AD/JBK 117/36 - Pressure Altitude Limitation and Max N1 Check

The instrument rests on a short set of technical and operational concepts stated in the AD text. These concepts are: applicability, a mandatory hardware-modification requirement, an effective date for compliance, and the technical rationale connected to engine fuel flow and FCU acceleration laws.

• Applicability. The AD explicitly applies to "Kawasaki BK117C-1 and C-2 helicopters." That is the exclusive scope stated in the document (Applicability). No other airframes or sub-types are listed in the supplied text.

• Mandatory hardware conformity. The AD's operative restriction is categorical: "Fuel Control Units which have not been Modified in accordance with Turboméca Service Bulletin No.292 73 0358 (TU358) must not be installed in any helicopter." This changes permissible aircraft component installation practice, effectively requiring FCUs to be modified per TU358 before they can be installed in the affected helicopters (Requirement).

• Effective timing. The compliance directive becomes active "After the effective date of this Directive." The instrument specifies an effective date of 24 December 2010. Practically that means from that date forward, installation of non-TU358 FCUs is proscribed (Compliance; Effective date).

• Remedial modification and conditional removal of operational restrictions. The AD states that Turboméca developed TU358 and that "when accomplished on both engines installed on the helicopter, cancel the required checks and allow the removal of the placard and flight manual changes." This identifies a two-engine accomplishment condition to remove previously required operational controls (Background).

• Problem mechanism. The AD records the proximate technical problem: under high-altitude "MAX N1 CHECK" testing, some helicopters failed to reach the N1 threshold because "delivered fuel flow [was] lower than the engine fuel flow demand to achieve the OEI rating at high altitude," with the limitation traced to the FCU acceleration law. The AD notes the altitude sensitivity: "could potentially occur at altitudes exceeding 10,000 feet, depending on the engine and FCU characteristics" (Background).

• Cross-reference to another authority. The AD includes a Note: "JCAB AD TCD-7000-1-2008 refers" (Requirement, Note). That records a link to a Japanese Civil Aviation Bureau directive, but the AD text does not reproduce or summarise that foreign directive here.

These concepts combine a strict parts-installation constraint with an identified technical fix that, if applied to both engines, will permit the operator to remove temporary operational placards and flight manual amendments. The AD does not itself provide the technical content of TU358, nor does it set out inspection regimes, recordkeeping rules, or explicit enforcement penalties in the supplied text.

The AD names the affected helicopter types and several categories of parties who must change behaviour as a result.

• Owners and operators of Kawasaki BK117C-1 and C-2 helicopters. The Applicability clause identifies these types as the AD's universe. Owners and operators who install, replace, maintain or certify FCUs on these helicopters are directly affected because after the effective date they may not install FCUs that have not been modified in accordance with TU358 (Applicability; Requirement; Compliance).

• Maintenance providers and engineers. Any organisation or personnel responsible for installing or approving FCUs for service on the applicable helicopters must ensure the component has been modified per TU358 before installation. The AD's language makes the modification status the qualifying condition for lawful installation (Requirement). Maintenance organisations will need to ensure, before installation, either that the FCU has the TU358 modification or that it will not be installed.

• Component suppliers and overhaul houses. Entities supplying FCUs for BK117C-1/C-2 operators must supply items modified per TU358 if those FCUs are to be installed after the effective date. The AD therefore affects inventory management, refurbishment processes, and procurement specifications for suppliers who service these helicopter types.

• Flight operations decision-makers. The Background records that a failure to reach the "MAX N1" threshold occurred at high altitudes, potentially above 10,000 feet "depending on the engine and FCU characteristics." This is an operational constraint; flight operations staff and flight crew must be mindful of any placards or flight manual entries presently required until the TU358 modification is accomplished on both engines. The AD states that TU358 "allow[s] the removal of the placard and flight manual changes" when applied to both engines (Background). Thus flight operations will be affected both in the short term (when placards/flight manual changes remain) and in the medium term (when the modification is applied and those constraints can be removed).

• Regulators and delegated certifying staff. The AD is issued under CASA delegated authority (signature block). Inspecting authorities, airworthiness inspectors and delegated approval personnel who verify compliance with ADs will need to enforce the "must not be installed" prohibition and to verify whether TU358 has been accomplished on both engines when removal of placard/flight manual changes is claimed (Compliance; Background; signature).

• International stakeholders referenced. The AD notes "JCAB AD TCD-7000-1-2008 refers" (Requirement, Note), signalling that there is a related action from the Japanese authority. Operators and maintenance organisations who interact with Japanese compliance regimes or operate internationally should be aware of the cross-reference, although the AD does not incorporate that foreign directive's text.

Who pays: the text requires the TU358 modification to the FCU as the remedy. That places the immediate cost of modification, installation labour and downtime on the helicopter owner/operator and/or their maintenance supplier. The AD states that Turboméca developed the modification (Background), which identifies the technical source of the fix; the AD text does not allocate costs or state any subsidy or alternative remedy.

Who decides: the AD sets the technical standard for installation (modified per TU358) and the effective date for compliance; it leaves the operational choice to operators whether to accomplish the TU358 modification on both engines to cancel checks and remove placards, subject to the directive's terms. The AD does not set alternative technical approvals or exemptions in the supplied text.

The AD imposes a narrow set of duties and records one conditional operational right.

Duties

• Do not install unmodified FCUs after the effective date. The directive states a clear duty: "Fuel Control Units which have not been Modified in accordance with Turboméca Service Bulletin No.292 73 0358 (TU358) must not be installed in any helicopter." That is mandatory and applies "After the effective date of this Directive" (Requirement; Compliance). The duty is expressed as an absolute prohibition on installation of FCUs that are not modified per TU358.

• Ensure compliance timing. The AD becomes effective on 24 December 2010; operators must ensure installations after that date meet the requirement (Compliance; Effective date).

• Observe existing placards and flight manual changes until modification completed on both engines. The Background records that a TU358 modification "when accomplished on both engines installed on the helicopter, cancel the required checks and allow the removal of the placard and flight manual changes." From that language the duty to observe any current placards and flight manual changes persists until the modification condition is met. The AD does not reproduce the specific placard or flight manual wording in the supplied text; it only records that such placard/flight manual changes exist and may be removed after TU358 is accomplished on both engines.

Rights / conditional privileges

• Removal of placard and flight manual changes after TU358 on both engines. The AD grants a conditional right or relief: if TU358 is "accomplished on both engines installed on the helicopter," that accomplishment will "cancel the required checks and allow the removal of the placard and flight manual changes" (Background). The right to remove those operational restrictions arises only after the bilateral-engine modification condition is satisfied.

• Use of modified FCUs. Installing FCUs that have been properly modified per TU358 is permitted; the AD's prohibition is limited to FCUs not modified per TU358. The AD does not specify that modified FCUs must be used, but the necessary effect is that modified FCUs are the only ones permitted for installation after the effective date.

Matters the AD does not address explicitly in the supplied text

• The AD does not specify how compliance is to be documented or what evidence will satisfy inspectors. It does not reproduce TU358 or provide technical verification steps. It does not state any alternative means of compliance, nor does it set express maintenance intervals or inspection protocols to monitor FCU behaviour post-modification. It does not set out procedures for installation of new FCUs in the field that may come unmodified. Any such enforcement or procedural detail would have to be sought in the AD's fuller text, TU358, or other CASA materials not included here.

• The AD does not state penalties for non-compliance in the supplied text. The primary duty language, however, is mandatory in form.

Concrete citations from the AD: Applicability; Requirement ("must not be installed"); Compliance ("After the effective date of this Directive"); Effective date ("This Airworthiness Directive becomes effective on 24 December 2010"); Background (description of problem and remedial TU358 effect).

The supplied AD text does not contain an enforcement or penalties section, nor does it specify sanctioning mechanisms, fines or administrative procedures in the document provided. The instrument uses mandatory wording to prohibit certain installations, but it does not set out punitive measures within the printed pages provided.

What the AD does provide that bears on enforcement procedures

• Mandatory prohibitions expressed as duties. The AD's core operative language is a prohibition: "must not be installed in any helicopter" (Requirement). That creates a clear compliance obligation. In practice, inspectors and regulatory staff will treat such mandatory AD language as a non-compliance trigger, but the AD text as supplied does not itself articulate the enforcement steps that follow non-compliance.

• Effective date for compliance. The AD specifies the effective date as 24 December 2010 (Compliance; Effective date). Enforcement actions or conformity assessments would logically reference that date as the compliance trigger. The AD does not, however, provide a grace period or staged timetable in its printed text.

• Certification context. The AD records that Turboméca developed the TU358 modification and indicates the pathways to restore full operational status (Background). The AD states that once TU358 is accomplished on both engines it will "cancel the required checks and allow the removal of the placard and flight manual changes." That implies a compliance verifiable by inspection of modification status on both engines, but the AD does not specify the documentation that will be deemed adequate evidence.

• Delegation. The AD is signed by "David Villiers, Delegate of the Civil Aviation Safety Authority" (signature block). This identifies the issuing authority but does not provide enforcement mechanics. The presence of an issuing delegate will usually mean the AD is part of the regulator's enforceable airworthiness instruments, but the AD text given does not itself specify sanctions.

What is not in the supplied text and must be sought elsewhere

• The AD does not list monetary penalties, administrative sanctioning procedures, or criminal consequences. It does not give inspectors a specified checklist or recordkeeping protocol. It does not state whether installation of non-modified FCUs is an absolute grounding event or whether an alternative equivalence approval can be sought.

• The AD references "JCAB AD TCD-7000-1-2008" but does not reproduce it or its enforcement provisions; any international enforcement implications or harmonised measures are not set out.

For compliance officers and lawyers, the practical implication of the AD's mandatory installation prohibition is that verifying whether an FCU has been modified per TU358 will be a key inspection point after 24 December 2010. The AD text does not specify how to demonstrate conformity; parties should rely on the AD plus the TU358 documentation and CASA inspection guidance for evidentiary standards. Any questions about penalties, exemptions or alternative means of compliance will need to be resolved by reference to other CASA instruments, enforcement policy, or legal frameworks outside the text provided.

The text of the AD itself provides limited direct cross-references. Two interaction points are explicitly recorded.

• Reference to a foreign airworthiness directive. The AD includes a note: "JCAB AD TCD-7000-1-2008 refers" (Requirement, Note). That records that a Japanese Civil Aviation Bureau AD is relevant or related. The AD does not reproduce the JCAB material or state whether CASA is adopting identical requirements; it simply records the reference. Practically, that signals cross-jurisdictional technical correspondence and suggests the technical issue has been addressed by at least one other authority. How that foreign AD interacts with Australian regulatory obligations is not stated in the supplied text.

• Flight manual and placard modifications. The AD records that, until TU358 is accomplished on both engines, certain checks and placard/flight manual changes are in place; and that TU358 "will ... allow the removal of the placard and flight manual changes" (Background). That creates an internal interaction with airworthiness documentation regimes: flight manuals and on-aircraft placards are typically approved or accepted under separate procedural regimes. The AD does not specify those approval processes in its text, but the AD's statement creates a relationship between component modification status and the validity of flight manual/placard entries. Removal of those entries is contingent on completing TU358 on both engines.

What the AD does not do or specify in the supplied text

• The AD does not purport to amend statutes, regulations or certificate conditions outside the narrow AD requirement; it does not cite a broader statutory provision by number. The AD text provided leaves any statutory enforcement frameworks implicit rather than explicit.

• The AD does not describe interactions with other CASA instruments such as maintenance data acceptance procedures, continuing airworthiness instructions, or delegated authority structures beyond the signature block.

• The AD does not provide an alternative means of compliance or equivalence procedure in the supplied text, nor does it reference processes to seek derogations, exemptions or special flight permits.

For readers concerned about legal interplay, the AD is a narrowly targeted regulatory instrument that imposes a technical installation requirement and references external materials (TU358 and JCAB AD). Complete understanding of how the AD functions in the broader legal ecosystem will require consulting the full CASA AD library, TU358 documentation, and the JCAB AD referenced, plus CASA enforcement and exemption policies that sit outside the text supplied here.

The supplied AD text does not record prior amendments to AD/JBK 117/36 and contains only the issuance metadata: the AD's identifier (AD/JBK 117/36), the title (Pressure Altitude Limitation and Max N1 Check), the designation 25/2010, and the effective date. Specific entries in the supplied text:

• AD identifier and date stamp: AD/JBK 117/36; 25/2010 appears in the heading rows.

• Effective date: "This Airworthiness Directive becomes effective on 24 December 2010." (Compliance; Effective date).

• Signature: The AD is signed "David Villiers, Delegate of the Civil Aviation Safety Authority" and dated 9 December 2010 (signature block).

No amendment timeline, prior versions, supersessions, or revocation clauses are present in the supplied text. The AD does not record that it supersedes or is superseded by any other CASA AD within the text provided. It does, however, note that "JCAB AD TCD-7000-1-2008 refers" which indicates a related foreign AD exists, but that is not the same as a CASA amendment history.

Implications for users seeking amendment records

• If an operator or maintenance organisation requires a formal amendment history, or needs to know whether this AD was later superseded or varied, that information is not in the supplied text and must be sought in CASA's AD repository or subsequent communications from CASA.

• The AD records a modification TU358 as the remedial action. Whether TU358 itself has versions, revisions or further updates is not recorded here. The AD refers to "Turboméca Service Bulletin No.292 73 0358 (TU358)" but the AD text does not indicate whether TU358 has multiple revisions, effective dates, or mandatory revisions.

• The AD does not include references to subsequent amendments, corrections or clarifying notices. Readers should consult the CASA AD index or aeronautical publications to establish whether later ADs amended, rescinded or replaced this directive.

In short, the supplied AD provides a single issuance snapshot with identifier, effective date, signatory and the specific operative requirement. It does not contain an explicit amendment history within the text supplied.

The supplied AD text contains no litigation history or references to legal challenges, appeals, tribunal determinations or case law. It does not record that the AD has been litigated, nor does it cite any judicial or administrative decisions.

What the instrument does record

• Issuance details: the AD was signed by a delegate of the Civil Aviation Safety Authority on 9 December 2010 and became effective on 24 December 2010. No mention is made of appeals, stays, or litigation.

• A cross-reference to JCAB AD TCD-7000-1-2008 is included, but that is a technical cross-reference rather than a litigation citation.

What is not included and next steps if litigation history is required

• The AD text does not indicate whether owners, operators, or suppliers sought review or relief in any tribunal or court, nor does it provide records of any compliance disputes or enforcement proceedings brought in relation to this AD.

• If a reader needs to know whether this directive has been subject to judicial or administrative review, or whether there is case-law interpreting the AD's obligations, they will need to search regulatory enforcement records, tribunal decisions (for example aviation appeals bodies or administrative tribunals), and court databases. That material is not contained in the supplied AD text.

Because the AD itself is a short technical instrument, its supplied text is consistent with being a stand-alone technical requirement without litigation narrative. However, absence of litigation history in the text does not mean litigation never occurred; it only means no such history is recorded in this document.

The AD is compact, but several practical pitfalls follow directly from the language used and the technical facts set out in the Background. These are operational and compliance-oriented matters readers should note.

• Absolute prohibition on installation of unmodified FCUs after the effective date. The AD's operative sentence is strict: "must not be installed in any helicopter" unless modified per TU358. That prohibition applies to any installation after the effective date, which raises immediate practical questions about inventory management and replacement parts. Operators must ensure that any FCU intended for installation is already modified per TU358. The AD does not provide a tolerance for temporary use of an unmodified FCU pending modification.

• The modification must be accomplished on both engines to remove other operational constraints. The AD states that TU358 "will, when accomplished on both engines installed on the helicopter, cancel the required checks and allow the removal of the placard and flight manual changes." Two-engine accomplishment is an explicit bilateral condition. Operators who modify only one engine will not be able to remove the placard or flight manual changes, nor cancel the checks. That makes partial modification strategies problematic from an operational-restoration perspective.

• The altitude sensitivity and variability. The Background describes failure to reach the "MAX N1" threshold under maximum certification altitude testing and notes the issue "could potentially occur at altitudes exceeding 10,000 feet, depending on the engine and FCU characteristics." The concrete implication is that operators should not assume the condition is immaterial for their operational profile; helicopters that operate frequently above 10,000 feet may be at greater risk. The AD does not quantify the altitude at which each FCU/engine combination will show the limitation; that variability remains a practical uncertainty users must manage.

• The AD does not reproduce TU358. The AD requires modification "in accordance with Turboméca Service Bulletin No.292 73 0358 (TU358)" but does not itself contain the technical steps, certification statements or acceptance criteria that TU358 provides. Operators will need to obtain and follow the TU358 documentation for the technical work, and they will need to ensure they can show evidence of its accomplishment. The AD text does not say what proof will be acceptable to inspectors.

• Cross-reference to JCAB AD TCD-7000-1-2008. The AD notes that JCAB AD TCD-7000-1-2008 "refers." Operators with international operations or parts sourced through international supply chains should check whether related foreign directives impose additional or different obligations. The AD text does not reconcile any differences between CASA and JCAB requirements.

• No explicit enforcement or remedial schedule in the text. The AD sets only an effective date and the install prohibition; it contains no stated penalties, no grace period and no stated process for alternative compliance. That means operators who want to pursue an alternative remedy or an acceptable level of safety different to TU358 must seek guidance or approval from CASA outside the AD text.

• Potential supply/downtime issues not specified. Although the AD requires TU358 modification, it does not provide guidance on parts availability, turnaround times or where the modification can be performed. The AD's silence on those practical matters creates a potential logistical "gotcha" for operators who may be unable promptly to acquire modified FCUs or obtain modification slots.

• Implicit continuation of placard/flight manual changes until bilateral modification. The AD implies but does not reproduce existing placards or flight manual text. Operators must be careful not to remove or alter those documents until both engines have TU358 accomplished.

These points are all grounded in the AD wording: the prohibition, the bilateral modification condition, the altitude caveat, the TU358 reference, and the JCAB note. Because the directive is terse, the practical implementation details and evidence expectations remain open and must be resolved via the TU358 documentation and CASA follow-up guidance.

The AD gives a narrow compliance route and one conditional relief mechanism. Compliance steps, grounded in the AD's text, are as follows.

1. Identify applicability. Confirm that the helicopter is a Kawasaki BK117C-1 or BK117C-2. The AD's Applicability restricts the requirement to those types (Applicability).

2. Do not install unmodified FCUs after the effective date. From 24 December 2010 onward, do not install any Fuel Control Unit that has not been modified per Turboméca Service Bulletin No.292 73 0358 (TU358). The AD's requirement is categorical: "must not be installed in any helicopter" (Requirement; Compliance; Effective date). Before installing an FCU on an applicable helicopter after that date, verify that the FCU has TU358 modification status.

3. Obtain and apply TU358 where necessary. The AD identifies TU358 as the modifying document produced by Turboméca. To comply with the AD and to restore full operational status, a helicopter operator must have TU358 "accomplished on both engines installed on the helicopter." The AD states that accomplishing TU358 on both engines will "cancel the required checks and allow the removal of the placard and flight manual changes" (Background). Therefore, to regain the right to remove placards and flight manual entries, ensure both engines are modified per TU358.

4. Coordinate maintenance and procurement. Because the AD prohibits installation of unmodified FCUs, maintenance managers should ensure procurement specifications and inventory procedures require that any FCU intended for installation be delivered with TU358 already accomplished, or else be scheduled for modification before installation.

5. Verify modification evidence. The AD itself does not specify what documentary evidence will be accepted, but operators should obtain and retain the TU358 modification certification documentation as issued by the Turboméca-approved maintenance organisation performing the work. That documentation will be the practical method by which compliance is demonstrated to inspectors or delegated certification staff.

6. Maintain flight manual and placard compliance until both engines are modified. The AD indicates existing placards and flight manual changes remain in force until TU358 is accomplished on both engines. Operators must continue to obey those placards and flight manual entries until the bilateral modification condition is met. Do not remove the relevant placards or make flight manual changes until you can show both engines have TU358 completed (Background).

7. Seek CASA clarification where needed. The AD does not provide procedures for alternative means of compliance, nor does it set out enforcement or evidentiary standards. If an operator has a technical alternative to TU358, or requires an exemption for operational reasons, the AD's text provides no mechanism; such matters will need to be raised with CASA directly through the regulator’s established channels.

8. Check related authorities. The AD notes "JCAB AD TCD-7000-1-2008 refers." If you operate internationally or source parts internationally, check the JCAB AD for any additional requirements or cross-acceptance arrangements.

9. Document timing and effective-date compliance. Ensure that any installation operations performed on or after 24 December 2010 comply with the AD. Keep records demonstrating that FCUs installed after that date were TU358-modified.

10. If uncertain, ground-change planning. Because the AD may have operational safety consequences at high altitude, and because partial modification does not permit removal of flight restrictions, plan maintenance schedule so that both engines can be modified within an operationally acceptable window. The AD does not specify permissible interim operating regimes beyond confirming that checks and placards exist until TU358 bilateral accomplishment.

These steps are drawn from the AD's Applicability, Requirement, Compliance, Background and Effective date statements. The TU358 service bulletin itself, and CASA procedural guidance, will be material to implement the physical modifications and to satisfy inspectors; the AD requires that any FCU installed after the effective date be modified per TU358, and that only bilateral accomplishment will restore full operational documentation.