AD/F100/53 Amdt 2 - Main Landing Gear Sliding Member

The AD introduces several operational and engineering concepts that are essential for compliance. Airworthiness Directive is a regulatory order issued by the national aviation authority to correct an unsafe condition. Non-compliance with an AD renders the aircraft unairworthy and may ground the fleet. The Applicability block defines precisely which aircraft and parts are captured. It references model numbers (F.28 Mk. 0100 and Mk. 070), main landing gear part numbers (201072011 through 201072016), and two specific sliding member part numbers (201072301 and 201072305). Operators must cross-check their aircraft and component logs against these numbers; any variation excludes the aircraft from the scope of this directive.

A sliding member is the inner tube of the main landing gear oleo-pneumatic shock strut. It slides within the outer cylinder when the gear extends, retracts, or compresses on landing. Fatigue cracking in this component can lead to catastrophic failure of the gear leg during ground handling or take-off. The AD mandates magnetic particle inspection (MPI) for crack detection. MPI is a non-destructive testing method that uses magnetic fields and ferrous particles to reveal surface and slightly subsurface cracks. It requires specialised equipment, trained technicians, and often removal of the component or at least disassembly of the gear to gain access.

The term flight cycle is the basic metric for the inspection intervals: one flight cycle equals one take-off and one landing. The AD uses 2,000 flight cycles as the interval for the repetitive MPI. Because the Fokker 100 is a short-to-medium range aircraft that may accumulate cycles faster than hours, a cycle-based limit is more risk-relevant than calendar time for fatigue cracking. However, the AD also includes a 4-calendar-month grace period for the first repeat inspection (requirement 2), which recognises that operator schedules may not align perfectly with cycle accumulation.

High drag load landing is a defined condition that triggers an immediate before-further-flight inspection. The term refers to a landing that exceeds normal operational limits , for example, a firm or heavy landing that places above-normal stresses on the landing gear structure. The Fokker 70/100 Aircraft Maintenance Manual (Task 05-51-01-220-826-A) provides criteria for identifying such a landing, likely based on acceleration data, pilot report, or maintenance logs. Similarly, brake application during backward movement occurs when the aircraft is pushed back or taxied in reverse and the brakes are inadvertently or deliberately applied. This event imposes a unique torsion and bending load on the sliding member because the aircraft is moving tail-first and the brakes act against the direction of motion.

The AD also cross-references Messier-Dowty Service Bulletin SB F100-32-110 (original issue or later UK CAA approved revision) for the inspection instructions, and Fokker Service Bulletin SBF100-32-144 as a related document. Service bulletins are manufacturer-issued instructions that may be voluntary or mandatory. The AD makes the inspection procedure mandatory. Finally, the reporting requirement is open-ended: operators must report “whatever the results” to the type certificate holder and the gear manufacturer. This creates a feedback loop for the manufacturer to monitor fleet condition and possibly develop a permanent fix or revised inspection thresholds.

The primary duty-holders under this AD are the registered operators of Fokker 100 and Fokker 70 aircraft. In Australia, such operators are typically airlines, charter operators, freight carriers, and aircraft leasing companies. Each operator must identify whether any of its fleet is within the applicability block. The AD affects a specific subset of aircraft: those with the listed main landing gear part numbers (the gear assemblies themselves) and the listed sliding member part numbers. Operators whose aircraft have different part numbers are not required to comply, but they must verify that fact from engineering records or component logbooks.

The AD also has direct consequences for maintenance organisations (approved Part 145 or CAR 30 maintenance providers). They must develop or incorporate the inspection procedures into their maintenance manuals, train staff on MPI techniques, procure or maintain MPI equipment, and maintain records of each inspection. The need for MPI capability may be costly for smaller repair stations, and some may outsource the work to specialists. The AD effectively forces operators and their maintenance providers to invest in non-destructive testing infrastructure or contractual arrangements.

The type certificate holder (historically Fokker Services B.V., now likely a separate entity or absorbed into a larger group) and the landing gear manufacturer (Messier-Dowty, now Safran Landing Systems) are indirect duty-holders: they must receive and process the mandatory reports. The AD does not explicitly require them to issue a corrective design change, but the reporting requirement imposes an administrative burden and creates liability pressure if many cracks are found.

The AD indirectly affects lessors and financiers, because a non-compliant aircraft loses airworthiness and thus its earning capacity or asset value. Lease agreements typically require compliance with all applicable ADs, so the lessee’s failure to comply can be a default event. Insurers may also be affected: non-compliance with an AD is a breach of statutory duty and could void coverage or affect liability assessment in the event of an accident.

The CASA delegate who issued the AD (David Villiers) is the official signatory, but the organisation itself bears the cost of monitoring compliance and taking enforcement action. Australian operators face the most direct burden because CASA’s regulatory reach is domestic; however, the AD also cross-references Dutch CAA ADs, meaning this directive aligns with European safety requirements for the same aircraft type. Operators operating under bilateral agreements (e.g., Australian aircraft wet-leased to European carriers) must ensure compliance with the relevant national variant.

The core duty is inspection: the operator must arrange and complete the initial and repetitive magnetic particle inspections of the sliding member at the stated intervals (2,000 flight cycles, or earlier event-driven triggers). The inspection must follow the Accomplishment Instructions of Messier-Dowty SB F100-32-110 (original or later UK CAA approved revision). This means the operator does not have discretion to use a different procedure; the AD mandates a specific manufacturer-approved method.

A second duty is replacement: if any crack is found, the affected sliding member must be replaced with a serviceable part before the next flight. The operator cannot defer replacement even if the crack is minor. The replacement must be performed in accordance with the Fokker 70/100 AMM Chapter 32-11-08. This duty imposes direct parts and labour costs and may involve aircraft downtime if a spare sliding member is not immediately available.

The third duty is reporting: all findings , cracked or not , must be reported to the type certificate holder and the landing gear manufacturer. The AD does not prescribe a format, but it implies a written report. This creates an ongoing administrative burden and a potential liability exposure if the operator fails to report a previously undetected crack that subsequently causes an incident.

Operators also have a duty to record and document compliance. The AD does not explicitly state record-keeping, but under CASR Part 42 and Part 145 maintenance records must include evidence of AD compliance. Operators should maintain logs of inspection dates, cycle counts, results, and any replacements.

The right that operators possess includes the right to use alternative means of compliance (AMOC) approved by CASA. The AD does not itself mention AMOC, but CASA’s AD policy generally permits operators to propose an equivalent method if it can be shown to provide an equivalent level of safety. This right allows an operator to substitute a different inspection technique (e.g., eddy current instead of MPI) if approved, which may reduce costs or downtime. However, seeking an AMOC requires time and regulatory engagement, and CASA may deny it.

Operators also have the right to rely on the serviceable part standard: a sliding member that passes the inspection without crack indication is considered airworthy and may continue in service subject to the next inspection. They also have the right to inspect at intervals longer than 2,000 flight cycles only if an AMOC is granted or if the AD is later revised.

There is a subtle right in the “whichever occurs later” phrasing for the first repeat inspection (Requirement 2). This allows the operator to defer the first repeat inspection to the later of 2,000 flight cycles or 4 calendar months if they have not reached 2,000 cycles within that time, giving flexibility for low-utilisation aircraft. However, this is not a right to skip; it is a compliance deadline calculation.

Non-compliance with an Airworthiness Directive issued under CASA’s enabling legislation is a serious regulatory breach. The Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998 (CASR) make it an offence to operate an aircraft that does not conform to its approved design or applicable ADs. Specifically, CASR Part 42 (continuing airworthiness) requires that an aircraft be maintained in a condition that complies with all applicable ADs. Operating an aircraft in breach is an offence under CASR 42.250 and on conviction can attract a penalty of up to 50 penalty units for an individual (currently $25,000 if a penalty unit is $500, though that amount is indexed) or significantly more for a body corporate under Part 2 of the Crimes Act 1914 (Cth). In more severe cases, CASA can seek court orders including injunctions, and the Australian Federal Police or CASA investigators can pursue criminal prosecution if the non-compliance leads to an accident or recklessness.

Beyond court penalties, CASA has powerful administrative enforcement tools. It can ground the aircraft by issuing a direction not to fly under section 20BA of the Civil Aviation Act or by suspending or cancelling the aircraft’s certificate of airworthiness. It can also suspend or revoke the operator’s Air Operator Certificate (AOC) if systemic non-compliance is found. These actions effectively shut down the operator’s business. CASA can impose enforceable undertakings under the Regulatory Powers Act, requiring operators to commit to rectification and monitoring. Additionally, the AD itself states that cracked parts must be replaced before further flight; any deviation is a direct breach.

Enforcement is risk-based: CASA may prioritise high-risk operators (e.g., those with known maintenance issues) but theoretically any unaddressed non-compliance is a breach. The reporting requirement , “whatever the results” , is also enforceable: failing to report cracks or even clean results is a breach.

The AD also creates potential civil liability exposure. If a sliding member fails due to a crack that a proper inspection would have detected, the operator could face claims for damage to the aircraft, injury, or third-party harm. An operator’s failure to comply with the AD would likely be strong evidence of negligence, reducing the chance of a successful defence. Conversely, strict compliance with the AD does not automatically exclude liability if a crack is missed despite proper inspection , the standard is reasonable care , but it significantly mitigates risk.

This AD sits within a hierarchy of Australian aviation safety legislation. Its immediate statutory basis is the Civil Aviation Act 1988 (Cth), which empowers CASA to issue airworthiness directives as legislative instruments under section 98A (or similar provisions in the regulations). The AD is a form of delegated legislation and has the force of law. It must be read together with the Civil Aviation Safety Regulations 1998, particularly Part 42 (continuing airworthiness) and Part 145 (approved maintenance organisations). CASR Part 42 requires operators to maintain their aircraft in accordance with an approved maintenance program, and any AD automatically becomes part of that program.

The AD also references foreign regulatory actions: Netherlands CAA ADs 2002-060 and 2004-046, and UK CAA approval of the Messier-Dowty service bulletin. This reflects a system where CASA often adopts or harmonises with the airworthiness directives issued by the State of Design (the Netherlands) for aircraft types certificated there. This reduces duplication and ensures Australian operators meet the same safety standards as the European fleet. However, it also means that changes to those foreign ADs may flow through to CASA ADs, or operators must monitor both. The cross-reference to “CAA-NL AD NL-2005-012” indicates that the Dutch AD was the immediate trigger for this amendment.

The AD interacts with the Aircraft Maintenance Manual (AMM) and Maintenance Review Board Report (MRBR) for the Fokker 100. The AMM tasks (05-51-01-220-826-A and 05-51-01-220-876-A) are defined procedures that become mandatory through the AD. Operators must ensure that their maintenance documentation reflects the latest revisions of these tasks and that any Manual Change Notification (MCNM F100-083 Rev.1) is incorporated.

There is also interaction with insurance contracts. Most aircraft hull and liability policies require the operator to comply with all mandatory ADs. Non-compliance is a policy exclusion, meaning the insurer may decline cover for a claim arising from a failure that should have been prevented by AD compliance. Similarly, leasing agreements under Australian law typically require the lessee to adhere to ADs or face termination.

Under the Administrative Appeals Tribunal Act 1975 and the Judiciary Act 1903, an operator aggrieved by the AD could theoretically apply for judicial review of the delegate’s decision to issue it. However, courts give substantial deference to CASA’s technical safety assessments, and the bar for overturning an AD is very high. An operator would need to show that the decision was irrational or made without evidence , unlikely given the documented cracks in the background.

The source document is AD/F100/53 Amdt 2. The background section reveals that Amendment 1 was issued previously. Amendment 1 required a second one-time inspection in response to the earlier inspection findings. Amendment 2 replaces Amendment 1 entirely and imposes a repetitive inspection regime. The amendment history is sparse, but we can infer that the original AD (before Amdt 1) likely required a single one-time inspection. The background states: “a failure of the sliding member … occurred during a terminal departure push-back … Investigation of the fractured surface revealed overload, initiated by a fatigue crack. Inspection of other aircraft revealed cracking in the same area.” This failure led to the original AD.

Amendment 1 then added a second one-time inspection, presumably because the first inspection missed some cracks or the timing was insufficient. Amendment 2, issued in response to a new CAA-NL AD (NL-2005-012), concluded that even the second one-time inspection was inadequate and that ongoing repeat inspections are necessary. The effective date of Amdt 2 is 19 January 2006, with the instrument signed by the CASA delegate on 28 November 2005. The AD itself does not specify the date of the original AD or Amdt 1. However, the cross-references to Dutch ADs 2002-060 and 2004-046 indicate that the European regulatory activity dates from 2002 and 2004 respectively.

The AD number system (AD/F100/53) indicates that this is the 53rd AD issued for the Fokker 100 type. Amendment 2 is the third iteration (original, Amdt 1, Amdt 2). The document shows “1/2006” which likely denotes that it is the first CASA AD published in 2006 for this subject.

The amendment process is formal: the delegate considered the new knowledge from fleet inspections and the Dutch authority’s findings, and determined that a change was necessary. The AD does not provide a sunset or review date; it continues indefinitely until CASA amends or withdraws it.

The source document contains no reference to any litigation concerning this AD. That is typical: airworthiness directives are rarely litigated directly because they are technical safety decisions that courts generally defer to, and the compliance costs are often too low per operator to justify a challenge, or operators seek alternative means of compliance rather than judicial review. There is no recorded case in Australian courts where AD/F100/53 was challenged. However, one can conceive of scenarios that could lead to litigation.

A hypothetical challenge could arise if an operator believed CASA had no reasonable basis for prescribing such a costly repetitive inspection, especially for operators with low cycle accumulation. An application for judicial review under the Administrative Decisions (Judicial Review) Act 1977 on grounds of jurisdictional error or unreasonableness could be filed. However, the background provides evidence: a fracture event and subsequent cracks found in the fleet. That factual basis would likely satisfy a court that the decision was rationally open to the delegate.

If an operator ignored the AD and was prosecuted, the court would consider whether the AD was validly made and properly served. Technical arguments about the delegate’s authority or the interpretation of “high drag load landing” could arise. But no reported judgment exists.

In the United States or Europe, ADs on the Fokker 100 landing gear might have been the subject of litigation between operators and the manufacturer (e.g., product liability claims if cracks are due to design defect). But those would be private law matters, not challenges to the AD itself. There is no public indication of such proceedings.

The AD’s reference to “reporting to the type certificate holder” could create a paper trail that plaintiffs use in future product liability claims, but that is not litigation of the AD.

Thus, for the purposes of this deep dive, the litigation history is effectively nil. The deep dive should state that no litigation is recorded in the source, and note the practical hurdles to challenging an AD.

Several subtle features of this AD can trip up even experienced compliance managers. First, the compliance deadline for Requirement 2 is drafted as “within 2,000 flight cycles after the accomplishment of Messier-Dowty SB F100-32-103 … or Messier-Dowty SB F100-32-105 … or within the next 4 calendar months, whichever occurs later after 19 January 2006.” The “whichever occurs later” means the operator gets the more generous of the two limits (2,000 cycles vs. 4 months), but measured from the date of those earlier SBs. An operator who has already accomplished those SBs must carefully compute the starting point. The AD does not define the exact date that “accomplishment” occurred; it could be the date the SB entry was signed off. There is risk of misinterpreting the starting point and triggering a late inspection.

Second, Requirement 4 uses “Before further flight” without specifying a maximum deviation. In practice, “before further flight” means the next flight departing from the airport where the high drag load occurred. But if the aircraft subsequently flies a positioning flight without inspection, that flight would be illegal. The operator must have procedures to immediately identify high drag load landings and dispatch MPI personnel, which may be infeasible at remote airports. A thorough interpretation may require that the aircraft be grounded until inspection is performed, leading to operational disruption.

Third, Requirement 5 uses “Within the next 50 flight cycles thereafter” for the brake-during-backward-movement inspection. The “thereafter” refers to the event itself. However, the AD is silent on how to count the 50 cycles if multiple such events occur. It also does not define “backward movement” precisely , does it include push-back with tug attached? Or only self-propelled reverse using thrust reverse? The AMM task likely clarifies, but the ambiguity could cause disagreement between operators and inspectors.

Fourth, the reporting obligation applies “whatever the results of the inspections”. This means even if no crack is found, the operator must report. This is easy to overlook. Many operators may treat a clean inspection as having no reporting requirement, but the AD explicitly requires it. Failure to report is itself a breach.

Fifth, the AD refers to “UK CAA approved revision” of the service bulletin. If the UK CAA approves a later revision, the operator must use that revision. But the AD does not incorporate future revisions automatically; it says “original issue, or later UK CAA approved revision.” This open-ended language means the operator must monitor for new revisions and determine which revision is approved by the UK CAA. A slip in tracking could result in using a non-approved version.

Sixth, the AD applies to “all aircraft that are not compliant with the requirements of Netherlands CAA ADs 2002-060 and/or 2004-046”. This creates a category of aircraft that are already compliant with those ADs (and thus have a different initial requirement). Operators must know whether those ADs were complied with, and verify that the compliance was correctly recorded. If records are incomplete, the operator may be forced to assume non-compliance and perform the more onerous initial inspection.

Seventh, the AD does not specify what to do if a sliding member is replaced with a part that is not one of the listed part numbers but is still a sliding member (e.g., a modified part). The applicability ties to original part numbers; if the replacement part is a new part number not listed, it may fall outside the AD scope. But if the replacement part is a serviceable used part from the same part number pool, the AD still applies. The operator must ensure any replacement part is also inspected at the required intervals.

Finally, the AD’s indefinite repetition interval (2,000 flight cycles) means that high-cycle aircraft could be inspected dozens of times over their remaining life. The accumulated labour and downtime costs can exceed the value of the aircraft, creating an economic imperative to scrap the component or the aircraft itself. This is a hidden economic gotcha: the AD effectively imposes a permanent cost that may not have been factored into the initial purchase or lease.

1. Identify affected aircraft. Reference the Applicability section: any Fokker 100 or 70 with main landing gear part numbers 201072011-201072016 and sliding member part numbers 201072301 or 201072305. Check aircraft records, component logbooks, and the current configuration. If the gear has been replaced, determine the part numbers of the current unit.

2. Determine compliance baseline. For aircraft that have not previously complied with Netherlands CAA ADs 2002-060 or 2004-046 (which correspond to AD/F100/53 Amdt 1), perform a one-time magnetic particle inspection of the sliding members per Messier-Dowty SB F100-32-110 original issue or later UK CAA approved revision. Use note 1: Fokker SB F100-32-144 is related; review it for clarity but follow the Messier-Dowty SB. For aircraft that have complied with those earlier ADs, the initial inspection under Requirement 2 serves as the start of the repetitive cycle. Ensure the previous compliance is documented. If records are unclear, treat the aircraft as non-compliant and perform the initial inspection as per Requirement 1 to be safe.

3. Establish repetitive inspection schedule. After completing the initial inspection (or bringing the aircraft into the repetitive cycle via Requirement 2), schedule subsequent inspections at intervals not exceeding 2,000 flight cycles. Track flight cycles precisely; use the aircraft’s utilisation data. For the first repeat inspection, determine the later of: 2,000 flight cycles after the accomplishment of the earlier SB (F100-32-103 or F100-32-105), or 4 calendar months after 19 January 2006. This is a one-time calculation; thereafter adhere to 2,000 cycle intervals.

4. Incorporate event-driven inspections into the maintenance control system. For any high drag load landing (defined per the AMM), the aircraft must not fly again until the sliding members have undergone a magnetic particle inspection per AMM Task 05-51-01-220-826-A. Establish a procedure for the flight crew or maintenance team to identify such landings (e.g., reports, flight data monitoring) and immediately book inspection. Similarly, for any brake application during backward movement, schedule the inspection within 50 flight cycles of the event per AMM Task 05-51-01-220-876-A. Ensure the AMM tasks are available in current revision, and that MCNM F100-083 Rev.1 has been incorporated.

5. Train and equip maintenance personnel. Ensure the performing organisation has MPI capability (equipment and certified NDT Level 2 or 3 technicians). Review the Messier-Dowty SB F100-32-110 instructions for specific scan patterns and sensitivity requirements. If the organisation lacks in-house MPI, contract a qualified facility. Maintain calibration records.

6. Perform part replacement. If any crack is found, replace the sliding member with a serviceable part before further flight. Use the AMM Chapter 32-11-08 procedures. Ensure the new part is either a new production part that meets the type design, or a used part that has been inspected to the same AD requirements. After replacement, the new sliding member becomes subject to the same repetitive inspection regime. Document the replacement in the engine or component log and update the maintenance records.

7. Report findings. After each inspection (initial, repetitive, and event-driven), send a report to the type certificate holder (currently Fokker Services or its legal successor) and to Messier-Dowty (Safran Landing Systems). The report should include the aircraft registration, part numbers, flight cycles since new or last inspection, inspection results (crack findings or clean), and any corrective action taken. The AD does not specify a format, but a letter or email referencing the AD number and date is sufficient. Keep a copy in the aircraft records. Report “whatever the results”, so even clean inspections require a report. This creates a compliance oversight risk; automate reminders.

8. Monitor for future AD changes. The AD is Amdt 2 and may be further amended. Subscribe to CASA’s AD notification service and review updates to European ADs from EASA (which replaced CAA-NL). If a later UK CAA approved revision of the SB is issued, update the inspection procedures accordingly.

9. Integrate into the Continuing Airworthiness Management Exposition (CAME) and Maintenance Program. The AD should be listed in the operator’s AD compliance register. The inspection intervals should be scheduled in the maintenance plan. The event-driven triggers should be coded as conditional tasks. Ensure auditors and regulators can see full compliance history.

10. Consider alternative means of compliance if the fixed schedule imposes excessive cost or downtime. For example, if engineering analysis shows that a different NDT method or a longer interval is safe, apply to CASA for an AMOC. Be prepared to provide data and risk assessment. This may be worthwhile for low-cycle aircraft or where MPI access is difficult.