AD/F100/77 - Main Landing Gear Main Fitting - 4

Applicability is narrow and technical: the AD applies to F.28 Mk.0070 and Mk.0100 aircraft, all serial numbers, only if equipped with Messier‑Dowty (formerly Dowty Aerospace Gloucester) Main Landing Gears. That limitation defines the population of affected assets precisely by airframe model and supplier of the MLG Main Fitting. The AD repeatedly cross‑references manufacturer service bulletins and Fokker Services documents as the operative methods: SB F100‑32‑111 (Messier‑Dowty), SB F100‑32‑106 (Messier‑Dowty), and Fokker Services SBF100‑32‑146 and SBF100‑32‑141. The AD conditions compliance on following those Accomplishment Instructions or later EASA approved revisions; compliance therefore depends on both the content of the service documents and the status of any subsequent EASA approvals.

The AD uses three technical levers:

• Inspection and rework: physical examination of the MLG Main Fitting units and corrective rework where necessary, following prescribed procedures in the SBs. The AD requires these actions at specified initial and repetitive intervals.
• Continued flight allowances tied to crack thresholds: when cracks are found, the AD requires determination of whether flights may be continued, and for how many, in accordance with crack size and location thresholds listed in Fokker Services SBF100‑32‑146.
• Supply‑chain control: prohibition of installation of replacement MLG Main Fitting units unless they have been inspected and reworked in accordance with specified SBs, except where the unit is new or already reworked as permitted under Requirements 2 or 4.

The AD also includes mandatory reporting to Fokker Services "irrespective of the results" within seven calendar days following each inspection as required by Requirements 1-4. The reporting must use the questionnaire attached to SBF100‑32‑146. That creates an information flow from operators/maintenance organisations to Fokker Services on an event and recurring basis.

The AD is positioned as corrective and preventive. The Background records two reported failures when aircraft were being moved backwards for maintenance and brakes were applied. Earlier CAA‑NL ADs had required one‑time inspections and operational mitigations (an AFM change and a placard), and this AD adds repetitive inspections and rework to prevent recurrence.

EASA approval linkage is central. The AD permits conformity with "later EASA approved revision" of the referenced SBs and Fokker Services documents. That ties the practical content of the mandatory tasks to the ongoing service bulletin revision process and EASA's approval decisions.

Terminology used in the source: "inspect and as necessary, rework", "new", "reworked", "replacement", "crack size and location thresholds", "accomplishment instructions", "EASA approved revision", and "report all findings". The AD numbers and cross‑references (CAA‑NL ADs, AD/F100/55 Amdt 1, AD/F100/64 etc.) are included in the text; they remain part of the regulatory web an operator must track.

The instrument directly affects operators of Fokker F100 (F28 Mk 100) series aircraft that are fitted with Messier‑Dowty main landing gears. The Applicability clause in the AD states the models and the supplier condition explicitly: Model F.28 Mk. 0070 and Mk. 0100 aircraft, all serial numbers, if equipped with Messier‑Dowty (formerly Dowty Aerospace Gloucester) Main Landing Gears. Therefore the primary economic actors affected are aircraft operators (airlines, charter operators, maintenance organisations operating under their authority) that fly and maintain those specific airframes with those gear installations.

Maintenance organisations and persons authorised to carry out inspections and rework are operationally affected because the AD requires inspections "in accordance with the Accomplishment Instructions" of specified Messier‑Dowty and Fokker Services documents. That assigns technical work to maintenance shops, factory service centres, or approved repair stations that can perform the required rework procedures. Parts suppliers, notably Dowty Aerospace Gloucester / Messier‑Dowty, and Fokker Services are affected as sources of service bulletins, possible rework kits, and the recipients of the mandatory reporting.

Regulators are affected in the sense that the AD requires the use of EASA approved revisions of SBs; the Civil Aviation Safety Authority (CASA) issued the AD (signed by the CASA delegate), and the text also references CAA‑NL ADs and EASA approval status, which embeds the AD within an international airworthiness oversight framework. Fokker Services is explicitly named as the party to which inspection findings must be reported.

Operators who hold spare MLG Main Fitting units are affected because Requirement 5 prohibits installation of Dowty/Messier‑Dowty MLG Main Fitting units as replacements unless they have been inspected and, as necessary, reworked per SB F100‑32‑106 or SB F100‑32‑111, except where a unit is new or already reworked as indicated in Requirements 2 or 4. This creates an inventory control obligation: operators and maintenance organisations must trace the status of replacement parts and ensure compliance before fitting.

Passengers and insurers are indirectly affected because the AD addresses a structural failure mode (MLG Main Fitting failure) that could impact safety and aircraft dispatch reliability. However, the AD text does not allocate insurance liability or premium changes; it mandates technical mitigations and reporting.

Finally, the AD references prior CAA‑NL ADs (AD 2002‑115/2 and NL‑2005‑002). Organisations already complying with those ADs remain subject to them; the current AD states those earlier ADs "still apply", so anyone affected must continue to satisfy both sets of requirements.

Duties.

• Inspect and rework MLG Main Fitting units: The AD requires, in Requirement 1, inspection and as necessary rework of all installed MLG Main Fitting units in accordance with the Accomplishment Instructions of Messier‑Dowty SB F100‑32‑111, dated 20 December 2005, or later EASA approved revision. Requirement 2 extends the same duty to new units and units reworked on both bores under earlier ADs. Requirements 3 and 4 impose repetitive inspection and rework after rework or replacement respectively. The AD therefore creates an ongoing maintenance duty attached to the airframe and specific components.

• Observe specified compliance intervals: The Compliance paragraph sets concrete time windows for these duties , e.g. within the next 2,000 flight cycles since the last inspection under specified earlier SBs or within four months after 13 April 2006, whichever occurs later; recurrent inspections at intervals not to exceed 2,000 flight cycles; and certain actions within 4,000 flight cycles since new or rework as applicable. Operators must track flight cycles and calendar time to meet these obligations.

• Report findings to Fokker Services: The AD mandates, "Irrespective of the results, within 7 calendar days after each inspection as required by Requirements 1, 2, 3, and 4 of this Directive, report all findings to Fokker Services using the questionnaire attached to Fokker Services SBF100‑32‑146." That is a strict, short reporting window that requires administrative coordination and timely submission.

• Follow crack thresholds to permit continued operation: Where cracks are found, the AD requires determination of whether and for how many flights continuation is permitted in accordance with crack size and location thresholds listed in Fokker Services SBF100‑32‑146. That places decision authority for limited continued operation on maintenance/engineering staff using the thresholds provided in the Fokker Services document.

• Do not install non‑compliant replacement parts: Requirement 5 forbids installation of Dowty/Messier‑Dowty MLG Main Fitting units as replacement parts unless they have been inspected and, as necessary, reworked in accordance with SB F100‑32‑106 or SB F100‑32‑111, or are new/reworked units as permitted by Requirements 2 or 4.

Rights and conditional permissions.

• Use of later EASA approved revisions: The AD repeatedly allows compliance by following "later EASA approved revision" of the referenced SBs and Fokker Services documents. That allows operators to adopt approved refinements or clarifications to the procedures without seeking additional local approval, subject to EASA’s approval process. In practice this means operators can rely on updates to the SBs once they carry EASA approval.

• Continued operation under defined thresholds: Where cracks are found, the AD does not mandate immediate grounding in all cases; rather it requires that the operator determine whether flights may continue and for how many, following the thresholds in SBF100‑32‑146. This creates a limited conditional right to continue flights pending repair where the crack size/location and number of permitted flights meet the document’s thresholds.

• Exceptions for new or properly reworked parts: Requirement 5 explicitly excepts "new or reworked units, as indicated in Requirements 2 or 4" from the prohibition on installing replacement parts that have not been inspected/reworked. That preserves operational flexibility where units are demonstrably new or already subject to the required rework.

Decision points and delegated authority.

• Maintenance engineers and organisations make technical determinations required by the AD (inspection results, rework need, whether continued flights are permissible under the SBF thresholds). The AD mandates following specified documents but leaves operational decisions , scheduling of inspections, acceptance of cracks under threshold rules, and execution of rework , to authorised maintenance personnel.

• Fokker Services receives inspection findings and will be an information hub; EASA’s approval process determines which revisions of the SBs are accepted for conformity with the AD. The AD text itself was issued by CASA (through its delegate), establishing the legal duty to comply on regulated aircraft operators.

The AD text supplied states the effective date and the technical and reporting requirements but does not specify monetary penalties, sanctions, or the procedural enforcement mechanisms within its own text. The directive announces that "This Airworthiness Directive becomes effective on 13 April 2006" and is presented and signed by a CASA delegate (David Punshon, 1 March 2006), which indicates it is a regulatory instrument to be complied with from that effective date.

Because the text does not set out explicit penalty provisions, the document should be read as imposing mandatory airworthiness obligations whose enforcement would be effected through the standard regulatory oversight and enforcement mechanisms available to the issuing authority. The AD does not itself state what enforcement steps CASA will take for non‑compliance, nor does it quantify fines, suspension powers, grounding procedures or criminal liability in this text. The AD does, however, create plainly enforceable technical duties and reporting obligations (inspection, rework, reporting within seven days, and restrictions on part installation). In practice, airworthiness directives are typically enforced by the responsible aviation authority through its regulatory powers, including airworthiness certificates, continuing oversight of operators and maintenance organisations, and the ability to ground aircraft or suspend approvals, but none of these enforcement devices are detailed in the AD text provided.

Practical enforcement implications flowing from the AD’s content include:

• An operator who fails to perform the required inspections or rework within the prescribed flight cycle or calendar deadlines will be unable to represent compliance with the AD, which may affect the aircraft’s airworthiness status.
• Failure to report inspection findings within the seven calendar day window to Fokker Services would breach the reporting duty the AD creates.
• Installation of replacement MLG Main Fitting units that have not been inspected and reworked as required would conflict directly with Requirement 5.

The absence of explicit penalties in the AD text means legal consequences of non‑compliance would be determined under the broader regulatory framework that grants CASA its enforcement powers. The AD itself does not provide an internal penalty schedule or process; it sets substantive technical duties and a compliance schedule and leaves enforcement to be applied under the authority’s standard regulatory tools.

The AD explicitly sits within a network of prior airworthiness directives and international approvals and cross‑references earlier CAA‑NL ADs. The Background states that CAA‑NL previously issued AD 2002‑115/2 and NL‑2005‑002 to address the same problem; the AD in this instrument says both of those ADs "still apply" and required an AFM change and a placard prohibiting brake application during backwards movement. The Requirements and Compliance sections further reference CAA‑NL AD 2002‑115/2 (also cited as AD/F100/55 Amdt 1) and NL‑2005‑002 (AD/F100/64) when specifying which units must be inspected and reworked under SB F100‑32‑111. The AD also remarks that "CAA‑NL AD NL‑2006‑003 refers," indicating that other national ADs are part of the regulatory context.

The AD conditions technical conformity on following service bulletins or "later EASA approved revision." That introduces EASA approval as a legal pivot: the AD accepts later EASA approved revisions of the specified SBs and SBFs as compliant means. Consequently, operators must monitor EASA approvals to know which versions of the SBs they may rely upon for compliance.

The AD also operates together with the aircraft’s Airworthiness Flight Manual (AFM) changes and placard requirements mandated by prior ADs. Those prior requirements remain in force and are part of the continuing legal obligation. Therefore, an operator must ensure compliance with both the prior operational mitigations (AFM change and placard) and the new inspection/rework/reporting requirements to be fully compliant across the instruments.

Because the AD is a regulatory instrument from the Civil Aviation Safety Authority (CASA, via its delegate), it functions as an instrument of administrative law within Australian civil aviation regulation. The text does not invoke specific sections of Australian statutes within the AD itself, but in practice CASA’s power to issue ADs and enforce them derives from the broader aviation safety regulatory framework. The AD’s reference to EASA approvals and to CAA‑NL ADs reflects transnational regulatory coordination: the AD binds Australian operators to procedures that are framed by manufacturer service bulletins and by EASA’s approval process and mirrors actions taken by other national authorities.

There is no explicit interaction detailed in the AD with general commercial laws, contract law, or insurance law in its text. However, the AD’s parts traceability requirement (Requirement 5) and reporting obligations create practical intersections with procurement and maintenance contracting, supply‑chain record keeping, and potentially warranty or supplier liability claims if a fitting fails and was not reworked per the SBs. Those practical intersections are not elaborated in the AD text; the AD focuses on mandatory technical steps and reporting.

The AD itself is identified as AD/F100/77, Main Landing Gear Main Fitting - 4, 4/2006. It is dated and signed by the CASA delegate on 1 March 2006 and the AD states it becomes effective on 13 April 2006. The document expressly references earlier CAA‑NL airworthiness directives and amendments and incorporates them into its operational history:

• CAA‑NL AD 2002‑115/2 is cited as AD/F100/55 Amdt 1 in the Requirements. The AD refers to units that were reworked as required by that earlier directive.
• NL‑2005‑002 is cited as AD/F100/64 and is similarly referenced in relation to which MLG Main Fitting units must be reworked under the current AD.
• The AD text also notes that "CAA‑NL AD NL‑2006‑003 refers," indicating a contemporaneous Dutch AD that relates to the same or similar issues.

The Compliance paragraph cross‑references Messier‑Dowty SB F100‑32‑106 and Fokker Services SBF100‑32‑141 as prior inspection benchmarks under AD NL‑2005‑002. The current AD requires additional or repetitive inspections in accordance with Messier‑Dowty SB F100‑32‑111 (20 December 2005) and Fokker Services SBF100‑32‑146 (2 February 2006), and it allows for later EASA approved revisions of those documents to be used for compliance.

No subsequent amendments to AD/F100/77 itself are contained in the text provided. The AD does, however, embed a mechanism for adopting later EASA approved revisions of the specified SBs and SBFs as compliant methods. Practically, that means the content of the AD can be operationally amended through EASA approval of revised service documents without a formal amendment of the AD text if those later revisions become EASA approved and are used by operators to meet the AD's requirements.

The AD also documents its position in a sequence of regulatory acts addressing the same hazard: earlier ADs addressed operational mitigations and one‑time inspections; this AD adds a repetitive inspection and rework regime to the regulatory response. The background narrative notes two reported failures that prompted the chain of ADs, and the current AD completes that chain by mandating repetitive inspections and rework with reporting.

The AD text provided contains no references to litigation, court proceedings, disputes or judicial reviews related to this directive or its subject matter. It cites reported incidents of failure of the MLG Main Fitting (two cases), and references prior CAA‑NL ADs and the related service bulletins, but it does not record any legal challenges or cases in which the AD was litigated. The document is an administrative regulatory instrument and the text does not indicate any judicial review or enforcement litigation.

Because the AD does not include any litigation history, researchers and practitioners looking for dispute records or case law connected to this AD will need to consult court or tribunal databases and enforcement records outside the text provided. Within this AD document itself, no claim of litigation history is made.

Traceability and parts status: Requirement 5 forbids installing any Dowty Aerospace Gloucester or Messier‑Dowty MLG Main Fitting unit as a replacement unless it has been inspected and, as necessary, reworked per SB F100‑32‑106 or SB F100‑32‑111, except for the specific exceptions in Requirements 2 and 4. That creates a strict traceability obligation: replacement units must have verifiable work records showing they meet the inspection/rework criteria, or operators risk non‑compliance. Shops must therefore maintain clear provenance records for spare fittings and confirm whether a unit is "new" or "reworked" under the AD’s exceptions.

Reporting timing is short: the AD requires that "Irrespective of the results, within 7 calendar days after each inspection ... report all findings to Fokker Services using the questionnaire attached to Fokker Services SBF100‑32‑146." Seven calendar days is a tight administrative deadline following inspections that may happen during unscheduled or out‑of‑hours maintenance; operators must plan for prompt data capture and submission.

EASA approval dependency: The AD authorises compliance via "later EASA approved revision" of the specified SBs and SBFs. Where an operator wishes to follow an updated SB, that update must be EASA approved to qualify under the AD. Operators that rely on internal engineering changes, alternative methods of compliance, or non‑EASA‑approved SB revisions will not meet the AD as written. This ties operational compliance to an external approval process and can create lag or uncertainty where manufacturers issue revisions pending approval.

Continued flight thresholds depend on SBF content: When cracks are found, the AD requires determining if flights may be continued and for how many, in accordance with crack size and location thresholds listed in Fokker Services SBF100‑32‑146. The AD does not itself list those thresholds; it delegates the substantive decision to the SBF. That means maintenance decision‑makers must have immediate access to SBF100‑32‑146 and must apply its thresholds correctly to make permissible continued flight decisions. Misapplication risks non‑compliance and safety exposure.

Interplay with prior ADs and AFM changes: The Background confirms that earlier ADs (AD 2002‑115/2 and NL‑2005‑002) remain in force and required an AFM change and an aircraft placard prohibiting brake application during backward movement. Operators must ensure those operational mitigations remain in place even as they implement the inspection/rework regime. Failing to maintain the AFM change/placard in place could mean incomplete compliance across the interlocking ADs.

Ambiguity in compliance sequencing: The Compliance item 1 reads as a compound condition: inspections are required "Within the next 2,000 flight cycles since the last inspection in accordance with Messier‑Dowty SB F100‑32‑106 and Fokker Services SBF100‑32‑141, as required by AD NL‑2005‑002 (AD/F100/64), or within the next 4 months after 13 April 2006, whichever occurs later." Operators must interpret and apply "since the last inspection" and the "whichever occurs later" clause precisely. That requires accurate records of prior inspections and current flight cycle counts, and an understanding of whether the calendar date or the flight cycle count yields the later deadline for each aircraft.

Supply and downtime risk: The AD requires rework or replacement of MLG Main Fitting units where necessary. The AD does not discuss parts availability or lead times. Where rework facilities are limited, or replacement parts require lead time, operators may face aircraft downtime. The AD’s 2,000 flight cycle recurring interval may create concentrated demand for rework capacity among fleets using the same MLG type; operators should plan maintenance resources accordingly.

No penalties specified within the text: The AD does not set out explicit penalties or enforcement procedures. Operators should not interpret that as absence of enforcement risk. The AD imposes mandatory matters that regulators can enforce under their general powers, but the AD itself gives no procedural detail on enforcement remedies or extrastatutory processes.

Stepwise compliance actions drawn from the AD text and practical implications:

1. Confirm applicability for each aircraft in fleet: Check model and MLG supplier. The AD applies only to Model F.28 Mk.0070 and Mk.0100 aircraft fitted with Messier‑Dowty (formerly Dowty Aerospace Gloucester) MLGs. Operators should query maintenance records and parts tags to identify which aircraft and which installed MLG Main Fitting serials are within scope.

2. Assemble the required documents and approved revisions: Obtain Messier‑Dowty SB F100‑32‑111 (dated 20 December 2005) and SB F100‑32‑106 (dated 18 February 2005), and Fokker Services SBF100‑32‑146 (dated 2 February 2006) and SBF100‑32‑141. Monitor EASA for later approved revisions of these SBs/SBFs, because the AD allows compliance by following "later EASA approved revision." Ensure the maintenance organisation has the Accomplishment Instructions available and that personnel are trained in them.

3. Schedule initial inspections per the Compliance schedule: For aircraft that previously underwent inspection under Messier‑Dowty SB F100‑32‑106 and Fokker SBF100‑32‑141 as required by AD NL‑2005‑002, plan the next inspection within 2,000 flight cycles since that last inspection, or within four months after 13 April 2006, whichever is later. For other units, comply with the applicable items in the Compliance paragraph (e.g. within 4,000 flight cycles since new or rework for certain categories). Maintain accurate flight cycle counts to determine the correct deadlines.

4. Conduct inspections and rework per SB F100‑32‑111: Inspect all installed MLG Main Fitting units as required by Requirement 1 (and corresponding Requirements 2-4 where applicable). Where the inspection identifies defects or cracks, perform the rework specified by the Accomplishment Instructions. If a fitting is reworked (both bores) or replaced, perform the inspection and rework required by Requirement 4.

5. Apply SBF100‑32‑146 for crack thresholds and flight continuation: If cracks are found, use the crack size and location thresholds in Fokker Services SBF100‑32‑146 to determine whether continuation of flight is permissible and, if so, how many flights may be made before rework/replacement. Document the engineering assessment that supports any decision to continue flights under those thresholds.

6. Report findings to Fokker Services within seven calendar days: After each inspection required by Requirements 1-4, submit all findings to Fokker Services using the questionnaire attached to SBF100‑32‑146, irrespective of whether the inspection found defects. Ensure administrative processes capture the inspection date and the seven‑day reporting deadline so reports are sent promptly.

7. Control replacement parts: Before installing any Dowty/Aerospace Gloucester or Messier‑Dowty MLG Main Fitting as a replacement part, confirm the unit has been inspected and reworked in accordance with SB F100‑32‑106 or SB F100‑32‑111, unless it is a new unit or one already reworked as permitted in Requirements 2 or 4. Maintain arrival inspection records and certification that demonstrate the unit’s compliance status before installation.

8. Maintain records and track recurring intervals: Because the AD requires recurring inspections at intervals not to exceed 2,000 flight cycles (and in some contexts within 4,000 cycles since new or rework), operators must track flight cycles for each relevant fitting, record inspection and rework dates, and schedule the next inspection accordingly. Integrate these intervals into maintenance planning and the aircraft’s maintenance tracking system.

9. Maintain prior AD mitigations: Do not remove AFM changes or the placard required by the prior CAA‑NL ADs. The Background explicitly states that AD 2002‑115/2 and NL‑2005‑002 "still apply" and required the AFM change and placard prohibiting brake application during backward movement. Ensure those operational mitigations remain in effect.

10. Liaise with regulators and service providers: Because the AD accepts later EASA approved revisions of the SBs, coordinate with Messier‑Dowty and Fokker Services about any revisions and their EASA approval status. Keep CASA informed as appropriate through normal airworthiness reporting channels. If maintenance organisations consider alternative means of compliance, confirm whether regulatory approval is required (the AD mandates the specified SBs or EASA approved revisions).

Operational and administrative practices to reduce compliance risk:

• Implement a standard operating procedure that captures inspection scheduling, performance, reporting to Fokker Services, and record retention in compliance with the AD.
• Ensure maintenance data and parts provenance are recorded on the unit’s workcards and in the operator’s maintenance control system to evidence that replacement parts meet the AD’s rework/inspection requirement before installation.
• Train engineers and planners in the crack threshold rules in SBF100‑32‑146 to make consistent decisions about permissible continuation of flights.
• Plan maintenance capacity in advance to manage rework demand given the 2,000 flight cycle recurring interval; where possible, stagger inspections across the fleet to avoid capacity bottlenecks.

The AD becomes effective on 13 April 2006; ensure all steps are completed in accord with the compliance schedule and maintain copies of submitted questionnaires and records of SBs/SBFs used to demonstrate compliance.