AD/DO 228/11 - Honeywell CAS 67A ACAS II - LBA STC SA1310

The Directive rests on a small number of tightly specified technical and administrative concepts, each stated in the AD text and constraining how the requirement applies and is implemented.

• Applicability by model, serial number and STC installation date. The AD is limited to particular Dornier 228 models and excludes specified serial numbers. Applicability is further limited to aircraft "modified in accordance with Luftfahrtbundesamt (LBA) Supplemental Type Certificate (STC) No.SA1310 before 31 January 2005." That triple-condition approach narrows the population of aircraft subject to the requirement.

• Specified remedial action tied to a Service Bulletin. The Directive does not authorise alternative fixes in its text. It requires modification "in accordance with Aerotechnic Vertriebs und Service GmbH Service Bulletin DO228-119780-0104 Revision 2 dated 21 December 2006." The Service Bulletin is the operative technical mandatum: it determines the work scope, parts and installation method required by the AD.

• A dual compliance metric set by time and utilisation. Compliance must occur "within 200 flight cycles or 8 weeks, whichever comes first, after the effective date of this Directive." This creates a strict deadline for higher-utilisation aircraft (200 cycles may be reached faster than 8 weeks for some operators) while giving a short calendar-window for low-utilisation aircraft.

• Technical failure mode described. The background recites a particular electrical design deficiency: missing isolation diodes in the heading and attitude valid lines may permit "reverse feed" from the TPU67A processor into open (invalid) lines, so that the navigation "valid" flag may remain set despite a gyro fault. The safety hazard posed is the delivery of "erroneous navigation information" to flight crew. The AD therefore prescribes installation of isolation diodes to "prevent reverse feed of the valid lines."

• Cross-reference to foreign authority. The AD notes "EASA AD 2007-0059 refers," signalling that the matter is the subject of a related European AD and that CASA is aligning its directive with that broader action. The Directive also references the LBA STC SA1310 as the installation basis it is addressing.

• Authority and administrative finality. The AD is signed by a CASA delegate and carries an explicit effective date, establishing the date from which the compliance timeframe runs. The document itself does not set out penalty provisions or enforcement steps beyond the requirement and effective date.

These concepts define the legal and operational shape of the obligation: a narrowly targeted, time-limited mandatory hardware modification that must be performed as specified by a named Service Bulletin on a defined subset of aircraft, with the declared objective of preventing a specific failure mode that can mask gyro faults.

The text identifies a precise set of affected parties by reference to aircraft model, serial number, STC status and the installed equipment. From that textual picture the affected parties are as follows.

• Owners and operators of Dornier 228 aircraft of models 228-100, 228-101, 228-200, 228-201 and 228-212 that were modified under LBA STC SA1310 before 31 January 2005. The AD applies only to aircraft meeting all three conditions. The operator or owner is the practical addressee of the modification requirement because they control maintenance scheduling and funding.

• Maintenance organisations or maintenance personnel tasked with performing the work required by Aerotechnic Service Bulletin DO228-119780-0104 Revision 2. The AD requires performance "in accordance with" that Service Bulletin; consequently, technicians and organisations doing the work must have the Service Bulletin and execute its procedures.

• The STC holder and the party that provided the Service Bulletin. The AD notes that "the European Aviation Safety Agency (EASA) has received advice from the STC holder" and the Service Bulletin is the technical document implementing the fix. The STC holder and Aerotechnic Vertriebs und Service GmbH are implicated as originators of the remedial technical instructions.

• Regulatory administrators within CASA. The Directive is signed by a CASA delegate and sets an effective date. CASA is the issuing authority responsible for promulgation and for any further administrative follow-up.

• Flight crew and passengers indirectly. The stated safety risk concerns erroneous navigation information being provided to flight crew because the TPU67A could hold a "valid" flag despite gyro invalidity. That risk affects those who fly and are carried on the affected aircraft.

Excluded or unaffected parties are also explicit in the text. The AD expressly excludes aircraft with serial numbers 8191, 8232, 8233, 8244 and 8245, and excludes aircraft not modified under LBA STC SA1310 before 31 January 2005. Operators of aircraft outside these parameters do not have obligations under this specific AD as written.

The document does not spell out who pays, but the commercial and operational incidence is reasonably clear from the text: those who control the aircraft and its maintenance programme must implement the Service Bulletin. The Directive does not set out funding arrangements, subsidy or reimbursement; that remains a private contract or operator decision. The AD likewise does not state enforcement sanctions in its text; it provides the obligation, the technical prescription and the deadline. The practical consequence is that owners/operators must plan for parts acquisition, maintenance downtime and scheduling within the prescribed compliance window.

The Directive sets one substantive duty and structures it with clear technical and temporal parameters. The AD’s text defines what must be done, to which aircraft, by when, and by reference to which technical document.

• Core duty. The Directive requires that "the Honeywell CAS67A Airborne Collision Avoidance System (ACAS) II, installed under LBA STC SA1310" be modified "in accordance with Aerotechnic Vertriebs und Service GmbH Service Bulletin DO228-119780-0104 Revision 2 dated 21 December 2006." That duty is specific: the modification must follow the procedures and scope set out in that Service Bulletin.

• Applicability constraint. The obligation applies only to specified Dornier 228 models, excluding listed serial numbers, and only to aircraft "modified in accordance with LBA STC SA1310 before 31 January 2005." The duty therefore is not universal across all Dornier 228s; it attaches to the intersection of model, serial number and STC installation date.

• Temporal duty. The modification must be completed "Within 200 flight cycles or 8 weeks, whichever comes first, after the effective date of this Directive." The effective date is specified as 10 May 2007. This creates a short calendar deadline for lower-utilisation aircraft and a potentially shorter operational deadline for higher-utilisation aircraft when 200 flight cycles are reached sooner than eight weeks.

• Technical duty. The AD prescribes installation of "isolation diodes into the signal lines to the TPU67A" with the expressed purpose to "prevent reverse feed of the valid lines." The AD ties the technical duty to the exact Service Bulletin revision date and number; it does not authorise an alternative technical solution in the text.

• Rights or authorised actions. The Directive does not, in its text, enumerate rights such as extensions, alternatives, or exemptions. It does reference EASA AD 2007-0059, suggesting alignment with external authority, but the AD itself does not on its face provide a mechanism for deviation, compliance extension or approval of alternative methods of compliance. Any such process is not contained in the text provided.

• Documentation and provenance. The AD names the Service Bulletin and the STC; possession of those documents and proof of execution will be necessary to demonstrate that the requirement was met. The Directive itself is signed and dated by a CASA delegate and gives an effective date, establishing the administrative provenance of the duty.

What the AD does not state is also material. The text does not specify fines, criminal penalties, or an enforcement procedure. It does not provide an alternative means of compliance or a prescribed documentation form for recording the modification. It does not address continuing airworthiness beyond the modification described, nor does it articulate a provisioning schedule for parts or a mandatory grounding until compliance. Accordingly, the duty created by the AD is precise in technical terms but leaves administrative enforcement and ancillary processes unspecified in this text.

The AD text itself contains no explicit penalties, sanction schedule, or enforcement procedure. The Directive confines its content to applicability, the technical requirement, compliance timing and an effective date. The document states: "This Airworthiness Directive becomes effective on 10 May 2007," and prescribes the mandatory modification "within 200 flight cycles or 8 weeks, whichever comes first" but it does not set out what penalties follow non-compliance or how CASA will enforce the requirement.

From the text one can record the following observable enforcement-related facts and limits.

• No penalty provision included. There is no language in the provided AD text that specifies civil penalties, licence consequences, or criminal sanctions. The AD does not specify an inspection regime or list enforcement actions.

• Issuing authority identified. The AD is signed by "Charles Lenarcic, Delegate of the Civil Aviation Safety Authority." This identifies the regulatory origin and the delegating official. The presence of an explicit effective date gives the requirement administrative finality as of that date.

• Compliance requirement as the enforcement trigger. The AD’s principal enforcement mechanism, insofar as it is stated, is the clear compliance requirement and deadline. The text imposes an obligation to make the specified hardware modification within the defined timeframe. How CASA will monitor compliance, inspect aircraft, or apply administrative penalties for non-compliance is not set out in the document.

• Referential enforcement context. The AD references "EASA AD 2007-0059 refers," which indicates that a related European AD exists. This cross-reference may imply harmonised international expectations for compliance, but no enforcement measures tied to that reference are detailed here.

• Practical enforcement implications for operators. Because the AD prescribes a technical modification to aircraft equipment that affects the validity of navigation indications, operators will generally be expected to schedule and document the modification to maintain the airworthiness of affected aircraft. The text makes the obligation explicit; however the AD does not state the consequences of operating an affected aircraft without having completed the modification.

In short, the AD asserts a mandatory technical obligation with a binding effective date but does not itself enumerate enforcement measures or penalties. The document places the onus on operators and maintainers to comply within the stated timeframe, while the specific regulatory consequences of non-compliance are not articulated in this text.

The AD text makes two cross-references to external regulatory and technical instruments and therefore interacts with those instruments in a limited way. Beyond these explicit references, the AD does not set out further inter-legislative relationships.

• Reference to EASA AD 2007-0059. The Directive notes "Note: EASA AD 2007-0059 refers." This signals that the Australian AD is aligned with a corresponding European Aviation Safety Agency action. The presence of that reference indicates regulatory consonance across jurisdictions for this safety issue but the AD does not reproduce or restate the provisions of the EASA AD. The Australian AD therefore interacts with the EASA measure by acknowledging it as related material, though the AD itself prescribes the specific action required in the Australian context.

• Reliance on LBA STC SA1310. The AD addresses installations "modified in accordance with Luftfahrtbundesamt (LBA) Supplemental Type Certificate (STC) No.SA1310 before 31 January 2005." By specifying the STC as the installation basis for applicability, the Directive ties its reach to aircraft altered under a foreign STC. The STC provides the technical provenance of the ACAS II installation that is now being remediated. The interaction is therefore with an earlier approval instrument that authorised the relevant modification to the airframe and equipment.

• Dependence on the Service Bulletin as operative technical law. The AD mandates modification "in accordance with Aerotechnic Vertriebs und Service GmbH Service Bulletin DO228-119780-0104 Revision 2 dated 21 December 2006." That Service Bulletin functions as the operative technical specification within the AD. The AD interacts with this private technical document by incorporating it, making the SB the technical standard that must be followed for compliance.

• No other statutes or regulations cited. The AD text does not itself reference domestic statutes, civil aviation regulations, or administrative procedures beyond these three documents and the issuing authority. The AD does not specify how it sits within any broader regulatory enforcement architecture in the text provided.

Therefore the AD's inter-instrument interactions are narrow and concrete: it aligns with an EASA AD, limits its scope to aircraft modified under a named LBA STC, and incorporates by reference a named Service Bulletin. The AD makes these external documents the relevant points of legal-technical interaction for affected operators and maintainers.

The AD text contains limited documentary references that form the relevant amendment history for the equipment and the remediation process. From the material provided the following timeline and documentary milestones can be extracted.

• Original STC installation date threshold. The AD targets aircraft "modified in accordance with LBA STC SA1310 before 31 January 2005." That date is used as a cut-off to identify earlier installations that may have lacked the necessary isolation diodes. The AD therefore treats installations before that date as a cohort potentially affected by the defect.

• Service Bulletin revision requirement. The AD requires modification in accordance with Aerotechnic Service Bulletin DO228-119780-0104 Revision 2 dated 21 December 2006. The fact that the AD specifies Revision 2 of the Service Bulletin and gives an exact date indicates that the technical fix underwent at least two iterations and that the AD adopts the later, dated revision as the required standard. The AD does not include earlier revisions or allow for later ones; it binds to the named revision.

• Relation to EASA AD 2007-0059. The AD notes that "EASA AD 2007-0059 refers." That European AD reference ties the Australian directive to the contemporaneous regulatory response in Europe. The AD does not reproduce the text of EASA AD 2007-0059 nor set out any substantive divergence. The reference suggests that the EASA action is part of the procedural history leading to CASA issuing this AD.

• Dates of issuance and effectiveness. The AD bears the signatory date "16 March 2007" under the signature of the CASA delegate. The document states that the AD "becomes effective on 10 May 2007." The AD is numbered AD/DO 228/11 and carries the identifier "5/2007." These metadata items situate the AD chronologically and administratively.

• No later amendments recorded in the text. The provided AD contains no later amendments, superseding instruments, or revision notes. The Service Bulletin revision number is fixed in the AD text. The AD does not itself include a mechanism to accept subsequent revisions of the Service Bulletin, nor does it record any post-issuance amendments.

In summary, the AD embeds a technical amendment path: earlier STC installations (pre-31 January 2005) are the cohort; Aerotechnic Service Bulletin DO228-119780-0104 Revision 2 (21 December 2006) is the operative remedy; EASA AD 2007-0059 is referenced as related authority; and CASA issued the AD with an effective date of 10 May 2007. The AD does not provide an ongoing amendment mechanism or identify subsequent revisions of this CASA instrument in the text provided.

The AD text contains no reference to litigation, court decisions, administrative appeals, or formal disputes arising from the Directive. The document is an administrative safety instrument that records technical facts, an obligation to modify equipment and a compliance deadline; it does not recount any legal challenges or judicial review processes.

Specifically, the AD does not:

• Name any judicial proceedings or appeals against the AD.
• Record any interpretations by a court or tribunal of the AD’s legality, scope or enforcement.
• State that the AD has been stayed, suspended, varied by a court decision or otherwise subject to litigation.

On that basis, the only legally relevant history present in the document is administrative: the AD references the EASA AD 2007-0059 and the LBA STC SA1310, and it sets an effective date and compliance timeframe. Any litigation history,either in relation to the STC, the Service Bulletin, the EASA AD, or the CASA AD,would need to be sourced from other materials outside this document. The AD itself provides no litigation-related material.

Therefore, as of the content of this text, there is no litigation history to report. If a practitioner needs to know whether the AD was subsequently challenged or whether any enforcement action followed, that is not disclosed here and would require consultation of CASA administrative records or court files beyond this AD.

The AD contains several elements that can trip up implementers if read too quickly. The following are concrete practical pitfalls directly drawn from the text.

• Applicability is conjunctive and narrow. The AD applies only to models 228-100, 228-101, 228-200, 228-201 and 228-212, and then excludes specific serial numbers and requires that the aircraft be "modified in accordance with LBA STC SA1310 before 31 January 2005." Operators who assume the AD applies simply because they have a Dornier 228 or because they have an ACAS II installed risk misapplying the rule. The AD’s applicability is an intersection of model, serial number and STC installation date and must be checked for each aircraft.

• Excluded serial numbers must be checked precisely. Five serial numbers are explicitly excluded: 8191, 8232, 8233, 8244 and 8245. Failure to verify serial numbers could lead to unnecessary work or to missing aircraft that are actually within scope.

• Date cut-off matters. The STC installation date cut-off is 31 January 2005. An installation under the same STC after that date appears not to be within scope of this AD as written. Operators must verify the date of the STC modification, not only that the STC was used.

• Strict compliance window creates operational risk. The compliance requirement is "Within 200 flight cycles or 8 weeks, whichever comes first, after the effective date of this Directive." That combination means an aircraft with high flight-cycle utilisation may hit 200 cycles well before eight weeks; consequently, operators with high utilisation must track cycles from the effective date (10 May 2007) and schedule the modification promptly. Conversely, even low-utilisation aircraft still have an eight-week calendar deadline.

• Exact Service Bulletin revision is mandated. The AD mandates work "in accordance with Aerotechnic Vertriebs und Service GmbH Service Bulletin DO228-119780-0104 Revision 2 dated 21 December 2006." Using an earlier or later revision without formal authority could fail to meet the AD’s explicit terms, since the AD binds to a named revision and date.

• Technical hazard affects two signal lines though one was detected. The background says the problem "has only been detected for heading valid lines but could equally affect the attitude valid lines." Implementers must not assume the hazard is restricted to heading lines; the AD prescribes diode installation into the signal lines to the TPU67A broadly to address both heading and attitude valid lines.

• The AD does not state alternatives or extensions. The Directive does not list an alternative method of compliance, nor does it provide an avenue for seeking an administrative variation in the text. If an operator needs an alternative approach, that process is not articulated here and would require separate engagement with CASA or reference to other CASA procedures not contained in the AD.

• No penalties or enforcement steps are set out in the AD. The instrument mandates the obligation and the deadline but does not specify how compliance will be confirmed or what penalties apply for non-compliance. Operators should not assume that the lack of an explicit penalty means non-compliance is without consequence; the AD imposes a binding obligation and the absence of enforcement detail in the AD does not negate other regulatory frameworks that may apply.

• Documentation and proof of compliance are not described. The AD requires the work but does not prescribe the documentation that will constitute proof of compliance. Operational and maintenance control systems should plan to record compliance in a clear and verifiable form.

Each of these points is drawn directly from the wording of the AD and its background. They are practical implementation risks and attention points that operators, maintainers and compliance officers should handle when applying the AD.

The AD prescribes a single, specific path to compliance. The following steps, grounded in the wording of the Directive, describe what an operator or maintenance organisation needs to do to meet the Directive’s mandate.

1. Determine applicability precisely. Confirm that the aircraft is one of the specified models (228-100, 228-101, 228-200, 228-201, 228-212), confirm the serial number is not one of the excluded numbers (8191, 8232, 8233, 8244, 8245) and confirm the ACAS II installation was effected "in accordance with LBA STC SA1310 before 31 January 2005." Only if all three conditions are met does the AD apply.

2. Note the effective date and calculate the compliance deadline. The AD "becomes effective on 10 May 2007." Count flight cycles from that date and note whether the aircraft will reach 200 flight cycles within eight weeks; compliance is required "within 200 flight cycles or 8 weeks, whichever comes first." For planning, set the earlier of the two as the deadline.

3. Obtain the mandated Service Bulletin. The AD requires modification "in accordance with Aerotechnic Vertriebs und Service GmbH Service Bulletin DO228-119780-0104 Revision 2 dated 21 December 2006." Acquire that exact revision and date of the Service Bulletin and any referenced parts lists, diagrams or procedural steps contained in it.

4. Engage qualified maintenance personnel. The Service Bulletin procedures are technical and involve installation of electrical isolation diodes into the signal lines to the TPU67A. Arrange for appropriately qualified maintenance personnel or an approved maintenance organisation to perform the work following the Service Bulletin.

5. Perform the diode installation as specified. Implement the technical remedy specified by the Service Bulletin, which the AD describes in summary as installation of isolation diodes into the heading and attitude valid lines to the TPU67A to "prevent reverse feed of the valid lines." Ensure the work follows the Service Bulletin’s steps and any referenced test procedures.

6. Test and verify. The AD background identifies the failure mechanism that permits the TPU67A to feed current into open-state valid lines, preventing the valid flag from indicating an invalid gyro. After diode installation, operational and electrical testing consistent with the Service Bulletin should verify that the valid flags behave as intended under both valid and invalid gyro conditions. The AD does not specify test protocols in its text; the Service Bulletin will contain specific instructions.

7. Record compliance. The AD does not set out a documentation form, so prepare and retain records that show (a) the aircraft identification and serial number, (b) proof the aircraft was modified under LBA STC SA1310 before 31 January 2005 (if applicable), (c) the Service Bulletin revision used, (d) the date the modification was completed, and (e) signatures and maintenance release issued by authorised personnel. These records will be necessary to demonstrate to regulators or auditors that the AD obligation was met.

8. Coordinate operational scheduling. The compliance window may require planning for maintenance downtime, parts procurement and scheduling with the maintenance provider. High-utilisation aircraft may reach 200 cycles quickly; plan the work early to avoid potential conflict with operational commitments and the compliance deadline.

9. Confirm whether related regulatory references require any additional steps. The AD notes "EASA AD 2007-0059 refers." While the Australian AD mandates the Service Bulletin action, operators should ensure any documentation or verification steps required under the related EASA AD, if applicable to their operations, are observed. The AD itself is the binding instrument for Australian operations.

10. Maintain awareness of excluded serial numbers and STC dates. If any uncertainty exists about serial numbers or STC installation dates, obtain original modification records or STC documentation to confirm applicability. Misclassification could either expose an operator to non-compliance or lead to unnecessary work.

Costs and procurement. The AD does not specify parts, labour hours or cost-sharing arrangements. Those commercial elements must be resolved between owners/operators and maintenance providers. The Service Bulletin will contain parts lists and technical detail required to source diodes and associated hardware.

By following this sequence, an operator or maintenance organisation will meet the AD's explicit requirements as stated in the text: modify the Honeywell CAS67A ACAS II installation as per the named Service Bulletin Revision 2 dated 21 December 2006, and complete that work within the stated compliance window measured from the effective date of 10 May 2007.