AD/SWSA226/81 - Generator System Rework

The AD operates on a catalogue-of-fixes model. It links identified failure modes , specifically simultaneous loss of both generators during flight , to a set of hardware and wiring modifications intended to alter electrical routing, protective device behaviour and component accessibility. The AD is structured into multiple, model/serial-specific corrective actions rather than a one-size-fits-all retrofit. The principal technical concepts appearing in the AD are:

• Targeted wiring replacement: Requirement (a) mandates replacing generator fault transformer wiring with dual conductor shielded wire, a change focused on conductor integrity, shielding and likely EMI (electromagnetic interference) or insulation improvements. The SB numbers and revision dates are specified (SB 226-24-027, issued 19 May 1988, revised 22 February 1989; SB 227-24-008, issued 18 March 1988, revised 22 February 1989).

• Rewiring to protect current limiter: Requirement (b) targets the 325-amp current limiter failure mode by rewiring the electrical power generation system per SB 226-24-023 or SB 227-24-005 (issued 25 October 1985, revised 23 January 1989).

• Access and connector changes for regulators: Requirement (c) is a panel and connector modification to the voltage regulator access panel and wire bundle per SB 226-24-026 (issued 27 May 1987).

• Voltage regulator and panel replacement: Requirement (d) is a substantive hardware replacement of the entire voltage regulator panel and installation of new regulators, with wire rerouting, per SB 24-018 (issued 22 October 1980, revised 7 January 1981).

• DC generator control logic and breaker changes: Requirement (e) prescribes modifications so each DC generator control operates off its own generator output. The steps include removing field current and reset resistors, removing reset and generator relays and associated diodes, installing 10-amp generator control circuit breakers in the left-hand and right-hand essential bus panels, and replacing 10-amp circuit breakers in the wheelwells with 15-amp circuit breakers wired in series with the generator control breakers. SBs referred are SB 226-24-031 dated 27 July 1989 and SB 227-24-012 issued 4 May 1989 and revised 27 July 1989.

Conceptually the AD addresses both redundancy management and failure mode mitigation. Some modifications change how generator control circuits source and isolate themselves (Requirement (e)), others improve wiring robustness or current-limiter behaviour (Requirements (a) and (b)), and some improve access and replace ageing regulator hardware (Requirements (c) and (d)). The AD is serial-number specific because Fairchild’s production and retrofit history produced aircraft with differing original electrical configurations; functionally the AD requires operators to map a specific aircraft to the set of SBs that apply.

The AD is prescriptive about compliance method: each action must be accomplished “in accordance with” the relevant Fairchild SB, with the SB issue/revision dates provided. That phrase ties compliance to the technical content and steps of the SBs rather than leaving scope for unspecified alternative methods in the AD text itself. The AD also explicitly links its raison d’être to safety-critical flight phases (night, icing) and observed incidents (three aircraft with both generators off-line), giving the technical changes a stated operational objective: avoid simultaneous generator loss that could otherwise lead to loss of control.

The AD affects owners, operators, registrants, and maintenance organisations responsible for operating or maintaining Fairchild (Swearingen) SA226 and SA227 series aeroplanes that fall within the serial-number ranges enumerated in the Requirement. The AD lists multiple model/serial groupings for each specific remedial action (a) through (e); some aircraft will be subject to several of the listed requirements depending on model and serial. The models named are SA226 variants (SA226-T, SA226-T(B), SA226-AT, SA226-TC) and SA227 variants (SA227-TT, SA227-AT, SA227-AC). Examples of how affected parties are identified in the text are:

• Requirement (a) applies to SA226-T serials T201-T275 and T277-T291; SA226-T(B) serials T(B)276 and T(B)292-T(B)417; SA226-AT serials AT001-AT074; SA226-TC serials TC201-TC419; and a set of SA227 serial ranges for the SA227-TT, SA227-AT and SA227-AC models.

• Requirement (b) applies to a narrower or shifted set of serial ranges for some models, for example SA226-T serials T249-T275 and T277-T291, and SA226-AT serials ATO25-ATO74 (note the typographical variants of serial prefixes in the source), plus corresponding SA227 ranges.

• Requirement (e) has its own often-expanded serial ranges, for example SA227-AT up to AT695 for the DC generator control change.

The practical implication is that operators must determine for each individual airframe whether each subparagraph applies. An operator of a fleet containing different serials will need to audit serial numbers against each requirement column. Maintenance organisations executing the SBs must also confirm serial-number applicability before proceeding.

Financially and operationally, affected parties bear the direct cost of parts, labour, aircraft downtime and possibly specialised tooling to implement the SBs. The AD does not provide funding, credits, or government-subsidised modification programmes in the text; the owner/operator is the responsible party to arrange and pay for implementation. The AD prescribes the technical documents to be used for the work, which are Fairchild Service Bulletins with exact issue and revision dates provided; operators must obtain and follow those SBs to satisfy the AD. The AD’s compliance window imposes timing pressure because the required work must be done within 2,000 hours time-in-service from the effective date. The AD’s cross-reference to FAA AD 97-11-13 is a signalling element for operators that the FAA has taken the matter up as well, which may affect international operators or insurers who orient to FAA compliance.

Regulators and inspectors who enforce airworthiness directives are affected in the sense that the fleet lists they monitor must be checked and maintenance documents reviewed for sign-off; however, the AD text itself does not specify inspection or enforcement mechanisms beyond the compliance prescription. The AD places technical decision-making about how to execute each SB with maintenance providers acting under the SB instructions, subject to the AD’s mandatory nature for affected aircraft.

The AD prescribes a primary duty of action: owners/operators of aircraft meeting the model and serial-number applicability must accomplish the specified modifications as set out in requirements (a) through (e). The duty is both technical and temporal. Technically the duty is to accomplish the described wiring and hardware changes “in accordance with” the listed Fairchild Service Bulletins and their stated issue and revision dates. Temporally the AD sets a firm scheduling constraint: each required action is to be incorporated “within the next 2,000 hours time-in-service after the effective date of this AD” (Compliance). The AD’s effective date is 11 September 1997. The combination of technical specificity and a stated time-in-service deadline creates an obligation to plan maintenance, parts procurement and aircraft downtime accordingly.

Duties by requirement can be summarised from the text:

• Under (a) the duty is to replace existing generator fault transformer wiring with dual conductor shielded wire, per SB 226-24-027 or SB 227-24-008, depending on model (SBs and dates are specified in the AD).

• Under (b) the duty is to rewire the electrical power generation system to reduce the possibility of 325-amp current limiter failure, per SB 226-24-023 or SB 227-24-005.

• Under (c) the duty is to modify the voltage regulator access panel and install a connector in the wire bundle, per SB 226-24-026.

• Under (d) the duty is to install new voltage regulators, reroute wires and replace the entire voltage regulator panel assembly, per SB 24-018.

• Under (e) the duty is to modify the DC generator control system so it will operate off its respective generator output and to perform the specified removal and installation of resistors, relays, diodes and circuit breakers, per SB 226-24-031 or SB 227-24-012.

The AD ties the duty to specific documentation. That means the technical scope of compliance is bounded by the SB content as issued or revised on the dates listed. Where an SB is identified with revision dates, the AD requires compliance in accordance with the revised SB (for example SB 226-24-027 revised 22 February 1989). Owners are therefore obligated to use the correct version of the SB.

The AD does not, in the provided text, state explicit rights such as an appeal mechanism, a provision for alternative means of compliance (AMOC), or compensation for costs. It does, however, contain a Note pointing to FAA AD 97-11-13 Amendment 39-10042, which may provide further reference material for operators. Because the AD is framed as an airworthiness directive under Part 39, the implied regulatory structure is that affected airframes must be modified to remain airworthy; the AD text itself, however, does not set out procedures for requesting equivalence, exemptions, or extensions. Any such rights, procedures or administrative remedies would have to be sought in the broader Civil Aviation Regulations or from the Civil Aviation Safety Authority using their normal administrative instruments, but those are not specified in the AD text provided.

Operationally, the duty to comply within 2,000 hours time-in-service requires owners to schedule the work and to record completion in maintenance logs and certificates of release to service in accordance with aviation maintenance practise. The AD’s specificity as to which SB to use removes technical discretion about the corrective steps, although execution quality and record-keeping remain duties of maintenance organisations and certifying personnel.

The AD text provided does not specify criminal penalties, fines, or a detailed enforcement procedure within its body. It does state that the directive is issued under the Commonwealth of Australia Civil Aviation Regulations Part 39 schedule of Airworthiness Directives, which is the regulatory instrument under which airworthiness directives are promulgated. The AD sets out the mandatory compliance action and the temporal deadline: the required modifications must be incorporated within the next 2,000 hours time-in-service after the AD’s effective date of 11 September 1997 (Compliance). The AD also records the safety justification and cross-references FAA AD 97-11-13.

Because the AD itself does not spell out enforcement mechanisms, the only text-grounded statement that can be made is that compliance is required and that the AD is part of the Part 39 schedule. The AD does not list sanctions for non-compliance in the text supplied. For a reader seeking to understand legal liability or enforcement consequences beyond the AD’s own compliance requirement, the AD as provided does not contain those details and refers to the wider regulatory framework (Part 39) without reproducing enforcement provisions.

Practically, the AD’s mandatory language and its placement under Part 39 signal that the directive is part of the national airworthiness regulatory regime and that regulatory authorities would use their normal oversight tools to ensure adherence. The AD itself sets the obligations but not the penalty ladder in the provided excerpt. The only enforcement-specific element in the AD is the compliance deadline tied to time-in-service; the presence of that timeframe converts the AD from advisory to mandatory in practical effect because aircraft operating without the required modifications after the deadline will not have complied with the directive.

Operators and maintenance organisations must therefore treat the AD as a mandatory compliance task. Any question as to the specific sanctions for failing to comply would need to be resolved by reference to the Civil Aviation Regulations and enforcement policies of the Civil Aviation Safety Authority, which are not reproduced in this AD text. Readers should note the AD’s express linkage to FAA AD 97-11-13 if they are seeking harmonised enforcement or follow-on regulatory action by other authorities, because that cross-reference is explicitly provided in the AD’s Note.

The AD is issued under the authority of the Commonwealth Civil Aviation Regulations Part 39 schedule, placing it within the statutory framework that governs airworthiness directives in Australia. The AD itself cross-references an FAA AD (FAA AD 97-11-13 Amendment 39-10042) in a Note. This cross-reference functions as an informational linkage to parallel action taken by the United States Federal Aviation Administration, and signals that the AD’s technical remedy set may align with international regulatory action on the same aircraft models.

Interaction points identifiable from the AD text are:

• Regulatory hierarchy: The AD is a Part 39 instrument. By stating its origin in the Part 39 schedule and the Civil Aviation Safety Authority (header), it sits as an airworthiness requirement designed to control continuing airworthiness under national aviation law. The AD text itself does not reproduce Part 39 enforcement provisions, but it does rely on that statutory apparatus to confer mandatory status.

• Manufacturer service bulletins: The AD mandates compliance with certain Fairchild Service Bulletins by issue and revision date. Those SBs are manufacturer-issued technical documents. The AD links the regulatory instrument (the AD) to private technical documents (SBs). In effect the AD incorporates the SBs by reference as the method of achieving compliance. That creates an interaction where private technical standards (the SBs) become regulatory obligations for affected operators by virtue of the AD.

• International regulatory alignment: By referring to FAA AD 97-11-13, the AD establishes an information link that could be relevant for operators that are also subject to FAA oversight, or for maintenance programmes that rely on FAA-type approvals. The AD does not state that FAA compliance satisfies the Australian AD, but the Note gives operators a pointer to the corresponding FAA action.

• Maintenance regulatory obligations: Because the AD specifies technical steps to be undertaken “in accordance with” Fairchild SBs, there is an interaction with regulated maintenance practises. Work must be performed to the standards required for maintenance certification and release to service under Australian rules. The AD does not supply those maintenance certification rules, but those rules operate in combination with the AD; for instance a maintenance organisation will need to comply both with the AD’s substantive steps and with the statutory requirements for personnel certification, documentation and release.

• Record-keeping and continuing airworthiness: The AD’s compliance timing and prescribed modifications will affect an operator’s continuing airworthiness records. Although the AD does not set out the record-keeping or certification steps, those obligations will interact with other statutory requirements about maintenance records, logbook entries and certificates of release to service.

• No apparent inconsistency or displacement: The AD does not identify any conflict with other laws or directives in the provided text. The AD’s cross-reference to the FAA AD does not in itself create a legal inconsistency, rather it is an informational alignment. Where a tension could arise between manufacturer instructions and regulatory mandates, this AD resolves scope by requiring compliance with the specified SB versions, thereby elevating those SBs to regulatory force for applicable airframes.

Operators seeking to reconcile this AD with other legal obligations (for example export/import controls on parts, obligations imposed by insurers, or other state regulators) must do so by reference to those regimes; the AD itself imposes the technical requirement and identifies the SBs to be used, but it does not address non-airworthiness legal constraints such as customs, commerce or contractual obligations.

The AD itself contains internal references to Service Bulletin issue and revision dates and lists an effective date and compliance timing. The AD becomes effective on 11 September 1997, and requires incorporation of the specified modifications within the next 2,000 hours time-in-service after that effective date (Compliance). The AD text documents the lineage of the Fairchild Service Bulletins referenced; those dates and revision histories are part of the AD’s operative content because the AD requires compliance “in accordance with” these SBs as issued or revised. The specific SB dates and revisions cited in the AD are:

• SB 226-24-027: Issued 19 May 1988, Revised 22 February 1989 (referenced in Requirement (a)).
• SB 227-24-008: Issued 18 March 1988, Revised 22 February 1989 (referenced in Requirement (a)).
• SB 226-24-023: Issued 25 October 1985, Revised 23 January 1989 (referenced in Requirement (b)).
• SB 227-24-005: Issued 25 October 1985, Revised 23 January 1989 (referenced in Requirement (b)).
• SB 226-24-026: Issued 27 May 1987 (referenced in Requirement (c)).
• SB 24-018: Issued 22 October 1980, Revised 7 January 1981 (referenced in Requirement (d)).
• SB 226-24-031: Dated 27 July 1989 (referenced in Requirement (e)).
• SB 227-24-012: Issued 4 May 1989, Revised 27 July 1989 (referenced in Requirement (e)).

These SB issue and revision dates are the only formal amendment-history items included in the AD text. The AD also includes a Note that “FAA AD 97-11-13 Amdt 39-10042 refers,” which indicates a parallel FAA amendment action. The AD does not itself include prior versions of the AD or an explicit amendment log for the AD; it is presented as AD/SWSA226/81 with an effective date and the set of referenced SBs.

Where a Service Bulletin has been revised, the AD explicitly names the revised version (for example SB 226-24-027 revised 22 February 1989). That communicates that the AD requires compliance with the revised SB content as of the revision dates listed. The AD does not provide an open-ended approach to later revisions; it specifies particular SB versions. If operators wish to rely on later SB revisions, or to perform different modifications as an alternative method of compliance, the AD text provided does not set out a mechanism for that,operators would need to reference the wider regulatory regime or seek approval from the regulator to deviate from the SB-specified steps.

The AD does not show any amendment to its own text after the effective date within the extract provided. The AD can therefore be read as a single-issue directive effective 11 September 1997, incorporating specified SBs as the required implementation standard.

The AD text supplies no litigation history. It notes that the FAA received reports of both generators going off-line during flight on three affected aircraft and that corresponding FAA AD 97-11-13 Amendment 39-10042 refers (Background and Note). Beyond that, the AD contains no references to judicial or administrative litigation, appeals, or contested enforcement proceedings. There are no court decisions, administrative law challenges, or case citations contained in the AD text.

For readers looking for precedent or disputes over the AD, the source material here does not provide any such record. Any litigation that may have followed issuance of the AD (for example disputes between operators and the regulator, or between operators and manufacturers over parts, labour or costs) is not recorded in the AD itself and therefore cannot be reported from this text. Where a reader needs litigation or adjudicative history, that material must be sought from court or administrative records external to the AD.

The AD’s Note pointing to the FAA AD could be the origin of parallel compliance requirements in other jurisdictions; if disputes occurred in other jurisdictions they would appear in separate FAA or judicial records, but again those are not included in this AD. The AD, as provided, is a technical airworthiness directive without embedded litigation annotations.

Operators and maintenance providers should be attentive to several concrete traps in the AD text that arise from its serial-specific structure, the multiplicity of SBs, and the versioning of service documents. The AD text itself contains the items below; each is grounded in the AD wording and requires attention during compliance planning.

1. Serial-number specificity and overlapping ranges: The AD assigns different requirements to overlapping but not identical serial ranges across subparagraphs (a) through (e). An airframe may be within the scope of some but not all requirements, or within the scope of multiple requirements. For example, SA226-T serials T201-T275 are included in Requirement (a) and Requirement (d), but Requirement (b) and (c) apply only to T249-T275 and T277-T291. Operators must map exact serial numbers against each subparagraph rather than assume a model-wide applicability.

2. Typographical variations in serial prefixes: The AD text exhibits variations in how serial prefixes are shown, for example “AT001” versus “ATO01” or “ATO25,” and uses bracketed serial notation such as T(B)276 or T(B)292. These are the exact tokens used in the AD; when matching an aircraft to applicability, confirm the airframe’s serial format against the AD’s serial tokens and, where doubt exists, consult the regulator or the aircraft manufacturer to avoid misinterpretation.

3. Multiple SBs and version lock: The AD requires compliance “in accordance with” specific Fairchild Service Bulletins, and it includes issue and revision dates. The AD therefore locks compliance to particular versions of the SBs cited (for example SB 226-24-027 revised 22 February 1989). Do not assume that later SB revisions automatically satisfy the AD without formal acceptance. If an operator proposes to use a later SB revision or an alternative method, that departure is not contained within the AD text and will likely require regulator approval.

4. Incremental and interacting modifications: Some SBs replace the entire voltage regulator panel (Requirement (d)), while others involve rerouting wires, installing connectors or changing circuit breaker arrangements (Requirements (b), (c), (e)). The interaction of these changes could create sequence or compatibility issues. For example, replacing the voltage regulator panel may change access or wiring paths that other SB steps also modify. Planning must coordinate the work packages to avoid rework or incompatible installations.

5. Breaker rating and sequencing detail: Requirement (e) specifies a particular breaker reconfiguration: install 10-amp generator control circuit breakers to the left and right essential bus panels and replace the 10-amp generator control circuit breakers in left and right wheelwells with 15-amp breakers wired in series with the generator control breakers. That wiring-in-series step is specific and must be executed per the SB instructions; a simplistic replacement of breaker ratings without correct wiring could fail to achieve the AD’s intended effect.

6. Time-in-service clock: Compliance is measured by hours time-in-service, not by calendar date. The AD sets a window of 2,000 hours time-in-service after the effective date. This requires operators to track flight hours and schedule works before exceeding the 2,000-hour threshold; it cannot be satisfied by a calendar-only plan.

7. Multiple model variants with different scopes: The SA227-AC ranges are treated differently across paragraphs; some serial ranges are included in some requirements but excluded in others. For example (a) lists SA227-AC serials AC406, AC415, AC416, AC420-AC705 and AC707-AC733, while (b) lists AC420-AC594 and later (e) lists AC420-AC556 then AC558-AC705 etc. Operators must parse the AD carefully to identify which portion of the fleet requires which work.

8. Absence of alternatives or AMOC text in the AD: The AD does not state explicit alternative compliance procedures or a process for obtaining approval for alternate methods of compliance within the AD text provided. Where an operator wants to pursue a different technical solution, they must assume additional regulatory interaction outside the AD.

9. Reliance on manufacturer SBs: The AD makes the SBs normative. If parts or revision documentation are difficult to obtain because of manufacturer issues, supply-chain constraints or obsolescence, that practical problem is not covered by the AD and will have to be managed separately.

10. Cross-reference to FAA AD without legal substitution: The Note refers to FAA AD 97-11-13, but the AD does not state that complying with FAA AD alone satisfies the Australian AD. Treat the FAA AD reference as information, not as an automatic substitute for the obligations under this AD.

Careful reading of serial ranges, adherence to the exact SB versions, careful planning of work sequencing and parts procurement, and proper documentation against the time-in-service compliance clock are the concrete operational risks embedded in the AD text.

Compliance under this AD requires a stepwise, recordable programme tailored to each individual aeroplane and its serial number. The AD requires actions to be incorporated within the next 2,000 hours time-in-service after the effective date of 11 September 1997, and specifies that each action be accomplished in accordance with the identified Fairchild Service Bulletin issue and revision dates. The practical compliance steps grounded in the AD text are:

1. Identify applicability by airframe: For each airframe, determine the exact model and serial number and map it to the subparagraphs (a)-(e). The AD lists model/serial sets separately for each requirement, so do not assume model-wide coverage. Use the exact serial tokens and ranges as given in the AD to confirm whether each requirement applies.

2. Compile the required SBs: Obtain the Fairchild Service Bulletin or Bulletins specifically cited for the applicable requirements and the precise issue/revision versions stated in the AD. For example, if Requirement (a) applies, secure SB 226-24-027 (issued 19 May 1988, revised 22 February 1989) or SB 227-24-008 (issued 18 March 1988, revised 22 February 1989) as applicable.

3. Plan the work package and sequencing: If multiple requirements apply to a single airframe, coordinate the SB tasks to avoid rework or conflicts. Some SBs replace whole assemblies (for example SB 24-018 replaces the entire voltage regulator panel), which may affect or preclude other wiring actions if not sequenced correctly.

4. Schedule within the time-in-service window: The AD requires compliance within 2,000 hours time-in-service after 11 September 1997. Track your aircraft’s hours and schedule maintenance so the SB modifications are incorporated before exceeding that threshold.

5. Engage appropriately rated maintenance organisation and personnel: Use licensed maintenance organisations and certificated persons to perform the work, following the SB instructions precisely. The AD requires the work “in accordance with” the SBs; therefore, the SBs’ procedural, testing and inspection steps should be followed to the letter.

6. Procure parts and materials specified in the SBs: Parts such as dual conductor shielded wire, voltage regulators, panel assemblies, circuit breakers (10-amp and 15-amp as required), connectors and any specified relays or diodes must be sourced in time. The AD does not provide substitutes; use the SB-specified parts or obtain regulator acceptance if proposing alternatives.

7. Perform functional checks and testing: Execute any test procedures specified in the SBs to demonstrate proper operation after modification, for example generator on-line behaviour, breaker operation, and regulator output checks. Document test results in the aircraft’s maintenance records.

8. Record compliance: Enter completion of the AD-required work into the aircraft’s maintenance records and logbooks. Include references to the AD identification (AD/SWSA226/81), the SB number and revision used, dates of work and signatures/certificates of release to service by the authorised personnel. These records will be the primary proof of compliance with the AD’s obligations.

9. Retain documentation for oversight: Keep copies of the SBs used, parts invoices, and test results available for inspection by the regulator or auditors. The AD requires compliance with SBs by specific versions; retain those SB versions as evidence.

10. Coordinate with regulatory and operational stakeholders: If the aircraft is operated under multiple jurisdictions, advise operators, insurers and any lessors of the AD requirements and completion. Note that the AD includes a reference to FAA AD 97-11-13 as informational; confirm whether equivalent steps are required by other authorities.

11. Address deviations and alternatives proactively: The AD text does not state an AMOC process; if an operator believes an alternate means of compliance is necessary, they should seek formal approval from the Civil Aviation Safety Authority or follow the regulator’s established process for alternative compliance. Do not proceed on an alternative without regulatory sign-off.

12. Confirm release-to-service: After the SBs have been incorporated and testing completed, certify the aircraft’s release to service in accordance with regulatory maintenance certification requirements.

By following the AD’s serial-number mapping, adhering to the exact SB versions, scheduling work within the 2,000-hour compliance window, and keeping full maintenance and test records, operators will meet the AD’s textual obligations. The AD does not provide text for alternative compliance or an exemption process in its body; therefore assume formal engagement with the regulator is required for any departure from the SB-specified procedures.