AD/B737/294 Amdt 2 - Flightcrew Oxygen Masks

Several key concepts underpin this directive. Airworthiness Directive (AD): A legally enforceable notice issued by CASA requiring mandatory action on an aircraft, engine, propeller, or component to correct an unsafe condition. Non-compliance renders the aircraft unairworthy and illegal to operate under the Civil Aviation Safety Regulations. Airplane Flight Manual (AFM): The FAA-approved or CASA-approved manual for each aircraft type that contains operating procedures, limitations, performance data, and systems information. The AD requires revisions to both the Normal and Emergency/Non-Normal sections of the AFM, making the new procedures part of the approved operating documentation. Cabin Altitude Warning Horn: An aural warning system that sounds when cabin altitude exceeds 10,000 feet (intermittent in flight) or indicating improper takeoff/landing configuration (intermittent on ground, steady in flight). The directive clarifies the three conditions under which the horn sounds and prescribes the crew response. Hypoxia: A deficiency of oxygen reaching the body tissues, which can impair judgment and coordination and lead to unconsciousness. The AD’s background identifies hypoxia as the critical risk if flight crew fail to recognise and react to the cabin altitude warning. Pressurization Mode Selector: A cockpit control that determines whether the cabin pressurisation system operates automatically (AUTO) or manually. The AD mandates that, for normal operations, this selector must be in AUTO prior to takeoff, standardising the procedure across all affected models. Alternate Means of Compliance (AMOC): An alternative method approved by the relevant aviation authority that achieves an equivalent level of safety to the method prescribed in the AD. The directive explicitly accepts AMOC Letter 130S-09-134a as complying with requirement 2. AFM Revision by Insertion vs General Revision: The AD permits two methods for amending the AFM: (1) inserting a copy of the AD into the AFM as a temporary revision, or (2) incorporating the identical statements into a subsequent general revision of the AFM. Once a general revision includes the required text, the AD copy may be removed from the applicable sections, though the compliance record must still show when the action was completed. Effective Date and Compliance Time: The amendment takes effect on 27 September 2013. Operators must complete the AFM revision within 60 days after that date, making the deadline 26 November 2013. Optional Notation for Prior ADs: The directive allows operators of earlier 737 models to use updated wording from this AD when revising the “Cabin Altitude Warning or Rapid Depressurization” procedure required by AD/B737/255, AD/B737/208, or AD/B737/216, provided they make a notation in the compliance summary for those earlier ADs. This avoids duplicative changes and clarifies that the newer wording is acceptable.

This directive directly affects operators of Boeing 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800, and -900 series aeroplanes that are registered in Australia or operated under an Australian air operator certificate. That includes airlines, charter operators, cargo carriers, corporate flight departments, and any person or entity that conducts air operations with those types under Australian jurisdiction. The AFM revisions must be completed within 60 days, so maintenance organisations, flight operations departments, and technical record keepers are responsible for implementing the changes. Flight crews are the ultimate end-users: they must be briefed on the revised procedures for pressurisation mode selection and for the warning horn response checklists. Training departments must update initial and recurrent training syllabuses to reflect the new AFM wording, particularly the distinction between intermittent and steady warning horn conditions and the associated oxygen mask actions. Because the directive revises the AFM, it also affects the aircraft’s continued airworthiness management - any maintenance release or airworthiness review must confirm that the AFM has been revised in accordance with the AD. Foreign operators flying Australian-registered 737s are also caught. The directive does not apply to 737 models not listed (e.g., 737 MAX series, as those were not in service at the time of this AD) nor to operators outside Australian jurisdiction unless they operate under an Australian certificate. Additionally, CASA itself is affected as the regulator issuing and enforcing the AD, and its delegates (like Peter Nikolic, who signed the directive) are involved in approval processes such as AMOCs. The FAA is indirectly affected because the AD references an FAA AD (2006-13-13) and an FAA AMOC letter, reflecting the harmonisation of US and Australian airworthiness requirements for a common aircraft type. Suppliers of AFM revision materials - such as Boeing itself or third-party manual publishers - may need to ensure that their updated AFM content matches this AD. Finally, insurers may require evidence of AD compliance as part of risk assessments, linking this directive to insurance markets and liability considerations. The concentrated effect falls on the relatively small number of Australian operators of older 737 models, which face a low-cost but mandatory administrative task with safety implications.

The directive imposes a primary duty on the aircraft operator or registered owner to revise the AFM within 60 days of the effective date (27 September 2013). This duty is not delegable to the flight crew or a third-party maintenance provider unless the operator ensures the revision is actually completed and documented. The duty to revise includes two specific requirements: insert the pressurisation mode selector procedure into Normal Procedures, and insert the warning horn/oxygen mask procedure into Emergency or Non-Normal Procedures as appropriate for the model. Operators have the right to choose between two revision methods: inserting a copy of the AD into the AFM, or incorporating the identical statements into a general revision of the AFM. If they choose the latter, they may later remove the AD copy from the relevant sections provided the general revision already contains the required wording. This gives flexibility to operators who maintain structured manual revision programs. For operators with older 737-100/200/200C models, the directive grants a right to use revised wording (“If the intermittent cabin altitude/configuration warning horn sounds in flight:” instead of “If the cabin altitude warning horn sounds:”) when complying with AD/B737/255, provided they note this in the compliance summary for that AD. Similar rights exist for 737-300/400/500 operators (using wording in place of AD/B737/208 wording) and 737-600/700/800/900 operators (using wording in place of AD/B737/216 wording). This optional action saves operators from having to maintain two slightly different sets of wording. Operators also have the right to use an approved AMOC - specifically FAA AMOC Letter 130S-09-134a dated 28 April 2009 - as an alternative way to satisfy requirement 2 of the AD. This is a significant right because it may allow operators to use less burdensome or more integrated procedures if the FAA has already approved them. However, that AMOC must be followed exactly; any deviation would require separate CASA approval. Operators are not required to place the AD in the AFM permanently; once a general revision covers the statements, they can remove the copy of the AD from the revised sections. There is no duty to notify CASA of compliance unless the operator is otherwise audited or the AD is checked during an airworthiness review. The background to the AD also implies a duty on flight crews to be familiar with the AFM revisions; failure to follow the procedure during an incident could be used as evidence of non-compliance with operational rules. The directive does not create private rights of action, but non-compliance could be used in civil litigation as evidence of a breach of the duty of care to maintain an airworthy aircraft.

The directive itself does not set out penalties, but as an airworthiness directive issued under the Civil Aviation Safety Regulations, non-compliance attracts the penalty framework of the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998. Operating an aircraft that is not compliant with an applicable AD is an offence under regulation 42.105 of CASR, which can lead to civil penalties, criminal prosecution, or both. Penalties for individuals can include fines of up to $10,000 or more per offence, and for corporations, significantly higher amounts (potentially hundreds of thousands of dollars under the Regulatory Powers (Standard Provisions) Act 2014). More practically, CASA can suspend or cancel the aircraft’s certificate of airworthiness or the operator’s air operator certificate for systematic non-compliance. When a defect is found, CASA may issue an enforceable undertaking or a direction to rectify, and failure to comply with that direction is a further offence. Enforcement is typically initiated after a ramp inspection, audit, or incident. The AD also has a direct safety consequence: failure to follow the revised procedure could result in hypoxia and loss of the aircraft, exposing the operator to criminal negligence or manslaughter charges if deaths occur. For the specific AD, compliance is due within 60 days, so CASA would likely treat non-compliance after that date as a serious matter. The AD’s background notes that it was triggered by reports of aeroplanes that failed to pressurise and flight crews that failed to react to the warning horn - this history would inform CASA’s enforcement discretion. Since the AD does not require a one-time physical modification but only a manual revision, enforcement action would centre on whether the AFM contains the required language and whether the crew operated in accordance with it. Records of AFM revision (such as a sign-off in the technical log or a revision sheet) are key evidence. CASA can also impose conditions on the air operator certificate requiring proof of compliance. The AD references FAA AD 2006-13-13, meaning non-compliance could affect Australia’s bilateral aviation safety agreement with the United States, potentially leading to grounding orders if the aircraft flies into US airspace. In practice, enforcement of this AD is likely to be reactive: triggered during audits or after an incident. The AMOC provision provides a defence if the operator used the approved alternate means, but the burden of proof lies with the operator to show compliance with the AMOC letter.

This directive operates within the hierarchy of Australian aviation safety law. It is issued under the Civil Aviation Safety Regulations 1998, specifically under a delegation from CASA (the delegate is Peter Nikolic). It interacts directly with three earlier Australian airworthiness directives: AD/B737/255 (for -100/200/200C models), AD/B737/208 (for -300/400/500 models), and AD/B737/216 (for -600/700/800/900 models). The directive allows operators to use the updated warning horn wording from this AD in place of the phrasing required by those earlier ADs, provided they note the substitution in the compliance summary. This creates a form of supersession without formally cancelling the earlier ADs - the earlier requirements remain in force, but the acceptable wording is updated. The directive also references FAA AD 2006-13-13 Amdt 38-14666 dated 15 June 2006. That FAA AD is the US equivalent from which this Australian AD is likely derived. The FAA AD originally mandated similar AFM revisions. Because the Boeing 737 is a US type-certificated aircraft, CASA relies on FAA airworthiness standards (14 CFR Part 25) and existing FAA ADs as a base. This AD harmonizes Australian requirements with the US baseline. The AMOC accepted by this AD is an FAA letter (130S-09-134a), which demonstrates recognition of US approvals under the bilateral agreement. The directive must also be read with Part 4 of the Civil Aviation Regulations 1988 (CAR) concerning flight manuals, and with regulation 42.105 of CASR which requires compliance with ADs. State and territory laws against reckless operation or endangerment could also apply if non-compliance leads to an incident. Because the directive concerns flight crew procedures, it interacts with the operational rules under CASR Part 61 (pilot licensing), Part 91 (general operating rules), and Part 121 or 135 (air transport operations) requiring pilots to use the AFM. The AFM itself is a legal document under the type certificate and is referenced by the aircraft’s certificate of airworthiness. Changes to the AFM must be approved or otherwise authorised; this AD provides that authorisation. The directive also interacts with workplace health and safety laws - Part 2 of the Work Health and Safety Act 2011 (Cth) imposes duties on persons conducting a business or undertaking to ensure the health and safety of workers (flight crew), and failure to maintain an up-to-date AFM could be a breach of that duty. However, aviation safety law likely operates as a specific regime that displaces general WHS in case of inconsistency. The directive does not directly interact with contract law, but operators may have contractual obligations with lessors or insurers to maintain AD compliance, and non-compliance could constitute a breach of an aircraft lease or insurance policy condition.

This document is Amendment 2 to AD/B737/294. It was issued on 4 September 2013 by Peter Nikolic, Delegate of CASA, and took effect on 27 September 2013. The original issue of AD/B737/294 became effective on 28 September 2006. That original AD would have contained the core requirements to revise the AFM for pressurisation mode selector (AUTO prior to takeoff) and the warning horn/oxygen mask procedure, without the later modifications. Amendment 1 became effective on 26 October 2006 and removed the word “RECALL” from the AFM amendment detailed in Requirement 2, placing that word on the second line of the AFM. The background notes explain that in the original wording, the heading for the warning horn procedure likely read “WARNING HORN - CABIN ALTITUDE OR CONFIGURATION RECALL” and Amdt 1 deleted “RECALL” from that heading, moving it to the second line (presumably becoming part of the condition description or a separate line). The current wording in the AD shows “RECALL” as part of the main heading: “WARNING HORN - CABIN ALTITUDE OR CONFIGURATION RECALL”. This appears inconsistent with the background statement that Amdt 1 removed it. One interpretation is that the heading was changed so that “RECALL” now appears on the second line, yet the text of the AD as published in Amdt 2 still shows the full heading. The likely explanation is that the published AD incorporates the heading as revised by Amdt 1, but the presentation in this document may have been formatted to include “RECALL” as part of the heading for interpretative clarity. Regardless, the current version is what operators must use. Amendment 2, which is the subject of this analysis, does two things: it allows the revising of the AFM using the approved FAA AMOC Letter 130S-09-134a dated 28 April 2009 as an alternate means of complying with requirement 2 (the warning horn procedure), and it incorporates the optional action provisions for older ADs. Amendment 2 also likely clarifies or updates the wording slightly, though the core requirements remain identical to the original AD except for the AMOC addition. The directive also indicates that a “Note: FAA AD 2006-13-13 Amdt 38-14666 dated 15 June 2006 refers” - that note likely appeared in the original AD and was retained. The amendment history shows that the directive has been adjusted over seven years to accommodate operating experience (the RECALL removal clarified the procedure) and to allow alternative compliance (the AMOC addition reduced burden on operators who had already obtained FAA approval). No further amendments have been made, meaning Amdt 2 remains current for the affected models. Operators should ensure they have the Amdt 2 version, not the earlier versions, in their compliance records.

The source document does not cite or mention any litigation history related to this AD specifically. There are no references to court cases, administrative appeals, or tribunal decisions involving AD/B737/294 or its amendments. That is typical for airworthiness directives: they are rarely directly litigated because they are regulatory instruments that operators generally comply with, and any dispute is more likely to arise from enforcement action (which may settle before hearing) or from a broader challenge to CASA’s authority. Indirectly, the AD may have been referenced in litigation concerning an incident where hypoxia was alleged. For example, if an operator failed to implement the revised AFM procedure and a crew was incapacitated in a depressurisation event, the AD would be evidence of the standard of care. However, no such Australian case is publicly known. The AD’s background references “reports that aeroplanes have failed to pressurize, and that the flight crews failed to react properly to the cabin altitude warning horn.” Those reports may have come from US NTSB or Australian Transport Safety Bureau investigations, but the source does not name any specific occurrences. The AD is a preventive regulatory response, not a retrospective penalty. The FAA AD (2006-13-13) that this Australian AD mirrors may have been litigated in the US: some FAA ADs have been challenged in the US Court of Appeals under the FAA’s authority, but no such challenge is recorded for this particular AD. In Australia, judicial review of CASA’s decisions under the Administrative Decisions (Judicial Review) Act 1977 is possible, but there is no evidence that any operator sought review of AD/B737/294. The cost of compliance (revising a few pages of the AFM) is modest, making litigation a disproportionate response. The AMOC provision may have been requested by an operator that otherwise might have considered seeking a variation, but the AMOC was approved without litigation. The only possible litigation angle would be an enforcement action by CASA against an operator for non-compliance, and then the operator might argue that the AD was invalid or that the AMOC was not properly considered. No such case has been identified. Therefore, the litigation history can be described as none to report from the source itself. A careful analyst should state that there is no litigation mentioned in the document and that independent research beyond the source reveals no significant court decisions specifically on this AD.

Several nuances in the directive could trip up operators if read quickly. First, the compliance time is “Within 60 days after the effective date of this AD.” The effective date is 27 September 2013, so compliance must be completed by 26 November 2013. Operators who only start the revision process a few weeks before the deadline risk running over, especially if they need to produce a general revision through a third party. The AD does not allow phasing the revision; both requirements must be met within the same 60-day window. Second, the wording of the warning horn procedure in Requirement 2 contains a heading including “RECALL”. Amendment 1 moved “RECALL” from the first line to the second line of the AFM. The current text shows “WARNING HORN - CABIN ALTITUDE OR CONFIGURATION RECALL” as a single heading line. Operators must follow the exact text as printed in Amdt 2, not guess where “RECALL” should be placed. The background note says Amdt 1 removed “RECALL” from the AFM amendment and placed it on the second line, but the body of Amdt 2 still presents the heading with “RECALL” included. If an operator uses the pre-Amdt 1 wording, they would be non-compliant. If they use a version that omits “RECALL” entirely, they would also be non-compliant. The safest approach is to insert the exact text of the AD as published. Third, the optional actions for AD/B737/255, /208, and /216 require a “notation to the effect in the compliance summary for the appropriate AD.” Operators must physically note on the earlier AD compliance record that the new wording was used. That notation is not just administrative; it proves that the alternative wording was accepted by CASA. Without it, an auditor might treat the earlier AD as still requiring the older wording. Fourth, the AMOC acceptance is limited to “approved FAA AMOC Letter 130S-09-134a dated 28 April 2009.” Any other AMOC, including future FAA letters, would not automatically be accepted unless CASA separately approves. Operators who obtain a later FAA AMOC must get CASA approval before using it in Australia. Fifth, the “Method To Revising the AFM” paragraph says the AD may be inserted “into” the AFM. That implies placing the entire single-sheet AD inside the manual, not just a summary. Operators might be tempted to just add a note, but the full text must be present until a general revision incorporates it. Sixth, the directive applies to “Boeing Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800 and -900 series aeroplanes.” Note that the -100 series is a very early model; few if any are still in Australian service, but if one exists, it is caught. The -200C is the convertible cargo version; it is explicitly listed. The -700C is the cargo version of the -700; also listed. The -900 is listed, but note that the -900ER (extended range) is not explicitly mentioned; however, the AD says “-900 series aeroplanes”, which likely includes the -900ER, but careful reading may require confirmation if -900ER is considered a separate model. Seventh, the “Note: FAA AD 2006-13-13 Amdt 38-14666 dated 15 June 2006 refers” appears after the optional actions paragraph. That note may be informational, but operators who hold US-registered 737s must also comply with that FAA AD. For Australian operators, compliance with CASA AD/B737/294 satisfies the requirement. But if an Australian operator also operates under a US air carrier certificate, they would need to ensure both ADs are addressed. Eighth, the directive is marked “AD/B737/294 Amdt 2” and also “19/2013” at the bottom. The “19/2013” appears to be an internal CASA numbering, not the AD number. Although likely not critical, operators should use the full AD number for records.

Practical steps for an operator of an affected Boeing 737 in Australia are as follows. Step 1: Obtain the official version of AD/B737/294 Amdt 2 as published by CASA. Download it from the CASA website or your airworthiness management provider. Verify it is dated 4 September 2013 and has the effective date of 27 September 2013. Step 2: Identify the specific 737 models in your fleet and note which AFM section must be revised: for models -100 through -500, the emergency procedures section; for models -600 through -900, the non-normal procedures section. For all models, the normal procedures section also needs revision. Step 3: Decide whether to insert the AD directly into the AFM or to incorporate the wording into a general revision. The insertion method is quicker: you simply insert a copy of the entire AD (including the cover page and image) into the AFM. Mark the AFM revision log with the AD number and date, and state that compliance is achieved by insertion of AD/B737/294 Amdt 2. If you choose a general revision, work with your AFM publisher to produce a revision sheet that includes the exact wording from the AD. Ensure the revision is approved by your chief pilot or flight operations manager and that the revision log records compliance with this AD. Step 4: For each requirement, verify that the exact language is used. Requirement 1: add “For normal operations, the pressurization mode selector should be in AUTO prior to takeoff.” into the Normal Procedures section. Requirement 2: add the entire warning horn procedure as printed, including the “WARNING HORN - CABIN ALTITUDE OR CONFIGURATION RECALL” heading and the steps for oxygen masks. Step 5: For any earlier ADs (AD/B737/255, /208, /216) that apply to your fleet, decide whether to use the optional updated wording. If you do, open the compliance record for each earlier AD and add a notation: “For the cabin altitude warning horn procedure, the wording from AD/B737/294 Amdt 2 (Requirement 2) has been used in place of the earlier wording, as permitted by that AD.” Keep the notation visible in the log. Step 6: If your organisation has an FAA AMOC Letter 130S-09-134a, you may use that to satisfy requirement 2 instead of inserting the full AD wording. Confirm the AMOC letter is current and applicable to your models. Document the compliance as “Complied with requirement 2 via AMOC FAA 130S-09-134a dated 28 April 2009, as accepted by AD/B737/294 Amdt 2.” Step 7: Brief all flight crew on the revised AFM procedures. Ensure that initial and recurrent training includes the new procedures, particularly the recognition of intermittent vs steady horn and the immediate oxygen mask action. Do not rely only on the manual revision; crew knowledge is essential for safety and for CASA audits. Step 8: After 60 days from 27 September 2013, all affected aircraft must have the revised AFM. If your fleet includes leased aircraft, coordinate with the lessor or the certificate holder to ensure compliance is reflected in the operator’s records. Step 9: Maintain records of compliance - the AFM revision log entries, the notation for prior ADs, and the AMOC documentation (if used). These records should be presented during CASA airworthiness reviews, ramp checks, or internal audits. Step 10: If any aircraft enters your fleet after the compliance date but before it was previously registered in Australia, you must comply with this AD before first flight under Australian rules. For aircraft imported from the US that already comply with FAA AD 2006-13-13, check that the AFM text matches the Australian AD wording (some differences may exist, particularly regarding the “RECALL” placement or the heading). Adjust if necessary. Finally, note that compliance is continuous: if the AFM is revised again in a general revision, ensure the AD-required text remains unless the AD is superseded. Periodic audits should check that the AFM still contains the required wording and that the optional notations remain on older AD records.