AD/SMA/2 Amdt 1 - Engine Electronic Control Unit

An airworthiness directive (AD) is a mandatory regulatory instrument issued under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations (CASR) Part 39. It requires the aircraft owner or operator to inspect, modify, replace, or restrict the operation of an aircraft or component within a specified timeframe. Non‑compliance renders the aircraft unairworthy and can lead to enforcement action including fines, suspension of certificates, or prosecution. The AD under analysis is an amendment to an earlier directive and therefore also has the full force of law.

The electronic control unit (ECU) is a component of the SMA SR305‑230 and SR305‑230‑1 engines - these are heavy‑fuel piston engines used primarily on light utility and trainer aircraft. The ECU manages engine parameters such as fuel mixture, ignition timing, and power output. A malfunction that causes an uncontrolled power increase is inherently dangerous because it may lead to loss of control, particularly during ground operations (engine start or warm‑up) when the aircraft may be near people or obstacles.

The concept of part number (P/N) and serial number (S/N) is central to the AD. The applicability table lists twelve specific P/Ns, such as SF01160009‑0 and SP01160051‑1. The AD applies only if the ECU bears one of those P/Ns and the S/N is 131 or below, with four excepted S/Ns (70, 71, 83, 88). This means that ECUs with S/N above 131, or the excepted ones, are not subject to the immediate restriction and replacement requirement in Requirement 2 - although Requirement 3 still mandates replacement of “all remaining affected P/N ECU” regardless of S/N, so those exempted by serial number from the urgent action are nonetheless caught by the later blanket replacement. The wording is ambiguous: Requirement 2 applies only to ECUs with P/N listed and S/N 131 or below (except four). Requirement 3 then says “Replace all remaining affected P/N ECU” - meaning ECUs with affected P/N but S/N above 131 or the excepted ones. The timeline differs: Requirement 2 must be complied with immediately after the determination; Requirement 3 must be complied with not later than 31 March 2007.

A service bulletin (SB) is a manufacturer‑issued document describing a modification or inspection. Here, SMA SB‑01‑76‑005 provides the installation instructions for the replacement ECU. The AD requires compliance with that SB “or later EASA approved revision”. This creates a dynamic link: if the manufacturer revises the SB and EASA approves it, the new revision automatically becomes the required method. Operators must stay aware of any changes.

A ferry flight is a one‑time flight to reposition the aircraft to a maintenance facility. The AD permits such a flight for the purpose of ECU replacement, but only if the pilot is prepared for a sudden power increase. This is a limited exception to the general prohibition on operating the aircraft with the defective ECU. The ferry flight is not an alternative to replacement; it merely allows the aircraft to be moved to a place where the replacement can be done.

The AD references EASA Emergency AD 2007‑0033, indicating that the Australian rule mirrors a European action. This is common for parts certificated under bilateral agreements. The background notes that EASA advised the engine manufacturer of the problem, implying that the directive is reactive to foreign regulatory information.

The AD directly affects any person or organisation that owns, operates, or maintains an aircraft fitted with an SMA SR305‑230 or SR305‑230‑1 engine that has an ECU bearing one of the twelve listed part numbers. According to Note 1 of the AD, these engines are known to be installed on, but not limited to, Cessna 182 and Reims F182 series aeroplanes. In Australia, that fleet is relatively small - perhaps several dozen aircraft used by flight schools, private owners, and aerial‑work operators. The AD thus imposes a concentrated cost on a niche market with little ability to spread the expense across a large manufacturing base.

Maintenance organisations (MROs) that service these engines must familiarise themselves with the SB and have the tooling and training to perform the ECU replacement. They also need to manage the supply chain for the replacement ECU SP01160089‑3. If that part is unavailable or has long lead times, MROs will face scheduling pressures and may need to advise customers of extended downtime. The spare‑parts prohibition in Requirement 4 also affects parts distributors and brokers: after 31 March 2007, they cannot sell or install any of the twelve listed ECU part numbers on any SMA SR305‑230 engine, which reduces the value of their inventory. Anyone holding a stock of those ECUs (whether as new spares or serviceable removed units) will suffer a financial loss unless they can return them to the manufacturer or sell them for non‑aviation use - itself unlikely.

Operators are the most impacted. They must immediately determine the P/N and S/N of their installed ECU (Requirement 1 - before further flight after 7 March 2007). If the ECU is affected, they face a choice: either immediately cease operations (except for a single ferry flight) and arrange replacement, or schedule the ferry flight quickly to avoid grounding. The compliance timeline is tight: Requirement 3 demands replacement of all affected ECUs (by P/N regardless of S/N) by 31 March 2007. Given that the AD becomes effective on 7 March, operators have less than four weeks to replace every affected ECU in their fleet. For operators with multiple aircraft or those based in remote locations, this creates logistical strain and possible loss of revenue during the grounding period.

The AD also indirectly affects insurance providers, financiers, and lessors. An aircraft that is not in compliance with an AD may be considered unairworthy, which can void hull and liability insurance coverage. Lease agreements often require the lessee to maintain the aircraft in an airworthy condition; non‑compliance could be a breach of contract. Buyers of used aircraft will place a premium on documentation proving that the ECU has been replaced properly.

Finally, the AD affects the manufacturer SMA and the regulatory chain. EASA and CASA coordinated on this action. The economic impact on the manufacturer is two‑fold: they incur the cost of producing the replacement ECUs (SP01160089‑3) and issuing the service bulletin, but they also potentially benefit from increased sales of the new part. Whether this creates a perverse incentive - a manufacturer self‑certifying a problem to drive replacement sales - cannot be determined from the AD alone, but it is a risk in any design‑change regulatory action.

The AD creates several discrete duties for the operator (or owner, if different) and corresponding rights, predominantly the right to perform a ferry flight and to rely on the manufacturer’s service bulletin as the approved method.

Duty 1 - determination of ECU identity (Requirement 1). Before further flight after 7 March 2007, the operator must ascertain the part number and serial number of the ECU installed. This duty applies regardless of whether the operator believes the aircraft is affected. It is a proactive inspection requirement that triggers further obligations. The cost and time of this inspection - essentially reading the data plate - is minimal, but the operator must document the result.

Duty 2 - operating restriction and replacement (Requirement 2). If the ECU has a P/N listed in the applicability and an S/N of 131 or below (excepting S/Ns 70,71,83,88), the operator must not operate the engine except under the ferry‑flight provision in the next paragraph. The operator must then remove and replace the ECU with the approved part per SB‑01‑76‑005. This duty is immediate - compliance time is “immediately after the Requirement 1 determination”. In practice, that means the aircraft is grounded unless a ferry flight is conducted.

Right - one ferry flight (implied by the text). The AD explicitly states: “One ferry flight to a location capable of completing the ECU replacement is allowed. The pilot should be ready to react appropriately to a sudden power increase.” This is a conditional right: the flight must be solely for the purpose of repositioning to a maintenance facility; the pilot must accept the risk; and the ferry flight must be conducted before the replacement. The AD does not impose a time limit on the ferry flight itself, but it is a one‑time allowance. Operators cannot use the aircraft for revenue‑generating passenger or cargo flights during the ferry flight; it is essentially a non‑revenue repositioning.

Duty 3 - blanket replacement of all affected P/N ECUs (Requirement 3). Regardless of S/N, any ECU with an affected P/N must be replaced with SP01160089‑3 by 31 March 2007. This catches the ECUs that were exempted by S/N from the immediate operating restriction. It also covers any affected ECUs on spare engines or in storage that are later installed. The deadline is absolute; after 31 March, any aircraft with an unreplaced ECU is not airworthy.

Duty 4 - prohibition on installing affected ECUs as spares (Requirement 4). After 31 March 2007, no person may install any of the listed P/N ECUs as a replacement part on any SMA SR305‑230 or SR305‑230‑1 engine. This applies even if the ECU is new, serviceable, and from a non‑affected S/N range. The effect is to retire the entire population of those P/Ns from service. Spare parts held in inventory become essentially worthless unless they can be returned to the manufacturer for credit.

Right - reliance on CASA as delegate. The AD is signed by a delegate of CASA, so the operator has the right to treat the AD as legally binding and to use it as a defence if challenged for performing the required work (e.g., against a contractual claim for downtime). The AD also incorporates the SMA service bulletin by reference; the operator may rely on that document as the approved technical data.

The AD does not provide a right to appeal or seek an alternative method of compliance (AMOC) in its text. However, under CASR Part 39, an operator can typically request an AMOC from CASA. The absence of an explicit AMOC clause in this AD does not preclude that possibility, but it is not guaranteed. Operators should be aware that the timeline is extremely tight, and a delay in obtaining an AMOC could result in non‑compliance.

The AD itself does not specify penalty amounts or enforcement procedures; those are found in the parent legislation - the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998 (CASR). Under CASR Part 39, a failure to comply with an airworthiness directive that applies to an aircraft is a contravention of a safety regulation. Depending on the provision, penalties can include fines (currently up to thousands of penalty units per contravention) and, for serious or repeated breaches, imprisonment. The operator (the person responsible for the aircraft) is primarily liable, but the owner, lessor, or maintenance organisation could also face liability if they directed or permitted non‑compliant operation.

In practical enforcement terms, CASA typically issues a notice of proposed suspension or cancellation of the aircraft’s certificate of airworthiness if an AD is not complied with. An aircraft that is flown while not airworthy because of a known non‑compliance risks being grounded during a ramp check or following an incident. Insurance implications are severe: most aviation insurance policies exclude cover for damage or liability arising from operation in breach of an AD. Therefore, even if CASA does not take enforcement action, the economic consequence of an accident could be total loss without indemnity.

The AD includes a ferry flight allowance, which is a form of limited operational permission. If a pilot conducts a ferry flight without being “ready to react appropriately to a sudden power increase” - a subjective requirement - and an accident occurs, enforcement could follow for operating contrary to the AD’s condition. The AD does not define what “ready to react” means, leaving it to the pilot’s discretion and later regulatory interpretation.

The background notes that the original issue of the AD had already required inspection and, if necessary, replacement. This amendment expands the requirement; any operator who had complied with the original AD by only inspecting and not replacing may now need to perform additional work. Those who had not complied with the original AD are now in a worse position - they must still meet the new deadlines, and CASA may take retrospective enforcement for the earlier non‑compliance.

Because the AD is issued by a CASA delegate and is effective on the date of publication, there is no grace period for operators who receive notice after the effective date. The duty to determine the ECU details exists “before further flight after 7 March 2007”. An operator who is unaware of the AD until after that date is still legally required to have achieved compliance before flying. This places a heavy burden on operators to monitor CASA’s airworthiness directive system, and on flying schools or fleet operators to quickly disseminate the information.

The AD references EASA Emergency AD 2007‑0033. If the Australian AD is not identical in scope or timeline, conflicts could arise for aircraft that operate under both regulatory jurisdictions (e.g., Australian‑registered aircraft flying in Europe). In such cases, the more stringent rule applies, but the operator must ensure compliance with both. Non‑compliance with either can lead to enforcement by that jurisdiction.

This Airworthiness Directive operates within a layered regulatory framework. Its immediate legal force comes from the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations (CASR) Part 39 - the part dealing with airworthiness directives. Under regulation 39.015, a person must not operate an aircraft unless each airworthiness directive that applies has been complied with. Therefore, this AD is directly enforceable, and non‑compliance triggers the penalty provisions of the Act and regulations.

The AD also interacts with EASA regulations, as the affected engines are European‑certified. The background states that EASA Emergency AD 2007‑0033 refers. Under the bilateral airworthiness agreement between Australia and the European Union, CASA may adopt EASA ADs with or without variation. This AD appears to be an Australian adoption of the EASA emergency AD, with adaptations to the Australian context (e.g., specifying the applicable serial numbers and part numbers that might differ from the European version). Practitioners should check whether the EASA version requires different actions or a different timeline, especially if the aircraft is operated in multiple jurisdictions.

The AD interacts with contract law and commercial agreements. For aircraft under lease or finance, the lessee/financier typically requires the aircraft to be maintained in an airworthy condition and in compliance with all ADs. Non‑compliance may constitute an event of default. The cost of the replacement ECU and downtime may be borne by the operator, but if the engine is still under warranty or a power‑by‑the‑hour agreement, there may be a question of who pays for the modification. The AD does not address cost allocation; that is left to private contracts.

Insurance policies generally cover aircraft if they are maintained in accordance with regulatory requirements. Operation contrary to an AD could void coverage. The ferry flight provision adds complexity: if an accident occurs during the ferry flight, the insurer may argue that the pilot was operating an aircraft known to have a defective ECU (since the replacement is not yet done) and that this constitutes an unairworthy condition. The AD’s express allowance of the ferry flight may provide a defence, but the insurer may still deny cover if the pilot failed to take precautions (e.g., if the pilot did not brief for a sudden power increase).

The AD also interacts with workplace health and safety laws. In Australia, under the model Work Health and Safety Act, an employer (including an aircraft operator) has a duty to ensure, so far as is reasonably practicable, the health and safety of workers and others. Operating an aircraft with a known ECU defect, even during an authorised ferry flight, could be argued to breach that duty if an incident occurs. The ferry flight allowance does not automatically exculpate the employer from WHS liability; it simply removes the regulatory prohibition.

For maintenance providers, the AD effectively mandates the use of SMA’s service bulletin. Under CASR Part 145, an approved maintenance organisation must perform work in accordance with approved data. The service bulletin, being incorporated by reference in the AD, becomes approved data. The MRO must also ensure that the replacement ECU is correctly documented and that the removal of the old ECU is recorded. The prohibitions on re‑installation of old ECUs affect the MRO’s stores and inventory management.

Finally, the AD may have cross‑border implications for imported aircraft, used‑parts sales, and aircraft registration. An aircraft that is imported into Australia after 31 March 2007 with an affected ECU installed would not be airworthy and could not be registered until the replacement is performed. Similarly, an aircraft that is exported from Australia to a country that has not adopted this AD might still face operational restrictions if that country’s regulator accepts the CASA AD.

The original airworthiness directive AD/SMA/2 was issued as a single document effective 17 October 2006. That original issue required inspection to determine the ECU serial number and, if necessary, replacement of the ECU. It also allowed a one‑time ferry flight to a location capable of effecting replacement. According to the background of this amendment, the original directive was considered a “temporary corrective action”.

This amendment (Amdt 1) was signed on 27 February 2007 and becomes effective 7 March 2007. It makes four substantive changes to the original directive. First, it clarifies the applicability by including a list of specific part numbers in a table, replacing a possibly vaguer original description. Second, it adds that the affected engines may be installed on Reims F182 aeroplanes (not just Cessna 182). Third, it identifies a replacement ECU part number (SP01160089-3) and requires replacement of all affected ECUs irrespective of their serial number. The original issue may have only required replacement based on serial number (the amendment text says “over a period of time, the alteration of one ECU electronic component can cause a rapid uncontrolled power increase … several occurrences have already been reported”). Fourth, it adds Requirement 4, which prohibits the installation of an affected ECU as a spare part after 31 March 2007. This goes beyond the original directive, essentially retiring the entire population of those part numbers from service.

The compliance dates are tiered. Requirement 1 (determine P/N and S/N) must be done before further flight after 7 March 2007. Requirement 2 (immediate restriction and replacement) must be done immediately after the determination. Requirement 3 (replace all remaining affected P/N ECUs) has a deadline of 31 March 2007. Requirement 4 (spare prohibition) applies after 31 March 2007. The effective date of the amendment is 7 March 2007.

The amendment also updates the Note to reference EASA Emergency AD 2007-0033, confirming the European basis.

There is no further amendment history provided in the source. It appears that this AD may have been superseded by later actions, but the source does not indicate that. The deep dive can only discuss what is in the text.

The source text does not mention any litigation related to this AD or the underlying defect. No cases are cited. Therefore, any litigation history must be inferred from general principles, not from the AD itself. It is possible that the reported “several occurrences” of rapid uncontrolled power increase led to incident or accident reports, but the AD does not reference any legal proceedings. The EASA emergency AD may have been prompted by incident investigations, but those are not necessarily litigation.

From a broader perspective, airworthiness directives are rarely the subject of direct litigation because operators typically comply to avoid grounding. However, disputes can arise over cost allocation between lessor and lessee, or over liability after an accident. For example, if an aircraft owner did not comply with this AD and an accident occurred due to ECU malfunction, a civil claim for negligence or breach of statutory duty could be brought. The AD would serve as evidence of the standard of care required. The ferry flight provision could be scrutinised: was the pilot adequately prepared? Did the operator properly brief the pilot? If not, liability may attach.

Insurance coverage disputes could also lead to litigation. If an insurer denies a claim on the basis that the aircraft was operated in a non‑airworthy condition, the policyholder might sue. The outcome would depend on the policy wording and whether the ferry flight was explicitly permitted as an exception.

There may also be judicial review proceedings if an operator challenges the AD itself - e.g., arguing that the regulator did not follow proper procedure or that the defect evidence was insufficient. However, courts generally defer to aviation safety regulators on technical matters. No such case is referenced.

Given the absence of case law in the source, the practitioner should treat this AD as a regulatory instrument that has not been tested in court, at least not in public record. The compliance burden is clear, and the safest approach is strict adherence.

Several nuances in the AD could catch out unwary operators or their advisors.

1. The serial number exception is narrow and may be misleading. Requirement 2 excepts S/Ns 70, 71, 83 and 88 from the immediate operating restriction. However, Requirement 3 requires replacement of “all remaining affected P/N ECU” by 31 March 2007 - that includes those excepted serial numbers. So the exception only delays the replacement deadline; it does not provide an exemption. Operators with those S/Ns might mistakenly believe they have no obligation, when in fact they must replace by 31 March. Furthermore, the phrase “all remaining affected P/N ECU” could be read as ECUs that have the affected P/N but were not covered by Requirement 2. That is the logical interpretation. But if an operator has an ECU with S/N 70 (excepted), they must still comply with Requirement 3 by 31 March. The AD does not say “except as noted in Requirement 2”; it uses the word “remaining”, which is ambiguous. A strict reading: Requirement 2 applies only to ECUs with S/N 131 or below except the four; Requirement 3 applies to “all remaining” - i.e., those not covered by Requirement 2? That would include S/N above 131 and the excepted four. But then what about ECUs with S/N 131 or below that are excepted? They are not covered by Requirement 2, and they are among the “remaining”. So they are caught. The upshot: no affected P/N ECU is exempt from eventual replacement; the only distinction is timing. Operators must replace all affected P/N ECUs by 31 March, regardless of S/N.

2. The ferry flight condition is a subjective risk. The AD says “The pilot should be ready to react appropriately to a sudden power increase.” The word “should” is not “must”, but in the context of a directive, it imposes an expectation. If a pilot conducts a ferry flight and suffers a sudden power increase and reacts poorly, they may be found in breach of the AD for not being ready. The AD does not define “appropriate reaction” - perhaps throttle back to idle, or shut down. This ambiguity creates legal risk. Furthermore, the ferry flight is only allowed to a location “capable of completing the ECU replacement”. If the pilot chooses a destination that cannot do the replacement, the flight may be non‑compliant. The AD does not require prior approval, but the operator bears the burden of selecting a suitable facility.

3. The replacement part SP01160089-3 may have its own issues. The AD assumes that this part is safe and available. But if the replacement part later turns out to have a different defect, the AD’s reliance on it could create problems. Operators should check if there are later service bulletins or ADs affecting that part. The AD also allows “later EASA approved revision” of the service bulletin, but not a revision of the replacement part itself. So if SMA later releases a SP01160089-4, it is not automatically approved; only the SB revision is dynamic.

4. The spare parts prohibition effectively creates a deadline for all parts in inventory. Anyone holding a stock of the listed ECU part numbers after 31 March 2007 cannot lawfully install them. That makes them essentially worthless for aviation use. The AD applies to “any aircraft with a SMA SR305-230 or SR305-230-1 engine”. So even if the part is intended for a different installation, it is prohibited. Parts removed from aircraft must be accounted for and cannot be resold as serviceable unless they are scrapped. This may surprise parts brokers who are not directly involved with the aircraft fleet.

5. The effective date is earlier than the publication date for some operators. The AD is signed on 27 February 2007 and becomes effective 7 March 2007. For operators who receive notice after that date via the CASA website or other channels, the requirement to determine P/N before further flight after 7 March may already be impossible to meet if they flew on that date. They could be inadvertently non‑compliant. The AD does not provide a grace period for knowledge.

6. The note “EASA Emergency AD 2007-0033 refers” implies a parallel foreign obligation. For operators who fly internationally, they may need to comply with both ADs if they differ. It is not clear if the CASA version is identical. Australian operators who fly to Europe may find that the EASA version has a different compliance date or different excepted S/Ns. They should check the text of the EASA AD.

7. The background states “several occurrences have already been reported during engine start or during engine warm‑up.” The ferry flight allowance permits flight, but the risk is most acute during start and warm‑up. The pilot must start the engine to begin the ferry flight, thus exposing him/herself to the very scenario that caused the reported problems. The AD does not provide any additional procedure for safe start. The operator may need to develop a specific procedure beyond “be ready”.

Compliance with AD/SMA/2 Amdt 1 involves a sequence of actions, documentation, and verification. The following steps apply to any person responsible for the aircraft (owner, operator, or registered operator under CASR Part 47).

Step 1 - Determine ECU part number and serial number (Requirement 1). Before further flight after 7 March 2007, inspect the ECU data plate. Record the P/N and S/N in the aircraft maintenance records. If the P/N is not among the twelve listed in the applicability table, no further action is required under this AD. However, compliance with Step 1 must still be documented to show that the operator has met the threshold duty. A simple logbook entry or maintenance release suffices. If the P/N is one of the twelve, proceed to Step 2.

Step 2 - Assess S/N and immediate restriction (Requirement 2). If the ECU P/N is affected and the S/N is 131 or below, except 70,71,83,88, the aircraft must not be operated except for a single ferry flight to a location capable of performing the replacement described in Step 3. The operator must arrange for the ferry flight or ground the aircraft. The ferry flight should be planned with the pilot briefed that a sudden power increase is possible. The operator should document the decision to make the ferry flight, the destination, and the pilot’s acknowledgement of the risk.

Step 3 - Replace ECU with approved part (Requirement 2b and Requirement 3). Obtain an ECU with part number SP01160089-3. This is the only acceptable replacement part. Remove the existing ECU and install the new one in accordance with SMA Service Bulletin SB‑01‑76‑005, dated 15 December 2006, or a later EASA‑approved revision. The service bulletin will specify the procedures for removal, installation, and any necessary adjustments or software loading. The replacement must be performed by appropriately authorised maintenance personnel (e.g., LAME holder or approved organisation). After installation, the aircraft must be tested as required by the SB.

If the original ECU had S/N 131 or below (except the four), the replacement must be done immediately (Step 2b). If the original ECU had an affected P/N but S/N not in that range, the replacement must be completed no later than 31 March 2007 (Requirement 3). For aircraft that had already complied with the original AD/SMA/2 by replacing the ECU earlier, the operator must verify that the replacement part is SP01160089-3. If the earlier replacement used a different P/N, it is not compliant, and the operator must now install SP01160089-3.

Step 4 - Document compliance. In the aircraft logbook or maintenance records, enter the following: the P/N and S/N of the removed ECU; the P/N and S/N of the installed SP01160089-3; the date of removal and installation; the SB reference used; the signature and licence number of the person performing the work; and a statement that AD/SMA/2 Amdt 1 has been complied with. Retain the removed ECU, but do not re‑install it anywhere - it is now prohibited from further use as a spare (Requirement 4). The removed unit may be returned to SMA or scrapped.

Step 5 - Monitor for revised SB or further AD action. The AD allows later EASA‑approved revisions of SB‑01‑76‑005. The operator should check with the manufacturer or CASA periodically to see if a later revision is required. Also, the replacement part SP01160089-3 may itself become subject to a future AD. The operator should subscribe to CASA’s airworthiness directive updates.

Step 6 - Spare parts management. Any inventory of the twelve listed ECU part numbers must not be installed on any SMA SR305‑230 engine after 31 March 2007. If the operator holds such spares, they should either return them to the manufacturer for credit or scrap them. Keeping them for future use is not permitted. The AD does not require removal of ECUs from spare‑stock before 31 March, but after that date installation is prohibited. Therefore, the operator should dispose of them before the deadline to avoid accidental re‑installation.

Step 7 - Aircraft‑wide compliance check. For operators with a fleet, each aircraft must be dealt with individually. A single logbook entry may reference multiple aircraft, but each aircraft’s records should reflect compliance. For aircraft not yet flown after 7 March, the determination under Requirement 1 must be done before that flight. For aircraft that were already in storage, the same rules apply.

Step 8 - Consider an Alternative Method of Compliance (AMOC) if needed. If the operator cannot obtain the replacement part before 31 March 2007, or if there are unique circumstances, the operator may apply to CASA for an AMOC under CASR Part 39. However, the AD does not explicitly mention AMOC, and the deadline is tight. An AMOC application should be made as early as possible, with supporting evidence of the proposed alternative design or procedure that achieves an equivalent level of safety. There is no guarantee of approval.