AD/THIELERT/1 Amdt 2 - Engine Failure Due to Electrical System Failure

The central concept is an airworthiness directive, which is a legally enforceable order issued by CASA under the Civil Aviation Regulations to correct an unsafe condition in an aircraft, engine, or component. Non-compliance renders the aircraft unairworthy and unlawful to operate. The directive addresses a specific failure mode: an electrical malfunction of the alternator. According to the background, during tests the engine manufacturer found that if the battery line, battery relay, or battery itself fails, the engine may fail if the alternator has an electrical malfunction. The directive does not specify the exact nature of the malfunction, but the solution targets the alternator and its voltage regulation. The concept of alternator sets is introduced: these are pre-configured assemblies combining the alternator with an integrated regulator, tailored to different aircraft types (Diamond vs. all other). For existing installations, the directive provides three alternative modification methods: (a) replace only the alternator with a newer part number (R3 variant), (b) replace with an alternator set that includes the regulator, or (c) install a stabilising capacitor. The stabilising capacitor option suggests that the failure mode may involve electrical noise or transient voltage issues that a capacitor can dampen, though the directive does not explain the engineering rationale. Another key concept is the battery capacity check required at each 100 hourly inspection until the electrical system modification is completed. This check follows the Gill Aircraft Battery Service Manual, specifically the "Continued Airworthiness Determination for Gill Aircraft Batteries" procedure. This manual is incorporated by reference. The directive distinguishes between existing installations (aircraft already fitted with the engine) and new installations (presumably new aircraft or engine retrofits after the effective date), which have different part numbers. The amendment also introduces a grandfathering provision for Diamond aircraft that had already replaced alternators under earlier issues of the directive: those replacements are considered acceptable for compliance with this amendment, meaning no rework is required. The compliance time frames create a cascade of obligations: battery checks at 100 hourly intervals until the modification is done at the next 300 hourly inspection, with an absolute deadline of 30 April 2005. This creates a hard stop that may force operators to complete the modification earlier than the next 300 hourly interval if that inspection would fall after 30 April.

The directive directly affects owners and operators of any aircraft fitted with a TAE125-01 engine. This engine is typically found in light aircraft, most commonly Diamond DA40 and DA42 series, but also in other aircraft types that have been retrofitted or originally equipped with this engine. The AD does not list specific aircraft models other than referencing "Diamond aircraft" in the part numbering, so all operators with this engine are caught. Maintenance organisations that perform inspections, modifications, and battery capacity checks are also affected. They must be familiar with the Thielert Service Bulletin TM TAE 125-008 Revision 2, the Gill battery manual, and the specific part numbers. They need to ensure they have access to the correct alternator sets and the stabilising capacitor components. Parts distributors and suppliers are affected because demand shifts to the new part numbers. They must manage inventory for the different alternator sets for Diamond vs. other aircraft, which are not interchangeable. Manufacturers and supplemental type certificate (STC) holders who have approved installations using the TAE125-01 engine are affected because their installation documentation must align with the directive. If their STC specifies a different alternator, the AD overrides it. Diamond Aircraft specifically get a grandfathering benefit, but only if they complied with earlier AD issues. Other aircraft in the "all other" category do not get that benefit. Insurers of aircraft may take an interest: non-compliance with an AD is a breach of airworthiness and could void insurance coverage. Regulators (CASA itself and potentially other national aviation authorities) are affected because this AD is harmonised with the German LBA AD and an EASA approval, affecting certificate holders who operate under bilateral agreements. The battery capacity check also affects battery manufacturers and service providers, as the Gill manual is referenced. The compliance burden is concentrated on a relatively small population of aircraft, but each operator faces significant direct outlay for parts and labour, plus opportunity cost of aircraft downtime. The directive does not offer any compensation for these costs. The distinction between Diamond and other aircraft creates an uneven compliance landscape: Diamond operators who acted early are grandfathered, but other aircraft operators must use the new part numbers even if they had already changed alternators under earlier AD versions.

The primary duty is to modify the electrical power supply system by accomplishing one of three specified modifications, in accordance with relevant aircraft manufacturer or STC holder documentation, and with reference to Thielert Service Bulletin TM TAE 125-008 Revision 2. The three options are prescribed in detail: (a) replace alternator P/N 02-7150-55002R2 with P/N 02-7150-55002R3; (b) for existing installations, replace the alternator with an alternator set (Diamond: P/N 02-7150-55008R1; all other: P/N 02-7150-55016R1); or (c) install a stabilising capacitor. Note that option (c) does not require replacing the alternator itself, only adding a capacitor. This may be a lower-cost route, but the directive does not mandate a particular documentation path: it must be "in accordance with relevant aircraft manufacturer or STC holder documentation". If that documentation is not available or does not describe a stabilising capacitor installation, compliance may be difficult. The duty to check battery capacity at each 100 hourly inspection until the electrical system modification is complete. This is an ongoing, repetitive duty with its own compliance schedule. For new installations (after 6 April 2005), the duty is to use only the specified alternator sets: for Diamond aircraft P/N 02-7150-55800R1, for all other aircraft P/N 02-7150-55018R1. There is no option to use the older parts. The directive also creates a right for operators who have already complied with previous issues on Diamond aircraft: their earlier alternator replacements (presumably using the earlier part numbers) are considered acceptable for compliance with this amendment (Note 1). This avoids requiring Diamond operators to rework their already modified aircraft. However, there is no equivalent right for non-Diamond operators who might have complied early. They must comply with the current part numbers. Operators also have a limited right to choose among the three modification options for existing installations, but that choice is constrained by availability of parts and approved data. The directive does not impose a duty to notify CASA of compliance; the duty is to ensure the aircraft conforms and is maintained in an airworthy condition with proper documentation. The operator's right to continue operating the aircraft is contingent on compliance with both duties (battery check and modification by deadline). The battery check duty does not cease until the modification is accomplished, so an operator who delays the modification accumulates more battery checks, incurring additional maintenance cost.

The AD itself does not specify penalties for non-compliance. However, as a CASA airworthiness directive, it is issued under the Civil Aviation Regulations (CAR) 1988, specifically Part 39 (Airworthiness Directives). Non-compliance with an AD is a breach of the requirement that an aircraft must be maintained in an airworthy condition. The Civil Aviation Act 1988 provides for enforcement measures. Under the Act, CASA can suspend or cancel an aircraft's certificate of airworthiness or registration for non-compliance. Operating an aircraft that does not conform to an applicable AD is also a breach of the operating rules. While the source does not quantify penalties, the general provisions of the Act allow for civil penalties. For a first offence, an individual may face a penalty of up to 50 penalty units (currently $13,750) and a body corporate up to 250 penalty units ($68,750). However, these amounts are not fixed in the AD and are subject to amendment; the precise figures at the time of the AD were lower. Additionally, CASA may issue infringement notices (on-the-spot fines) for less serious breaches. The AD is enforceable by CASA inspectors, Australian Federal Police, or other authorised officers. In practice, an aircraft found to be non-compliant may be grounded immediately, with the operator responsible for any economic loss. The directive does not offer any grace period or alternative means of compliance beyond what is stated. The background notes that the original directive was intended to prevent in-flight engine failure, so an operator who knowingly operates a non-compliant aircraft could also face charges related to endangering the safety of the aircraft or persons on board, which carry higher penalties and potential imprisonment. The repetitive battery check requirement until modification is a strong enforcement lever: operators must produce logbook entries showing the check was done, otherwise the aircraft is non-compliant. The absence of a specific penalty schedule in the AD means that enforcement discretion lies with CASA. However, given the safety-critical nature of engine failure, enforcement is likely to be strict. There is no provision for exemptions. Operators who cannot obtain parts or documentation within the compliance time face a hard choice: ground the aircraft or seek a diplomatic extension from CASA, which is not provided for in this AD.

The AD explicitly references the German LBA Airworthiness Directive D-2004-457R2 and EASA approval 2005-1968. This indicates that the Australian AD is harmonised with European regulatory action, likely because the engine is of European design. An operator whose aircraft is registered in multiple jurisdictions must comply with the most restrictive requirement. The AD also incorporates by reference Thielert Aircraft Engine GmbH Service Bulletin TM TAE 125-008 Revision 2 dated 4 February 2005, and Gill Aircraft Battery Service Manual (Q01-1120) Chapter 7.7. These documents become binding. The AD is issued under the Civil Aviation Regulations 1988 (Cth), specifically Part 39 which governs airworthiness directives. It overrides any inconsistent maintenance or modification provisions in the aircraft's maintenance manual or operator's continuing airworthiness management exposition unless those manuals specifically incorporate the AD. It interacts with the Civil Aviation Safety Regulations 1998 (CASR) Part 21 (Design and production of aircraft) in that the modifications prescribed must be made in accordance with approved data (i.e., the service bulletin or manufacturer documentation). The AD also interacts with the aircraft's type certificate or supplemental type certificate. If an STC holder has approved a different alternator configuration, that STC is effectively modified by the AD unless the STC already addresses the unsafe condition. The AD does not mention any interaction with maintenance release requirements (CASR Part 145) but any maintenance organisation performing the work must hold appropriate approvals. The battery capacity check references an industry standard, the Gill manual, which is not a regulatory document per se but becomes mandatory by reference. There is no conflict with any other Australian AD specifically mentioned, but operators must ensure compliance with all applicable ADs for the engine and aircraft. The AD also has implications under contract and insurance law: a lease or purchase agreement may require compliance with all ADs, and an insurer may deny coverage for a loss if the aircraft was operated in breach of an AD. The directive does not affect other legal obligations such as workers' compensation for maintenance staff or environmental regulations for disposal of old alternators. It is a standalone technical regulation that operates within the broader framework of Australian aviation safety law.

The original issue of this AD became effective on 23 December 2004. The background does not detail its content, but it presumably required the electrical system modifications now seen in the current version. Amendment 1, effective 19 January 2005, extended the compliance time and introduced the repetitive battery capacity check requirement. It also made minor formatting changes. Amendment 2, the present version effective 6 April 2005, introduces two substantive changes: first, for existing installations, it revises the part numbers for replacement alternator sets for all aircraft except Diamond aircraft. In the original and Amendment 1, the part numbers for existing installations in non-Diamond aircraft are not specified in this source, but Amendment 2 introduces specific sets (P/N 02-7150-55016R1 for all other, replacing what was likely a single part number). Second, Amendment 2 adds entirely new requirements for new installations (requirements 3a and 3b), specifying separate alternator sets for Diamond and others. This suggests that between Amendment 1 and Amendment 2, the manufacturer identified that new installations needed different configuration. The compliance deadline for requirement 1 remains tied to the next 300 hourly inspection but no later than 30 April 2005, which is unchanged from Amendment 1. However, Amendment 2 came into effect on 6 April 2005, only 24 days before the absolute deadline, giving operators little additional time to adapt to the new part numbers if they had already procured parts under Amendment 1 assumptions. The battery capacity check requirement (requirement 2) continues unchanged from Amendment 1. The AD also includes Note 1, which grandfathers prior alternator replacements on Diamond aircraft regardless of whether they used part numbers from the original or Amendment 1. That grandfather clause did not appear in previous versions and is new to Amendment 2. The effective dates show a rapid sequence of regulatory change: three versions in less than four months, reflecting an evolving understanding of the unsafe condition and the necessary corrective actions. This creates uncertainty for operators who may have acted quickly under an earlier version only to face revised part numbers later.

The source does not record any litigation history related to this AD. No cases, appeals, or judicial reviews are mentioned. In Australian administrative law, an airworthiness directive is a legislative instrument made by a delegate of CASA. It can be challenged on grounds of procedural error, unreasonableness, or ultra vires under the Administrative Decisions (Judicial Review) Act 1977 or under the common law. However, because ADs are typically technical and safety-critical, courts rarely overturn them. There is no known public litigation specifically concerning AD/THIELERT/1 or its amendments. The absence of litigation may reflect that the directive is relatively narrow in scope and affects a small fleet. Engine failures resulting from non-compliance could give rise to civil liability under negligence or product liability, but those proceedings would not be litigation of the AD itself. If an operator incurred economic loss from grounding due to parts unavailability, they could theoretically challenge the compliance time as unreasonable, but the background provides a safety rationale that would likely defeat such a challenge. The fact that the AD is backdated (original Dec 2004, Amdt 1 Jan 2005, Amdt 2 April 2005) with short compliance windows could have motivated some operators to seek extension or variation, but if those requests were made, they are not recorded in the source. There is also no known case where a regulator prosecuted an operator for non-compliance specifically under this AD. The litigation history, in sum, is blank. That is not unusual for a safety directive of this kind; most compliance occurs without courtroom dispute, and any judicial review would be a matter of record accessible via CASA's consultation history or AustLII, but the source provides no such references. Therefore, a reader must treat litigation risk as low but not impossible, particularly if an operator were to suffer an accident involving the electrical system and the AD was found to have been unaddressed.

Several aspects of this AD can trap an unwary operator. First, the compliance deadline for requirement 1 is "at the next 300 hourly inspection, but no later than 30 April 2005." If the next 300 hourly inspection is scheduled after 30 April, the operator must perform the modification before that inspection, at an earlier maintenance event. This could mean pulling the aircraft out of service for an unscheduled downtime. Second, the battery check (requirement 2) must be done at each 100 hourly inspection until the main modification is completed. If the 300 hourly inspection (where the modification is done) falls on the same interval as a 100 hourly check, the battery check must still have been done. The operator must track this carefully to avoid logbook gaps. Third, there is a difference in part numbers for Diamond versus all other aircraft for both existing and new installations. Using the wrong alternator set is non-compliance. The risk is increased because the part numbers are visually similar: for example, existing all other uses 02-7150-55016R1, while new all other uses 02-7150-55018R1. Misreading could lead to costly rework. Fourth, the grandfather clause (Note 1) only applies to Diamond aircraft that replaced alternators in accordance with previous issues of the AD. It does not apply to non-Diamond aircraft that might have done early replacements under the original AD. Those non-Diamond operators must redo or upgrade to the new part numbers listed in this amendment. Fifth, the alternative of installing a stabilising capacitor (option c) may appear simpler, but the AD requires it to be done "in accordance with relevant aircraft manufacturer or STC holder documentation". If the manufacturer has not published such documentation for the specific capacitor, this option may be unavailable in practice. The AD does not include a technical description of the required capacitor, so operators cannot simply buy a generic part. Sixth, the directive references the Gill Aircraft Battery Service Manual for the battery capacity check. If the aircraft uses a different battery brand, the check procedure may not be directly applicable, or the manual must be obtained. The AD does not allow a substitute method. Seventh, the compliance for new installations (requirement 3) applies "as of the effective date of this Directive". Any engine installed after 6 April 2005 without the correct alternator set is automatically non-compliant, even if the aircraft was manufactured earlier. Eighth, the timing of Amendment 2 (effective 6 April 2005) within 24 days of the absolute deadline (30 April 2005) gives operators little time to source the new part numbers if they had already ordered parts under Amendment 1 assumptions. The cost of cancelled orders or rushed shipping falls on the operator. Finally, the AD does not provide for alternative means of compliance (AMOC) in its text. An operator with a different engineering solution must apply to CASA separately, and the outcome is uncertain.

Compliance requires a series of steps, each with documentation and timing requirements. Step one: identify all aircraft in the operator's fleet that have a TAE125-01 engine. Separate them by make: Diamond aircraft and all other aircraft. Step two: for each such aircraft, determine its current electrical system configuration. If the aircraft is a Diamond and the alternator was replaced under the original AD or Amendment 1, that replacement is acceptable for this AD (Note 1). No further modification is required, but the battery check requirement must still be observed until the modification was done (if the earlier replacement already satisfied requirement 1, the battery checks cease). For all other aircraft, and for Diamond aircraft that have not yet been modified, proceed to step three. Step three: choose one of the three modifications allowed for existing installations: (a) replace the alternator with P/N 02-7150-55002R3; (b) replace the alternator with an alternator set: for Diamond, P/N 02-7150-55008R1; for all other, P/N 02-7150-55016R1; or (c) install a stabilising capacitor. Obtain the correct parts and the required documentation (Thielert Service Bulletin TM TAE 125-008 Revision 2 and applicable aircraft manufacturer or STC holder data). Step four: schedule the modification at the next 300 hourly inspection, but in any event no later than 30 April 2005. If the next 300 hourly inspection is after that date, bring the modification forward. Step five: until the modification is completed, perform a battery capacity check at each 100 hourly inspection, strictly following Gill Aircraft Battery Service Manual Chapter 7.7. Record the results in the aircraft maintenance log. Step six: for any new installation (engine installed after 6 April 2005), ensure the alternator set is the required part: for Diamond, P/N 02-7150-55800R1; for all other aircraft, P/N 02-7150-55018R1. This applies to new aircraft delivery or engine retrofit. Step seven: maintain all records of the modification, including part numbers, serial numbers, service bulletin compliance, and battery check results. The AD does not require submission of these records to CASA, but they must be available for inspection. Step eight: train maintenance staff on the differences between Diamond and other aircraft part numbers to avoid mix-ups. Step nine: monitor any subsequent CASA actions or manufacturer service bulletins that might supersede this AD. Step ten: if parts are unavailable or the approved data cannot be obtained, the operator must consider grounding the aircraft or seeking a formal exemption or alternative means of compliance from CASA, although the AD itself does not provide a mechanism. In practice, contacting CASA's airworthiness section early is prudent. The battery check obligation is an ongoing cost, incentivising timely completion of the modification to end the check cycle. The total compliance cost includes parts, labour, downtime, and potential premium freight for parts ordered after the amendment.