AD/AB139/5 - Exhaust Tailpipe Assembly

The directive contains a compact set of engineering and compliance concepts constrained to a particular component and configuration. The principal technical concept is crack initiation and propagation in the tailpipe assembly of the AB139/AW139 series, and the safety response is a maintenance regime tailored by crack location and severity, and by whether defects occur inside or outside the cowling.

Key operational concepts appearing in the text are:

• Applicability by serial number exclusion and by specific part numbers. The AD applies to all serial numbers except 31002, 31003, 31004 and 31007, and only where tailpipe assemblies have P/N 3G7800L00131 (LH) or 3G7800L00231 (RH). This transforms maintenance obligations into a function of aircraft identity and installed hardware.

• Hierarchy of technical references. The inspection baseline is Agusta BT 139-069 Revision A dated 8 November 2006 or later approved revision. Repair and replacement are to be performed in accordance with the Agusta AW139 Aircraft Maintenance Publication. The AD thereby delegates the detailed inspection technique and allowable limits to Agusta’s documents, which are incorporated by reference.

• Distinction by defect location. The AD treats heat damage or cracks inside the cowling (Requirement 3) as immediately warranting replacement, whereas cracks outside the cowling are subject to graded responses depending on whether they are abrupt or exceed allowable limits (Requirement 4), or fall within allowable limits and can be managed by stop-drilling and monitoring or bulletin-specified repair (Requirement 5).

• Repetitive inspection cadence. The directive imposes a mandatory repeat interval not exceeding 25 flight hours for the inspections. The directive explicitly states that repair or replacement does not terminate this repetitive inspection obligation.

• Timing of initial compliance. Inspections under Requirements 1 and 2 are required within 30 days of the effective date, unless already done. Any required replacement or repair identified by those inspections must be completed before further flight.

The AD is framed as a preventive, maintenance-based intervention to prevent crack growth “into failure of the exhaust tailpipe assembly,” as stated in the Background. The instrument uses the manufacturer’s technical materials to operationalise the inspections and remedial work, therefore making the maintenance regime dependent on Agusta’s BT and AMP documents and any later approved revisions.

The directive affects three distinct groups as defined by the text: aircraft owners and operators who have AB139 or AW139 helicopters; maintenance organisations and personnel performing inspections, repairs and replacements on the relevant tailpipe assemblies; and the supply chain for spare parts matching the specified part numbers.

Owners and operators: Any owner or operator of an AB139 or AW139 helicopter with the listed part numbers 3G7800L00131 (LH) or 3G7800L00231 (RH) must comply with the inspection and remedial schedule. The Applicability clause limits coverage by excluding serial numbers 31002, 31003, 31004 and 31007. The compliance timings impose immediate obligations: inspections within 30 days after the effective date unless already done, and any detected defects that trigger Requirements 3 through 5 must be addressed before the helicopter’s next flight.

Maintenance organisations and technicians: The directive requires inspections “in accordance with the instructions of Agusta BT 139-069 Revision A dated 8 November 2006 or later approved revision,” and repairs or replacements “in accordance with the Agusta AW139 Aircraft Maintenance Publication (AMP).” This places responsibility on licensed maintenance personnel to obtain and follow these Agusta documents and to interpret allowable limits indicated in the bulletin. The AD also permits a specific mitigative action, drilling a stop hole and performing follow-up inspections, subject to the bulletin limits, which requires maintenance judgement and documentation.

Parts suppliers and logistics: Requirement to replace with “an airworthy part in accordance with the Agusta AW139 AMP” means operators will need access to compliant replacement tailpipe assemblies meeting Agusta specifications. Where replacement is necessary before further flight, lead times or availability of parts may affect grounding duration.

Regulatory decision makers: The instrument was issued by CASA and signed by a delegate, David Punshon. The AD’s incorporation of Agusta documents and reference to EASA AD 2006-0360-E indicates engagement with manufacturer and foreign regulator material, but the directive text itself is the operative instrument for those affected.

The directive does not list exemptions, alternative compliance paths beyond the stated repair options, or monetary penalties. It does not specify who bears the cost, but the operative obligations fall on aircraft owners/operators and their maintenance providers to conduct inspections, repair or replace parts, and repeat inspections every 25 flight hours.

Duties established by the directive are procedural and component-specific. The primary duties are:

• Inspect the tailpipe assembly. Requirements 1 and 2 require inspections for AB139 and AW139 helicopters respectively, in accordance with Agusta BT 139-069 Revision A dated 8 November 2006 or later approved revision. These inspections must be completed within 30 days after the AD’s effective date unless already done.

• Repair or replace when defects are found. Requirement 3 requires replacement if heat damage or cracks are found in the exhaust area inside the cowling, with replacement performed with an airworthy part according to the Agusta AW139 AMP, before further flight. Requirement 4 requires replacement for certain cracks outside the cowling that turn off abruptly or are outside the allowable limits established in the bulletin, again before further flight.

• Conditional repair options. Requirement 5 provides two alternatives where cracks outside the cowling are within allowable limits. Option 5(a) requires drilling a stop hole at the end of the crack and subsequent inspection to confirm no crack growth; if the crack grows to the bulletin limit, the tailpipe must be replaced per the AMP. Option 5(b) allows repair in accordance with Agusta BT 139-069 Rev A. Both options must be completed before further flight when applicable.

• Repetitive inspections. Requirement 6 requires repetition of the applicable inspection at intervals not to exceed 25 flight hours, and includes the instruction to “accomplish the follow-up actions, as required.”

Rights and constraints implied by the text:

• Right to use specified repair options. Where cracks are within allowable limits, operators have the right to choose between the stop-drill-and-monitor approach or the bulletin’s prescribed repair, subject to completing the relevant procedures and documenting the actions. The AD does not describe any alternative methods of compliance or exemptions.

• Constraint that repair/replacement does not terminate inspections. The directive expressly states that “Repair or replacement of the affected tailpipe assembly does not constitute terminating action for the repetitive inspection as detailed in Requirement 6 of this AD.” Therefore operators cannot rely on replacement alone to end the inspection cadence.

• Reliance on manufacturer documents. The AD binds operators and maintainers to the content of Agusta BT 139-069 Rev A and the Agusta AW139 AMP. The AD also allows dependence on “later approved revisions” of the bulletin, implying a process for approving revisions, though the AD does not detail that approval process within the text.

• Timing obligations. Inspections must be done within 30 days of effect unless already accomplished. Replacements or repairs required by the inspections must be completed before further flight. This creates a duty to ground or refrain from flight until the specified remedial actions are completed if defects are found.

No rights to contest, appeal or seek alternative compliance are specified in the directive text. The instrument also does not specify documentation or record-keeping format, nor monetary penalties or enforcement mechanisms; the duty framework is narrowly confined to inspections, repairs, replacements and repeat inspections at the specified intervals.

The directive text does not set out specific penalties, sanctions, or an enforcement regime. The document records the issuing authority as the Civil Aviation Safety Authority and is signed by a CASA delegate, David Punshon, dated 27 February 2008, with the AD effective on 10 April 2008. Beyond setting mandatory inspection and remedial timelines, the AD does not contain language about fines, administrative sanctions, certificate suspension, or criminal penalties in its text.

What the AD does provide that is relevant to enforcement is precise compliance timing and conditions. It requires initial inspections within 30 days of the effective date (Requirements 1 and 2), immediate remedial action before further flight if certain defects are found (Requirements 3, 4 and 5), and ongoing repetitive inspections at intervals not to exceed 25 flight hours (Requirement 6). These required timings create objective measures of compliance. The directive also clarifies what constitutes acceptable remedial action by referencing Agusta BT 139-069 Rev A and the Agusta AW139 AMP and by stating that repair or replacement does not terminate repetitive inspection obligations.

Because the AD itself contains no penalty clauses, the text does not identify who enforces compliance, or the process by which non-compliance would be detected, investigated or sanctioned. The absence of explicit enforcement provisions in the AD means that, within the four corners of this document, compliance is defined by the work required and the specified deadlines rather than by an enumerated set of consequences for failure to comply. The AD does reference EASA AD 2006-0360-E, but does not incorporate any enforcement terms from that instrument into its own text.

Practically, the AD’s effectiveness date and signature indicate its status as an operative regulatory instrument. The directive’s mandatory language creates clear obligations for operators and maintainers in the affected fleet. Any enforcement action, including sanctions or remedial directions beyond those required by the AD, is not described in this directive and would need to be sought in other regulatory texts, directions, or enforcement policies not included in this document.

The AD explicitly references other documents and thereby creates interdependence between this directive and manufacturer and foreign regulatory materials. The directive lists Agusta BT 139-069 Revision A dated 8 November 2006 or later approved revision as the inspection standard for Requirements 1 and 2. It also requires repair or replacement “in accordance with the Agusta AW139 Aircraft Maintenance Publication (AMP).” These incorporations mean the AD’s operative requirements are in part implemented by compliance with those external technical documents.

The directive further references EASA AD 2006-0360-E dated 29 November 2006 in a note. That reference signals that this CASA AD is aligned with or responsive to an EASA airworthiness directive, but the CASA AD does not adopt EASA’s text verbatim; rather it cites it as relevant background. The AD does not reproduce EASA’s enforcement or procedural details, nor does it incorporate any EASA-specific compliance mechanisms into the CASA AD text.

Within the AD’s text there is an implicit hierarchy: the directive requires actions “in accordance with” specified Agusta materials. Those materials therefore operationally interact with the directive, because the AW139 AMP and BT 139-069 contain the detailed inspection procedures, allowable crack length limits, and repair instructions. The AD also allows “later approved revision” of BT 139-069, which indicates that revisions to the Agusta bulletin, if approved, will modify the inspection protocol that satisfies the AD. The AD itself does not specify who approves later revisions, what approval criteria apply, or whether approval is to be obtained from CASA, Agusta, or another body.

The directive is silent on interactions with other domestic aviation safety regulations, certification conditions, or maintenance record-keeping rules. No cross-references to particular Australian aviation statutes, regulations or enforcement instruments appear in the AD text. The AD likewise does not state how compliance with its requirements should be recorded, whether compliance variance or alternative methods of compliance may be sought, or whether compliance with EASA AD 2006-0360-E by itself satisfies the CASA AD. The only cross-referenced materials within the AD are the Agusta bulletin, the Agusta AMP, and EASA AD 2006-0360-E.

Therefore, the AD’s interaction with other instruments is limited to mandating conformity with named manufacturer documents and acknowledging a related EASA AD. Any broader legal interactions, such as enforcement, approvals for alternate methods, or record-keeping obligations, are not specified in this instrument and would need to be located in other regulatory texts or agency procedures outside the AD.

The directive text itself provides a narrow amendment history limited to the documents it invokes and the AD’s dates. The AD identifies the inspection baseline as Agusta BT 139-069 Revision A dated 8 November 2006 and permits “later approved revision” of that bulletin. This language creates a mechanism by which the inspection instructions may be changed over time through later revisions of the manufacturer’s bulletin, subject to approval; however, the AD does not record any subsequent approved revisions within its text.

The AD also refers to EASA AD 2006-0360-E dated 29 November 2006. That reference situates the CASA AD in a temporal sequence of manufacturer and foreign regulator activity, but the AD does not record any later amendments to itself. The document identifies the AD number as AD/AB139/5 and provides both the signature date, 27 February 2008, and an effective date, 10 April 2008. The AD is labelled 4/2008 which indicates its publication indexing in 2008.

There are no explicit amendment or revocation clauses contained in the directive text. The AD does not record any superseding CAS A instruments, nor does it note any prior CASA AD that it amends or replaces. The text does not list an expiry or sunset provision. The AD’s allowance for “later approved revision” of the Agusta bulletin is the only built-in path for technical change contemplated within the instrument. The AD does not itself set a process for its own amendment, nor does it state whether updates to the Agusta AMP require separate CASA action to be treated as compliance with the directive.

In short, the recorded amendment history in the AD consists of the initial bulletin revision date relied on for inspection procedures, the EASA AD reference, the CAS A delegate’s signature date, and the AD’s effective date and indexing. The text does not report any subsequent amendments, revocations, or replacements to AD/AB139/5.

The directive text contains no litigation history. The document does not reference any legal challenges, court rulings, or administrative review outcomes relating to AD/AB139/5. It does not report any disputes over its scope, the technical content of Agusta BT 139-069 Rev A, or the correctness of the specified remedies. The AD does not mention any proceedings brought by operators, manufacturers or other parties challenging the directive.

Because the instrument is limited to the AD text and associated dates, the only available legal-history data within this document are procedural: the CASA delegate, David Punshon, signed on 27 February 2008, and the AD became effective on 10 April 2008. No subsequent notices, stays, amendments, or court orders are recorded in the directive text supplied.

Therefore, from the source itself, there is no litigation history to summarise. Any information about legal challenges, judicial interpretation, administrative appeals, or compliance disputes would need to be obtained from other sources, which are not included in this AD.

The AD contains several operational details and subtle constraints that create practical pitfalls for affected operators and maintainers.

Applicability is narrow but specific. The AD applies only to AB139 and AW139 helicopters “all serial numbers, except 31002, 31003, 31004 and 31007,” and only if the tailpipe assembly installed has P/N 3G7800L00131 (LH) or 3G7800L00231 (RH). Operators must check both the aircraft serial number and the installed part numbers. An aircraft outside the excluded serial numbers but with different tailpipe P/Ns is not within this AD’s scope, and conversely an excluded serial number is exempt even if fitted with a part having the listed P/Ns, per the AD text.

Different responses by defect location. Defects inside the cowling and defects outside the cowling are treated differently. Heat damage or cracks inside the cowling require replacement (Requirement 3). Cracks outside the cowling that turn off abruptly or exceed allowable limits require replacement (Requirement 4). Cracks outside the cowling that are within allowable limits may be managed by a stop-drill-and-monitor option or by bulletin-specified repair (Requirement 5). Maintaining correct classification of a crack’s position and whether it “turns off abruptly” or exceeds allowable limits thus directly determines whether an aircraft may be repaired and returned to service, or must be grounded until replacement is fitted.

Reliance on manufacturer limits. The AD frequently refers to the “allowable limits established by Agusta BT 139-069 Rev. A, or later approved revision.” Operators must have access to the bulletin’s specific allowable limits. The AD does not itself list crack length thresholds, nor does it specify the exact “later approved revision” approval process. Lack of the bulletin or uncertainty about which revision is approved could create compliance risk.

Repetitive inspections survive replacement. The AD explicitly states that repair or replacement is not terminating action for the repetitive inspection regime. Operators replacing a tailpipe cannot assume they are freed from the 25 flight hour inspection cadence.

Timing requirements are strict. Initial inspections must be carried out within 30 days of the AD taking effect unless already completed. If a defect triggering repair or replacement is found, the AD requires completion “before further flight,” which may impose immediate grounding pending parts or repair capability. There is no grace period specified for sourcing parts.

Multiple documents required. The AD requires compliance with both Agusta BT 139-069 Rev A and the Agusta AW139 AMP. Some operators might have one but not both documents. The AD’s silent position on how to obtain or who may approve later revisions to the bulletin creates an administrative gap.

No explicit alternative compliance route in the AD. The AD provides two alternatives for certain cracks, but it does not allow other methods of compliance or specify a process for seeking an alternative method. Operators seeking a novel repair technique or material substitution would find no procedure described in the AD for approval of such alternatives.

Reference to EASA AD is background. The AD notes EASA AD 2006-0360-E but does not explain whether compliance with EASA’s AD alone suffices or how the two directives interrelate in operational terms.

Documentation and record-keeping expectations are unstated. The AD requires inspections and repairs but does not specify how actions must be recorded or which authority must be notified. Practitioners should note these procedural gaps when planning compliance actions.

The AD sets a prescriptive sequence of actions. The following is an operational checklist grounded in the AD’s text.

1. Establish applicability. For each AB139 or AW139 helicopter in the operator’s fleet, confirm the aircraft serial number and the tailpipe assembly part numbers. The AD applies to “AB 139 and AW 139 helicopters, all serial numbers, except 31002, 31003, 31004 and 31007,” when fitted with tailpipe P/N 3G7800L00131 (LH) or 3G7800L00231 (RH). If either serial number is excluded or the tailpipe P/N differs, the AD does not apply to that aircraft.

2. Obtain required technical documents. Secure Agusta BT 139-069 Revision A dated 8 November 2006, and the Agusta AW139 Aircraft Maintenance Publication (AMP). The AD requires inspections “in accordance with the instructions of Agusta BT 139-069 Revision A dated 8 November 2006 or later approved revision,” and repair/replacement “in accordance with the Agusta AW139 Aircraft Maintenance Publication (AMP).” Determine whether any later approved revision of BT 139-069 exists and is relevant.

3. Initial inspections within 30 days. For aircraft to which the AD applies, perform the inspection referenced in Requirement 1 for AB139 helicopters or Requirement 2 for AW139 helicopters, within 30 days of the AD effective date unless the inspection has already been completed. Follow the inspection procedures and acceptance criteria in BT 139-069 Rev A.

4. Assess findings by defect location and severity. If inspection reveals heat damage or cracks in the exhaust area inside the cowling, proceed to replacement as required by Requirement 3. If cracks are found outside the cowling that “turn off abruptly from the original direction” or are outside the allowable limits in the bulletin, proceed to replacement as required by Requirement 4. If cracks outside the cowling are within the allowable limits, implement one of the two options under Requirement 5: either drill a stop hole and monitor crack length per 5(a) or perform the bulletin repair per 5(b).

5. Execute repairs or replacements before further flight. Any replacement or repair action required by the inspection outcomes must be accomplished before further flight after the effective date, according to Requirements 3, 4 and 5. Replacements must use an airworthy tailpipe assembly and be performed in accordance with the Agusta AW139 AMP.

6. If using stop-drill monitoring. For stop-drill option 5(a), drill a stop hole at the end of the crack and establish an inspection regime to verify that the crack length does not increase. If crack length increases to the limits established in BT 139-069 Rev A or later approved revision, replace the tailpipe per the AMP.

7. Record and document work. Although the AD does not specify documentary form, document the inspection findings, the selected remedial option, repair records if BT 139-069 repair is used, or replacement records if a new tailpipe is installed in accordance with the Agusta AW139 AMP. Given the AD’s pre-flight repair requirement, ensure maintenance release or equivalent authorisation is completed before returning the aircraft to service.

8. Commence repetitive inspection cycle. After the initial and any remedial actions, repeat the applicable inspection at intervals not exceeding 25 flight hours, per Requirement 6. The AD states that repair or replacement does not terminate the repetitive inspection requirement, so include every replaced tailpipe in the inspection cycle.

9. Maintain an inventory and logistics plan. Because replacements must be effected before further flight where certain defects are found, operators should plan for spare tailpipe availability or rapid procurement paths for P/Ns 3G7800L00131 and 3G7800L00231 to minimise aircraft grounding.

10. Refer to EASA AD if needed. The AD notes EASA AD 2006-0360-E dated 29 November 2006, which may provide related technical context. The CASA AD itself governs Australian compliance obligations.

11. Follow any approval processes for later bulletin revisions. The AD allows inspection “in accordance with … later approved revision” of BT 139-069. Operators should confirm which authority approves such revisions and obtain or rely on an approved revision only when such approval is documented.

12. Safety-first operations. When an inspection reveals defects requiring repair or replacement before further flight, ground the helicopter until the required remedial action is completed, and document compliance with the AD.

This checklist is confined to the actions the AD requires. The AD does not describe administrative notifications of CASA, alternative method of compliance processes, or enforcement mechanisms. Operators should therefore maintain clear records proving inspections and remedial actions were carried out in the manner and within the timeframes specified by the AD.