AD/A320/162 Amdt 1 - Integrated Standby Instrument System

This AD operates through a short set of technical and temporal concepts that determine who must act and how often.

• Applicability gating. The Directive applies only to Airbus A318, A319, A320 and A321 aeroplanes that meet specific configuration criteria: fitted with Airbus Modification 27620 during production or with Airbus Service Bulletin A320-34-1261 embodied in service, and that have not had modification 35536 installed during production or SB A320-34-1335 embodied in service (Applicability). The AD therefore differentiates aircraft by embodied modifications and service bulletins. The Amendment states it "reduces the scope of the applicability" relative to the original issue (Background).

• Preventive periodic reset. The primary mitigation is a preventive, periodic reset of the ISIS. The reset is framed as clearing a time counter that otherwise can fail after long continuous power intervals: the failure mode is identified as "a time counter fault after 145 hours of ISIS continuous power supply" (Background). The periodicity fixes operational behaviour , operators must interrupt continuous ISIS power at specified intervals.

• Two equivalent reset methods. The AD prescribes a simple circuit breaker operation: open the NAV/STBY/HORIZON circuit breaker on the 49VU panel (5FN, location F12) for more than five seconds, then close it, and wait until the INIT page appears (Requirement). The AD also recognises a complete electrical shutdown of the aircraft as an alternative means of resetting ISIS (Requirement). The text describes both procedures as sufficient to clear the time counter.

• Temporal constraint and initial window. A specific initial compliance window applies: the work must be performed "Within three calendar days after the effective date of this Directive, but not exceeding five calendar days from the last ISIS reset or aeroplane complete power off" (Compliance). Thereafter, subsequent resets must occur "at intervals not exceeding five calendar days" (Compliance). The initial three-day window from the AD's effective date mandates near-term action by operators on the affected fleet.

• Operational caveat. The Directive includes an explicit operational caution: "Do not reset ISIS in flight" (Requirement). The background also notes that simultaneous unavailability of EIS DUs and ISIS "may result in hazardous consequences in certain phases of flight" (Background). The safety rationale thus links the reset procedure to preventing combined instrument loss.

• Cross-references. The AD cross-references DGAC F-2004-168 R1 and EASA Approval 2005-6439 as related authorities (Requirement, Note). It also refers to earlier AD/A320/157 Amdt 1 that mandated operational recovery procedures for lost EIS DUs pending an EIS standard fix (Background).

These concepts determine the compliance universe: aircraft selection by embodied mods/SBs, execution of a simple but regularly repeated technical operation, prohibition on doing so in flight, and an alternative of full electrical shutdown. The AD’s mechanism trades frequent, short ground interventions for avoidance of a known time-counter failure that can coincide with EIS DU loss.

The text identifies three categories of stakeholders by implication and direct reference.

1. Operators of the specified aircraft. The AD applies to "Airbus A318, A319, A320 and A321 aeroplanes, all serial numbers, fitted with Airbus Modification 27620 during production or Airbus Service Bulletin (SB) A320-34-1261 embodied whilst in service and that have not had modification 35536 installed during production or SB A320-34-1335 embodied whilst in service" (Applicability). That language means the owners/operators of those particular aeroplanes must comply with the reset requirement and timing. The obligation is operational: the reset must be performed within days and repeated at intervals not exceeding five calendar days (Compliance).

2. Flight and maintenance crews who execute the reset. The required procedure is a specific circuit-breaker operation on the 49VU panel (5FN, location F12) and a monitored wait for the INIT page to appear (Requirement). That work is on-aircraft, so it is likely to fall to maintenance personnel or qualified flight-crew/technicians authorised to operate circuit breakers and perform power resets. The Directive does not explicitly allocate responsibility between flight crew and maintenance, but the instruction "Do not reset ISIS in flight" places a duty on operational personnel to schedule resets on the ground (Requirement).

3. Regulators and their delegates. The AD is signed by "Charles Lenarcic, Delegate of the Civil Aviation Safety Authority" and is an official AD with an effective date (signed 20 December 2005; Amendment effective 16 February 2006) (signature block; Compliance). The regulator issues the AD and establishes compliance timing, so CASA as regulator and its delegates implement and publish the requirement.

Indirectly, the AD affects passengers in that the reset obligation can impose short ground-time activities or require the aircraft be power-cycled; the text acknowledges that "A complete electrical shut down of the aircraft is also sufficient" (Requirement), which may require more prolonged ground time.

Aircraft that have had modification 35536 installed during production or SB A320-34-1335 embodied are expressly excluded from applicability (Applicability). The Amendment reduces the scope of applicability relative to the original AD, so operators who have implemented those later modifications are not required to follow the reset procedure under this AD (Background).

The AD therefore targets a defined subset of the A318-A321 fleet, assigns operational actions to the entity controlling aircraft configuration and ground procedures, and leaves scope exclusions based on implemented design fixes or service bulletin embodiment.

The Directive imposes concrete duties and specifies one procedural right (an alternative means), all stated in the text.

Duties

• Perform the reset. The primary duty is to "Perform a reset of Integrated Standby Instrument System (ISIS) according to the following procedure" (Requirement). The AD describes the circuit breaker operation as the prescribed procedure.

• Timing and recurrence. Operators must carry out the first required reset "Within three calendar days after the effective date of this Directive, but not exceeding five calendar days from the last ISIS reset or aeroplane complete power off" and thereafter at "intervals not exceeding five calendar days" (Compliance). This creates a recurring duty on a maximum five-day cadence.

• Do not reset in flight. There is an explicit duty not to reset while airborne: "Caution: Do not reset ISIS in flight" (Requirement). That constrains when the duty may be performed and places an operational constraint on flight operations and maintenance scheduling.

Rights / permitted alternatives

• Alternative reset method. The Directive permits an alternative: "A complete electrical shut down of the aircraft is also sufficient to reset ISIS and is an alternative means to the above procedure" (Requirement). That gives operators two authorised methods to meet the duty: a brief circuit-breaker interrupt or a full aircraft electrical power-down.

Conditional non-applicability

• Exemption by embodied modification. Aircraft that have "had modification 35536 installed during production or SB A320-34-1335 embodied whilst in service" are excluded by the Applicability wording. In effect, installing Mod 35536 or embodying SB A320-34-1335 removes the duty imposed by this AD for that aeroplane (Applicability, Background).

Scope of the duty

• Applies only to configured fleet subset. The duty is confined to A318-A321 aeroplanes fitted with Mod 27620 or SB A320-34-1261 and without Mod 35536 or SB A320-34-1335 (Applicability). The Amendment reduces scope relative to the original AD (Background), which affects who must meet the duty.

What the AD does not specify

• The Directive does not set out record-keeping obligations, responsible role designation, or specific maintenance task cards. It prescribes the technical action and timing but leaves allocation of responsibility within an operator's procedures implicitly to the operator.

In short, the AD creates an operationally specific, recurring duty to interrupt ISIS power on a short cadence, prohibits in-flight resets, allows a full electrical shutdown as an authorised alternative, and removes the duty for aeroplanes that have the specified design corrections embodied.

The AD text itself does not set out statutory penalties or enforcement procedures. The document registers the effective date and contains the signature of a CASA delegate: "Charles Lenarcic, Delegate of the Civil Aviation Safety Authority" (signature block). The AD language specifies the compliance schedule and the technical steps required, for example the mandatory reset procedure and timing (Requirement; Compliance). The text does not otherwise describe sanctions, inspection powers, or enforcement mechanisms within the document.

Consequently, readers of the AD must note two things from the text only. First, the Instrument imposes a mandatory compliance obligation defined by timing and procedure; it states an initial compliance window and a maximum recurrence interval (Compliance). Second, the issuing authority is identified by delegate signature and effective date (signature block; Compliance), but the AD contains no express penalty provisions or enforcement process details.

Because the Directive is framed as an airworthiness measure that becomes effective on a stated date ("This Amendment becomes effective on 16 February 2006") and is signed by a CASA delegate, the text implies regulator-led oversight consistent with the usual role of an airworthiness authority, but the AD itself does not specify the enforcement instruments that may follow non-compliance. The document also cross-references other regulatory materials (DGAC F-2004-168 R1 and EASA Approval 2005-6439) (Requirement, Note), however those references are cited as supporting approvals rather than enforcement texts within this AD.

Practically, if stakeholders need clarity about statutory sanctions, enforcement procedures, or how the AD fits into inspectors' powers, that information would appear in the broader regulatory framework outside of this document. The AD as published sets the technical and temporal obligations but leaves enforcement details unspecified in the text.

The Amendment text references and situates itself alongside other airworthiness instruments and approvals, but it does not attempt to amend primary statute. The AD explicitly cross-references earlier and external approvals and directives.

• Relationship to earlier ADs and service material. The Background notes that "AD/A320/157 Amdt 1 (DGAC AD F-2004-104 R1) mandates the operational procedure to recover lost EIS Display Units, pending a new EIS standard addressing the misbehavior" (Background). The present AD continues the reset requirement introduced by the original Directive but "reduces the scope of the applicability" (Background). The AD therefore operates in sequence with prior ADs addressing related EIS/ISIS failures.

• References to foreign approvals. The Requirement contains a Note: "DGAC F-2004-168 R1 (EASA Approval 2005-6439) refers" (Requirement, Note). That reference indicates that the Directive aligns with or draws on determinations made in DGAC and EASA materials, but the AD does not incorporate those documents by reference beyond citation.

• Interplay with design change embodiment. Applicability is explicitly tied to embodiment of certain Airbus modifications and service bulletins. If an aircraft has "had modification 35536 installed during production or SB A320-34-1335 embodied whilst in service" then it falls outside the AD's applicability (Applicability). Conversely, if it has Mod 27620 or SB A320-34-1261 embodied, it falls within it. Thus compliance status depends on the aircraft's modification history and SB embodiment.

• No statutory amendment. The AD is administrative in form and specifies operational requirements; it does not amend any statute or declare changes to civil aviation primary legislation within the document text. It is an operational airworthiness directive that takes effect on a stated date (Compliance).

• Safety rationale continuity. The Background explains that the AD responds to a reported incident and an identified time-counter failure that could coincide with loss of EIS DUs, which could "result in hazardous consequences in certain phases of flight" (Background). The AD therefore interacts functionally with safety obligations that operators already hold under broader aviation regulation, although those obligations are not restated in the AD.

In sum, within the text the AD interacts with prior ADs, Airbus service material and DGAC/EASA approvals, and it conditions applicability on the embodiment of specified design changes. The document does not state how it modifies or trumps other regulatory instruments beyond that sequencing and cross-reference.

The AD contains its own amendment genealogy and dates.

• Original Directive. The text records that "The original issue of this Directive became effective on 25 October 2004" (Background). That original AD introduced the periodic on-ground-reset requirement to clear the ISIS time counter.

• Relationship to AD/A320/157. The Background relates this AD to AD/A320/157 Amdt 1, noting that AD/A320/157 Amdt 1 "mandates the operational procedure to recover lost EIS Display Units, pending a new EIS standard addressing the misbehavior" (Background). The present AD continues the preventive periodic reset while reducing applicability.

• This Amendment. The instrument before the reader is "AD/A320/162 Amdt 1" and the text states "This Amendment becomes effective on 16 February 2006" (Compliance). The signature block shows the document was signed by the CASA delegate on 20 December 2005, providing context for the amendment’s publication and effective date (signature block).

• Scope change. The Background explicitly states that "This Amendment continues that requirement but reduces the scope of the applicability" (Background). The change in scope is effected by the Applicability paragraph, which limits affected aeroplanes to those with specific modifications or service bulletin embodiment and without a subsequent correction embodied.

• Cross-reference approvals. The Requirement includes a Note that "DGAC F-2004-168 R1 (EASA Approval 2005-6439) refers" (Requirement, Note), indicating the AD is consistent with a DGAC revision and EASA approval process that post-dates the original AD.

The Amendment history in the text is concise: initial AD effective 25 October 2004; Amendment 1 signed 20 December 2005 and effective 16 February 2006; the Amendment narrows applicability while keeping the preventive reset requirement intact. The AD does not include further subsequent amendments, revocations, or incorporation of later design changes beyond the specific modifications and service bulletins cited.

The AD text does not record any litigation, judicial decisions, or legal challenges. It contains only administrative history, cross-references, technical requirements and a signature block. There are no cases named or judicial outcomes discussed in the document. The Background cites a reported operator incident and refers to other regulatory approvals and ADs, but it does not mention court proceedings or litigation arising from issuance or implementation of the Directive.

Therefore, from the text alone, there is no recorded litigation history to summarise. If stakeholders require whether this AD has been subject to challenge in a tribunal or whether enforcement actions have been litigated, that material falls outside the content of the Directive and is not provided in the document text.

The AD text contains several operational and compliance details that can produce practical surprises if overlooked.

• Narrow applicability dependencies. Applicability is not simply "A318-A321 aircraft" but is conditioned on embodiment of particular Airbus modifications or service bulletins and the non-embodiment of a later correction. The AD applies only to aeroplanes "fitted with Airbus Modification 27620 during production or Airbus Service Bulletin (SB) A320-34-1261 embodied whilst in service and that have not had modification 35536 installed during production or SB A320-34-1335 embodied whilst in service" (Applicability). Misreading applicability as blanket for all A320 family aircraft would be an error. Operators must verify aircraft configuration and SB embodiment status before treating the AD as applicable.

• Initial compliance window tightness. The Compliance paragraph requires action "Within three calendar days after the effective date of this Directive, but not exceeding five calendar days from the last ISIS reset or aeroplane complete power off" (Compliance). If an operator delays verification of applicability, or miscalculates the last reset date, they risk missing the initial window. The interplay of the three-day initial window and the five-day maximum-from-last-reset constraint can create scheduling complexity.

• Prohibition on in-flight reset. The Requirement cautions "Do not reset ISIS in flight" and Background warns of hazardous consequences if EIS DUs and ISIS are simultaneously unavailable in certain phases of flight. Thus, attempting to perform the breaker action while airborne, whether to remedy an in-flight anomaly or to comply with an on-duty schedule, is expressly forbidden and logically hazardous (Requirement; Background).

• Human factors on circuit-breaker operation. The required operation is to open the NAV/STBY/HORIZON circuit breaker on the 49VU panel (5FN, location F12) for more than five seconds (Requirement). Incorrect identification of the panel or breaker, or improper operating procedure, can cause unintended system interruptions. The AD does not provide a step-by-step recovery checklist beyond waiting for the INIT page, so operators must ensure personnel are trained and that the correct breaker is used.

• Alternative reset vs operational disruption. The alternative method is a full electrical shutdown, which "is also sufficient to reset ISIS and is an alternative means" (Requirement). While functionally equivalent for clearing the time-counter, full shutdown may require more time on ground and complicate turnaround operations. Operators that choose the shutdown method must account for increased downtime and procedural checks.

• No record-keeping or role assignment spelled out. The AD does not specify who within an operator's organisation must perform or record the reset, nor does it require entry in a logbook. That leaves room for procedural inconsistency. Operators need to ensure internal procedures translate the AD's requirements into assigned roles and auditable records, because the AD itself is silent on those operational control points.

• Relationship to other ADs and service fixes. The Background notes the original AD and pending EIS standard corrections; the Amendment reduces applicability in recognition of some fleet receiving corrective modifications (Background). Operators may incorrectly assume that the presence of any service bulletin means the AD is inapplicable; in fact the AD names specific SB/mod numbers. Verifying embodiment of exactly those referenced SBs or mods is necessary.

• Safety-critical concurrency. The AD arises from an event where an ISIS loss was followed by loss of all EIS DUs; the Background flags concurrent unavailability as hazardous (Background). That indicates that any actions that risk temporarily disabling ISIS or EIS DUs in flight merit extreme caution, and that resetting ISIS in flight is explicitly cautioned against.

These gotchas are not speculative; they are direct corollaries of the AD’s strict applicability wording, timing constraints, the specified breaker location and duration, the no-in-flight caveat, and the alternative of full electrical shutdown, all stated in the text.

The Directive supplies a concise, prescriptive compliance sequence and a small set of compliance-related checks. To meet the AD's obligations as written, an operator should take the following steps, each grounded in the AD text.

1. Determine applicability precisely. Confirm whether each aeroplane is an Airbus A318, A319, A320 or A321 fitted with Airbus Modification 27620 during production or has Airbus Service Bulletin A320-34-1261 embodied whilst in service, and confirm that modification 35536 or SB A320-34-1335 has not been embodied. The Applicability paragraph defines who must comply.

2. Schedule the initial reset within the AD window. The AD requires the first reset "Within three calendar days after the effective date of this Directive" and not exceeding "five calendar days from the last ISIS reset or aeroplane complete power off" (Compliance). Operators must therefore schedule a reset within that initial three-day window or ensure the reset falls within five days of the prior reset/power off.

3. Execute the prescribed technical procedure on the ground. The Requirement provides the direct method: "Open the NAV/STBY/HORIZON circuit breaker on the 49VU panel (5FN, location F12) for more than 5 seconds, then close it. After some seconds, the INIT page comes into view" (Requirement). Personnel executing this must be trained to identify the correct breaker and to perform the open-wait-close operation.

4. Do not reset in flight. Strictly adhere to the explicit caution: "Do not reset ISIS in flight" (Requirement). Schedule resets to occur during ground time only.

5. Use full electrical shutdown if preferred or operationally necessary. The AD authorises an alternative method: "A complete electrical shut down of the aircraft is also sufficient to reset ISIS and is an alternative means to the above procedure" (Requirement). That can be used instead of the breaker operation where operationally convenient, bearing in mind the likely additional time and procedural steps needed to power down and power up the aircraft.

6. Repeat the reset at intervals not exceeding five calendar days. The Compliance paragraph mandates ongoing compliance: after the initial reset, perform repeats "at intervals not exceeding five calendar days" (Compliance). Operators must implement a scheduling regime to ensure the five-day maximum is not breached.

7. Incorporate the AD into operator's maintenance and safety procedures. Although the AD does not mandate record keeping, an operator should include the reset requirement in maintenance task cards or operational procedures to ensure consistent execution and to demonstrate compliance if queried. The AD itself prescribes the technical action and timing but is silent on documentation; therefore the operator must translate the AD into internal control processes.

8. Verify for modifications that remove applicability. If an aircraft later has Mod 35536 or SB A320-34-1335 embodied, the operator should record that change in configuration to confirm the aircraft is no longer subject to this AD (Applicability; Background). Likewise, if an aircraft joins the fleet with Mod 27620 or SB A320-34-1261, ensure the AD's duties are imposed accordingly.

9. Communicate with relevant personnel. Ensure flight crews, line maintenance, and engineering understand the location of the NAV/STBY/HORIZON circuit breaker (49VU panel, 5FN, location F12), the required wait time, the display confirmation (INIT page), and the prohibition on in-flight resets. The Requirement provides these precise operational cues.

10. Monitor regulatory updates and related SBs. The AD references DGAC and EASA approvals and earlier ADs (Requirement; Background). Operators should monitor for follow-on service bulletins or design changes that address the ISIS time-counter fault permanently, and for any further ADs that amend or cancel this requirement.

Following the AD as written demands straightforward physical action on the aircraft and a predictable recurring scheduling obligation. The main compliance burden is operational planning to ensure resets occur on the ground at least every five days for aircraft within the AD’s applicability, and proper verification of configuration to determine applicability or exemption.