AD/F100/84 - Fuel Crossfeed Valve and Fire Shut-Off Actuators

The central concept is the Airworthiness Directive, a mandatory continuing airworthiness instrument under Part 39 of the Civil Aviation Safety Regulations. This particular AD is short‑form, dealing with a single known physical failure mode: ice formation on an actuator that can cause the valve to freeze stuck. The key component is the actuator P/N 9409122, which applies to both the fuel crossfeed valve and the fuel fire shut-off valve. The grease layer specified is a temporary countermeasure: by covering the actuator with a layer of grease (approximately 2-3 mm thick) the design expects to prevent or delay ice bridging that can lock the mechanism. The operational check involves confirming that the actuator can move the valve through its normal range of travel, while the visual inspection simply verifies that the grease layer remains intact and of sufficient thickness. The language "NAA approved revision" in the service bulletin reference means that the operator must use only the version of SBF-100-28-049 that has been approved by the National Airworthiness Authority (in Australia, CASA) - so later revisions published by Fokker Services must be separately approved before they become acceptable. The MMEL option for the crossfeed valve actuator is a risk‑based concession: it permits dispatch with one actuator inoperative provided the operator complies with the conditions and remarks listed in the MMEL for item 28-23-1. This is not a free pass - it typically imposes restrictions such as limitations on fuel transfer, additional inspections, or reduced operating conditions. The concept of "before further flight" appears three times in the compliance table: for requirement 3 (insufficient grease found after compliance with requirement 2a) and for requirements 4 and 5 (failed operational check). This means no grace period for these findings - the aircraft cannot be flown again until the corrective action (grease reapplication or actuator replacement) is completed. The AD distinguishes between the two valve types: replacement is mandatory for a failed fire shut-off valve actuator (no MMEL relief), but for a failed crossfeed valve actuator the operator may choose replacement or MMEL dispatch. Finally the background statement that the new actuator is being developed but the interim actions are required until that actuator is installed creates a state of indefinite recurring compliance with no known end date - a factor that drives long-term maintenance planning.

The AD directly affects the registered operators and maintenance organisations responsible for the 442 aircraft in the serial number range 11244 through 11585 inclusive, of the F28 Mark 0070 and Mark 0100 types (the Fokker 70 and Fokker 100). The triggering condition is not the aircraft type alone but the presence of actuators P/N 9409122 on the fuel crossfeed valve and the fuel fire shut-off valve. If an operator has already replaced those actuators with a different P/N (including the new actuator referenced in the background), the AD does not apply. However the AD uses the phrase "if equipped with" so the operator must first determine whether the aircraft has the relevant part number. This places an initial identification burden on maintenance planners. The AD also indirectly affects engineering staff who must perform the operational checks (likely requiring access to flight deck controls and possible engine runs or power transfers), the grease application (which involves access to the actuators in the wing or nacelle), and the recurring visual inspections. The 7‑day visual check interval imposes a high frequency of line‑maintenance access, which may require additional man‑hours per aircraft per week. For an operator flying a small fleet of Fokker 70/100 aircraft, the recurring cost of these inspections (including planning, tooling, grease supply, record‑keeping, and potential downtime) is a direct addition to direct maintenance cost. The AD also affects spare parts inventory: operators must stock serviceable replacement actuators P/N 9409122 (or an alternative approved part) to cover potential failures found during checks. The MMEL relief option for the crossfeed valve affects flight dispatch and operational planning: if an aircraft has a failed crossfeed valve actuator and the operator chooses to use the MMEL, the flight crew must be briefed, and the MMEL restrictions (e.g., no fuel crossfeed permitted, possible fuel‑imbalance limitations) become operational constraints. Part 145 maintenance organisations are affected because the AD requires them to have the approved revision of SBF-100-28-049, the necessary grease, the tools for operational checks, and the training to apply the grease layer thickness correctly. Finally the AD indirectly affects the manufacturer (Fokker Services) because the background indicates a new actuator is being developed - the AD effectively creates a market for that upgrade as a means of terminating these recurring tasks.

The primary duty is on the registered operator of each affected aircraft, under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations, to ensure compliance with the AD. The duty is not delegable to a maintenance organisation; the operator remains ultimately responsible for airworthiness. The AD imposes five numbered requirements. First, within 30 days of the effective date (5 July 2007 - so by 4 August 2007), the operator must perform an operational check of and apply grease to both left and right fuel crossfeed valve actuators and fuel fire shut-off valve actuators. Second, after that initial compliance, the operator must (2a) at intervals not exceeding 7 days perform a visual inspection of the grease layer on both sets of actuators, and (2b) at intervals not exceeding 28 days perform an operational check and visual inspection. Note that the 7‑day and 28‑day intervals are separate and independent: the 7‑day clock starts after the initial compliance and ticks continuously, while the 28‑day clock also starts after initial compliance but runs on a different cycle. These are not alternating tasks - the operator must meet both intervals simultaneously. Third, if during any visual inspection under requirement 2a the grease layer is found to be insufficient (less than approximately 2-3 mm), the operator must repeat the grease application from Part 1 of the service bulletin before further flight. Fourth, if a fuel fire shut-off valve actuator fails the operational check (either initial or recurring), the operator must replace that actuator with a serviceable part before further flight; no MMEL relief is permitted for this valve. Fifth, if a fuel crossfeed valve actuator fails the operational check, the operator has a right under the AD to choose either replacement (before further flight) or operation under the conditions and remarks of MMEL item 28-23-1. This right is conditional: the operator must ensure that the MMEL restrictions are observed and that the aircraft’s Minimum Equipment List is approved and current. The MMEL option does not permit indefinite deferral - typically MMEL relief includes time limits (e.g., Category C or D dispatch) so the operator must eventually replace the failed actuator. The operator also has the right to use a later NAA‑approved revision of SBF-100-28-049 if CASA or the NAA has approved it. The AD does not require the operator to install the redesigned actuator mentioned in the background; the AD only demands the interim actions until such installation occurs voluntarily. That is an important right: the operator can choose the cost‑benefit trade‑off of embodying the modification versus maintaining the recurring inspection regime.

The AD itself does not contain penalty provisions; it derives its legal force from the wider regulatory framework. Under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998, operating an aircraft that does not conform to an applicable AD is a breach of the airworthiness requirements. The applicable penalty provisions are found in the Act and Regulations rather than in this instrument. Typically, an operator who flies an aircraft without having complied with an AD is committing an offence that can attract civil penalties (as high as thousands of penalty units for a body corporate) or criminal prosecution in serious cases where the breach causes or risks danger. CASA may also suspend or cancel the aircraft’s Certificate of Airworthiness, effectively grounding the fleet until compliance is demonstrated. Enforcement action for this particular AD would focus on the recurring intervals. Because the AD requires checks at intervals not exceeding 7 days and 28 days, a single missed inspection (for example, if a visual check is due on day 7 but performed on day 9) is technically a non‑compliance. The phrase “not to exceed” leaves no grace period beyond the stated maximum. However CASA may exercise discretion in enforcement depending on the severity and the safety risk. The AD also names a specific service bulletin revision: SBF-100-28-049 or later NAA approved revision. Using an unapproved revision (e.g., a later revision that CASA has not accepted) would also be a non‑compliance. The note referencing EASA AD 2007-0122 indicates that the Australian AD is aligned with a European requirement; an operator that complies only with the foreign AD but fails to meet the Australian AD (if there are differences in wording or approval of revisions) would still be in breach under Australian law. CASA may audit compliance through maintenance records, and an operator’s failure to keep accurate records of the grease application dates, inspection results, and any MMEL usage would expose it to penalties under the record‑keeping provisions of the Regulations. The enforcement focus is likely on the recurring visual inspections: a 7‑day interval is tight and easy to overlook during schedule changes. Civil penalties under Part 4A of the Civil Aviation Act (as amended) can reach significant sums; for a corporation the maximum penalty can be hundreds of thousands of dollars per breach. There is also the possibility of enforceable undertakings or directions from CASA.

This AD interacts with several other legal instruments and standards. First, it expressly references EASA AD 2007-0122 dated 3 May 2007. The Australian AD is not identical to the EASA AD in its wording, but it notes that the EASA AD “refers”. This likely means that the European requirement is the source document, and the Australian AD adopts the same service bulletin and compliance logic. For an Australian operator with aircraft also registered in Europe (unlikely but possible for lessor‑owned aircraft) there may be a need to comply with both ADs and manage any differences. Second, the AD references the Aircraft Maintenance Manual (AMM) for the replacement procedure. The AMM is an approved document under the type certificate and Part 145. The interaction means that any replacement must follow the specific procedures in the AMM, which may themselves require special tools or inspections. Third, the AD references the MMEL item 28-23-1 for the crossfeed valve actuator failure. The MMEL itself is a document approved by CASA under Civil Aviation Safety Regulation Part 25 or Part 121/135. The MMEL provisions impose operational restrictions, and the operator’s own Minimum Equipment List (MEL) - approved for its operations - must incorporate that item. Using the MMEL relief without having the specific MEL approval or without observing the remarks is itself a breach of the Regulations. Fourth, the AD interacts with the general requirement under Civil Aviation Safety Regulation 42.040 that an aircraft must be maintained in an airworthy condition and that any maintenance must be performed in accordance with the approved data - the AD constitutes approved data. Fifth, the AD does not explicitly reference the type certificate data sheet or any other AD for the Fokker F28 series, but it sits within a family of ADs for these aircraft. The serial number range 11244-11585 is relatively narrow, meaning that other Fokker 70/100 aircraft with the same actuator but outside that serial range are not subject to this AD. There is a potential gap in coverage if those aircraft have the same failure mode. Sixth, the grease application and inspection tasks may also interact with other maintenance requirements, such as corrosion prevention or fuel system integrity checks. There is no specific interaction noted in the AD with workplace health and safety laws (for handling grease or working near fuel systems), but in practice, the grease application will require compliance with Occupational Health and Safety regulations and safe systems of work for access to high‑wing areas. Finally, the AD may interact with export or import requirements: a Fokker aircraft imported into Australia with a foreign airworthiness approval that does not include compliance with this AD would need to have the AD record reviewed.

The document provided is the complete text of Airworthiness Directive AD/F100/84, with an effective date of 5 July 2007 and a signature date of 14 May 2007. There is no indication in the source of any amendment to this AD after its publication. The instrument is a final AD (not a proposal), issued by a delegate of CASA. There is no amendment history included within the document itself. However AD/F100/84 may have been amended after the initial issue: under normal CASA practice, ADs can be revised to extend applicability, modify compliance times, or incorporate new service bulletin revisions. The note “[or] later NAA approved revision” in the requirement text provides a mechanism for updating the service bulletin without formally reissuing the AD itself, as long as the new revision receives NAA approval. That is a form of dynamic amendment authority vested in the National Airworthiness Authority (CASA) rather than in the AD text. For instance, if Fokker Services issues SBF-100-28-049 Revision 1 with minor procedural changes, and CASA approves it, operators would be required to use that revision as the approved data. Without CASA approval, the later revision is not acceptable. The background to the AD mentions that a new actuator was being developed; once that actuator became available and was installed on aircraft, the AD would no longer apply because the triggering part (actuator P/N 9409122) would no longer be installed. However the AD itself does not contain a terminating action or a requirement to install the new actuator. So in practice, the amendment history for operators consists of tracking whether CASA has approved any later revision of the service bulletin, and whether the new actuator has been certified as a terminating action. As a separate matter, the AD could have been superseded by a later AD that covers the same issue (e.g., AD/F100/XX requiring installation of the new actuator). There is no such supersession mentioned in the source. An operator researching the current status of this AD would need to check the CASA AD database for any revisions, amendments, or withdrawals since 2007. The source appears to be a snapshot of the AD as originally issued.

The source document does not mention any litigation, court cases, or tribunal decisions related to AD/F100/84. Given that this is a specific, technical airworthiness directive affecting a relatively small fleet (442 aircraft in serial range), it is unlikely to have generated significant litigation. However the legal framework for challenging ADs exists: an affected operator could seek judicial review under the Administrative Decisions (Judicial Review) Act 1977 or the Civil Aviation Act to challenge the validity of the AD, for example on grounds that the decision‑maker did not have power, or that the direction was unreasonable. No such cases are known or referenced. It is also possible that enforcement actions by CASA under this AD - for example, a penalty for non‑compliance - could be litigated in the Federal Court or the Administrative Appeals Tribunal (if CASA issues a decision on an application for an extension of time or a variation). But again no such litigation is recorded in the source. The note referencing EASA AD 2007-0122 suggests that any litigation in Europe relating to that European AD (e.g., an appeal by Fokker Services or an operator) might indirectly affect the Australian AD if the European AD was found invalid, but the Australian AD is a separate legal instrument and would stand on its own merits. There is also the possibility of product liability claims by operators against Fokker Services for the defective actuator, but that is private law, not litigation under the AD. In summary, the litigation history for this specific AD is a blank slate. The deep dive should note that there is no recorded case law interpreting or challenging AD/F100/84, but the possibility of administrative review exists if an operator believes the compliance times are unreasonable or the applicability is incorrect. Given the high threshold for judicially reviewing technical, safety‑based decisions, such litigation would be very rare.

Several subtle features of this AD could trip up even experienced compliance staff. First, the compliance intervals for requirements 2a and 2b are not aligned. Requirement 2a demands a visual inspection at intervals not exceeding 7 days; requirement 2b demands an operational check and visual inspection at intervals not exceeding 28 days. Both intervals start after compliance with requirement 1. This means an operator must maintain two separate recurring cycles. If the operator treats the 28-day check as satisfying the 7-day check, the visual inspection could become overdue after 7 days because the 28-day check does not cover the gap between cycles. For example, if the operator performs the 28-day operational check on day 28, the next 7-day visual inspection would be due on day 35, but the operator might mistakenly think the 28-day check resets both clocks. The AD is clear: they are separate. Second, the grease layer thickness is specified as “approx. 2-3 mm”. This is a visual estimate, not a precision measurement. An engineer may apply a layer that looks adequate but is actually too thin, and then a later visual inspection might deem it insufficient, triggering a reapplication before further flight. The subjective nature of this condition could lead to differing interpretations between shifts or between maintenance organisations. Third, the MMEL relief for the crossfeed valve actuator is not unconditional. The AD says “operate the aircraft in accordance with (the conditions and remarks in) MMEL item 28-23-1.” This requires the operator to have an approved MEL that incorporates that item. If the operator’s MEL has not been approved by CASA for that item, or if the operator is not authorised to use an MMEL (e.g., private operations under Part 91 without an MEL), then the MMEL relief is not available. In that case, a failed crossfeed valve actuator mandates replacement before further flight. Fourth, the AD applies only to aircraft serial numbers 11244 through 11585 inclusive. However the background describes a failure mode that could logically affect any F28 Mark 0070 or Mark 0100 with the same actuator P/N regardless of serial number. Operators of aircraft outside this serial range should not assume the AD is irrelevant; they may still have the same actuator, but the AD does not capture them. That is a potential gap - an operator of serial number 11586 with the same actuator is not required to perform these checks, but the failure mode is identical. This might create confusion if a maintenance engineer applies the AD voluntarily and then later finds the aircraft is not in the applicability range. Fifth, the phrase “later NAA approved revision” in the requirement means that an operator cannot rely on a service bulletin revision that has not been approved by the National Airworthiness Authority (CASA). If Fokker Services publishes Revision 1 of SBF-100-28-049 without CASA approval, using it for compliance would be non‑compliant. The operator must actively check CASA’s approval status. Sixth, the effective date is 5 July 2007. The initial compliance (30 days) would be by 4 August 2007. Any aircraft not in compliance by that date would be grounded. Seventh, the AD does not include a provision for alternate means of compliance (AMOC) in the text, but under the Regulations an operator can apply to CASA for an AMOC. That application process itself takes time and may not be granted, adding uncertainty.

Compliance with AD/F100/84 is a multi‑step process that must be documented and integrated into the operator’s continuing airworthiness management system. The first step is to determine applicability. The operator must identify each F28 Mark 0070 or Mark 0100 it operates with a serial number between 11244 and 11585, and then verify whether those aircraft are fitted with fuel crossfeed valve and fuel fire shut‑off valve actuators bearing P/N 9409122. If only one or neither actuator type has that P/N, the obligations attach only to the affected ones. However the AD uses the phrases “fuel crossfeed valve- and fuel fire shut-off valve actuators” together, suggesting the checks apply to both types. An aircraft with only one actuator of that P/N may still be subject; read carefully.

Second, the operator must obtain the approved revision of Fokker Service Bulletin SBF-100-28-049. As of 2007, the original issue of the bulletin may have been approved. The operator must check with CASA or the CASA AD database to confirm that revision remains current or if a later revision has been approved. The bulletin will contain the detailed procedural steps for the operational check and the grease application method.

Third, the initial compliance must be accomplished within 30 days after 5 July 2007 - that is, by 4 August 2007. The work includes an operational check of each actuator (LH and RH for both crossfeed and fire shut‑off) and application of grease to a layer of approximately 2-3 mm. The operator should document the date of this initial compliance in the aircraft maintenance log.

Fourth, after initial compliance, the operator must establish recurring inspection intervals. A 7‑day visual inspection of the grease layer is required. This inspection does not require an operational check; it is purely visual to confirm the grease layer is still present and sufficient. The operator must schedule this at intervals not exceeding 7 calendar days. It is good practice to set the interval at 7 days with no grace period, but the regulatory requirement is “not to exceed 7 days”, meaning if the inspection is performed on day 7, it complies. However performing it on day 8 would be late. A practical approach is to schedule it every 7 days with a one‑day buffer.

Fifth, a separate operational check and visual inspection must be performed at intervals not exceeding 28 days. This check requires the actual movement of the valve actuator (likely via flight deck controls or test equipment) to confirm the actuator operates freely. Because the operational check also includes a visual inspection, the 28‑day check may be combined with the 7‑day visual inspection if the timing aligns, but the operator must ensure the 7‑day requirement is not exceeded by waiting for the 28‑day check.

Sixth, whenever a visual inspection reveals insufficient grease (less than approx. 2-3 mm), the operator must reapply grease before the next flight. This is a repetitive corrective action. The AD does not give a fixed compliance time; it says “before further flight”. The operator must have grease and the service bulletin available to perform this reapplication immediately.

Seventh, if any actuator fails an operational check (either initial or recurring), the operator must determine whether it is a fire shut‑off valve actuator (requiring replacement before further flight with no alternative) or a crossfeed valve actuator (replacement before further flight or operation under MMEL item 28-23-1). For MMEL operation, the operator must ensure that its MEL has been approved for that item and that the dispatch conditions (likely a limit on the number of days or cycles) are met. The operator must also document the MMEL usage in the technical log.

Eighth, the operator must maintain auditable records: dates of initial compliance, dates of each visual inspection and each operational check, results, any findings of insufficient grease, any grease reapplications, any actuator replacements, and any MMEL usage. These records must be retained for the life of the aircraft under the applicable airworthiness regulations.

Ninth, because the AD does not expire, the operator should consider a terminating action: fitting the redesigned actuator (when available) that eliminates the ice formation issue. Installing the new actuator removes the need for the recurring checks, reducing long‑term maintenance costs and compliance risk. The operator should monitor for availability of a service bulletin that installs the new actuator and for a new AD that would supersede AD/F100/84 or make the recurring actions no longer necessary.

Tenth, if the operator finds compliance with the 7‑day interval impracticable for some operations (e.g., aircraft in storage or infrequent use), it may apply to CASA for an alternative means of compliance or an extension. The AD itself does not provide any relief; any relief must be formally approved by CASA under the regulations. The operator should plan for the recurring interval as a hard requirement.