This Airworthiness Directive, AD/AIRCON/12 Amdt 5 (20/2019), imposes mandatory inspection, testing, overhaul or disablement or replacement requirements on a defined set of aircraft cabin combustion heaters. It applies to Hartzell Engine Technologies, Kelly Aerospace Power Systems and Janaero Devices B‑Series heaters (models B1500, B2030, B3040, B4050 and B‑Series Extended Life models B2500, B3500 and B4500) that are marked as meeting FAA TSO‑C20 and are fitted to an aircraft, as stated in the Applicability section. Mechanically, the AD requires operators to carry out recurring tasks: (a) a suite of visual and functional inspections of heater installations and associated airframe‑mounted components (Requirement 1); (b) either a pressure decay test (following specified Janitrol manuals) or a quantitative carbon monoxide measurement of heated air entering the cabin, with a numerical pass threshold (Requirement 2); (c) an operational test of the air pressure switch (Requirement 3), with a specified parts exemption (P/N 94E42); and (d) overhaul according to the manufacturer’s Time Between Overhaul schedule or disablement/replacement where tests fail (Requirements 4 and 5). The AD also prescribes the specific actions to “disable” a heater if required, including capping the fuel line, disconnecting electrical power, testing that heaters are inoperative and fabricating a pilot‑visible placard reading “System Inoperative”.

The AD sets compliance timing: initial compliance for Requirements 1-3 by the earlier of 100 heater hours or 12 months from the AD’s effective date unless already done under the previous amendment, and thereafter at intervals not exceeding the earlier of 100 heater hours or 24 months time in service (TIS). Overhaul intervals are set by the manufacturer’s published Time Between Overhaul for each heater model. The AD commenced on 16 October 2019 and is signed by the CASA delegate named in the instrument. In the Background the AD records two heater failures, one leading to an explosion and one to a baggage compartment fire, as the operational incidents motivating the Directive. AD/AIRCON/12 Amdt 5 specifically removes a prior Note 1 from the applicability that referenced a cancelled AD, AD/AIRCON/9.

The instrument revolves around a small set of technical and administrative concepts expressed as Requirements and Compliance rules. These concepts, and where they appear in the AD, are:

• Applicability: the AD applies narrowly to identified heater makes and B‑Series model numbers that carry an FAA TSO‑C20 marking, and only when these heaters are fitted to an aircraft. The Applicability box lists the precise models and the TSO marking condition.

• Inspection and maintenance tasks (Requirement 1): a prescribed checklist of physical inspections and minor maintenance actions. These include condition and security checks of the installation and airframe‑mounted components necessary for heater operation; inspection of hot air outlet ducting adjacent to the heater for exhaust contamination and corrosion; cleaning the heater fuel filter where installed; checking fuel system connections and leaks using system pressure; inspecting heater drain lines for obstructions; and inspection and adjustment of spark plugs and contact breaker points in accordance with the manufacturer’s published instructions.

• Pressure decay test or CO measurement (Requirement 2): operators must take at least one of two options. Option one is a pressure decay test performed according to Janitrol overhaul and maintenance manuals P/N 24E25‑1 (standard B‑Series) and P/N 94E47 (B‑Series EL), “as in force from time to time”. Option two is a functional check where a quantitative carbon monoxide (CO) measurement is taken of the heated air entering the cabin; the AD sets the pass threshold as less than 1 part in 20 000 parts of air, equivalent to 50 parts per million.

• Failures and remediations (Requirement 2(2)): if the heater fails any part of the pressure or CO test, the AD requires either an overhaul in accordance with Requirement 4, disablement in accordance with Requirement 5, or replacement.

• Pressure switch operational test (Requirement 3): an operational test of the heater air pressure switch “in accordance with the combustion heater manufacturer’s Overhaul and Maintenance Manual”, unless an air pressure switch P/N 94E42 is installed; if the switch fails, the operator must either disable the switch per Requirement 5 or replace it.

• Overhaul (Requirement 4): overhaul of the heater and associated airframe‑mounted components in accordance with the particular model’s overhaul and maintenance manual, “as in force from time to time”, with intervals governed by the manufacturer’s published Time Between Overhaul.

The primary actors obliged by the AD are aircraft operators and owners who have aircraft fitted with the applicable B‑Series cabin combustion heaters marked to FAA TSO‑C20. That is, individuals, companies and maintenance organisations responsible for the continuing airworthiness of aircraft using Hartzell Engine Technologies, Kelly Aerospace Power Systems or Janaero Devices B‑Series or B‑Series EL heaters. The Applicability box explicitly limits the AD to listed heater models and the FAA TSO marking; aircraft without those heaters are out of scope.

Maintenance organisations and certificated mechanics who perform inspections, pressure decay tests, CO measurements, pressure switch tests, overhauls and disablements are secondarily affected because the AD prescribes specific tasks to be done “in accordance with” manufacturer manuals or service bulletins. The AD references specific Janitrol manuals (P/N 24E25‑1 and P/N 94E47) for the pressure decay test, and Kelly Aerospace Service Bulletin No. 25 for temporary disablement procedures. Use of these documents means authorised maintenance providers must have access to and follow the versions “as in force from time to time”.

Aircraft operators who rely on cabin heating services are affected operationally if a heater must be disabled or replaced under the AD. Requirement 5 requires disabled heaters to be clearly placarded “System Inoperative” at the heater control valve within the pilot’s clear view, and any disablement must respect minimum equipment lists and permissible unserviceabilities approved under Civil Aviation Regulations 1988 regulation 37, which the AD cites. The AD therefore interacts with pre‑existing MEL arrangements that affect dispatch decisions.

Regulators and CASA delegates are affected in that the AD is a regulatory instrument imposed by the Civil Aviation Safety Authority; it notes the delegate who signed the Directive. The AD also cross‑references a FAA airworthiness directive (FAA AD 2004‑21‑05) as consistent, so aircraft owners and maintainers who operate internationally or follow FAA guidance must reconcile both instruments.

Finally, costs fall to those who own and operate affected aircraft. The AD imposes recurring inspection and test obligations and potentially expensive outcomes such as overhaul, replacement or permanent modification where failures occur. The instrument provides a practical accommodation for tallying heater hours where a heater hour meter is not installed, by allowing aircraft hours divided by two to be used, which affects operator recordkeeping practices.

Duties

• Perform the inspection tasks listed in Requirement 1: inspect the heater installation and necessary airframe‑mounted components for general condition and security; inspect hot air outlet ducting adjacent to the heater for exhaust contamination and corrosion; clean the heater fuel filter if one is installed; check the heater fuel system for loose connections and leaks using system pressure; inspect heater drain lines for obstructions; inspect and adjust spark plugs and contact breaker points where necessary in accordance with the manufacturer’s published instructions. These are mandatory actions mandated by the AD.

• Conduct either the pressure decay test or the CO measurement in Requirement 2. The pressure decay test must be done in accordance with the Janitrol manuals P/N 24E25‑1 (B‑Series standard) and P/N 94E47 (B‑Series EL), “as in force from time to time”. The alternative functional check requires measurement of quantitative CO of the heated air entering the cabin and a pass value of less than 1 part in 20 000 parts of air (50 ppm).

• If the heater or pressure switch fails the specified test, operators must either overhaul (Requirement 4), disable (Requirement 5) or replace the heater or component, according to the pathways set out. Requirement 2(2) and 3(2) specify these mandatory remedial options.

• Perform an operational test of the air pressure switch in accordance with the manufacturer’s Overhaul and Maintenance Manual, unless the air pressure switch P/N 94E42 is installed (Requirement 3(1) and 3(3)). If the switch fails, follow Requirement 3(2).

• Overhaul the heater and associated airframe components in accordance with the applicable overhaul manual and manufacturer’s published Time Between Overhaul (Requirement 4).

• If disabling the heater under Requirement 5, perform the detailed disablement steps (cap fuel supply line; disconnect electrical power and secure connections; inspect and test to ensure heater system is disabled and cabin fans are operative; ensure no other aircraft system is affected; ensure no fuel leaks; fabricate and install “System Inoperative” placard in pilot’s clear view).

Rights and constraints

• Operators have a limited choice of compliance route under Requirement 2: either the pressure decay test or the quantitative CO check. The AD does not prescribe one as mandatory, but sets an acceptability threshold for the CO option.

The text of the AD itself does not set out criminal penalties or administrative fines in the instrument. As an Airworthiness Directive issued by the Civil Aviation Safety Authority, it is a mandatory safety requirement; non‑compliance with an AD generally means an aircraft is not maintained in accordance with applicable airworthiness requirements, which can have regulatory consequences under the Civil Aviation Act framework and associated regulations. The AD cross‑references regulation 37 of the Civil Aviation Regulations 1988 in relation to permissible unserviceabilities, which indicates that the AD is integrated with existing regulatory tools governing aircraft dispatch and equipment status.

Enforcement mechanisms that are implicit in the instrument arise from the AD’s mandatory nature. Civil aviation regulators typically use a combination of surveillance, audit of maintenance records, airworthiness certification checks and, where appropriate, administrative sanctions or grounding actions to enforce AD compliance. The AD requires actions to be performed “in accordance with” specified manuals and notes that permanent disablement requires approved modification data before return to service. These elements create documentary obligations (maintenance records, compliance referencing manuals and service bulletins) that are verifiable by regulator inspectors.

The AD also locates remedial responsibilities on operators and maintainers: if tests fail, operators must overhaul, disable or replace heaters, and if disabling, must follow the listed steps and placard the control. Failure to carry out these steps would leave an aircraft potentially uncertified for flight or in breach of MEL/regulatory permissions. The AD’s reference to the Civil Aviation Regulations 1988 makes regulation 37 relevant to whether a discrepant heater may be accepted for flight, and so regulatory discretion arises in decisions on permissible unserviceabilities.

The AD does not itself specify time limits for enforcement actions or appellate avenues. It does, however, specify commencement and compliance timeframes, which are objective measures an inspector would use to assess compliance. The AD also reiterates consistency with an earlier FAA AD, which may inform cross‑jurisdictional enforcement practices for internationally operated aircraft. The instrument therefore creates enforceable technical obligations and leaves enforcement and any sanctions for non‑compliance to the broader civil aviation regulatory regime rather than spelling out penalties within the AD text.

The AD explicitly cross‑references the Civil Aviation Regulations 1988 by citing regulation 37 in Requirement 5 when addressing disablement and permissible unserviceabilities or minimum equipment lists. That means the AD does not operate in isolation: disablement options and any continued dispatch of an aircraft with a disabled heater must be consistent with MEL provisions or approved permissive unserviceability arrangements under regulation 37. The AD therefore defers to regulation 37 where operational exceptions to equipment requirements are at issue.

The AD also references an FAA airworthiness directive, stating that FAA AD 2004‑21‑05 Amdt 39‑13826 is consistent with this AD (Note 3). That establishes cross‑jurisdictional alignment between CASA’s AD and the FAA AD on the same heater types, and suggests that affected aircraft operating internationally or in multiple regulatory environments will need to ensure compliance with both instruments as applicable.

The AD incorporates technical documentation by reference and in a way that allows those documents to be updated. Requirements 2(1)(a) and 2(1)(b) require tests “in accordance with the instructions contained in Janitrol Aircraft Heaters - Overhaul and Maintenance Manual part number (P/N) 24E25‑1 (for the B‑Series (standard) units), and P/N 94E47 (for the B‑Series (EL) units) as in force from time to time” and Requirement 3 refers to “the combustion heater manufacturer’s Overhaul and Maintenance Manual, as in force from time to time”. This phrasing integrates external manufacturer documents into regulatory obligations and gives those documents a continuing role even as they are updated, thereby creating a de facto link to private technical publications that affect compliance standards.

The AD references Kelly Aerospace Power Systems Service Bulletin No. 25 for procedures to temporarily disable the heater (Note 1). The AD’s Amdt 5 removes an earlier Note 1 from the applicability that referenced AD/AIRCON/9 which has been cancelled. That history links the current AD to prior CASA instruments and to particular manufacturer service guidance.

The AD interacts with maintenance and certification approval processes: permanent disablement will require “approved modification data” and internal inspection and functional tests before return to service (Note 2). Those approvals are part of the wider airworthiness framework that governs modifications and approvals for changes to type‑certificated aircraft systems.

Finally, because the AD concerns equipment marked to FAA TSO‑C20, there is an implicit connection to FAA technical standards for that TSO. The instrument confines itself to heaters marked to that TSO and consequently has effects where aircraft certification or equipment acceptance relies on FAA TSO standards. In short, the AD sits within, and defers at points to, an existing set of regulatory and technical instruments: Civil Aviation Regulations, manufacturer manuals and service bulletins, FAA ADs and TSO requirements, and the administrative approval mechanisms for modifications and MELs.

The AD record in the Background provides a concise amendment history which must be read as part of the current instrument. The history, as stated in the Background, is:

• AD/AIRCON/12 original: became effective on 2 January 1997. This is the originating airworthiness directive for this subject matter.

• AD/AIRCON/12 Amdt 1: became effective on 13 June 2002. The AD text does not set out the content of that amendment, but the date is recorded.

• AD/AIRCON/12 Amdt 2: became effective on 20 January 2005. Amdt 2 removed the terminating action that had been provided by the fitment of ceramic‑coated combustion tubes. The Background states the reason for this removal: ceramic‑coated combustion tubes were demonstrated to suffer from the same problems as uncoated combustion tubes, so the earlier terminating action was no longer appropriate.

• AD/AIRCON/12 Amdt 3: became effective on 14 April 2005. Amdt 3 changed the overhaul period to include an option to follow the manufacturer’s recommended overhaul period and clarified aspects relating to the disabling of the heater.

• AD/AIRCON/12 Amdt 4: effective date not restated in the Background for the original but Amdt 4 made reference to the overhaul and maintenance manual for the B‑Series (EL) units and pertinent manufacturer’s data relative to heater disabling and return to service. The Amdt 4 statement simplified the overhaul compliance statement to reflect manufacturer requirements and included minor editorial changes.

• AD/AIRCON/12 Amdt 5 (this instrument): removes Note 1 from the applicability section of the AD. Note 1 had referenced AD/AIRCON/9, which has been cancelled. Amdt 5 is published as AD/AIRCON/12 Amdt 5 with the AD number repeated and signed by the CASA delegate. The AD commences on 16 October 2019 according to the Compliance box.

The document records cause and consequence over time: the removal of the ceramic‑coated combustion tube as a terminating action reflects a technical reassessment; subsequent amendments have shifted the focus to aligning overhaul periods with manufacturer recommendations and to clarifying disablement and return to service processes. Amdt 5 is a limited textual amendment removing a now‑obsolete cross‑reference to a cancelled AD. The AD also notes consistency with FAA AD 2004‑21‑05 Amdt 39‑13826, connecting the amendment history to earlier international directives.

The AD does not record any litigation arising from the instrument. The Background and other parts of the AD provide administrative history and the rationale for changes but do not mention court challenges or judicial decisions. There are no cases or judicial outcomes cited in the text of the AD, and no statutory appeals or judicial review pathways are described within it.

Given the absence of litigation references in the AD, practitioners should treat the instrument as an administrative regulatory action recorded by CASA and signed by the delegate named in the instrument. Where interested parties seek to challenge an AD, usual avenues under administrative law would be the processes available in the Civil Aviation Act and related legislation or general administrative law remedies, but such avenues and their applicability are not explored or specified in this AD text. The AD does cross‑reference Civil Aviation Regulations 1988 regulation 37 in relation to permissible unserviceabilities; that regulatory framework governs operational acceptance of equipment defects but the AD does not record any disputes or enforcement proceedings under those provisions.

Because the AD incorporates manufacturer manuals and service bulletins “as in force from time to time”, a potential area of dispute could involve which version of a manual was applicable at a particular date or whether compliance with an updated manual meets the AD requirements. The AD’s phrasing that manuals are applicable “as in force from time to time” creates an administrative linkage that could give rise to factual disputes about versions and compliance records. However, the AD itself does not document any litigation or dispute resolution outcomes.

Practitioners who require the existence of any litigation or court precedents should note that this instrument contains no such material and should look to judicial databases, regulatory enforcement records or CASA administrative records outside this AD text for any enforcement or contestation history.

The AD contains several practical traps for operators and maintainers; these are not legal conclusions but fact‑based elements in the AD text that commonly cause compliance failure if overlooked.

• Applicability narrowness: the AD applies only to the specified B‑Series models and only when marked as meeting FAA TSO‑C20. Operators may assume any B‑Series heater is covered, but the TSO marking is a necessary condition. Confirm the heater model and TSO marking before deciding AD applicability.

• Manuals “as in force from time to time”: several Requirements mandate actions “in accordance with” manufacturer Overhaul and Maintenance Manuals or Janitrol P/N manuals, “as in force from time to time”. That language binds the operator to the version of the manual current at the time of the action rather than to a single static edition. Keep an auditable record of which manual version was used for each action.

• CO measurement requires quantitative instruments and a specific pass threshold: the AD permits a CO functional check as an alternative to a pressure decay test, but it requires quantitative CO measurement and sets the threshold at less than 1 part in 20 000 parts of air (50 ppm). Ensure that the CO meter used is capable of quantitative measurement, appropriately calibrated, and that the measurement location is the heated air entering the cabin. Failure to use a quantitative instrument or to measure at the prescribed point could be grounds for non‑compliance.

• Pressure switch exemption limited by part number: Requirement 3(3) exempts operators from performing Requirement 3 if air pressure switch P/N 94E42 is installed. That exemption is precise , it is for that part number only. Maintain parts records to demonstrate whether this exemption applies.

• Failure pathways mandatory and immediate: if a heater fails any part of the pressure/CO test, the AD mandates one of three actions: overhaul per Requirement 4, disable per Requirement 5, or replacement. There is no temporary “operate with caution” status unless an MEL or permissible unserviceability under regulation 37 applies. Operators must be prepared with approved maintenance facilities or parts to effect overhaul or replacement or to implement disablement.

• Disablement is constrained by MEL/regulation 37: Requirement 5 is expressly “subject to any minimum equipment list requirements or permissible unserviceabilities approved under regulation 37 of the Civil Aviation Regulations 1988”. If an operator’s MEL does not permit flying with a disabled heater, then disablement may not be an immediate option in operational contexts.

This AD prescribes a clear, stepwise compliance regime. Below is a practical checklist and explanation grounded in the AD text, with references to the relevant Requirements and Compliance provisions.

1. Confirm applicability

• Verify the heater model is one of: B1500, B2030, B3040, B4050, B2500 (EL), B3500 (EL), B4500 (EL) and that the heater is marked as meeting FAA TSO‑C20. If both conditions are met and the heater is fitted to an aircraft, the AD applies.

2. Schedule initial work

• If Requirements 1-3 have not already been accomplished under AD/AIRCON/12 Amdt 4, perform them by the earlier of 100 heater hours or 12 months after the AD’s effective date, as stated in the Compliance box. Thereafter perform Requirements 1-3 at intervals not exceeding the earlier of 100 heater hours or 24 months TIS. If a heater hour meter is absent, estimate heater TIS by dividing aircraft hours by two (Note 4).

3. Perform Requirement 1 (inspection and minor maintenance)

• Inspect the combustion heater installation and any necessary airframe‑mounted components for general condition and security.
• Inspect the hot air outlet ducting adjacent to the heater for freedom from exhaust contamination and corrosion.
• Clean the heater fuel filter, if installed.
• Check the heater fuel system for loose connections and leaks using system pressure.
• Inspect heater drain lines for freedom from obstructions.
• Inspect and adjust spark plugs and contact breaker points where necessary, following the manufacturer’s published instructions.
• Document findings, corrective actions, and reference the manufacturer manual edition used.

4. Perform Requirement 2 (pressure test or CO measurement)

• Option A: Pressure decay test. Carry out a pressure decay test in accordance with Janitrol Aircraft Heaters - Overhaul and Maintenance Manual P/N 24E25‑1 (B‑Series standard) or P/N 94E47 (B‑Series EL), as applicable, and “as in force from time to time”.
• Option B: Functional CO check. Use a quantitative CO analyser to measure the CO level in the heated air entering the cabin. Ensure the measurement point is the heated air entering the cabin and that instruments are calibrated. The CO level must be less than 1 part in 20 000 parts of air, equivalent to 50 ppm, to pass.