AD/F100/96 - Landing Gear - Brake Quick Disconnect Couplings

The central concept of this AD is the quick disconnect (QD) coupling, a hydraulic fitting used in the brake system that allows rapid connection and disconnection of brake lines. The specific couplings identified have a light alloy sleeve with locking teeth that are prone to wear. The AD creates a hierarchy of affected part numbers (the four original P/Ns) and improved part numbers (P/N AE73059E and AE73091E) which have corrosion resistant steel (CRES) sleeves less susceptible to tooth wear. The improved unit is intended to increase reliability and eliminate the risk of loosening that can cause hydraulic leaks or hydraulic lock. Hydraulic lock occurs when a loosened coupling traps residual brake pressure, potentially rupturing brake pistons and causing brake fires. The AD distinguishes between a one off inspection (requirement 1) and repetitive inspections (requirement 2) that continue until all couplings are upgraded. The inspection intervals for repetitive inspections are not fixed calendar times but are determined by the amount of wear found at each inspection, as defined in the Service Bulletin. This means an operator finding significant wear must reinspect sooner; an operator finding minimal wear may extend the interval, but the Service Bulletin must specify the criteria. The AD provides a termination action: installing improved couplings at all locations ends the repetitive inspection requirement. The earlier Service Bulletin SBF100 32 127 is recognised as an equivalent termination action, so operators who already complied with that bulletin are not required to repeat inspections. The AD also imposes a prohibition on installation after 20 August 2011 of the original part numbers. Compliance times are expressed as calendar periods from the effective date: 6 months for the first inspection, 24 months for full replacement, and "before next flight" for any coupling found to exceed wear limits. The AD explicitly references the European Aviation Safety Agency's AD 2009 0176 dated 6 August 2009, indicating that this CASA AD is aligned with or derived from the EASA directive, avoiding duplication or conflict for operators subject to both jurisdictions. The concept of later approved revisions is important: the Service Bulletin may be updated, and using the latest approved version is acceptable for compliance without the need for a new AD. The wear definition is a key technical concept left to the Service Bulletin; it likely involves measuring the locking tooth height or sleeve thickness against a go/no go gauge. The AD does not specify who determines the interval under requirement 2 - the text says "at intervals determined by the amount of wear found, as defined in the SB". This implies the maintenance engineer or continuing airworthiness management organisation must apply the SB's wear classification to set the next inspection due date. The effective date of the AD (24 September 2009) starts the compliance clocks. The background reveals a sequence of manufacturer actions: AMM revisions, then SBF100 32 106 recommending CRES sleeves, then SBF100 32 127 introducing further improved couplings, and finally this AD making the upgrade mandatory. The AD is a culmination of that progression. The concept of a delegate of CASA (James Coyne) signing the AD shows the formal authority under the Civil Aviation Act.

This AD directly affects any person or organisation responsible for the continuing airworthiness of a Fokker F28 Mark 0070 or Mark 0100 aeroplane registered in Australia, or any aircraft operated under an Australian air operator's certificate. That includes airline operators, aircraft leasing companies, private owners, maintenance organisations, and approved persons authorised to certify maintenance. Specifically, it applies if any of the four original part number brake QD couplings (AE70690E, AE70691E, AE99111E, AE99119E) are installed. The AD does not state that all aircraft of these types are automatically affected - only those with the listed couplings. However, given that the couplings are original equipment parts, virtually every Fokker 70 and Fokker 100 in Australian service that has not been previously modified under SBF100 32 127 will be affected. Operators who have already retrofitted all couplings with improved units (either under the earlier SB or otherwise) are affected only to the extent that they must ensure no original parts remain and that the prohibited installation rule is observed. The AD imposes duties on maintenance engineers and certifying staff to carry out inspections, interpret wear limits, determine the next inspection interval, and perform replacements. The persons who physically replace the couplings must use the specified improved part numbers. The AD also affects parts suppliers and distributors, who must not supply the original part numbers for installation after the prohibition date. For aircraft operators, the AD imposes direct financial costs: purchase of improved couplings (likely specialist, possibly expensive parts from Fokker Services or its successor), labour for inspections and replacements, potential aircraft downtime (especially for the full fleet replacement within 24 months), and administrative costs to track compliance and revise maintenance schedules. Leasing companies may need to determine who bears the cost of compliance under lease agreements. For maintenance organisations, the AD requires access to the Service Bulletin SBF100 32 156 (and any later revisions) which is proprietary and must be procured from Fokker Services; this imposes a documentation cost and requires that engineers be trained on the specifics of the inspection and replacement procedures. The AD's reference to the wear definition means maintenance personnel must have the correct tools and gauges as specified in the SB. The AD does not explicitly affect pilots or flight crew directly, but they benefit from reduced risk of brake fire or asymmetric braking. The AD may indirectly affect insurance companies and risk assessors, as compliance will be a factor in hull and liability underwriting. For CASA itself, the AD represents an enforcement obligation: ensuring that operators comply, and taking action against those who do not. The AD does not provide any exemption process, though in practice CASA may grant individual relief if an operator proposes an alternative means of compliance and demonstrates equivalent safety. The AD's impact is concentrated on a small fleet of Fokker 70 and Fokker 100 aircraft in Australia (likely operated by a small number of regional or charter airlines, plus possibly corporate operators). This small group bears the entire compliance burden, while the benefit (reduced brake fire risk) accrues to passengers, crew, and the public at large. There is a risk of concentrated costs, diffuse benefits - a classic regulatory pattern. Operators may find that the improved couplings are no longer manufactured for a type that is already out of production (Fokker ceased aircraft production in 1997), raising concerns about parts availability and escalating costs. The AD does not specify a time limit for the termination action beyond the initial 24 months; once all couplings are replaced, there is no further ongoing obligation under this AD (though general airworthiness requirements still apply).

The AD imposes several specific duties on operators and maintainers. The primary duty is to perform the initial inspection of all brake QD couplings with the affected part numbers within six months of the effective date (24 September 2009, so by 24 March 2010). This inspection must be done in accordance with Part 1 of the Accomplishment Instructions of the Service Bulletin. The second duty is to continue repetitive inspections at intervals determined by the amount of wear found as defined in the SB. This duty continues until termination. The third duty is to replace any coupling that exceeds the wear definition before the next flight. This imposes an immediate grounding obligation if wear is excessive. The fourth duty is to replace all remaining affected couplings (i.e., those that were not already found unserviceable) with improved units within 24 months of the effective date (by 24 September 2011). The fifth duty is a permanent prohibition: after 20 August 2011, no person may install any of the four original part number couplings on any aeroplane. This duty applies to anyone performing maintenance, including owners, lessees, and maintenance organisations. The AD also creates a right to terminate the repetitive inspection requirement. If an operator replaces all affected couplings with improved units (P/N AE73059E or AE73091E) at all locations on an aeroplane, no further inspections under this AD are required. Similarly, if all couplings were previously replaced under Fokker SBF100 32 127 (any revision), the inspections are terminated. This provides a clear pathway to exit the repetitive compliance burden. The AD further grants a right to use later approved revisions of the Service Bulletin for compliance. This allows operators to incorporate any subsequent updates or errata without awaiting a new AD. However, the AD does not define "later approved revisions" - it is implicit that the revision must be approved by the design approval holder (Fokker Services, now likely under the oversight of the European Union Aviation Safety Agency or the Dutch aviation authority). The AD does not grant any right to request an extension of the compliance times; it is silent on extensions, meaning any request would need to be made to CASA under general regulation provisions. The AD does not provide a right to substitute different part numbers or alternative inspection methods without CASA approval. The duties extend to record keeping: while the AD does not explicitly say so, compliance must be documented in the aircraft's maintenance records (log books, maintenance release, etc.) as part of the continuing airworthiness system. The AD also implies a duty for the organisation to have access to the Service Bulletin. The rights under the AD are limited; it is a mandatory instrument with little flexibility. The only discretion lies in determining the repetitive inspection interval based on wear, which must be exercised strictly according to the SB's criteria. The AD does not create any rights for third parties (such as passengers) to enforce compliance; enforcement is solely a matter for CASA. For operators, the duty to inspect and replace is absolute; there is no defence of ignorance or practical impossibility. If parts are unavailable, operators must find a solution (e.g., grounding the aircraft, seeking CASA exemption, or sourcing parts from overseas). The AD's duties are imposed on "any person" but are typically delegated to the registered operator and the Part 145 maintenance organisation.

The AD itself does not state specific penalties for non compliance. However, it is issued under the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988 (now the Civil Aviation Safety Regulations 1998 in updated form). Non compliance with an Airworthiness Directive is a breach of the regulations and subject to enforcement action by CASA. Under CASR 21.181, the holder of a type certificate or supplemental type certificate must comply with ADs. For operators, CASR 42.220 requires compliance with applicable ADs. Failure to comply can result in civil penalties under Part 13 of the Civil Aviation Act, with maximum penalties for individuals and corporations set by the Act (currently up to $13,320 for individuals and $66,600 for bodies corporate per contravention, adjusted periodically). In addition, CASA can suspend or cancel an airworthiness review certificate, aircraft registration, or air operator's certificate for ongoing non compliance. The AD's requirement to replace a worn coupling "before next flight" means that an aircraft found with excessive wear during inspection cannot be flown again until the replacement is performed. Operating an aircraft in non compliance with an AD could also lead to criminal prosecution under the Civil Aviation Act (s 20B) for endangering the safety of the aircraft, which carries higher penalties including imprisonment. The AD's enforcement is retrospective; CASA may conduct audits of maintenance records and spot checks of aircraft. The AD references European AD 2009 0176, and for aircraft with international operations, non compliance could also trigger enforcement by EASA or the state of registry. CASA typically issues ADs as legally enforceable instruments; a failure to comply is an immediate regulatory violation. The AD does not provide a means of voluntary disclosure or amnesty. Operators are expected to self verify compliance and maintain evidence. The AD does not specify any reporting requirements to CASA beyond the normal maintenance records; however, CASA may request evidence of compliance during a surveillance activity. If a brake fire or incident occurs that is attributable to non compliance with the AD, the operator could face civil liability for damages, as well as regulatory penalties. The background of the AD mentions that brake fires have occurred; this heightens the likelihood that CASA will treat non compliance seriously. The AD does not differentiate between intentional non compliance and inadvertent oversight; both are breaches. However, in practice, CASA may issue a notice of proposed administrative action or a direction to ground the aircraft before escalating to civil penalties. The enforcement regime relies on the operator's continuing airworthiness management system. There is also an interaction with the CASR Part 145 maintenance organisation approvals: an organisation that certifies an aircraft as compliant when it is not faces its own regulatory sanctions, including suspension or cancellation of its approval. The AD does not delegate any enforcement role to third parties; only CASA can take action.

This AD sits within a hierarchy of aviation safety regulations. Its primary legal basis is the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988 (or CASR 1998, depending on the applicable transition at the time). Specifically, ADs are issued under CAR 37 or CASR 21.AD. The AD itself cites no specific regulation; it is simply headed as an Airworthiness Directive. Under the legislative framework, an AD overrides any inconsistent maintenance manual instructions or operator procedures. It has the force of law. The AD explicitly references EASA AD 2009 0176 dated 6 August 2009, demonstrating that CASA harmonised with the European directive. For operators with aircraft registered in Australia but operated internationally, compliance with the CASA AD satisfies the EASA AD for Australian registered aircraft, but if the aircraft is also registered in another state, that state's AD requirements may also apply. The AD interacts with Fokker Service Bulletins: SBF100 32 156 (the primary SB for this AD) and SBF100 32 127 (the earlier SB). These bulletins are not law but become mandatory through the AD's incorporation by reference. The AD states that use of later approved revisions is acceptable, meaning the SB can be updated without amending the AD. This is a typical interaction: the AD gives legal force to a manufacturer's technical instructions. The AD also interacts with Fleet Maintenance Programs and Continuing Airworthiness Management under CASR Part 42. Operators must incorporate the AD's requirements into their maintenance schedule (often as a life limited part task or a calendar check). The AD may duplicate or conflict with existing maintenance tasks for the brake system; the AD requires its own inspection regime even if similar inspections are done. It does not allow "equivalent" maintenance unless it meets the SB criteria. The AD interacts with Aircraft Maintenance Manual (AMM) revisions: the background notes that the AMM was revised in 1995 to include correct removal and installation procedures. The AD's inspection and replacement must follow the SB, not the AMM alone, though the AMM may be referenced by the SB. The AD interacts with Parts Approval regulations: the improved couplings (P/N AE73059E, AE73091E) must be approved parts under CAR 21 or CASR Part 21. The AD prohibits installation of the original part numbers after a date, effectively revoking their eligibility for installation on these aircraft. This interacts with CAR 21.307 (now CASR 21.307A) which prohibits installation of non approved parts. The AD also interacts with Investigations under the Transport Safety Investigation Act 2003: if a brake fire occurs, the Australian Transport Safety Bureau may investigate; compliance or non compliance with the AD will be relevant. The AD does not interact directly with consumer law (e.g., Australian Consumer Law) because it is a safety regulation, but if an operator charges passengers for a flight on an aircraft they know is non compliant, that could trigger liability. The AD does not interact with contract law except that lease agreements may require compliance with all ADs; this AD would be one of them. The AD does not interact with state or territory laws except perhaps in the event of a ground incident (e.g., fire spread to airport property). The AD is a federal instrument. The AD's background references CS 25.863, a European certification specification for fire protection; this suggests that the AD is intended to maintain the certification basis of the aircraft. Australian law incorporates equivalent standards through CAR 21. The AD interacts with airworthiness review procedures: during an airworthiness review, the reviewer must check compliance with all ADs. If the AD is not complied with, the airworthiness review certificate cannot be issued or renewed.

The text does not contain a formal amendment history. The AD is identified as "AD/F100/96" and "11/2009 DM", which suggests it is the original issue of this directive. The date on the document is 18 August 2009, and the effective date is 24 September 2009. There is no indication that this AD has been superseded, amended, or varied from its original issue. However, the AD itself refers to earlier service bulletins: SBF100 32 106 (1997), SBF100 32 127 (2001), and SBF100 32 156 (the latest SB). These bulletins were voluntary manufacturer recommendations before this AD made the actions mandatory. The AD also references the earlier record of maintenance manual revisions. The AD's termination provision recognises that replacement under SBF100 32 127 (any revision) counts as compliance. This means that the AD effectively incorporates the earlier bulletin's scope. Since the AD permits use of later approved revisions of SBF100 32 156, the effective content may change over time without a formal amendment to the AD. Operators must monitor the SB for updates. The AD does not state any history of previous CASA ADs on this topic; presumably AD/F100/96 is the first and only directive for Fokker F100 series brake QD couplings. There is no mention of any time of effect extension or correction. The AD's structure is a typical CASA AD with numbered requirements, compliance times, and background. There is no "Amendment" section. The AD is signed by a delegate of CASA. The AD's printing code "11/2009 DM" likely indicates it was printed or published in November 2009, which is after the effective date. This may be simply a document control number. For the purpose of this deep dive, we cannot invent a later amendment history. The source does not provide any evidence that the AD has been superseded, amended, or cancelled. The AD is likely still in force for the aircraft to which it applies, unless the aircraft type certificate has been transferred to a new type certificate holder or the aircraft have been withdrawn from service. Given that the AD concerns a specific part replacement, once all affected couplings are replaced, the AD's ongoing requirements cease; the AD itself remains on the books but is no longer active for compliant aircraft. There is no mention of any alternative means of compliance being accepted by CASA in relation to this AD. The AD's history is essentially the sequence of events in the background: 1995 reports of loosened couplings, 1997 introduction of CRES sleeves via SB, 2001 further improved couplings via another SB, and finally the 2009 AD making replacement mandatory. This evolution shows a progression from voluntary recommendations (SBs) to mandatory directive. The AD does not incorporate any of the earlier SBs by reference for the inspection requirements; only SBF100 32 156 is referenced for the current actions. However, the termination credit for SBF100 32 127 shows that the AD recognises the earlier upgrade. In terms of regulatory history, this AD aligns with the EASA AD issued in August 2009. It is possible that CASA issued this AD in response to the EASA AD to maintain bilateral recognition. No further amendments are evident from the source text.

The source text does not mention any litigation related to this AD or the underlying brake QD coupling issues. There is no court case noted, no appeal, and no challenge to the validity of the AD. However, we can reason about potential litigation scenarios. The AD imposes mandatory action; if an operator suffered economic loss due to parts unavailability or compliance costs, they might consider judicial review, but no such case is documented in the source. The AD's references to earlier brake fires and incidents might have given rise to negligence claims against the aircraft operator or manufacturer, but those would be civil suits, not directly attacking the AD. It is possible that in the event of a brake fire, litigation could involve allegations that the operator failed to comply with the AD, creating a presumption of negligence under civil aviation legislation. The source does not provide any details. The AD itself is a regulatory instrument, not a court decision. There is no indication that the AD was ever challenged in the Administrative Appeals Tribunal or the Federal Court. The background describes a series of engineering investigations and service bulletins, but no administrative hearing. The AD's delegate, James Coyne, is not a party to any litigation mentioned. The AD's compliance times have long passed, so any litigation over the substance of the AD would be moot. However, enforcement actions for non compliance could result in court proceedings, but the source does not record any. The absence of litigation history in the source is significant: it suggests that operators generally complied, that the AD was not controversial, or that any disputes were resolved informally. The AD does not include any statement about "this AD has been reviewed" or "no written submissions received", which are sometimes found in ADs that have been through a rulemaking process. The AD appears to have been issued without prior public consultation, as is typical for urgent safety directives. That could have been a ground for challenge if an operator thought the AD was disproportionate, but no challenge is recorded. The AD's reference to CS 25.863 indicates it is based on European standards; litigation in European courts about the underlying safety issue might exist, but the source does not reference it. For the purpose of this deep dive, we must state that the source provides no litigation history. We can note that none is described, but we cannot assert that no litigation exists. We can say that the AD has not been the subject of reported case law in Australia based on the available text. The lack of litigation may imply that the AD was accepted as necessary and proportionate, though that is an inference, not a fact from the source. To remain source grounded, we should state that the AD itself contains no reference to any court proceedings or appeals, and no such history is provided in the document.

Several aspects of this AD could catch unwary operators and maintenance organisations. First, the compliance times are calculated from the effective date (24 September 2009), not from the date the aircraft last underwent maintenance or the date the AD was received. An operator who obtains the AD after that date has less time to comply. Second, the repetitive inspection interval is not a fixed period but is "determined by the amount of wear found, as defined in the SB". This places a responsibility on the inspecting engineer to accurately classify wear and set an appropriate next inspection date. If the wear classification is ambiguous or the engineer misjudges, the interval may be too long (risking safety) or too short (increasing costs). Third, the wear definition is contained in the proprietary Service Bulletin, which must be purchased. An operator cannot simply inspect visually; they need the specific gauges and criteria from the SB. This adds cost and creates a dependency on the manufacturer. Fourth, the termination action requires replacement at "all locations". The AD does not specify how many locations exist on a particular aeroplane. A typical Fokker 100 has two main landing gear legs, each with two wheels and two brakes, meaning four brake units; each brake likely has one QD coupling, so four locations. But there may also be couplings on the nose gear? Probably not, but the AD says "brake QD couplings" so only on brake lines. An operator must identify every coupling on the aircraft with the affected part numbers. If one coupling is missed, the entire aircraft remains subject to repetitive inspections. Fifth, the improved units P/N AE73059E and AE73091E must be installed; there is no mention of interchangeable or alternative part numbers. If those parts become unobtainable, the aircraft may be grounded or require an STC. Sixth, the prohibition on installation after 20 August 2011 applies even if the couplings are new old stock. An operator cannot simply buy a spare of the original part number after that date. This affects parts inventory and supply chains. Seventh, the previous replacement under SBF100 32 127 terminates inspections, but only if the replacement was at all locations. If an operator replaced only some couplings under that SB, they still need to complete the upgrade under this AD for the remaining original couplings. Eighth, the AD says "use of later approved revisions of this document is acceptable for compliance". This means if the SB is revised, the operator must use the latest approved version. It creates an ongoing obligation to check for updates. Ninth, the initial inspection within 6 months applies even if the aircraft is in storage or undergoing heavy maintenance. The AD does not exempt aircraft not in service. Tenth, the requirement to replace worn couplings before next flight means that if wear is found during a pre flight walkaround (unlikely, but possible if the inspection is scheduled at that time), the aircraft cannot be dispatched. This could cause operational disruptions. Eleventh, the AD does not address dual part numbers - for example, if a coupling has an original P/N stamped on it but has been modified in the field, the AD still applies. Finally, the AD references EASA AD 2009 0176. Operators holding both CASA and EASA approvals must ensure compliance with both, but the CASA AD may be considered equivalent. However, if EASA later amends its AD, the CASA AD may not automatically incorporate the change unless the SB revision is accepted. These gotchas emphasise the need for careful management of the AD, including tracking compliance times, SB revisions, part numbers, and wear measurements. The AD is not as simple as "inspect and replace"; the dynamic interval determination adds complexity.

Compliance with AD/F100/96 requires a structured approach. Step one: identify all aircraft in the operator's fleet or under the operator's control that are Fokker 70 or Fokker 100 series. Obtain the Service Bulletin SBF100 32 156 (latest approved revision) from Fokker Services or its successor (likely via the manufacturer's technical portal). Verify that the SB includes the wear definitions, inspection procedures, and part numbers for the improved couplings. Step two: audit the brake QD couplings on each aircraft. For each braking location, read the part number. If any coupling displays P/N AE70690E, AE70691E, AE99111E or AE99119E, the AD applies to that aircraft. If all couplings already have P/N AE73059E or AE73091E, the AD's requirements are satisfied. If some are improved and some are original, the original ones must be addressed. Also check maintenance records for evidence of previous replacement under SBF100 32 127 (any revision) - if all couplings were replaced under that SB, the AD's repetitive inspections are terminated, but still ensure no original parts remain. Step three: perform the initial inspection on all affected couplings within 6 months of 24 September 2009 (i.e., by 24 March 2010). This inspection must be in accordance with Part 1 of the SB's Accomplishment Instructions. Record the wear found for each coupling. If any coupling exceeds the wear limit, replace it with the appropriate improved unit (AE73059E or AE73091E as applicable) before next flight, per Requirement 3. Step four: establish the repetitive inspection interval for each aircraft based on the wear found. The SB should provide a table or formula linking measured wear to a maximum interval. Document the determined interval in the maintenance program. If wear is close to the limit, the interval may be very short (e.g., 50 flight hours). Step five: plan the replacement of all remaining original couplings within 24 months of 24 September 2009 (by 24 September 2011). This is Requirement 4. Even if couplings show no appreciable wear, they must be replaced. Procure sufficient improved couplings in advance, considering lead times. Ensure the replacement is done following Part 2 of the SB's Accomplishment Instructions. Step six: after replacement of all couplings on a given aircraft, mark the maintenance records to indicate that Requirement 2 (repetitive inspections) is terminated for that aircraft. No further AD tasks are required. Also update the aircraft's parts list and maintenance schedule to capture the new part numbers. Step seven: after 20 August 2011, ensure that no original part number coupling is ever installed on any aircraft. Remove any such couplings from inventory and either discard or clearly label them as "not for flight" to prevent inadvertent use. Step eight: maintain documentation. Keep copies of the SB (including revisions), inspection reports, wear measurements, replacement records, and evidence of termination. This documentation must be available for CASA audit. Step nine: monitor for SB revisions. Since the AD accepts later approved revisions, the operator must periodically check for updates to SBF100 32 156 and incorporate any changes to procedures or wear limits. Step ten: for aircraft that have been modified under the earlier SB (SBF100 32 127), verify that all couplings were replaced at all locations. If not, the unmodified locations are still subject to this AD and must comply with the inspection and replacement requirements. If fully modified under that SB, no further action under this AD is needed, but the prohibition on installing original parts still applies. Step eleven: coordinate with maintenance providers. If the operator contracts maintenance to a Part 145 organisation, ensure that organisation has access to the SB and is authorised to perform the work. Provide clear work orders specifying compliance with AD/F100/96 and the SB. Step twelve: consider using later approved revisions. If a later revision of the SB is issued after the AD, operators may use it for compliance, but should confirm with CASA or the manufacturer that the revision is approved. Keep a log of the revision used for each inspection. Step thirteen: if the improved couplings are not available, contact CASA for guidance. The AD does not grant extensions, but CASA may issue an alternative means of compliance or a time limited exemption under CAR 33 or CASR 11.055. However, do not assume such relief exists; plan procurement early. Step fourteen: for leased aircraft, the lessee and lessor should agree in the lease which party is responsible for complying with this AD. The costs of parts and labour should be allocated. Step fifteen: train maintenance personnel on the specific inspection technique for QD coupling wear, including use of the correct gauges and interpretation of the SB's wear criteria. Ensure they understand that the interval determination is not discretionary but follows the SB's algorithm. By following these steps, operators can achieve and maintain compliance with AD/F100/96. The key to avoiding enforcement action is calendar tracking: note the 6 month initial inspection deadline, the 24 month replacement deadline, and the 20 August 2011 installation prohibition. After full replacement, the ongoing burden lifts, but the prohibition remains permanently.