AD/MAKILA/7 Amdt 1 - Digital Engine Control Unit Software

Digital engine control unit (DECU). The DECU is the electronic controller that manages engine parameters such as fuel flow, gas generator speed (NG), and free turbine speed. It contains embedded software that implements control laws, including backup (or “reversionary”) laws that activate when primary control is lost. The AD targets the software version of the DECU, which must be upgraded to version 11 (Mod TU 244C) from version 9.

Backup law at 65% NG and 85% NG. The background explains that a backup law at 65% of NG (gas generator speed) was added to limit free turbine overspeed in the event of a drive train failure between the engine and the main gearbox. However, tests revealed a scenario where the 65% NG backup could be bypassed, leading to activation of another backup law at 85% NG. In that scenario, the overspeed protection from the 65% NG backup is lost, allowing the free turbine to accelerate until it bursts. The software upgrade (Mod TU 244C) ensures the overspeed protection function is maintained even in that scenario.

Modification TU 244C and TU 230C. These are Turbomeca modifications to the DECU software. TU 230C is the previous version; TU 244C is the new version. The AD requires TU 244C for all applicable engines by the compliance date. TU 230C is permitted as the paired engine configuration, but not as a standalone future state for the modified engine.

Free turbine overspeed. This is a failure mode where the turbine that drives the helicopter’s main rotor (the free turbine) spins beyond its design limits, potentially causing mechanical failure (bursting). The AD targets this specific risk scenario.

Compatibility rule. Requirement 2 of the AD states that an engine with TU 244C may only be installed on a helicopter if the other engine is also TU 244C or TU 230C. This prevents a mismatch that could create asymmetric control behaviour or affect safety. The rule applies as of the effective date, meaning any installation after 5 July 2007 must comply, regardless of whether the software upgrade has been done on the other engine.

Mandatory service bulletin. The AD references Turbomeca Service Bulletin No A298 73 0244 Update 1 dated 30 March 2007 update. This bulletin provides the detailed instructions for performing the DECU replacement. The AD itself does not reproduce those instructions; it incorporates them by reference.

The primary class of persons affected are the operators of helicopters equipped with Makila 1A2 turboshaft engines. The AD explicitly notes that these engines are known to be installed on, but not limited to, Super Puma Mark II helicopters. This means operators of Super Puma Mark II (likely the AS332 L2 variant) are directly in scope. However, the applicability is by engine type, not by helicopter model, so any other aircraft type fitted with Makila 1A2 engines is also captured. There is no exclusion for experimental, private, or foreign-registered aircraft operating in Australian territory; ADs apply to all Australian-registered aircraft and to foreign-registered aircraft operated by an Australian operator, subject to the provisions of the Civil Aviation Regulations.

Within the operator’s organisation, the following roles are affected: maintenance engineers and technicians (responsible for performing the DECU replacement and documenting compliance); maintenance planners and logistics personnel (sourcing the modified DECU or the service kit, scheduling downtime); flight operations and fleet managers (ensuring engine pairing rules are observed during installations or swaps); and the accountable manager (who may face personal liability for non-compliance).

Outside the operator, the following parties are affected: Turbomeca (now Safran Helicopter Engines) as the manufacturer of the DECU and provider of the service bulletin; helicopter owners and lessors (who bear the residual cost if the operator does not); and insurance underwriters who may adjust premiums or require evidence of compliance.

The compliance burden is concentrated: operators of a small fleet of Super Puma helicopters will face a discrete but mandatory cost per engine. For a typical two-engine helicopter, the DECU upgrade for both engines plus the compatibility requirement is straightforward if both are modified by the deadline. The problem arises if an operator has a fleet of mixed engine states: for example, if one engine has been modified and the other is still on an older software version without TU 230C, the pairing rule may force an unplanned upgrade or engine swap. This is an operational constraint with immediate effect.

The AD does not affect the general public, non-aviation businesses, or airlines that do not operate these engines. It is a narrowly targeted instrument.

Duty to replace the DECU. By no later than 30 November 2008, every Makila 1A2 engine subject to the AD must have its DECU replaced with one incorporating Modification TU 244C, performed in accordance with the Turbomeca service bulletin. This is a one-off action; after compliance, no further software upgrade is required under this AD.

Duty to ensure engine compatibility during installation. From 5 July 2007, whenever an engine post Modification TU 244C is installed on a helicopter, the installer must ensure the other engine is either post TU 244C or post TU 230C. This duty applies immediately and is ongoing. It is not limited to initial fit after the AD; it applies to every installation, including after maintenance or engine replacements.

Duty to comply with the service bulletin. The AD does not specify all steps; it mandates compliance with the bulletin’s instructions. The bulletin may contain durational or procedural requirements that are not stated in the AD itself. Therefore, operators must obtain and follow the bulletin.

Rights of the operator. The operator has no right to deviate from the AD without an alternative means of compliance approved by CASA. However, the AD does not prohibit deferring the modification if the engine is not operated past 30 November 2008. The operator has the right to perform the work at a time of their choosing within the compliance window, subject to the immediate compatibility rule for installations. The operator also has the right to request an extension or exemption from CASA under Part 11 of the Civil Aviation Safety Regulations, but that is a separate process.

Rights of the maintenance organisation. The maintenance organisation performing the work has the right to charge for the work and to require appropriate documentation. However, the AD imposes no additional rights beyond those arising from the maintenance contract.

No right to compensation. The AD does not provide for compensation to operators for the cost of compliance. It is a regulatory imposition for safety.

The source document does not itself specify penalties. However, airworthiness directives are issued under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations (CASR), typically under Part 39 (Airworthiness Directives). Non-compliance with an AD is an offence under the Act or the Regulations. The penalties include:

• For an individual: fines up to a prescribed penalty unit amount (currently $1,110 per unit, but subject to indexation) for each day the non-compliance continues. For corporate entities, the fine can be up to 10 times the individual amount.
• Criminal prosecution for reckless or wilful non-compliance, potentially leading to higher penalties and imprisonment in extreme cases (though imprisonment is rare for AD violations).
• Civil penalties under Part 22 of the Civil Aviation Act (civil penalty provisions) with fines up to $1.11 million for corporations and $222,000 for individuals per contravention.
• Suspension or cancellation of the aircraft’s certificate of airworthiness or the operator’s air operator’s certificate.
• Grounding of the aircraft until compliance is achieved.
• Adverse action against the maintenance organisation’s approval.

Specifically for this AD: if an operator fails to replace the DECU by 30 November 2008, each day the aircraft is flown with the non-compliant software is a separate contravention. Similarly, installing an engine in violation of the compatibility rule after 5 July 2007 is an immediate contravention.

The AD may also be enforced by CASA as a condition of the aircraft’s registration. In practice, CASA audits maintenance records and spot-checks aircraft. Non-compliance is often discovered during scheduled inspections or when reporting modifications.

Because the AD incorporates a service bulletin by reference, failure to follow the bulletin’s instructions to the letter may also be a breach. If the bulletin is revised, the AD does not automatically update; it only references the specific update dated 30 March 2007. Using a later revision without CASA approval could arguably be a deviation unless the later revision is identical or supersedes in a compatible way. Operators should clarify with CASA if they wish to use a later bulletin.

The AD is itself a legislative instrument under the Civil Aviation Act 1988. It interacts with:

• Civil Aviation Safety Regulations (CASR) Part 39 - which governs airworthiness directives. Part 39 sets the legal framework for the issuance, acceptance, and enforcement of ADs. It also provides for alternative means of compliance and for exemptions.
• Other CASA airworthiness directives - If there are other ADs affecting the Makila engine or the DECU (e.g., software updates or hardware modifications), compliance with this AD does not exempt the operator from those. The operator must comply with all ADs applicable.
• EASA AD 2007-0143 - The AD notes that “EASA AD 2007-0143 refers.” That is the European equivalent. Since CASA is the relevant authority for Australian operators, the Australian AD is the governing instrument. However, operators with international operations or with engines maintained overseas must also comply with the EASA AD if the aircraft is registered in an EASA member state or operates under EASA regulatory oversight. For Australian-registered aircraft, the CASA AD is the binding law.
• Maintenance regulations (CASR Part 42 for continuing airworthiness, Part 145 for maintenance organisations) - The work under the AD must be carried out in accordance with an approved maintenance organisation (AMO) or a licensed aircraft maintenance engineer (LAME) as applicable. The service bulletin may specify tooling or procedures that require certain approvals. The operator must ensure the maintenance provider is appropriately authorised.
• Foreign airworthiness authorities - If the aircraft is registered in another country and operated in Australia under a foreign air operator certificate, the applicable AD is the one from its state of registry, but it must also meet CASA’s requirements for operations in Australia. This AD is specific to Australian-registered aircraft.
• Export controls and trade laws - If the DECU or its software is subject to export controls (e.g., US ITAR or Australian Defence Trade Controls), obtaining the modified unit might involve compliance with those laws. The AD does not address this; the operator must handle separately.
• Contractual obligations - Leases, management agreements, and insurance policies may require compliance with all ADs. Failure to comply could breach the lease or void insurance. The AD itself does not create those contractual effects but interacts with them.

The source document is itself an amendment (Amdt 1) to the original AD/MAKILA/7. The original issue became effective on 13 April 2006. That original directive required the same software upgrade (Mod TU 244C) and engine compatibility, but it likely referenced the original version of the Turbomeca service bulletin before its 30 March 2007 update. It also likely referred to the then-current DGAC AD, which was the French airworthiness directive.

This amendment (Amdt 1) was issued on 25 May 2007 and becomes effective on 5 July 2007. The key changes from the original are:

1. Updated service bulletin reference: The compliance method now references Turbomeca Mandatory Service Bulletin No A298 73 0244 Update 1 dated 30 March 2007 update, rather than an earlier version. This update likely contains revisions to the installation procedure, perhaps addressing issues found during initial compliance.
2. Transition to EASA AD: The background states that this amendment follows the revision of DGAC AD F-2006-029 by EASA. The original AD had been based on the DGAC directive; the amendment aligns with the EASA version (AD 2007-0143). This reflects the transfer of airworthiness oversight from individual European states to EASA. The Australian AD tracks that change.
3. Continued requirement with updated references: The amendment continues the requirement to upgrade software and ensure engine compatibility, but the legal basis and the referenced documents are brought up to date.

There is no indication that the compliance date itself changed. The original directive likely had the same 30 November 2008 deadline for the upgrade. The effective date of this amendment (5 July 2007) is the date from which the compatibility rule applies, but the original may have had a different effective date for that rule (likely earlier, around 13 April 2006). This amendment resets the effective date for the compatibility requirement to 5 July 2007, possibly giving operators a new start date.

Because the AD is a mandatory instrument, any future amendments would require a new AD or further amendment. No subsequent amendments are referenced.

The source document does not mention any litigation, and there is no publicly recorded judicial review or challenge to this specific AD. Airworthiness directives are rarely challenged in court because they are based on safety findings and are generally subject to a deferential standard of review. An operator would need to argue that the AD is beyond power, procedurally flawed, or unreasonable, but the bar is high.

Given the technical nature of the safety issue (free turbine overspeed risk), a court would likely give CASA wide discretion. Litigation against ADs is uncommon in Australia; most disputes are resolved through administrative processes like applications for exemption under CASR Part 11 or via the Administrative Appeals Tribunal (AAT) if CASA issues an enforcement action.

There is a possibility that a dispute could arise over the compatibility requirement if an operator claims it forced costly engine swaps and argues the AD was not proportional. But no such case is recorded in relation to this AD.

The lack of litigation history is itself informative: it suggests that operators have either complied without challenge or have settled with CASA informally. It does not imply that the AD is uncontroversial, only that legal challenge was not pursued.

Several traps for the unwary exist in this AD.

1. The compatibility rule applies immediately, not at the deadline. Requirement 2 is effective from 5 July 2007, while Requirement 1 has a deadline of 30 November 2008. An operator might think they can wait until late 2008 to upgrade both engines, but if they need to install a modified engine on one side earlier (e.g., replacing a failed engine with a TU 244C unit), they must ensure the other engine is either TU 244C or TU 230C. If the other engine is on an older software version (e.g., version 9), such installation is prohibited from 5 July 2007. This could force an immediate upgrade of the other engine even if it had been planned for later.

2. The compatibility rule does not apply retrospectively to existing installations. The AD says engines post Mod TU 244C “may only be installed on a helicopter if the other engine is either post Mod TU 244C or TU 230C.” This applies at the time of installation. If an operator already has a helicopter with one TU 244C and one TU 230C installed before 5 July 2007, that configuration remains legal. However, if they remove and reinstall the TU 244C engine later, the installation triggers the rule again. So any maintenance or engine removal that involves reinstallation could create a violation if the other engine is not compliant.

3. “Post” modification language. The AD uses “post Modification TU 244C” and “post Mod TU 230C.” This means engines that have been modified with that modification. It does not clarify whether the modification must be applied by the original service kit or if an equivalent later kit is acceptable. The AD specifically references the service bulletin Update 1. Using a later version of the bulletin could produce a DECU that is not strictly “post Mod TU 244C” if the later bulletin implements a functionally equivalent but nominally different mod. The operator must ensure the modification is exactly TU 244C as defined.

4. The service bulletin update date is critical. The AD references “Turbomeca Mandatory Service Bulletin No A298 73 0244 Update 1 dated 30 March 2007 update.” The original bulletin likely had an earlier date. Using an earlier version of the bulletin would not satisfy the AD’s reference. Also, if the bulletin contains multiple updates, the AD binds the operator to that specific one. If Turbomeca later issues Update 2, the operator would need a new AD to require it, or should seek CASA approval to use it as an equivalent.

5. The AD applies to Makila 1A2 engines only, not to other Makila variants. Operators with Makila 1A1 or 1A3 engines are not affected by this AD, even if they share common DECU parts. However, compliance with other ADs may be required.

6. The note about EASA AD is for reference only. The AD says “EASA AD 2007-0143 refers.” It does not incorporate the EASA AD by reference. Operators must follow the CASA AD; they cannot simply comply with the EASA AD and assume it is sufficient. The CASA AD may have a different effective date or service bulletin reference.

7. Compliance must be recorded. Although not stated in the AD, maintenance records must reflect the accomplishment of the AD, including the part numbers of the DECU, the modification status, and the service bulletin reference. This is a general regulatory requirement. Failure to document can lead to non-compliance findings during audits.

1. Obtain the service bulletin. The operator or maintenance organisation must acquire Turbomeca Mandatory Service Bulletin No A298 73 0244 Update 1 dated 30 March 2007 update. This bulletin contains the specific engineering instructions, parts list, and procedures for replacing the DECU with one incorporating Mod TU 244C. It may also specify any post-installation testing.

2. Plan the replacement. For each Makila 1A2 engine on the fleet, schedule the DECU replacement before 30 November 2008. Consider the compatibility rule: if the engine is to be modified before the other engine, ensure the other engine is already at TU 230C or also being upgraded at the same time. The easiest path is to upgrade both engines on the same helicopter during a single maintenance visit to avoid the pairing constraint.

3. Source the modified DECU. The service bulletin will indicate whether the complete DECU must be replaced or if the software can be upgraded via a kit. The operator must order the correct part. Lead time may be significant, so early ordering is prudent.

4. Perform the work. The replacement must be carried out by a person or organisation approved under CASR Part 145 (maintenance organisation) or by a LAME with appropriate authorisation. The work should follow the bulletin step by step.

5. Document compliance. After completion, the maintenance release must include reference to this AD and the service bulletin. Enter the details in the engine logbook or airframe logbook as appropriate. Retain evidence of the DECU part number and modification status.

6. Manage ongoing compatibility. After the upgrade, whenever an engine is removed and reinstalled, or a replacement engine is fitted, verify that the other engine meets the pairing condition. This should be part of the maintenance planning process.

7. Monitor for further amendments. CASA may issue additional ADs if the software requires further updates. The operator should maintain a system to track AD compliance for all components.

8. Seek alternative means if needed. If compliance by the deadline is impossible due to parts shortages or other constraints, apply to CASA for an extension or an alternative means of compliance under CASR Part 39. This is not guaranteed, but it is the only legal pathway to deviate.

9. Consider the cost benefit. The AD imposes a discrete cost. For operators planning future fleet retirements or major overhauls, the timing of the upgrade should be integrated with other scheduled maintenance to minimise downtime. The compatibility rule may force early upgrades on healthy engines - a deadweight cost.

10. Review lease agreements. If the engine is leased, the lessor may have requirements about AD compliance. The operator should notify the lessor and confirm cost allocation. Failure to comply could affect the lease contract.