AD/F100/69 - Landing Gear Integrated Axle Nut and Spacer

The AD encodes several distinct concepts: applicability, mandatory modification, means of compliance, documentation amendment, timing, and cross‑reference to prior manufacturer and authority actions.

Applicability is narrowly defined and essential to legal effect: it covers Fokker F28 Mark 0070 and Mark 0100 airframes that are equipped with Messier‑Dowty main landing gear units. The textual formulation "all serial numbers equipped with Messier‑Dowty ... MLG units" confines the requirement to those aircraft with that specific supplier's landing gear. The AD does not on its face extend to Fokker F100s fitted with other manufacturers' MLG units.

Mandatory modification is effected by the requirement to replace the current two‑piece axle nut and spacer assembly with a single integrated axle‑nut/spacer assembly. The AD prescribes an approved avenue of compliance: "in accordance with the accomplishment instructions of Messier‑Dowty SB F100‑32‑72 dated 25 January 1995 or later CAA (United Kingdom) approved revisions." That links mandatory compliance to a manufacturer service bulletin and its later CAA‑approved revisions, meaning the SB provides the technical steps, but compliance requires the operator to follow the SB as approved by the relevant authority.

Documentation control is the second regulatory lever. Requirement 2 compels amendment of the AMM and IPC per Fokker MCNM F100‑033 dated 30 April 1999. The stated purpose in the Background is explicit: amend the AMM/IPC "to prevent reversal to a separate axle‑nut and spacer installation during a subsequent wheel change." Thus the AD uses maintenance documentation change to alter future maintenance choices.

Temporal requirements: the AD sets a compliance window , replacement within 12 calendar months of the AD's effective date. It also mandates sequencing: the AMM/IPC amendment must be made "prior to or at the same time as the replacement", which imposes a deadline for documentation work that coincides with, or precedes, the physical retrofit.

Means of proof and authority references appear by cross‑reference: the AD ties the technical solution to a Messier‑Dowty SB (1995), references Fokker SBs and Service Letters that pertain (SL 102 Rev 1; Fokker SB F100‑32‑096 Rev 2), and notes an associated Dutch CAA AD (NrNL‑2005‑008). The AD is issued by the Civil Aviation Safety Authority and signed by its delegate (David Villiers). The Background sets out the safety finding that justifies the intervention: repeated wheel losses traced to omitted spacers causing lateral wheel movement, bearing failure and wheel loss, which in turn could lead to loss of control during take‑off, landing rollout or taxi operations.

Mechanically, the AD shifts the maintenance decision from a two‑item assembly where omission of a spacer was possible, to a single integral component that removes the opportunity to omit the spacer. It also shifts a part‑selection control into the AMM/IPC so that future maintenance actions reference the integrated assembly rather than the previous separate items.

The AD identifies several actors by name or implication and allocates obligations and potential impacts among them.

Primary legal obligors are aircraft operators of Fokker F28 Mark 0070 and Mark 0100 aeroplanes that have Messier‑Dowty MLG units installed. The Applicability provision fixes the class of affected aircraft: "Fokker Aircraft B.V. F28 Mark 0070 and Mark 0100 aircraft, all serial numbers equipped with Messier‑Dowty ... MLG units." Those operators must carry out the required retrofit within the prescribed timeframe and ensure the AMM/IPC are amended as required.

Maintenance organisations and maintenance personnel are operationally affected. The AD prescribes that the replacement be executed "in accordance with the accomplishment instructions of Messier‑Dowty SB F100‑32‑72 dated 25 January 1995 or later CAA (United Kingdom) approved revisions." Therefore maintenance providers must obtain, understand and follow the SB (or its later approved revisions) when performing the modification. The AMM and IPC amendments required by Fokker MCNM F100‑033 will change the maintenance instructions and part numbering in operators' manuals, which maintenance organisations must adopt and use to prevent reversion to the two‑piece configuration.

Messier‑Dowty and Fokker are indirectly implicated. Messier‑Dowty supplied the SB that contains the technical method of compliance and the integrated axle‑nut/spacer assembly design. Fokker produced the MCNM that instructs AMM/IPC amendments and earlier SBs and Service Letters that communicated the issue; the AD explicitly references Fokker SB F100‑32‑096 and Service Letter SL 102 Rev 1 as documents that "also pertain to this subject."

Civil Aviation Safety Authority (CASA) acts as the issuing regulator. The AD was signed by "David Villiers, Delegate of the Civil Aviation Safety Authority" and becomes effective on 1 September 2005. The AD therefore operates as a regulatory instrument issued by CASA and binds the affected operators in the Australian regulatory environment.

Other authorities are present in cross‑reference form. The AD permits compliance using "later CAA (United Kingdom) approved revisions" of the Messier‑Dowty SB and refers to a Civil Aviation Authority Netherlands Airworthiness Directive NrNL‑2005‑008. That indicates interaction with European authorities' approvals and parallel AD action in the Netherlands.

Costs and operational impacts fall primarily on operators and maintenance providers. They must obtain the integrated assemblies, schedule and perform the retrofit within 12 months of the effective date, and implement AMM/IPC amendments prior to or alongside the physical modification. The AD does not state who reimburses parts or labour costs; the source text prescribes the actions but does not allocate cost reimbursement. The AD also does not detail supply arrangements, spare parts logistics or availability, leaving those practical matters to operators, maintenance organisations and part suppliers.

Finally, aircraft not equipped with Messier‑Dowty MLG units are outside the AD’s stated applicability and therefore not subject to these specific mandatory measures under this AD text.

The AD sets out two discrete duties and a sequencing constraint; it does not state administrative rights, appeals or exemptions within the text provided.

Primary duties:

• Duty to retrofit: Requirement 1 imposes a duty on operators of applicable aircraft to "Replace each MLG wheel axle‑nut and spacer with an integrated axle‑nut/spacer assembly" using the technical instructions supplied in Messier‑Dowty SB F100‑32‑72 dated 25 January 1995, or in later CAA (UK)‑approved revisions of that SB. The duty is specific about means of compliance by reference to the SB, thereby constraining the acceptable method to the SB's accomplishment instructions or later approved revisions.
• Duty to amend documentation: Requirement 2 imposes a duty to "Amend the Aircraft Maintenance Manual (AMM) and Illustrated Parts Catalogue (IPC) in accordance with the instructions of Fokker Manual Change Notification - Maintenance (MCNM) F100‑033 dated 30 April 1999." This is a preventive duty aimed at ensuring future maintenance references the integrated assembly and not the separate spacer and axle‑nut.

Temporal sequencing and deadlines:

• The Compliance provision mandates the hardware replacement "within the next 12 calendar months after the effective date of this directive." The AD gives an effective date of "1 September 2005," so the operative deadline in the directive text is 12 months from that date. The AMM/IPC amendment must be made "prior to or at the same time as" the physical replacement, which creates a sequencing requirement: the documentation change cannot lawfully occur after the physical change is completed.

Means of compliance:

• The AD ties compliance to specific technical documents (Messier‑Dowty SB F100‑32‑72 and Fokker MCNM F100‑033). Operators must follow those documents' instructions; the AD explicitly allows later "CAA (United Kingdom) approved revisions" of the Messier‑Dowty SB. That creates a narrow route to compliance: adopt the SB as approved.

Rights and procedural matters:

• The AD document itself does not contain explicit procedural rights, appeal mechanisms, or exemption clauses. It is silent on provisions for relief, alternative methods of compliance (AMOCs), or how to certify an alternative solution. It also does not include explicit recordkeeping or reporting obligations within the text provided. Any procedural rights, applications for alternative compliance, or enforcement processes are not set out in the AD text supplied.

Regulatory issuer:

• The AD is issued by the Civil Aviation Safety Authority and was signed by its delegate. This identifies the regulator as the issuer of the duty but the AD text does not expand on appeal routes or administrative review. The operator's duty is direct and binary: carry out the specified replacement and document amendments within the required timeframe and in accordance with the named SB and MCNM.

The AD expresses the regulator's safety finding in the Background: the repeated loss of wheels due to missing spacers could "lead to further wheel loss incidents" and "could conceivably result in loss of control of the aircraft during the take‑off run, landing rollout or taxiing operations." That safety finding functions as the legal predicate for imposing the duties above.

The AD text provided specifies required actions, an issuer, and an effective date, but it does not set out explicit penalties, fines, criminal sanctions or a detailed enforcement regime within the document text supplied.

What the AD does state about enforceability is implicit: it is an instrument issued by the Civil Aviation Safety Authority (CASA), signed by a CASA delegate (David Villiers), and becoming effective on a specified date. The instrument therefore functions as a directive requiring operators to undertake particular corrective and documentation actions for safety reasons. The AD makes compliance a narrated obligation by issuing mandatory language , "Replace ...", "Amend the AMM and IPC ..." , and sets compliance deadlines.

However, the AD does not, within the supplied text, articulate the administrative mechanisms for verifying compliance (for example, mandatory reporting of completed work to CASA), nor does it specify what sanctions follow non‑compliance. The AD text similarly does not provide a mechanism for approval of alternative actions (alternative means of compliance) or an express process for seeking exemptions. There is also no mention in the document of post‑compliance inspections, audits or certification steps that would evidence to CASA the completion of the mandated tasks.

The practical consequence of this textual silence is that the AD imposes duties whose legal force depends upon the regulatory framework within which CASA enforces ADs. The AD itself, as written, functions as the regulatory statement of required acts; enforcement detail and any administrative processes (inspection, enforcement notices, penalties) are not contained in the AD text provided.

The AD does cite other authorities and documents (for example, the CAA Netherlands AD NrNL‑2005‑008 and the instruction that later CAA (UK) approved revisions of the SB may be used), but it does not append or restate any enforcement-related provisions from those external instruments.

In sum, the AD mandates action and deadlines but does not specify within its own text what penalties or enforcement steps will follow failure to comply. Any enforcement or penalty consequences would need to be determined from the broader regulatory framework or follow‑on directions from CASA, which are not contained in the provided AD text.

The AD interacts with other regulatory and manufacturer instruments primarily by cross‑reference; it does not repeal or amend other laws within the supplied text but instead imposes a mandatory requirement that utilises and overrides prior manufacturer "recommendations" by converting those measures into a binding regulatory obligation for the class of aircraft specified.

Interaction by cross‑reference:

• The AD requires compliance "in accordance with the accomplishment instructions of Messier‑Dowty SB F100‑32‑72 dated 25 January 1995 or later CAA (United Kingdom) approved revisions." This ties the AD's technical compliance pathway directly to a manufacturer service bulletin and its subsequent CAA‑approved revisions. The AD therefore places the SB within the legal compliance framework: where previously the SB may have been advisory, the AD makes the SB (as approved) the mandated method for compliance on affected aircraft.
• Requirement 2 mandates AMM and IPC amendment "in accordance with the instructions of Fokker Manual Change Notification - Maintenance (MCNM) F100‑033 dated 30 April 1999." That creates a direct interaction with the Fokker maintenance documentation regime: operators must change their AMM/IPC consistent with the Fokker MCNM.

Parallel ADs and authority references:

• The document acknowledges that "Civil Aviation Authority Netherlands Airworthiness Directive NrNL‑2005‑008 refers." That indicates contemporaneous action at another national authority level; the AD therefore interacts indirectly with parallel national regulatory measures in Europe. The AD also allows later "CAA (United Kingdom) approved revisions" of the Messier‑Dowty SB as acceptable means of compliance, which creates an interaction between Australian regulatory requirements and UK CAA approvals of manufacturer service documents.

Prior manufacturer communications:

• The Background notes that Messier‑Dowty issued SB F100‑32‑72 in 1995, and that Fokker issued SB F100‑32‑096 to notify operators of the Messier‑Dowty SB's existence. It also notes that at a later stage Fokker revised the SB to the status of "recommended". The AD overlays these earlier manufacturer communications , some of which were advisory or recommended , with a legal requirement. In practice that means operators who had previously treated the SB as recommended must now treat the action as mandatory under the AD.

Scope interactions:

• The AD's Applicability clause specifically narrows the legal effect to Fokker F28 Mark 0070 and Mark 0100 aircraft with Messier‑Dowty MLG units. Aircraft outside that description (for example, Fokker F100s with other MLG suppliers) are not within the AD's stated scope. Thus the AD interacts with the legal principle of type‑certification and equipment configuration: the same airframe may be subject to different regulatory obligations depending on supplier fitment.

What the AD does not do:

• The supplied text does not claim to amend legislation, nor does it specify how it interacts with criminal or administrative penalty provisions. It does not include cross‑references to Civil Aviation Regulations or statutory penalty provisions. It also does not contain a direct waiver or amendment of other ADs. All interactions set out in the text are by reference to other ADs, service bulletins, and manual change notifications.

Operationally, the AD converts a previously recommended technical measure into a mandated compliance obligation and integrates manufacturer SBs and Fokker MCNMs into the enforceable compliance pathway. The AD thereby converts cross‑industry technical guidance into a regulatorily binding requirement for the specifically applicable aircraft.

The AD itself contains internal references to a limited set of manufacturer documents and prior communications, which together form the amendment history relevant to the measure. The AD was signed on 21 July 2005 by a CASA delegate and is stated in the Compliance block to "become effective on 1 September 2005." The table header lists "9/2005", which corresponds to the AD's month/year issuance coding.

Key documentary timestamps included in the AD text:

• Messier‑Dowty Service Bulletin F100‑32‑72 dated 25 January 1995. The AD requires the retrofit "in accordance with the accomplishment instructions of Messier‑Dowty SB F100‑32‑72 dated 25 January 1995 or later CAA (United Kingdom) approved revisions." The SB is therefore the foundational technical document; the AD continues to allow later UK CAA‑approved revisions of that SB to be used for compliance.
• Fokker Manual Change Notification - Maintenance (MCNM) F100‑033 dated 30 April 1999. The AD requires AMM and IPC amendments "in accordance with the instructions" of this MCNM. That MCNM therefore forms the mandated documentation amendment instrument.
• Fokker 70/100 Service Letter (SL) 102 Revision 1 dated 12 February 1998 is cited in a Note as also pertaining to the subject. The AD does not mandate compliance with the Service Letter in the same mandatory language as the SB/MCNM, but it recognises the Service Letter as relevant.
• Fokker Services Service Bulletin F100‑32‑096 Revision 2 dated 29 April 2005 is likewise cited in a Note as pertaining to the subject and as a means by which Fokker notified operators of the Messier‑Dowty SB's existence.
• The AD references Civil Aviation Authority Netherlands Airworthiness Directive NrNL‑2005‑008 as a related directive in another jurisdiction.

The narrative in the Background summarises events over time: in 1995 Messier‑Dowty issued SB F100‑32‑72 to address omission of the spacer; Fokker subsequently issued SB F100‑32‑096 to notify operators; at a later stage Fokker revised the SB to "recommended" status; despite these actions, wheel losses continued to be reported. The AD responds to that chronology by converting the action into a mandatory requirement and by requiring maintenance documentation changes.

There is no text in the AD that amends or revokes previous ADs directly within the supplied document. The amendment history recorded is limited to the manufacturer SBs and the Fokker MCNM and the AD’s own issuance and effective dates. Any further amendment history (subsequent AD revisions, supersessions, or revocations) is not present in the supplied text.

The AD text supplied does not contain or reference any litigation history. It records incidents and investigative findings , "Over the years, several Fokker 100 ... operators reported that a MLG wheel fell off" , but it does not record any civil suits, administrative appeals, judicial review proceedings, or other litigation concerning the subject matter or the issuance of the AD.

The document includes no references to legal challenges to this AD, no summaries of court decisions, and no mention of contested enforcement actions. The AD does reference related regulatory documents in other jurisdictions (for example, Civil Aviation Authority Netherlands Airworthiness Directive NrNL‑2005‑008), but that is not litigation.

Because the supplied text contains no litigation record, readers seeking information on any legal challenges, appeals against the AD, or cases arising from wheel losses would need to consult external legal or regulatory records beyond the AD itself. The AD is silent on the existence of any appeals processes, decisions on contested matters, or case law developments.

Several practical pitfalls and potential misunderstandings arise directly from the AD text.

Applicability nuance: The AD applies only to "Fokker Aircraft B.V. F28 Mark 0070 and Mark 0100 aircraft ... equipped with Messier‑Dowty ... MLG units." Operators must verify the actual MLG supplier fitment for each airframe. If an F100 is fitted with a different MLG manufacturer, the AD language as supplied does not apply to that aircraft. Misreading the applicability clause and applying the AD requirement to non‑Messier‑Dowty MLG‑equipped aircraft would be an avoidable compliance error.

Means of compliance specificity: The hardware replacement must be performed "in accordance with the accomplishment instructions of Messier‑Dowty SB F100‑32‑72 dated 25 January 1995 or later CAA (United Kingdom) approved revisions." Using a different technique, an alternative component, or an unapproved revision risks non‑compliance because the AD narrows compliance to the SB (or later CAA‑approved revisions). Operators should ensure they have the correct SB revision and any CAA‑approved revisions on hand before undertaking work. The AD allows later CAA (UK)‑approved revisions, but the operator must confirm that any revision relied upon is indeed CAA‑approved.

Timing and sequencing trap: Requirement 2 requires AMM/IPC amendment "prior to or at the same time as the replacement." An operator who performs the physical replacement first and updates manuals afterwards could be in breach of the AD's sequencing requirement. The AD does not specify acceptable short delays; it sets a clear order. Practically, the AMM/IPC amendment must be on file before or concomitant with the first replacement.

Interpretation of "within the next 12 calendar months after the effective date": The AD's effective date is stated as 1 September 2005. That yields a compliance deadline of 1 September 2006. Operators must interpret "12 calendar months after the effective date" correctly and schedule interventions accordingly; common confusion between calendar months and working months or maintenance scheduling cycles is a practical risk.

Distinguishing mandated documents from related guidance: The AD notes that Fokker SL 102 Rev 1 (12 February 1998) and Fokker Services SB F100‑32‑096 Rev 2 (29 April 2005) "also pertain to this subject." Those documents are relevant but the AD's mandatory compliance is explicitly tied to Messier‑Dowty SB F100‑32‑72 and Fokker MCNM F100‑033. Treating the SL or Fokker SB as the principal compliance instrument rather than the Messier‑Dowty SB/MCNM could lead to non‑compliance.

Consequence of continued reliance on "recommended" status: The Background notes that Fokker had revised the SB to "recommended" at a later stage and that wheel losses continued despite the prior attention. The AD converts a previously recommended measure into a mandatory requirement. Operators who previously relied on the "recommended" status may have deferred action; the AD's imposition of a firm deadline creates a compliance rush and potential scheduling bottlenecks.

Documentation control to prevent reversal: The AD requires AMM and IPC changes "to prevent reversal to a separate axle‑nut and spacer installation during a subsequent wheel change." A gotcha for maintenance organisations is failing to ensure that the parts ordering and parts numbering in IPCs actually reference the integrated assembly; if the IPC still lists the separate spacer and axle‑nut, subsequent maintenance activities could inadvertently reintroduce the older configuration, defeating the AD's purpose and breaching its second requirement.

Supply and parts availability (implicit risk): While the AD does not comment on parts availability, operators should be alert that procuring integrated axle‑nut/spacer assemblies for the whole fleet within a 12‑month window may create supply timing risks. The AD does not allocate procurement responsibility or provide alternative arrangements; operators bear the practical burden of sourcing parts and scheduling maintenance.

Cross‑jurisdictional documentation: The AD permits "later CAA (United Kingdom) approved revisions" of the Messier‑Dowty SB. Operators must ensure they obtain the correct revision and that it carries the necessary CAA approval. Misassumption that any Messier‑Dowty revision is acceptable without verifying CAA approval would be a compliance risk.

Recordkeeping and proof: The AD text does not specify required records to be retained or submitted to CASA. Operators should nonetheless anticipate needing contemporary records demonstrating AMM/IPC amendment and physical replacement. Failing to maintain evidence of compliance may complicate interactions with the regulator if compliance is questioned, even though the AD does not prescribe specific reporting steps.

In short, operators must pay close attention to applicability, the exact SB and MCNM documents named, the sequencing of manual changes and physical retrofit, the 12‑month deadline, and parts/IPC ordering to avoid inadvertent reversion to the prior configuration.

The AD prescribes a clear, discrete compliance path. The following steps, distilled strictly from the AD text, set out the required sequence and documents to use.

1. Confirm applicability. Review each aircraft in the operator’s fleet and confirm whether it is a Fokker Aircraft B.V. F28 Mark 0070 or Mark 0100 and whether its main landing gear units are Messier‑Dowty units. The AD applies only to "aircraft ... equipped with Messier‑Dowty ... MLG units." If an aircraft does not meet that description, the AD’s requirements as written do not apply.

2. Identify the relevant compliance documents. The AD mandates the use of: (a) Messier‑Dowty Service Bulletin F100‑32‑72 dated 25 January 1995, or later CAA (United Kingdom) approved revisions, for the hardware replacement; and (b) Fokker Manual Change Notification - Maintenance (MCNM) F100‑033 dated 30 April 1999, for AMM and IPC amendments. Operators should obtain these documents and any later CAA‑approved revisions of the Messier‑Dowty SB. Notes in the AD also reference Fokker SL 102 Revision 1 (12 February 1998) and Fokker Services SB F100‑32‑096 Revision 2 (29 April 2005) as relevant background material.

3. Schedule the AMM/IPC amendment. Requirement 2 explicitly requires AMM and IPC amendment "prior to or at the same time as the replacement." Therefore, prepare and implement the changes to the AMM and IPC in accordance with Fokker MCNM F100‑033 so that the manuals and parts catalogues indicate the integrated axle‑nut/spacer assembly and do not permit reversion to the two‑piece assembly. Ensure that parts numbering and maintenance instructions reference the integrated assembly.

4. Plan and execute the retrofit within the time limit. The AD requires replacement of each MLG wheel axle‑nut and spacer assembly "within the next 12 calendar months after the effective date of this directive." The effective date is given as 1 September 2005, so the replacement must be completed within 12 months of that date. Schedule maintenance slots, procure the integrated assemblies, and perform the replacement in accordance with the accomplishment instructions of Messier‑Dowty SB F100‑32‑72 dated 25 January 1995, or a later CAA (UK)‑approved revision. Ensure the SB revision used is indeed CAA‑approved if relying on a later revision.

5. Use approved methods and revision control. Follow the SB's accomplishment instructions exactly as directed by the AD. If using a later SB revision, verify that the revision has CAA (UK) approval as permitted by the AD. Do not substitute an alternative technical method unless and until an alternative method is formally approved by the regulatory authority in writing; the AD itself limits compliance methods to the named SB or later CAA‑approved revisions.

6. Coordinate parts ordering and maintenance resources. Although the AD does not address procurement, practical compliance requires acquiring the integrated axle‑nut/spacer assemblies. Plan procurement to ensure parts are available for each affected aircraft within the 12‑month window and that the maintenance schedule permits completion in the specified time.

7. Ensure documentation alignment at the point of replacement. On the day of replacement, ensure that the AMM/IPC amendment is in effect "prior to or at the same time as" the physical replacement so that maintenance personnel are guided by documentation that specifies the integrated assembly.

8. Retain evidence of compliance. The AD text does not specify recordkeeping requirements, but operators should create and retain documentation proving that the AMM and IPC were amended and that the hardware replacement was completed in accordance with the specified SB and within the AD's timeframe. Evidence might reasonably include copies of the SB and MCNM used, maintenance releases, parts order records, work cards, and amended pages of the AMM and IPC showing the integrated part reference.

9. Monitor related manufacturer and authority communications. The AD allows later CAA (UK) approved revisions of Messier‑Dowty SB F100‑32‑72 to be used for compliance. Watch for subsequent approved SB revisions or other related service communications that may alter the practical work steps or confirm acceptable methods.

10. Verify configuration control prevents reversion. After implementing the AMM/IPC changes and performing the replacement, verify that parts ordering, IPC references and maintenance practices no longer permit the separate spacer and axle‑nut to be installed in future wheel changes. The AD's express intention is to "prevent reversal to a separate axle‑nut and spacer installation during a subsequent wheel change."

These steps reproduce the required compliance pathway present in the AD text: determine applicability, amend manuals per Fokker MCNM F100‑033, replace the axle nut and spacer with the integrated assembly per Messier‑Dowty SB F100‑32‑72 (or later CAA‑approved revision) within 12 calendar months of the AD's effective date, and ensure sequencing so the documentation change precedes or coincides with the physical modification.