AD/PREMIER/5 - Cabin Altitude and Barometric Pressure Switches

The AD revolves around a small set of technical and compliance concepts drawn directly from the mandatory service bulletin and the FAA AD it references.

• Applicability. The AD applies only to Model 390 aeroplanes with serial numbers RB-1 and RB-4 through RB-238 inclusive. That list is exclusive; other serial numbers are not included in the applicability statement. The document therefore targets a defined fleet subset rather than the entire model series.

• Modification versus test. The AD separates two discrete actions. Requirement 1 is a physical modification of the cabin barometric pressure switch and cabin altitude high switch installations in accordance with SB 21-3899 (original issue, May 2008). Requirement 2 is a functional test, specifically the Part I Ground Test Method described in Paragraph 3 of the SB. The AD treats the test as contingent on the modification: the ground functional test must be performed after the modification and, unless an exception applies, before further flight.

• Prohibition of flight test method. The AD expressly prohibits the flight test method described in Part II of the SB from being used after the effective date. That prohibition is a substantive constraint on acceptable verification procedures.

• Exceptions and equivalence. Note 1 provides a conditional exception: if the Part II flight test method was performed before the effective date of the Directive, and that flight test occurred after the Requirement 1 modification, then Requirement 2 (the ground functional test) is not required. Separately, the AD accepts equivalence by reference: later revisions of SB 21-3899 that are approved by the FAA as AMOCs to FAA AD 2008-21-04 are acceptable for compliance with the equivalent Requirements of this Directive.

• Timing metrics. Compliance is expressed in operational metrics familiar to aircraft operators: hours TIS and calendar days from the effective date. The AD sets the modification window as within 25 hours TIS or within 30 days after 20 October 2008, whichever occurs first. The functional test is required before further flight after the modification.

• Safety failure mode. The AD identifies the safety hazard in operational terms: incorrect connection or inadvertent disconnection of the switches may cause no CABIN ALT HI annunciation and no automatic deployment of oxygen masks, potentially resulting in hypoxia and incapacitation of crew, with loss of control consequences.

These concepts structure the AD’s demands: identify affected aeroplanes, apply the SB modification, verify by the permitted ground test, refuse the prohibited flight test method after the effective date, and accept FAA-approved AMOCs to the referenced FAA AD.

The AD affects a limited set of actors directly and implicates adjacent parties indirectly.

• Aircraft owners and operators of Model 390 aeroplanes with serial numbers RB-1 and RB-4 through RB-238 inclusive: They are the primary parties who must ensure compliance with the AD’s Requirements 1-3 within the specified windows. The compliance metrics (25 hours TIS or 30 days for the modification; before further flight for the functional test) impose operational decisions on these operators about scheduling maintenance, grounding aircraft and allocating resources.

• Maintenance organisations and certifying engineers: The modification and the functional ground test must be accomplished in accordance with Hawker Beechcraft Mandatory Service Bulletin SB 21-3899, original issue, May 2008, or an FAA-approved later revision as AMOC. Maintenance providers therefore must have access to the SB, the capability to implement the modification, and the competency to perform the Part I Ground Test Method in Paragraph 3 of the SB. They must also be aware that the flight test method in Part II is prohibited after the effective date.

• Design authority interfaces: The AD refers to FAA AD 2008-21-04 and accepts FAA-approved AMOCs of later SB revisions. That creates a channel in which FAA approvals and SB revisions play a decision role. Parties seeking alternative compliance methods would need FAA approval for an AMOC to FAA AD 2008-21-04 to be recognised by this AD. The AD therefore links Australian compliance status to FAA determinations.

• Regulators and delegated personnel: The AD is issued under the Civil Aviation Safety Authority (CASA) and is signed by a CASA delegate (Charles Lenarcic). Regulators or delegates will be the body that formally promulgates and enforces the AD, monitors compliance and maintains records. The AD itself does not set out enforcement mechanisms or penalties; however, it is a regulatory instrument that CASA administers.

• Pilots and flight crew: Indirectly affected. Operational decisions,such as grounding an aeroplane until the functional test is completed,affect crew rostering and dispatch. The AD’s safety rationale (risk of no CABIN ALT HI annunciation and no automatic mask deployment) is directly relevant to crew safety and the use of oxygen systems.

Who pays and who decides: The owner/operator pays for the parts, labour and grounding time required to implement the SB modification and perform the ground test. The maintenance organisation or certifying engineer decides how to implement the SB modification consistent with its instructions or with an FAA-approved AMOC. CASA, via its delegate, decides whether the AD is promulgated and will be the authority for subsequent regulatory action.

The AD creates a limited set of mandatory duties and recognises narrow equivalence rights via FAA AMOC approvals.

Key duties

• Perform the modification. Requirement 1 imposes a duty to modify the cabin barometric pressure switch and cabin altitude high switch installations in accordance with Hawker Beechcraft Mandatory Service Bulletin SB 21-3899, original issue, dated May 2008, if not previously accomplished. The duty is conditional on prior accomplishment; if the modification has already been done, an operator need not repeat it.

• Perform the functional test. Requirement 2 imposes a duty to perform a functional test of the switches and related systems using the Part I Ground Test Method in Paragraph 3 of the SB. The timing duty is explicit: the test must be performed before further flight after completing Requirement 1.

• Observe prohibition. Requirement 3 imposes a prohibitory duty: the flight test method described in Part II of the SB is prohibited after the effective date of the AD.

• Observe compliance timelines. The operator must meet the compliance window for Requirement 1 (within 25 hours TIS after 20 October 2008 or within 30 days after that date, whichever comes first) and ensure the Requirement 2 test is completed before the next flight after the modification.

Rights and limited equivalence

• Recognition of prior actions. Note 1 provides a narrow right: if the Part II flight test method was carried out before the effective date of the Directive and was performed after the Requirement 1 modification, then Requirement 2’s ground functional test is not required. That right is conditioned on the exact sequence of actions (modification first, then the Part II flight test, both before the effective date).

• Acceptance of FAA-approved AMOCs. The AD explicitly recognises later revisions of SB 21-3899 that have been approved by the FAA as an Alternate Method of Compliance to FAA AD 2008-21-04 as acceptable for compliance with the equivalent Requirements of this Directive. This creates an equivalence right for operators who follow an FAA AMOCed SB revision.

Operational implications of duties and rights

• Decisions on grounding: The duty to perform the modification within the stated window will require operators to schedule maintenance and accept aircraft downtime within 25 TIS or 30 days, whichever is earlier. The duty to complete ground testing before further flight effectively ties aircraft dispatch to completion of maintenance and verification.

• Proof and traceability: While the AD does not prescribe recordkeeping within the text, operators and maintenance organisations will need to establish documentary evidence that Requirement 1 and Requirement 2 (or the Note 1 exception or an FAA-approved AMOC) were complied with, to demonstrate compliance to CASA or an inspector.

• Discretion is limited: The AD prescribes the technical method (SB 21-3899 original issue) and prohibits one test method. The only explicit discretion allowed is the acceptance of FAA AMOCs for later SB revisions.

Each duty is express in the AD text under the headings “Requirement” and “Compliance” and in accompanying notes.

The AD text itself does not specify monetary penalties, sanctions or a detailed enforcement procedure. What the AD does provide in this document is the effective date (20 October 2008), the compliance timelines for each Requirement, and the identity of the issuer (Charles Lenarcic, Delegate of the Civil Aviation Safety Authority, dated 10 October 2008). The Directive frames the requirements as mandatory and ties compliance to a regulatory instrument.

Practical enforcement mechanisms and penalties are not described in the AD text presented. The AD does reference FAA AD 2008-21-04 and accepts FAA-approved AMOCs for later SB revisions; that cross-reference establishes an administrative relationship with FAA determinations but does not itself set out Australian enforcement procedures.

From the document content, the enforceable elements are the Requirements and the Compliance times: Requirement 1 (modify installations), Requirement 2 (perform Part I Ground Test Method), and Requirement 3 (prohibit the Part II flight test method). The compliance windows for these are specified: Requirement 1 within 25 hours TIS or 30 days after 20 October 2008, Requirement 2 before further flight after the modification, Requirement 3 after the effective date. These temporal constraints are the AD’s primary instruments for control.

Because the AD does not set out penalties or statutory enforcement processes in the supplied text, the AD leaves unanswered several practical enforcement questions in this instrument alone: how non-compliance is administratively detected, what remedial directions might be issued, whether overseas maintenance actions are accepted, and which civil penalties apply. Those matters are typically handled under the broader regulatory framework administered by the Civil Aviation Safety Authority, but they are not set out in this AD text.

The AD does, however, create a clear compliance expectation for operators and maintenance organisations. The absence of penalties or enforcement detail in the AD text does not affect the mandatory nature of an AD in practice, but any assertion about specific sanctioning mechanisms or penalty amounts would require consultation of the enabling statutes, CASA enforcement policies, or other regulatory instruments not contained in this document.

The AD explicitly interacts with a United States regulatory instrument and a manufacturer's service bulletin; beyond that, the AD does not cite other domestic laws or regulatory provisions within the supplied text.

• Cross-reference to FAA AD 2008-21-04. The Directive references FAA AD 2008-21-04 Amdt 39-15688 (Note 2) and accepts later revisions of SB 21-3899 that are approved by the FAA as Alternate Methods of Compliance (AMOCs) to FAA AD 2008-21-04 as acceptable for compliance with the equivalent Requirements of this Australian AD. That creates an explicit pathway by which an FAA approval or FAA-AMOCed SB revision is treated as an acceptable compliance method under this AD.

• Manufacturer's service bulletin as normative technical content. The AD makes Hawker Beechcraft Mandatory Service Bulletin SB 21-3899, original issue, May 2008, normative: Requirement 1 directs modification “in accordance with” the SB; Requirement 2 requires the functional test “in accordance with Part I - Ground Test Method in Paragraph 3 of the Accomplishment Instructions of SB 21-3899, original issue.” The AD therefore converts a manufacturer's SB into a regulatorily mandated method for the affected fleet, except where an FAA-approved later SB revision provides an alternative.

• Interaction of methods and dates. The AD privileges an FAA-approved AMOC for later SB revisions as equivalent. That linkage means FAA decisions on AMOCs to FAA AD 2008-21-04 have legal significance for compliance with this Australian AD. It also means that the scope and content of any acceptable alternative method are constrained by FAA approvals, rather than by CASA alone within the text of this AD.

• No direct references to domestic aviation statutes in the AD text. The AD is silent about how it sits within Australian statutory provisions or CASA enforcement frameworks. The AD itself is the instrument setting technical requirements for the identified aircraft; any interaction with primary legislation, penalties, or broader regulatory obligations is not specified here.

• Practical consequence: operators who have followed the FAA's path,either by complying with FAA AD 2008-21-04 or by using an FAA-approved AMOC,may have a clear route to compliance with this AD. Conversely, operators who have not sought FAA AMOCs must follow the SB as issued or establish compliance under the AD’s stated requirements.

In short, the AD integrates the manufacturer’s SB and the FAA AD into its compliance architecture: the SB provides the technical instructions; the FAA AD and FAA AMOC process provide an equivalence route recognised by this Australian Directive. No other legislative interactions are stated in this document.

The AD text provides limited chronological information about issuance and amendments.

• Effective date. The Directive states that it "becomes effective on 20 October 2008." The signature block shows the AD was signed on 10 October 2008 by Charles Lenarcic, Delegate of the Civil Aviation Safety Authority.

• Reference to FAA AD. The AD refers to FAA AD 2008-21-04 Amdt 39-15688 as a related instrument and notes that later revisions of SB 21-3899 approved by the FAA as AMOCs to FAA AD 2008-21-04 are acceptable for compliance. This implies an openness to later technical revisions at the manufacturer level, provided they are the subject of FAA AMOC approval.

• No internal amendments recorded. The AD text provided does not contain any internal amendment entries or a revision log for this Australian AD itself. There are no listed supersessions, cancellations, or later Australian amendments within the supplied document.

• Manufacturer SB revisions. Although the AD accepts later SB revisions approved by the FAA as AMOCs, the AD itself does not enumerate those later revisions or their dates. The AD therefore sets a baseline (SB 21-3899, original issue, May 2008) plus a pathway for later FAA-approved revisions to be treated as acceptable, but it does not catalogue any specific amendments to the SB or to the AD.

• Notes and exceptions. Note 1 and Note 2 in the AD provide conditional exceptions or cross-references rather than formal amendments. Note 1 creates a conditional exception for operators who conducted the Part II flight test before the effective date (if it occurred after the modification), and Note 2 identifies the FAA AD reference. These are part of the initial AD text rather than later amendments.

If users need a formal amendment history (dates of subsequent Australian AD revisions, cancellations or supersessions), that information is not present in the text supplied and would need to be obtained from CASA’s records or an authoritative AD repository. The AD as provided encapsulates a single issuance with an effective date of 20 October 2008 and an AMOC acceptance path referencing FAA processes.

The supplied AD contains no reference to litigation, legal challenges, court decisions, or tribunal proceedings. The text records the technical requirements, compliance times, notes and references to the FAA AD, and the signature of the CASA delegate. It does not include any record of disputes, appeals, or judicial review related to its issuance or application.

Because the AD text does not mention litigation or legal challenges, there is no litigation history to summarise from the provided document. Any litigation arising from compliance disputes, enforcement actions, or related matters would not appear in the AD itself and would require searching judicial records, regulatory enforcement logs or CASA administrative records beyond the content supplied.

For the purposes of compliance planning or risk assessment, stakeholders should treat the absence of litigation references in the AD as neutral: it is simply silent on that topic. If a party requires confirmation whether litigation has occurred about this AD, or whether any legal precedent addresses obligations or enforcement relating to it, that information is not available in the AD text and must be sought from court databases or regulatory records.

This AD contains several practical pitfalls and narrow drafting points that can lead to non-obvious compliance issues if not carefully managed.

• Narrow applicability list. The AD applies to Model 390 aeroplanes with serial numbers RB-1 and RB-4 through RB-238 inclusive. Serial numbers RB-2 and RB-3 are not included in the applicability statement. Operators must not assume broader model coverage: compliance obligations hinge on exact serial number inclusion. Misreading the serial number list may lead to unnecessary work or failure to comply where obligations do exist.

• Conditional equivalence for prior flight tests (Note 1). Note 1 provides a narrowly framed exception: if the Part II flight test method in Part II of the SB’s Accomplishment Instructions was carried out before the AD’s effective date and the flight test was done after Requirement 1 modification was accomplished, then Requirement 2’s ground functional test is not required. The exception depends on a precise sequence: (a) the SB modification was completed, (b) Part II flight test was then performed, and (c) both occurred before 20 October 2008. If any element of that sequence is missing or out of order, the operator must still perform the Part I ground test before further flight.

• Prohibition plus past-use tension. Requirement 3 explicitly prohibits the flight test method in Part II after the effective date. This interacts with Note 1: the AD allows prior use of Part II under the narrow condition described, but forbids its use going forward. Operators must therefore ensure that no Part II flight testing is scheduled after 20 October 2008 to meet the AD’s prohibition.

• Timing expressed in dual metrics. Requirement 1’s compliance window is “within 25 hours time-in-service (TIS) after 20 October 2008 or within 30 days after 20 October 2008, whichever occurs first.” Operators must track both hours TIS and calendar days. An aircraft with low utilisation may be obliged to complete the modification sooner in calendar time if 30 days occurs before 25 TIS elapse; conversely, a very high-utilisation aircraft might hit 25 TIS in fewer than 30 calendar days. Mis-tracking TIS or dates can create inadvertent non-compliance.

• “If not previously accomplished” phrase. Requirement 1 begins with “If not previously accomplished, modify…”. That language relieves operators who have already done the modification according to the SB from repeating it. However, operators must be able to demonstrate that the required modification was indeed previously accomplished in accordance with the SB; mere assertion without records is a compliance risk.

• Acceptance of FAA-approved AMOCs only. The AD accepts later SB revisions only if those revisions have been approved by the FAA as an AMOC to FAA AD 2008-21-04. That is a narrow equivalence path. An SB revision without an FAA AMOC to FAA AD 2008-21-04 is not, on the face of the AD text, automatically acceptable. Operators relying on alternative methods must ensure those alternatives have FAA AMOC status to satisfy the AD’s equivalence clause.

• Scope of the functional test. Requirement 2 requires performing “a functional test of the switches and related systems in accordance with Part I - Ground Test Method in Paragraph 3 of the Accomplishment Instructions of SB 21-3899.” The AD does not expand on what “related systems” entails; compliance therefore requires careful reading of Paragraph 3 in the SB itself. Maintenance providers who do not follow the SB’s Paragraph 3 precisely risk failing to meet the AD’s test requirement.

• No enforcement detail within the AD. The AD text does not specify how CASA will verify compliance, nor does it specify penalties for non-compliance. Operators should not construe that absence as lack of enforcement; rather, they should seek to satisfy the AD and maintain records because the AD sets out mandatory technical requirements regardless of the absence of procedural enforcement detail in this document.

• Recording and proof. The AD does not explicitly prescribe recordkeeping, but given the compliance windows and conditional exceptions, operators should obtain and retain clear evidence of modification completion dates, TIS at modification, and the date/method of any functional or flight tests. Lack of documentary proof will make it difficult to rely on Note 1’s exception or on having complied within the specified windows.

These are practical “gotchas” grounded in the AD text and the interplay of its timing, sequencing and method constraints. Operators and maintenance organisations should plan to read the SB’s Accomplishment Instructions carefully and to document each step to avoid inadvertent non-compliance.

The AD’s compliance path is direct but requires attention to sequence, timing and method. Below are concrete steps, strictly derived from the Directive’s text and notes.

1. Identify affected aeroplanes. Confirm whether the aircraft serial number is within the AD’s applicability: RB-1 and RB-4 through RB-238 inclusive. If the aircraft serial number is not listed, the AD does not apply to that airframe per the text.

2. Check prior modification status. Determine whether the modification to the cabin barometric pressure switch and cabin altitude high switch installations has already been accomplished in accordance with Hawker Beechcraft Mandatory Service Bulletin SB 21-3899, original issue, May 2008. Requirement 1 is prefaced by “If not previously accomplished,” so a properly documented prior compliance eliminates the need to repeat the modification.

3. If modification not previously accomplished, plan the SB modification. Carry out the modification in accordance with SB 21-3899, original issue (Requirement 1). Schedule the work so that it is completed within the compliance window: within 25 hours time-in-service (TIS) after the AD’s effective date (20 October 2008) or within 30 days after that date, whichever occurs first.

4. After modification, perform the functional test. Perform a functional test of the switches and related systems in accordance with Part I - Ground Test Method in Paragraph 3 of the SB (Requirement 2). The AD requires that this functional ground test be performed before further flight after the Requirement 1 modification.

5. Do not use the Part II flight test method after the AD’s effective date. Requirement 3 prohibits the flight test method described in Part II of the SB after 20 October 2008. Do not schedule or rely on that flight-test verification method going forward.

6. If Part II flight test was performed before the effective date. If, prior to the AD’s effective date, the Part II flight test method was carried out but only after the Requirement 1 modification was accomplished, then Requirement 2’s ground functional test is not required (Note 1). To rely on this exception, you must be able to demonstrate that the modification occurred first and that the Part II flight test was done afterward, both before 20 October 2008.

7. Consider FAA-approved AMOCs for later SB revisions. The AD accepts later revisions of SB 21-3899 that are approved by the FAA as AMOCs to FAA AD 2008-21-04 as acceptable for compliance with the equivalent Requirements of this Directive. If you intend to use a later SB revision, ensure it has FAA AMOC approval applicable to FAA AD 2008-21-04; otherwise the AD’s text requires adherence to the original SB.

8. Document every step. Although the AD does not itself spell out recordkeeping requirements, the sequencing and timing constraints, and the narrow exception in Note 1, mean operators should retain dated records showing: the serial number check, the date of SB modification completion and the aircraft’s TIS at that point, the date and method of the functional test or the prior Part II flight test (if applicable), and any FAA AMOC references relied upon.

9. Coordinate with maintenance organisations and certifying staff. Ensure the maintenance provider performing the SB modification and Part I ground test understands the AD’s prohibition on Part II flight testing after the effective date, and confirm that the work will be done “in accordance with” the SB’s Accomplishment Instructions or an FAA-approved AMOCed revision.

10. Be prepared for inspection. While the AD text does not specify enforcement mechanics, regulators will typically expect documentary proof of compliance. Keep evidence readily available for CASA inspection or during oversight activities.

These steps follow directly from the AD’s Requirements, Compliance section and Notes. They emphasise sequence, timing and adherence to the SB’s specified methods or to FAA-AMOCed SB revisions.