events.

A material technical concept is the serial‑numbered population. The AD identifies the precise suspect parts by referring to "The ducts, listed by serial number in Garrett SB TFE 731-72-3309 R1". The operative requirement therefore targets a defined subset of parts fitted in the broader fleet of TPE/TFE 731 engines.

Finally, the AD establishes corrective re‑inspection because of a procedural error in a prior inspection: the Background states the ducts are "considered suspect following advice of an error in the inspection procedure carried out on the affected ducts during compliance with Garrett SB TFE 731-72-3159 (AD/TFE731/7)." In effect, the current directive treats prior compliance under AD/TFE731/7 and the SB TFE 731‑72‑3159 as potentially unsafe or incomplete and mandates re‑inspection using the documents specified (including Garrett SB TFE 731‑72‑3309 R1).

Procedurally, therefore, the AD functions as a binding import of FAA AD 86‑03‑01 and specific Garrett service bulletin revisions into the Australian safety regulatory regime for the affected engines, with a defined population and a clear trigger for compliance.

The AD identifies a small, technically defined group of stakeholders by action and by implication. The primary affected parties are owners and operators of aircraft fitted with the listed TPE/TFE 731 engine models: the applicability line reads "Applicability: TPE 731‑2, ‑3, ‑3A, ‑3AR, ‑3B, ‑3BR, ‑3R engines." Any operator with one of these engine variants mounted on an aircraft therefore has an obligation to ensure the specified re‑inspection occurs in accordance with the directive.

Maintainers and approved maintenance organisations are the second set of affected actors. The AD requires a physical re‑inspection of specified turbine interstage transition ducts; the action will have to be performed by suitably qualified maintenance personnel using the procedures contained in the referenced FAA AD and Garrett service bulletins. The reference line , "Reference Documents: FAA AD 86‑03‑01 Amdt 39‑5212 Garrett SB TFE 731‑72‑3309 R1 Garrett SB TFE 731‑72‑3159 R5" , makes those documents the technical authority that the maintainer must follow.

Part and component suppliers, and records/airworthiness management staff, are also affected. The serial‑number specific list is contained in Garrett SB TFE 731‑72‑3309 R1; organisations that manage spare parts inventories, component tracking, and airworthiness records must check assemblies and serial numbers against that list. The Background explains the reason the list matters: ducts previously inspected under SB TFE 731‑72‑3159 (AD/TFE731/7) are "considered suspect" because of an error in the earlier inspection procedure, so parts thought to have been cleared may still be at risk.

The regulator, identified as the Civil Aviation Safety Authority in the instrument header, is the decision‑maker for issuing this directive and the enforcer of its requirements. The AD is published as part of CASA's schedule of airworthiness directives under the Civil Aviation Regulations 1998, Part 39, which establishes the regulatory logic that produced the instrument.

Who pays: the text itself does not itemise costs, but the structure of the requirement implies that owners/operators will cover the direct costs of inspection, any remedial work discovered by the re‑inspection, and downtime entailed by the inspection at the next major periodic inspection or next access. Maintenance organisations incur labour and tooling costs to perform the inspections. There is no text in the instrument indicating any central funding, indemnity, or subsidy; the AD places the onus of compliance upon the operators/maintainers by design.

The directive creates a clear, narrow duty: affected engines must have the turbine interstage transition ducts re‑inspected in accordance with the FAA AD and the specified service bulletins. The operative text under "Requirement" reads, "In accordance with requirements of FAA AD 86‑03‑01 Amdt 39‑5212." The AD thus makes compliance with the FAA AD mandatory for Australian operators of the listed engines. The "Reference Documents" clause identifies the manufacturer’s service bulletins that provide the serial‑number list and the inspection details: "Garrett SB TFE 731‑72‑3309 R1" and "Garrett SB TFE 731‑72‑3159 R5."

Timing is a duty parameter. The compliance clause states tasks must be performed "At next major periodic inspection or at next access of affected part, whichever occurs first after 30 June 1986." That creates a binding scheduling rule: if, after 30 June 1986, the part becomes accessible prior to the next scheduled major inspection then the inspection must be done at that access; otherwise it must wait until the next major periodic inspection. Operators therefore have a duty to track both schedules and physical access events and to act on the earlier trigger.

Identification duty. Because the AD targets specific ducts by serial number, there is a duty to verify serial numbers against Garrett SB TFE 731‑72‑3309 R1. The AD states that "The ducts, listed by serial number in Garrett SB TFE 731‑72‑3309 R1, are considered suspect ..." That language imposes a practical obligation on operators and maintainers to consult the SB and match part serial numbers.

The AD is silent on explicit rights such as appeal, alternative methods of compliance (AMOCs), or extension procedures. It does not, within its text, set out a process for seeking an alternative compliance method or for deferral. It also does not spell out record‑keeping obligations, although the requirement to inspect serial‑numbered parts necessarily creates a practical record‑keeping task. Because the AD is issued under the Part 39 schedule of airworthiness directives, any statutory rights or procedural options (for instance, seeking an alternative means of compliance or making submissions to the regulator), if they exist, would be found in the enabling regulatory framework rather than in the AD text itself; the AD does not articulate those statutory avenues.

The AD likewise does not specify remedial outcomes to be applied if defects are found on re‑inspection; instead it points operators and maintainers to the FAA AD and the Garrett SBs for the substantive inspection and corrective instructions. Practically, that means the duty is to follow the referenced documents in full, including any corrective actions they specify.

The AD is published under the heading that identifies the Civil Aviation Safety Authority and the Civil Aviation Regulations 1998, Part 39, which situates the instrument in the regulatory enforcement framework. The instrument’s header reads: "COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES." The directive itself, however, does not set out specific monetary fines, criminal offences, or a graduated penalty schedule within its text.

Because the AD is an item in CASA’s schedule of airworthiness directives under Part 39, its requirements become enforceable as airworthiness obligations under the Civil Aviation Regulations. The AD requires actions "In accordance with requirements of FAA AD 86‑03‑01 Amdt 39‑5212" and a compliance timing "At next major periodic inspection or at next access of affected part, whichever occurs first after 30 June 1986." Non‑compliance with an AD published in the schedule will thus expose an operator or maintainer to enforcement action available to the regulator under the enabling legislation and regulations. The AD itself, however, contains no text giving a bespoke enforcement mechanism or penalty quantum.

The practical enforcement risk therefore flows from the AD’s incorporation into the regulatory regime: the regulator may take regulatory measures available under Part 39 and the Civil Aviation Regulations for failure to maintain an aircraft or component in compliance with an airworthiness directive. The instrument does not describe procedural steps for enforcement, nor does it provide specific sanction amounts, administrative procedures, or timelines for regulator action. It is therefore necessary for practitioners to consult the Civil Aviation Regulations 1998, Part 39, and CASA guidance for the specific enforcement mechanisms and sanctions that may be applied to non‑compliance.

In short, the AD creates a mandatory duty to inspect but leaves the precise penalty mechanisms to the broader statutory enforcement framework. The directive itself is silent on fines, criminal offences, or remedial enforcement steps.

The AD explicitly imports technical content from external instruments rather than reproducing procedural detail. The Requirement clause binds Australian operators to comply "In accordance with requirements of FAA AD 86‑03‑01 Amdt 39‑5212." The AD’s Reference Documents list then identifies the manufacturer’s service bulletins that carry the serial‑number list and the inspection instruction: "Garrett SB TFE 731‑72‑3309 R1" and "Garrett SB TFE 731‑72‑3159 R5." By doing so, the AD creates a cross‑jurisdictional linkage: a United States FAA airworthiness directive and American manufacturer service bulletins become the operative technical standard for Australian aircraft fitted with the listed engines.

The AD also refers to a prior Australian directive, AD/TFE731/7, implicitly connecting the current instrument to the regulatory history for these parts. The Background states the ducts "were previously inspected by compliance with Garrett SB TFE731‑72‑3159 (AD/TFE731/7)" and that an error in that earlier inspection procedure prompted the current re‑inspection requirement. That establishes an internal sequencing: AD/TFE731/7 led to earlier inspections under a particular SB; discovery of an error in that SB’s inspection procedure resulted in AD/TFE731/13 importing new FAA and Garrett SB material to mandate re‑inspection.

Legally, the AD sits within the Civil Aviation Regulations 1998, Part 39 schedule of airworthiness directives. The instrument does not purport to amend the regulations themselves; it operates as a specific directive made under the regulatory scheme. The AD therefore interacts with the wider suite of aviation safety obligations: maintaining airworthiness, carrying out mandatory inspections, and following manufacturer’s instructions as incorporated by reference. Those broader obligations, and any procedural rights (for example, seeking an alternative compliance method) would be governed by the enabling statutory framework rather than by the AD’s text.

In practical terms, operators must consult three technical documents to comply: the FAA AD 86‑03‑01 Amdt 39‑5212 for the formal airworthiness directive content, and two Garrett service bulletins , TFE 731‑72‑3309 R1 (serial‑number list) and TFE 731‑72‑3159 R5 (the earlier SB whose inspection procedure is implicated). The AD therefore functions as a legal bridge that makes those foreign and manufacturer documents obligatory for Australian operators of the listed engines. Any conflict, gap, or interpretative uncertainty between the referenced documents and Australian regulatory requirements would need to be resolved by reference to the enabling regulations and regulator guidance; the AD itself does not attempt that resolution within its text.

The instrument itself provides a minimal explicit amendment trail in‑text. It carries the identifier "AD/TFE731/13 Turbine Interstage Transition Duct Re‑Inspection 6/86", which records its own issuance in June 1986. The Background references an earlier Australian directive, "AD/TFE731/7", and states that the ducts "were previously inspected by compliance with Garrett SB TFE731‑72‑3159 (AD/TFE731/7)." The current AD therefore operates as a follow‑up to that earlier directive because of an identified error in the inspection procedure used under SB TFE 731‑72‑3159 during compliance with AD/TFE731/7.

The Reference Documents list includes a Garrett service bulletin at revision R1, "Garrett SB TFE 731‑72‑3309 R1", and a revision R5 of the earlier bulletin, "Garrett SB TFE 731‑72‑3159 R5." Those revision identifiers are the only in‑instrument signposts to document versioning. The AD makes clear that the serial‑number list of suspect ducts is contained in SB TFE 731‑72‑3309 R1.

No further amendments, repeal schedule, or subsequent revision history is contained in the AD text provided. The instrument does not contain an express "supersedes" clause, nor does it reproduce text from any subsequent amendment; rather, it situates itself as an additional directive prompted by the discovery of an error in the earlier inspection procedure. The AD therefore represents, in the provided text, a discrete corrective measure (issuance 6/86) referencing the earlier AD/TFE731/7 and specifying the up‑to‑date SB revisions to be applied.

Users requiring a complete amendment history should consult CASA’s formal AD database and the full archival record of AD/TFE731 entries, and the revision history of the referenced Garrett service bulletins, because the AD text provided contains only the single issuance date (6/86), the prior AD identifier (AD/TFE731/7) and the cited revisions R1 and R5 of the SBs.

The instrument contains no litigation history, court citations, or references to legal challenges. The text supplied lists the technical background, applicability, requirement and references, but it does not mention any judicial or administrative proceedings, contested enforcement actions, or precedent‑setting disputes. The Background explains the safety rationale , an error in the prior inspection procedure , and directs re‑inspection; it does not narrate any litigation associated with that discovery.

From the text alone one can only record that no cases or legal disputes are mentioned. The AD does not reference any determinations, appeals or legal proceedings either challenging its predecessors or the referenced FAA AD and service bulletins. The directive therefore stands, within the provided material, as an administrative exercise of the regulator’s airworthiness mandate unaccompanied by any recorded litigation in the instrument.

Practitioners seeking to know whether any operator contested AD/TFE731/7 or AD/TFE731/13, or whether any enforcement action followed, will need to consult external records: regulatory enforcement logs, CASA administrative files, and court or tribunal databases. The AD itself does not provide that material. The absence of litigation references in the AD does not preclude the existence of disputes external to the instrument, but the text supplied contains no such history.

For purposes of compliance risk assessment, the lack of litigation history in the AD means the directive’s legal status is presented as administrative and technical rather than judicial; the AD makes no claim of being the product of litigation or settlement. Any legal challenge to the AD, its scope, or its implementation would have to be researched outside the AD text and within the wider legal records.

Several specific practical and interpretative pitfalls arise directly from the AD’s wording and structure.

1. Model designation inconsistency: The AD title, and the grouping of material, refers to AlliedSignal (Garrett/AiResearch) Turbine Engines , TFE731 Series, but the Applicability line reads "Applicability: TPE 731‑2, ‑3, ‑3A, ‑3AR, ‑3B, ‑3BR, ‑3R engines." That mismatch in engine code (TPE vs TFE) is present in the instrument text. Practitioners should not assume typographical neutrality; accurate identification of installed engine model number on the airframe is essential before concluding applicability.

2. Serial‑number dependence: The AD does not apply fleet‑wide to all TPE/TFE 731 engines; it targets ducts "listed by serial number in Garrett SB TFE 731‑72‑3309 R1." Compliance therefore requires checking the SB’s serial‑number list against the actual part installed. Failure to check serial numbers or relying on generic model matching could lead to unnecessary work or missed inspections.

3. Reliance on external documents: The AD’s substantive technical requirements are imported by reference. The AD states "In accordance with requirements of FAA AD 86‑03‑01 Amdt 39‑5212" and lists Garrett SBs. The AD does not reproduce the inspection procedure, criteria or corrective actions. Practitioners must obtain and follow the correct revision of the FAA AD and the Garrett SBs (the AD specifies FAA AD 86‑03‑01 Amdt 39‑5212 and Garrett SB TFE 731‑72‑3309 R1, Garrett SB TFE 731‑72‑3159 R5). Using the wrong revision, or failing to apply the exact referenced procedure, is a compliance risk.

4. Timing nuance: The compliance timing is defined as "At next major periodic inspection or at next access of affected part, whichever occurs first after 30 June 1986." Interpreting "access" requires care: any unplanned access (for example, removal for other maintenance) after 30 June 1986 triggers the requirement if the duct is affected. Operators who rely purely on scheduled major inspections may miss mandatory re‑inspections triggered by an earlier access.

5. Prior compliance may be insufficient: The Background explicitly notes that ducts previously inspected under Garrett SB TFE 731‑72‑3159 and AD/TFE731/7 "are considered suspect following advice of an error in the inspection procedure." That means documented past compliance with AD/TFE731/7 or the earlier SB is not conclusive proof that the part is cleared; re‑inspection under the current AD remains required where the part serial number is listed.

The AD sets out a tightly defined compliance pathway by reference. Follow these steps, each of which is directly compelled or implied by the instrument text.

1. Confirm applicability: Verify whether the engine installed is one of the listed models. The AD states "Applicability: TPE 731‑2, ‑3, ‑3A, ‑3AR, ‑3B, ‑3BR, ‑3R engines." Check the engine type designation on the airframe and engine data plate. Note the instrument’s use of "TPE" in the Applicability line and reconcile that with airframe/engine documentation to ensure correct model identification (see Gotchas).

2. Check serial numbers: Obtain Garrett SB TFE 731‑72‑3309 R1 and consult the serial‑number list. The AD requires re‑inspection of "The ducts, listed by serial number in Garrett SB TFE 731‑72‑3309 R1." Compare installed turbine interstage transition duct serial numbers to the SB list to determine whether the part is within the suspect population.

3. Obtain the referenced documents: The Requirement is to act "In accordance with requirements of FAA AD 86‑03‑01 Amdt 39‑5212." The AD lists the specific service bulletins required: Garrett SB TFE 731‑72‑3309 R1 and Garrett SB TFE 731‑72‑3159 R5. Secure copies of FAA AD 86‑03‑01 Amdt 39‑5212 and the two Garrett SBs at the specified revisions before commencing work. Do not rely on later or earlier revisions unless an authoritative bridging instrument permits them; the AD cites specific revision identifiers.

4. Schedule the inspection per the timing rule: The AD mandates re‑inspection "At next major periodic inspection or at next access of affected part, whichever occurs first after 30 June 1986." If the part is due to be accessed sooner than the next major periodic inspection (for example, removed for another maintenance action), perform the re‑inspection at that earlier access. If not, defer the inspection until the next major periodic inspection after 30 June 1986. Document the scheduling decision and the trigger event (access or periodic inspection).

5. Perform the re‑inspection to the referenced procedure: Conduct the inspection in full conformity with the procedures and acceptance criteria set out in FAA AD 86‑03‑01 Amdt 39‑5212 and the Garrett SBs. The AD does not reproduce the inspection procedures or corrective action steps; those are found in the referenced documents. Ensure qualified personnel and appropriate tooling are used.

6. Apply corrective actions per the FAA AD and SBs: If the inspection reveals defects or other conditions requiring action, follow the corrective procedures and disposition criteria stated in the referenced FAA AD and service bulletins. The AD itself is silent on corrective measures, so those external documents govern remediation.