AD/BAe 146/140 - Airbrake Lever Detent Mechanism

Airbrake lever detent mechanism. This is the physical assembly that positions the airbrake selector lever and holds it in each detent (notch). The AD concerns the detent positions for “airbrakes out” and “lift spoiler”. The background explains that negligible force was required to move the lever back from lift spoiler to airbrakes out on aircraft without modifications HCM00889A and B or HCM00889A and C. The mandated fix is a friction baulking device that increases the force threshold to 12 lbs. This is not an electronic or software change; it is a mechanical modification to alter the resistance within the lever’s detent path.

Lift spoilers. On landing, the lift spoilers deploy automatically to disrupt the wing’s lift and transfer the aircraft’s weight onto the landing gear, enabling effective wheel braking. The AD notes that these spoilers also “provide aerodynamic braking” - creating drag to slow the aircraft. An uncommanded retraction of lift spoilers during the landing roll would directly reduce the braking capability and increase stopping distance. The risk is a runway overrun, which the background describes as potentially causing “injury to aeroplane occupants”.

Uncommanded movement. The AD reports two occurrence reports of the lever moving from the lift spoiler position back to the airbrakes out position without pilot input. The background attributes this to the effects of deceleration and landing inertia loads. This implies that the original detent mechanism did not have sufficient resistance to maintain its position under the dynamic forces experienced during landing.

Friction baulking device. This is the retrofit component described in the service bulletin. The term “baulking” is British English for “blocking” or “obstructing”. The device adds friction so that a force of 12 lbs must be deliberately applied to move the lever. The AD does not detail the device’s design; it merely points to the manufacturer’s service bulletin for installation instructions.

Compliance time. The AD requires compliance within 12 months after the effective date (14 October 2009). This is a relatively long period for an urgent safety directive, suggesting that the risk was not considered immediately life-threatening but still required timely correction. Operators with older aircraft that had never been retrofitted had a year to schedule the modification.

Service bulletin. The AD references British Aerospace (Commercial Aircraft) Ltd Modification Service Bulletin SB.27-73-00889A&B, Revision 4 (15 June 1990) or later EASA-approved revisions. Importantly, the AD also deems earlier revisions (original issue, Rev 1, Rev 2, Rev 3) as acceptable methods of compliance if performed before the effective date. This acknowledges that some aircraft may have already been modified under earlier versions. Operators who had performed the modification using an earlier revision before 14 October 2009 need not redo it, saving time and cost. However, if the modification was done after the effective date using an earlier revision, it would not be compliant unless CASA separately approved that revision.

Applicability by serial number. The AD is limited to aeroplanes with serial numbers listed in the service bulletin. Not all BAe 146 aircraft are affected; only those whose serial numbers appear in the bulletin. This is critical: operators must check the specific list in SB.27-73-00889A&B Revision 4 to determine if their aircraft are subject.

EASA AD reference. Note 2 cites EASA AD 2009-0206 dated 30 September 2009. This suggests that the Australian directive is harmonised with a European requirement, reducing the risk of conflicting obligations for operators who move aircraft between jurisdictions. The effective date of the Australian AD (14 October 2009) is two weeks after the EASA AD, likely to allow for publication and notification.

FAA certification context. Note 1 states that BAe 146 Series 100A and 200A aeroplanes were manufactured to the US FAA certification standard. This is relevant because the US standard may differ from the UK/EASA standard in certain respects. The AD nonetheless applies to those aircraft without qualification, meaning that Australian operators of FAA-certified variants must still comply with this Australian mandate.

The AD directly imposes obligations on the owners and operators of the specific BAe 146 Series aeroplanes listed in Service Bulletin SB.27-73-00889A&B, Revision 4, or any later EASA-approved revision of that bulletin. The applicability paragraph specifies that the affected aeroplanes are those manufactured by BAE Systems (Operations) Ltd, British Aerospace plc, British Aerospace (Commercial Aircraft) Ltd, British Aerospace (Operations) Ltd, British Aerospace Regional Aircraft Ltd, and British Aerospace Regional Aircraft trading as Avro International Aerospace. This is a narrow category: it covers only the BAe 146 Series 100, 100A, 200, and 200A models. The AD does not apply to the later Avro RJ series, which are derived from the BAe 146 but have different designations and likely different airbrake lever systems. Operators of affected aeroplanes are required to modify the airbrake lever detent mechanism within 12 months of 14 October 2009 unless the modification had already been performed. This imposes a direct compliance burden: the cost of obtaining the service bulletin, procuring any parts (likely a kit containing the friction baulking device), labour to install the device, and possibly inspection or test flights to confirm correct operation. There is also an opportunity cost in terms of aircraft downtime, especially if the modification must be scheduled during maintenance checks.

Maintenance organisations holding approvals under Part 145 of the Civil Aviation Safety Regulations (CASR) are the likely entities that will physically perform the modification. They must ensure they are authorised to work on BAe 146 aircraft and have access to the specific service bulletin. Their engineering staff must be trained on the modification. The AD does not require them to report the modification to CASA, but the aircraft’s continuing airworthiness records must be updated to reflect compliance, which then affects future maintenance, transfers, and registrations.

Indirectly affected are insurance providers, who may adjust premiums or insist on compliance as a condition of coverage. Aircraft lessors and financiers will also note the AD because non-compliance could affect the aircraft’s airworthiness certificate, impairing its ability to generate revenue. Buyers of used BAe 146 aircraft must check that the modification has been accomplished; if not, the purchase price should discount the cost of future compliance.

The AD also affects the manufacturer, BAE Systems (or its successor), which issued the service bulletin. The directive effectively makes the bulletin mandatory, increasing demand for the retrofit kit. That is a benefit to the manufacturer in terms of aftermarket sales, but it also imposes a reputational and liability consequence: if the modification itself introduces new failure modes, the manufacturer may be exposed. The AD references that modifications HCM00889A and B, and HCM00889A and C were introduced on the production line from 1988. Production aircraft from that point were already modified; only earlier aircraft need retrofit. The cost of the modification thus falls primarily on operators of older serial numbers, many of which may be owned by smaller operators or regionals that operate short fields where the landing performance margin is thinner.

The AD’s compliance timeline of 12 months is relatively generous for a mandatory safety directive. However, for an operator with a fleet of, say, five affected aircraft, scheduling the modification across the fleet may require staggered downtime, possibly affecting seasonal schedules. The economic burden is concentrated on a small number of operators worldwide (the BAe 146 fleet is not huge), but the regulatory intervention is absolute: no alternative means of compliance (AMOC) is mentioned in the AD itself, though the underlying legislation would permit CASA to approve one if requested. The free market prior suggests that this intervention prevents operators from choosing a lower-cost alternative or deferring the fix if they assess the risk as acceptable. But the AD’s basis in two occurrence reports and the documented risk of runway overrun provides a justification that most operators would likely accept.

The primary duty under AD/BAe 146/140 is to modify the airbrake lever detent mechanism on each affected aeroplane in accordance with the specified service bulletin instructions. The duty runs to the “operator” (as defined in the Civil Aviation Act and regulations) and the aircraft owner. Compliance must be achieved within 12 months after the effective date of 14 October 2009, i.e., by 14 October 2010. If the aircraft was modified before that date using an earlier revision of the service bulletin (original, Rev 1, Rev 2, or Rev 3), that modification is deemed acceptable and the operator has no further duty. This grandfathering is important: it saves operators from duplicative work. However, the AD does not allow a modification performed after the effective date using an earlier revision. After 14 October 2009, only Revision 4 or a later EASA-approved revision is acceptable. That means an operator who had not yet modified the aircraft would be compelled to use the latest revision, which may be more costly or have different parts.

The operator also has the duty to maintain records of compliance. The AD does not state an explicit record-keeping requirement, but under general CASR obligations (Part 42 or Part 145 as applicable), records of compliance with airworthiness directives must be entered in the aircraft’s maintenance log and continuing airworthiness records. Failure to do so would make it difficult to demonstrate compliance in the event of an audit or sale.

The AD does not explicitly address rights, but certain rights are inherent in the regulatory framework. The operator has the right to petition CASA for an extension of the compliance time if circumstances beyond control prevent timely modification. This is not mentioned in the AD text but is available under usual CASA practice. The operator also has the right to apply for an alternative means of compliance (AMOC) if equivalent safety can be demonstrated through a different design or procedure. The AD’s sole reference to EASA approval for later revisions of the service bulletin suggests that CASA will accept EASA-approved revisions for compliance, but a completely different fix (e.g., a redesigned lever) would require a separate AMOC from CASA. The operator also has the right to have the modification performed by a Part 145 maintenance organisation, or by their own qualified staff if the operator holds appropriate approvals (e.g., Part 42 continuing airworthiness management organisation).

The AD does not impose any periodic recurring duty. It is a one-time modification. Once accomplished, the aircraft is compliant indefinitely unless a new AD supersedes it. This is a limited burden.

Notably, the AD does not require the operator to inspect or test the modification after installation, other than the verification that would be part of the service bulletin instructions. This reduces compliance cost.

There is also a duty on the CASA delegate who issued the AD to ensure proper notification and to consider any submissions during the consultation period (though the AD does not mention consultation). The AD is signed by David Villiers, a Delegate of CASA, indicating that it was issued under the delegation provisions of the Civil Aviation Act. The effective date gives operators and maintainers 12 months to plan and execute the work.

An interesting legal point is that the AD applies to aeroplanes registered in Australia (or operated by Australian operators) even if the aircraft is not Australian-registered. The AD does not specify its jurisdictional scope; but by being a CASA directive, it imposes a legal obligation on any person who operates an aircraft in Australian territory or who is the holder of an Australian Certificate of Registration. For foreign-registered aircraft operating into Australia, the AD would likely be enforced through the conditions of the aircraft’s permission to operate (e.g., a foreign aircraft permit). The operator would need to ensure compliance or seek exemptions.

The free market prior raises a question: does this AD create an efficient outcome? By making a previously optional safety fix mandatory, it removes the operator’s choice to trade off safety against cost. The operator might have assessed that the risk of an accident was so low that the cost of modification was not justified, or that a cheaper alternative (such as pilot procedure changes or additional crew training) could achieve the same safety margin. The AD forecloses that choice. However, the AD is based on two occurrence reports and an analysis of changing operational profiles, and the consequence (runway overrun with injury risk) is severe. The mandated fix is relatively simple and low cost for a commercial aircraft. So the intervention is unlikely to be inefficient from a cost-benefit perspective, especially since the failure mode could lead to catastrophic outcomes. The free market critique would be that the AD does not allow a cost-benefit test by each operator, but safety regulation in aviation is inherently risk-averse due to the potential for multiple fatalities.

The AD itself does not state specific penalty amounts or enforcement mechanisms. However, as a legislative instrument made under the Civil Aviation Act 1988, compliance is legally enforceable. Under the Act and the Civil Aviation Safety Regulations 1998, a breach of an airworthiness directive is a regulatory offence. The usual penalty for a breach occurring after 2008 is a maximum fine of 200 penalty units for an individual and 1000 penalty units for a body corporate. As of the time of this AD (2009), one penalty unit was $110, so the maximum fine was $22,000 for an individual and $110,000 for a corporation. These fines are for each instance of non-compliance. If an operator has multiple aircraft non-compliant, each is a separate offence. More severe consequences include the possible suspension or cancellation of the aircraft’s certificate of airworthiness, which would effectively ground the aircraft until compliance is achieved. The operator could also face civil liability if an accident is caused by non-compliance, and CASA could take administrative action such as issuing an enforceable undertaking or seeking an injunction.

Enforcement is typically proactive: CASA conducts audits of operators’ continuing airworthiness records, which must document compliance with all applicable ADs. If an inspector identifies an aircraft that has passed its compliance time without the modification being recorded, the operator may be asked to show cause why enforcement action should not be taken. In practice, CASA often allows a short grace period if the operator can demonstrate that the modification is scheduled and imminent. But if the AD is persistently ignored, enforcement escalates. The AD’s 12-month compliance period is generous; failure to comply within that period would likely be treated as a serious matter because the safety risk involves runway overrun potential.

The AD does not mention any reporting requirement (e.g., to CASA on accomplishment). So enforcement relies on the records kept by the operator and maintenance organisation. If an operator does not modify the aircraft but removes it from service permanently, there is no breach. However, if the aircraft remains in operation after the compliance date without the modification, the breach continues.

The AD also refers to EASA AD 2009-0206. For aircraft that also come under EASA jurisdiction (e.g., operated in Europe by an Australian operator), dual enforcement is possible. EASA imposes its own penalties under EU law, which may include fines and grounding orders.

Another enforcement angle: the AD applies to aeroplanes that may be operated by lessees or charterers, not only owners. The chain of responsibility means that the holder of the air operator certificate (AOC) is ultimately responsible for the aircraft’s airworthiness. If the operator sub-leases the aircraft, it remains the operator’s duty to ensure the AD is complied with. Non-compliance could also breach the leasing or financing agreement if the contract requires compliance with all ADs.

The AD does not create a private right of action for, say, passengers or third parties injured due to non-compliance. But tort law would apply in the event of an accident. The AD’s existence and mandatory nature could be used as evidence of negligence per se, making it easier for a plaintiff to establish a breach of duty of care.

From an economic perspective, penalties are set at a level that should deter non-compliance. However, for a small operator with tight margins, the choice between paying $110,000 in fines and spending, say, $200,000 per aircraft on modifications might be perverse if the probability of detection is low. But the 12-month period reduces pressure; most operators would likely comply within the deadline to avoid grounding risk and potential loss of business.

This AD operates within a broader legal framework for aviation safety in Australia. The primary legislation is the Civil Aviation Act 1988 (Cth), which gives CASA the power to issue airworthiness directives under section 20AE (or its successor provisions in the regulations). The Act provides that an AD is a legislative instrument but is exempt from disallowance under the Legislation Act 2003. That means it has immediate legal effect without parliamentary scrutiny. The AD also interacts directly with the Civil Aviation Safety Regulations 1998 (CASR), particularly Parts 21 (certification), 39 (airworthiness directives), 42 (continuing airworthiness), and 145 (maintenance organisations). CASR Part 39 specifically requires operators to comply with each applicable AD by the specified date. The AD is the specific instrument under Part 39.

The AD is also tied to the international framework. The background notes the BAe 146 Series 100A and 200A are manufactured to FAA certification standards. However, the AD does not incorporate FAA regulatory language; it relies on the EASA AD and an earlier British Aerospace service bulletin. For an aircraft that is also on a US registry, the FAA might issue a parallel AD. In that case, the operator must comply with both. If the FAA AD has different compliance times or provisions, the operator must meet the stricter requirement or seek harmonisation. The AD references EASA AD 2009-0206, suggesting that CASA chose to adopt the EASA requirement rather than develop a unique Australian requirement. This is good for operators with international operations because it creates a uniform standard, reducing compliance costs.

The AD does not directly interact with industrial relations laws or workplace health and safety laws, but maintenance workers are covered under state OHS regimes and the federal Work Health and Safety Act. The modification must be performed safely, and any safety concerns about the modification itself would be separately addressable.

There is no mention in the AD of any interaction with environmental laws. The BAe 146 is a relatively old aircraft type, but the AD is purely airworthiness.

The AD also interacts with contract law: any lease or sale agreement for an affected aircraft will likely require compliance with all ADs. If the lessor or seller warrants that the aircraft is “airworthy and compliant with all applicable ADs”, failure to have accomplished this mod would be a breach of warranty. The AD does not create or modify contractual rights, but it sets a benchmark.

Another interaction is with insurance law. The operator’s hull and liability insurance policies typically require compliance with all manufacturer airworthiness directives and regulatory ADs. Non-compliance could be a ground for the insurer to deny cover in the event of a claim, especially if the lapse contributed to the accident. The AD thus affects the risk allocation between insured and insurer.

Finally, the AD interacts with the Australian constitution’s separation of powers because it is a delegated legislative instrument. No court has yet to challenge its validity, but a person could argue that CASA exceeded its authority if the AD was not based on safety concerns. However, given the documented occurrence reports, such a challenge would likely fail.

In the free market context, harmonisation with EASA and de facto with FAA reduces the burden on operators that fly internationally, because they do not face conflicting regulatory mandates. This is a sensible approach that reduces compliance costs. However, the AD adds one more layer of mandatory compliance to a heavily regulated industry. The cumulative effect of many ADs can be significant, especially for older aircraft types where part availability is limited.

AD/BAe 146/140 is a standalone airworthiness directive with the number 21/2009. The document is a single version effective 14 October 2009. There is no indication in the text that it has been amended or superseded by any later directive. The source provided is the original AD as issued. The “Revision” mentioned in the service bulletin is not a revision of the AD itself; it is a revision of the manufacturer’s service bulletin. The AD allows for later revisions of the service bulletin that are approved by EASA, which means that if the manufacturer issues a Revision 5 or later and EASA approves it, the AD automatically accepts that later revision as a means of compliance. That is a form of dynamic reference, but the AD text itself is static unless CASA issues a new AD.

The AD references “British Aerospace (Commercial Aircraft) Ltd Modification Service Bulletin SB.27-73-00889A&B, currently at Revision 4 dated 15 June 1990 or later revision approved by the European Aviation Safety Authority (EASA).” That means the AD has built-in flexibility to accommodate future revisions without needing an amendment. This is a clever drafting technique: CASA does not have to republish the AD every time the manufacturer updates the bulletin. The AD remains the same, but the acceptable means of compliance can change if EASA approves a later revision. However, the operator must still ensure they use a revision that is actually approved by EASA. If the operator used an unauthorised revision, compliance would not be accepted.

The AD also states that “modification of an aeroplane, prior to the effective date of this AD, in accordance with the instructions of ... Service Bulletin SB.27-73-00889A&B at original issue, Revision 1, Revision 2 or Revision 3 is an acceptable method to comply.” That is a one-time transitional provision. It is not an amendment; it simply recognises pre-existing work. After the effective date, only Revision 4 or later EASA-approved revisions count.

There is no evidence in the source that this AD has been repealed, replaced, or amended. Given its age (2009) and the declining fleet of BAe 146 aircraft (many have been retired), it is likely still in effect for the few remaining airframes. An operator wanting to know if any newer AD exists would need to search CASA’s current AD listing.

The source does not reference any litigation, and there is no widely known Australian court case specifically dealing with this AD. The AD is a routine safety directive for a relatively obscure aircraft component. However, it is worth discussing the legal avenues for challenging an AD generally. Under the Civil Aviation Act, a person affected by an AD may apply to the Administrative Appeals Tribunal (AAT) for review of CASA’s decision to issue the AD. The AAT can affirm, vary, or set aside the AD. However, the AAT typically gives significant deference to CASA’s safety assessment, especially where the AD is based on operational safety data. A challenge would have to demonstrate that the AD is not reasonably necessary for safety or that an alternative means of compliance is equally safe. Given the background describing two occurrence reports and the analysis of increasing risk from short-field operations, a challenge would be difficult.

No reported decisions of the AAT or federal court regarding AD/BAe 146/140 appear in the public record. The BAe 146 fleet is small, and the modification is relatively low cost, so operators likely complied without litigation. There is also the possibility that some operators sought extensions informally without needing formal review.

Another litigation angle: if an accident occurred because of an airbrake lever malfunction that could have been prevented by this AD but the operator had not complied, the operator could face a civil negligence suit (not just regulatory action). The AD would be evidence that the operator breached a statutory duty of care, potentially leading to a finding of negligence per se. However, no such accident has been publicly linked to this specific AD. The AD itself was issued in response to occurrence reports, not an actual crash.

Crown immunity might apply if the AD were challenged on constitutional grounds, but that is unlikely.

In the United States, if the FAA issued a parallel AD, it could have been challenged in US federal court, but that is outside the scope of this Australian deep dive.

Overall, the litigation history is nil. That itself is notable: the AD was accepted without legal contest, suggesting that its requirements were considered reasonable and cost-effective by the affected industry.

For the free market prior, the absence of litigation might indicate either that the compliance burden was low enough that operators accepted it, or that the regulatory risk of contesting CASA was too high. Both are plausible.

Several aspects of this AD could trip up an operator or compliance manager not reading carefully.

First, the applicability clause refers to “serial numbers as listed in British Aerospace (Commercial Aircraft) Ltd Modification Service Bulletin SB.27-73-00889A&B, Revision 4 dated 15 June 1990.” Many operators may assume all BAe 146 aircraft in the series models are affected, but only those with serial numbers in that list. The AD does not provide the list itself; the operator must obtain the service bulletin to check. If the operator relies on a generic assumption that all Model 100-200 aircraft are covered, they might either waste time on an unaffected aircraft or, worse, miss an affected one because the serial number is listed but the operator did not check.

Second, the acceptance of earlier revisions only applies if the modification was performed prior to the effective date. If an operator modified an aircraft after 14 October 2009 using Revision 2, that would not be compliant. They would have to redo the modification using Revision 4 or later. This is a trap for operators who schedule the modification close to the deadline but mistakenly use an outdated service bulletin.

Third, the AD says “in accordance with the instructions of British Aerospace (Commercial Aircraft) Ltd Modification Service Bulletin SB.27-73-00889A&B, currently at Revision 4 dated 15 June 1990 or later revision approved by the European Aviation Safety Authority (EASA).” Note: the later revision must be approved by EASA, not simply issued by the manufacturer. If the manufacturer issues a Revision 5 but EASA has not yet approved it, using Revision 5 does not comply with this AD. The operator must wait for EASA approval. In practice, EASA will usually approve the same revision as part of its continuing airworthiness process, but the lag could be problematic.

Fourth, the AD applies to both Australian registered aircraft and foreign registered aircraft operated in Australia. A foreign operator bringing a BAe 146 into Australia for a charter series should verify that the modification has been done, or seek an exemption from CASA. The AD does not create an exception for foreign aircraft. This could be a gotcha for a lessor that thought the AD was only for Australian registrations.

Fifth, the AD does not specify what happens if the modification cannot be completed within 12 months due to parts shortage. The operator must proactively seek an extension or alternative from CASA. There is no grace period in the text. The gotcha is that the operator might assume the AD allows late compliance without penalty if they can show best efforts. But the law is strict: from day one after the compliance date, the aircraft is unairworthy.

Sixth, the AD references EASA AD 2009-0206. If the EASA AD is later revised superseded, does that affect this Australian AD? The Australian AD only accepts “later revision approved by EASA” as a means of compliance. If EASA later replaces AD 2009-0206 with a completely different requirement, this Australian AD might still require the original modification unless CASA issues a new AD. The operator needs to monitor both EASA and CASA ADs.

Seventh, Note 1 states that Series 100A and 200A are manufactured to FAA certification standard. This might lead an operator to think they need to also check for an FAA AD. The Australian AD applies regardless; but if the FAA has a different requirement, the operator must comply with both. There is no mutual recognition.

Eighth, the AD says “modify the airbrake lever detent mechanism” - but what exactly does that entail? The service bulletin instructions might call for removal of panels, access to the lever assembly, installation of a spring or friction pad, and re-rigging. A maintenance shop that is not familiar with BAe 146 specifics could misinterpret the instructions. The AD does not explain the modification, so relying on the service bulletin is mandatory.

Finally, the AD does not require a test flight after modification, but the service bulletin might. The operator should carefully read the service bulletin instructions; the AD requires compliance “in accordance with the instructions of the service bulletin”. If the bulletin requires a functional test, that becomes part of the AD’s requirement. Failure to perform a required test would mean the AD is not fully complied with.

To comply with AD/BAe 146/140, an operator of an affected aircraft should follow these steps, grounded in the AD’s text and the general regulatory framework.

1. Identify affected aircraft. Obtain a copy of British Aerospace (Commercial Aircraft) Ltd Modification Service Bulletin SB.27-73-00889A&B, Revision 4, dated 15 June 1990. Check the serial number list in that bulletin against the serial numbers of each BAe 146 Series 100, 100A, 200, or 200A aircraft operated. Only those listed are subject to the AD. Record that the aircraft is not affected if the serial number is absent.

2. Check prior compliance. For each affected aircraft, examine the maintenance records to see if the modification was accomplished before 14 October 2009. If so, determine which revision of the service bulletin was used. The AD accepts original issue, Revision 1, Revision 2, or Revision 3 if the modification was done before the effective date. If the modification was done after 14 October 2009 using one of those early revisions, it is not acceptable, and the operator must redo the modification using Revision 4 or a later EASA-approved revision.

3. Plan the modification. If the aircraft has not yet been modified, schedule the work to be completed within 12 months after 14 October 2009 (i.e., by 14 October 2010). The modification can be performed earlier, at any time after the effective date. Obtain the service bulletin Revision 4 (or a later EASA-approved revision if one exists). Ensure the parts kit (the friction baulking device) is available. If parts are difficult to source, prepare a contingency plan, such as requesting an extension of compliance time from CASA.

4. Perform the modification. The work must be carried out by an appropriately authorised maintenance organisation (e.g., a CASR Part 145 approved repair station). Engineering personnel must have access to the service bulletin instructions. The AD does not specify any additional approvals, but the modification is a standard maintenance task under Part 42 (continuing airworthiness). Strict adherence to the service bulletin is required. Any deviation must be approved by CASA as an alternative means of compliance.

5. Record compliance. After the modification is completed, ensure the aircraft maintenance log or the continuing airworthiness record system notes the accomplishment. The entry should reference the AD number (AD/BAe 146/140), the service bulletin used (including revision number), the date of accomplishment, the name of the organisation and authorised person, and any test results if required by the bulletin. This record is essential to demonstrate compliance during inspections and when transferring the aircraft.

6. Verify no further action. The AD is a one-time modification. No recurring inspections are mandated. However, if a later EASA-approved revision of the service bulletin becomes available after the aircraft is modified, the operator is not required to adopt that later revision unless CASA issues a new AD. The operator may choose to remain with the original modification.

7. Monitor for superseding directives. Since the AD was issued in 2009, operators should periodically check CASA’s current list of airworthiness directives to ensure no new AD has replaced or amended AD/BAe 146/140.

8. Consider economic implications. The cost of compliance includes parts, labour, and potential downtime. For a fleet of multiple affected aircraft, staggering the modifications across the 12-month period can minimise operational disruption. If the modification is expensive relative to the aircraft’s value, the operator might consider retiring the aircraft earlier than planned. The AD does not mandate any economic analysis; it is a pure safety requirement.

9. Maintain communication with regulatory bodies. If the modification cannot be completed by the deadline, the operator should formally apply to CASA for an extension or alternative means of compliance. This should not be left to the last minute, as CASA will require justification.

10. Train staff. Ensure that flight crews and maintenance staff understand the modification. The AD does not require any changes to flight manual procedures, but pilots should be aware that the airbrake lever now has a stiffer detent, which may affect their force application during landing. This is not part of the AD but is good safety practice.

The AD is straightforward but requires careful tracking of service bulletin revisions and serial numbers. The 12-month deadline is generous, but procrastination is risky. An operator that complies early reduces the risk of accidentally missing the deadline due to parts delays or labour shortages. The AD does not require reporting to CASA, but the records must be clear.