AD/F50/93 - Propeller Blade De-icer Boot

The AD rests on a small set of technical and regulatory concepts. Each concept is operationally significant because compliance obligations, permissible work and the safety case are all tied to these definitions and references in the AD text.

• Applicability: The AD is limited to Fokker Aircraft B.V. Model F27 Mark 050, Mark 0502 and Mark 0604 aircraft equipped with Dowty Propellers Type R.352 or R.410 series propellers (Applicability). The limitation to these types defines the universe of operators and maintenance organisations that must take action.

• De-icer overshoe, or boot: The term in the AD refers to the removable de-icer assembly applied to propeller blades. The AD targets the bond between the boot and the blade. The specific failure mode reported is detachment of the overshoe during flight (Background).

• Adhesives identified: Two adhesives are named in the instrument. 3M 1300L adhesive is the adhesive linked to the in-service failures and is explicitly prohibited from further use for fitting de-icer boots on the affected types as of the effective date (Requirement 4). Bostik 2402 adhesive is treated as an acceptable alternative in the AD’s compliance logic: if records positively establish that Bostik 2402 was used, the operator need take no further action (Requirement 1).

• Inspection and repair instructions: The AD mandates inspection in accordance with Dowty Propellers Service Bulletin F50-61-158 dated 30 September 2005 or a later EASA-approved revision (Requirement 2). Where a defect is found, replacement must be done per Dowty Propellers Specification PS 5723, attached to the SB as Appendix 1, latest revision (Requirement 3). The AD therefore delegates the procedural detail to manufacturer technical documents and only accepts versions that are EASA-approved where applicable.

• Compliance intervals and triggers: The AD sets a short initial records-check timeline (within 30 days of the effective date) (Compliance 1). If 3M 1300L was used, inspections must be started within the next 650 flight hours and repeated at intervals not exceeding 650 flight hours (Compliance 2). Replacement of an affected boot is required before the next flight (Compliance 3). The ban on 3M starts immediately on the effective date (Compliance 4). These timing elements convert the AD into an operational maintenance regime, not a one-off action.

• Regulatory cross-reference: The AD explicitly references CAA Netherlands AD NL-2005-016 and the EASA approval number 2005-6448 dated 15 December 2005 (Note). It therefore sits in a chain of airworthiness regulatory action and technical approvals, not in isolation.

• Safety finding: The causal link asserted by the AD is that boots fitted with 3M 1300L adhesive detached in flight on three occasions; two caused fuselage damage and one shattered a cabin window causing injuries to two passengers, which forms the basis for declaring the condition as capable of causing hazardous events including serious or fatal injuries (Background). The AD uses this history to justify mandatory inspection, replacement and prohibition steps.

Understanding these concepts matters because the AD’s operational effect is entirely mediated by them: the scope is limited by aircraft and propeller model; the required technique and materials are limited by the Dowty SB and PS 5723; timing and immediate ground/flight safety considerations are set by the compliance windows; and the prohibition on a named adhesive changes procurement and maintenance practices. The AD delegates the "how" of inspections and repairs to manufacturer documents and to EASA-approved revisions of those documents, creating a chain of dependencies for ongoing compliance.

The AD identifies a narrow but clearly defined set of affected parties. The primary and immediate entities who must act are:

• Aircraft operators of Fokker F27 Mark 050, Mark 0502 and Mark 0604 types equipped with Dowty Propellers Type R.352 or R.410 series. The Applicability clause limits the direct regulatory obligations to these operators. These operators must check maintenance records, perform inspections where applicable, replace defective boots, and stop using the prohibited adhesive (Applicability; Requirement 1-4; Compliance 1-4).

• Maintenance organisations and licensed engineers carrying out propeller maintenance and de-icer boot installations on the affected types. They are the parties that must follow Dowty SB F50-61-158 and Dowty Propellers Specification PS 5723 when inspecting and replacing de-icer boots (Requirement 2-3). They will be responsible for material selection and installation technique, and for ensuring that 3M 1300L is not used.

• Dowty Propellers as the manufacturer/provider of the SB and Specification. The AD requires use of Dowty’s service instructions, including the attached Specification PS 5723 (Requirement 2-3). Dowty’s documentation is the technical standard for compliance.

• Adhesive suppliers and procurement teams for operators and maintenance providers. The AD names 3M 1300L and Bostik 2402 (Requirement 1, Requirement 4). Where maintenance records show Bostik 2402 was used, the AD says no further action is required; conversely, 3M 1300L is banned for future use. Procurement choices thus change immediately for the affected operators.

• Continued airworthiness record-keepers and compliance officers within operators. They must verify, within the 30-day window, which adhesive was used in the past and ensure records are sufficiently clear to avoid unnecessary inspections (Requirement 1; Compliance 1).

• Passengers and crew on affected aircraft, indirectly. The AD’s stated safety rationale cites past incidents where detached boots caused fuselage damage and passenger injuries, and the AD frames its requirements as intended to reduce the risk of recurrence (Background). While passengers do not have direct duties under the AD, the safety outcomes targeted by the AD directly pertain to them.

Less directly affected parties include insurers, which may face claims arising from the described incidents, and regulators in other jurisdictions that may mirror or reference the AD. The AD explicitly notes CAA Netherlands AD NL-2005-016 and an EASA approval (Note), which indicates that the issue has been considered across jurisdictions.

Operators that can positively establish via records that Bostik 2402 adhesive was used are explicitly exempted from further action under this AD, which concentrates the immediate inspection and replacement burden on those operators whose records show 3M 1300L or whose records are inconclusive. The compliance windows (30 days, 650 flight hours, before next flight for defective replacements) create timing pressures that fall on airlines’ maintenance scheduling and can affect aircraft availability.

This AD lays down discrete duties and a limited conditional right for operators. The text frames obligations in imperative terms and ties required methods to Dowty technical documents and EASA approval.

Duties (expressed in the AD):

• Verify adhesive used: Operators must check maintenance records to determine whether 3M 1300L adhesive has been used to fit de-icer boots (Requirement 1; Compliance 1). The timeline is binding: the check must be done within 30 days after the effective date of the AD (Compliance 1).

• Inspect propeller de-icer assemblies where 3M 1300L was used: If records show 3M 1300L was used, operators must inspect the propeller blade de-icer assemblies in accordance with Dowty Propellers SB F50-61-158 dated 30 September 2005 or a later EASA-approved revision (Requirement 2). The inspection must be performed within the next 650 flight hours after the AD’s effective date and then at intervals not to exceed 650 flight hours (Compliance 2).

• Replace defective boots: During inspections required under Requirement 2, where any signs of lifting or bubbling are found, the affected de-icer boot must be replaced in accordance with Dowty Propellers Specification PS 5723 (attached to the SB as Appendix 1), latest revision (Requirement 3). The replacement must be done before the next flight (Compliance 3).

• Cease use of 3M 1300L adhesive: The AD imposes an immediate prohibition on the use of 3M 1300L adhesive for fitting de-icer boots to propeller blades on the listed Fokker F27 series aircraft (Requirement 4; Compliance 4). The ban takes effect as of the AD’s effective date.

Rights and conditional exemptions stated in the AD:

• Right to no further action if Bostik 2402 used: The AD explicitly states that if it has been positively established via records that Bostik 2402 adhesive was used to fit the de-icer boots, then no further action under this directive is required (Requirement 1). That is a conditional exemption dependent on clear historical records.

Operational and procedural implications of these duties:

• The AD requires operators to follow Dowty's SB and Specification for inspections and replacements. The AD does not prescribe alternative inspection methods or repair specifications; it ties the required method to Dowty’s SB F50-61-158 and Specification PS 5723, and also accepts later EASA-approved revisions of the SB (Requirement 2). Therefore maintenance organisations must obtain and use the specified Dowty documents, and where a later EASA-approved revision exists, that revision is acceptable.

• Timing constraints: The AD contains explicit time windows that govern when the record checks and inspections must occur (Compliance 1-2) and a strict replacement-before-next-flight requirement for defective boots (Compliance 3). These timing elements require operators to incorporate the AD’s tasks into maintenance schedules promptly, and potentially to ground aircraft for immediate repairs where defects are found.

• Documentation duties: To claim the exemption for Bostik 2402, operators must have records that "positively establish" the adhesive used. The AD therefore places a practical record-keeping standard on operators: records must be sufficiently detailed and accessible to demonstrate the adhesive type.

• Delegation and conformity: The AD delegates technical details to a manufacturer SB and a specification, and accepts later EASA-approved revisions. This creates a duty to ensure that the version used is either the cited version or a later version approved by EASA. Maintenance organisations and operators must therefore be vigilant about conforming to the exact technical documents cited.

The AD’s duties are prescriptive; the only affirmative right it records is the no-action outcome where Bostik 2402’s use is established. There is no express appeal or variance mechanism in the AD’s text; the instrument instead relies on established airworthiness directive practice and cross-reference to EASA approvals and Dowty documentation for implementation detail.

The AD text supplied does not contain an explicit penalties or enforcement subsection. The instrument states the effective date (becomes effective on 16 March 2006) and is signed by a delegate of the Civil Aviation Safety Authority (James Coyne), but it does not specify fines, civil penalties, or criminal sanctions within its body (Compliance; signature block). The directive sets mandatory compliance actions and time limits but does not, within the provided text, outline the enforcement mechanism or penalties for non-compliance.

From the content of the AD itself the following points can be stated strictly on the basis of the supplied text:

• Mandatory nature: The AD prescribes actions and time frames in the imperative. It identifies required inspections, replacements, and a prohibition on use of a named adhesive, together with explicit compliance windows (Requirement 1-4; Compliance 1-4). The format and language of the AD indicates the intent that these are mandatory airworthiness actions for the affected aircraft.

• Absence of penalty detail in the AD: No monetary penalties, enforcement procedures, or administrative sanction processes are specified in the AD text as provided. The AD does not include a section on penalty amounts, notification procedures for non-compliance, or appeal processes.

• Regulatory provenance: The AD is issued by a CASA delegate and references a CAA Netherlands AD and an EASA approval (Note). The AD thus sits within a broader airworthiness regulatory framework. The AD’s enforceability, in practice, may be linked to the broader statutory and regulatory powers of the civil aviation authority, but those statutory enforcement powers are not set out in the AD text provided.

Practical effect for operators and maintenance organisations:

• Operators should treat the AD as a mandatory directive requiring prompt action because the instrument prescribes specific, time-limited duties and frames them as corrective measures for an identified unsafe condition (Background; Requirement; Compliance). The AD does not provide an internal enforcement clause; however, the fact of the directive and its signature by a CASA delegate in the document indicates regulatory authority.

• Because the AD ties required work to Dowty SB F50-61-158 and Specification PS 5723, maintenance organisations will need to use those documents and maintain records showing that the AD’s requirements were satisfied, in case any enforcement or oversight action is initiated by the relevant authority.

Where operators seek details about statutory enforcement measures, penalties, or variance provisions, they would need to consult the regulator’s broader statutory framework or contact the issuing authority. The AD itself does not supply those details.

The AD explicitly references at least one foreign airworthiness directive and an EASA approval, situating itself within a network of regulatory instruments rather than creating standalone obligations divorced from wider aviation safety approvals. The source text provides the following interaction points:

• CAA Netherlands AD and EASA approval: The AD contains a note that "CAA Netherlands AD NL-2005-016 EASA approval No. 2005-6448 dated 15 December 2005 refers" (Note). This indicates that the CASA AD is consistent with, and potentially derives technical or evidentiary basis from, the CAA Netherlands AD and the related EASA approval. The AD therefore cross-references earlier regulatory action by another national authority and a European-level approval number.

• Manufacturer technical documents subject to EASA approvals: The AD requires inspections to be carried out in accordance with Dowty Propellers Service Bulletin F50-61-158 dated 30 September 2005 or a later EASA-approved revision (Requirement 2). By conditioning acceptability on "EASA-approved revision", the AD links compliance not just to the manufacturer's documents but to EASA’s approval process. That creates an interaction where updates to the manufacturer’s SB require EASA approval to be acceptable under the AD.

• Dowty Specification attachment: The AD requires replacement in accordance with Dowty Propellers Specification PS 5723, attached as Appendix 1 to the SB, latest revision (Requirement 3). The AD therefore incorporates manufacturer specification text into its compliance regime. Any later changes or versions of PS 5723 would be relevant to compliance to the extent the SB/Specification are updated and approved as referenced.

• National and international regulatory threads: The AD shows how national airworthiness directives can harmonise or follow each other. The AD’s Note tying to NL-2005-016 and an EASA approval reflects a chain whereby an unsafe condition identified in one jurisdiction led to manufacturer and regulator responses that CASA adopted or mirrored. The AD’s technical acceptability language (EASA-approved revisions acceptable) also creates a mechanism for future alignment as the manufacturer and EASA update the SB.

Where the AD is silent or neutral:

• The AD does not reference domestic aviation statutes, penalty regimes, or administrative processes in the supplied text. It also does not reference other Australian legislation. Those points are therefore outside the text and cannot be stated here.

Operational consequences of the interaction:

• Operators must ensure any Dowty SB revision they rely on is EASA-approved to meet the AD’s requirements. This affects how operators and maintenance organisations track service bulletin revisions and approvals.

• The AD’s cross-reference to the CAA Netherlands AD and EASA approval suggests that operators who operate internationally or whose aircraft are registered in other jurisdictions may find corresponding or similar regulatory obligations in those jurisdictions. The AD itself does not state the effect of cross-jurisdictional compliance, but it embeds the work within existing international airworthiness documentation and approvals.

In summary, the AD interacts with other laws and approvals by referencing and depending upon Dowty manufacturer documents and EASA approvals, and by referencing a related Netherlands AD. The AD thereby creates a compliance pathway that requires coordination with manufacturer documentation and European regulatory approvals.

The supplied AD text contains limited material on amendment history. What is recorded in the document is as follows:

• Original issuance and effective date: The AD bears a signature block showing it was signed by James Coyne, Delegate of the Civil Aviation Safety Authority, dated 1 February 2006. The AD states that it becomes effective on 16 March 2006 (Compliance; signature block). There is no subsequent amendment or revision number printed in the supplied text.

• Reference to earlier foreign AD and approval: The AD explicitly refers to "CAA Netherlands AD NL-2005-016 EASA approval No. 2005-6448 dated 15 December 2005" (Note). That reference situates the AD in a chronology of related actions, but it is not an amendment to the CASA AD itself; rather it indicates an antecedent action by the Netherlands authority and EASA.

• Manufacturer documents and allowance for later revisions: The AD requires inspections according to Dowty Propellers SB F50-61-158 dated 30 September 2005 or a later EASA-approved revision and requires replacement per Dowty Propellers Specification PS 5723 latest revision (Requirement 2-3). While not an amendment history for the AD itself, the AD contemplates that the underlying manufacturer documentation may be revised and that later EASA-approved revisions will be acceptable for compliance. Thus, operationally, the AD anticipates that the technical documents it relies on could be amended over time by the manufacturer and approved by EASA, and that such later approvals will change what satisfies the AD.

• No amendment record in the supplied text: There is no text in the AD that indicates any amendment to AD/F50/93, no cancellation, and no superseding directive recorded in the material supplied.

Given the absence of explicit subsequent amendments in the supplied document, the amendment history within this AD is limited to the original issue and the AD’s connective references to an earlier Netherlands AD and an EASA approval. If a reader needs to know whether the AD has been amended, superseded, or revoked since the effective date stated, that information is not contained in the supplied text and would need to be obtained from the issuing authority’s records or subsequent official publications.

The AD text supplied contains no information about any litigation arising from the directive or from the incidents described in the Background section. The document records the facts of three in-service events leading to the AD, the technical and procedural requirements imposed, and the cross-reference to a Netherlands AD and EASA approval, but it does not mention any legal proceedings, court decisions, administrative appeals, or challenges related to the AD or the underlying incidents.

Specifically, the AD’s "Background" section reports the operational incidents and their consequences (detachment of de-icer boots, fuselage damage, window shattering and passenger injury) and states the safety analysis outcome that the condition could result in hazardous events including serious or fatal injury. However, the AD does not state that any litigation followed those incidents.

Because the supplied instrument contains no litigation record, the following points are strictly descriptive of the content of the document:

• No judicial or administrative proceedings are recorded or referenced in this AD text.

• The AD does not list any appeals, stays, or orders affecting its effective date of 16 March 2006 as stated (Compliance; signature block).

If a reader requires an authoritative account of any litigation or administrative challenges related to the incidents or the AD, they would need to consult court records, tribunal records or regulator enforcement records outside the AD text. The AD itself does not provide such material.

The AD contains several details and traps that can cause compliance errors if not handled carefully. These "gotchas" are drawn directly from the AD text and concern scope, timing, documentation, and the precise technical references the AD mandates.

1. Narrow applicability but absolute prohibition: The AD applies only to Fokker Aircraft B.V. Model F27 Mark 050, Mark 0502 and Mark 0604 aircraft fitted with Dowty Propellers Type R.352 or R.410 series propellers (Applicability). Operators of other Fokker models or with different propeller types might assume they are unaffected. Conversely, operators of the specified combinations must treat the AD’s prohibition on 3M 1300L as absolute from the effective date (Requirement 4; Compliance 4). Do not conflate model names or propeller subtypes.

2. Reliance on maintenance records for exemption: The AD allows "no further action" only if it is positively established that Bostik 2402 adhesive was used to fit the boots (Requirement 1). Operators with incomplete, ambiguous or inaccessible records cannot take the exemption and therefore will need to perform inspections. The record-check must be completed within 30 days of the AD’s effective date (Compliance 1). The practical gotcha is that poor record-keeping converts an otherwise light duty into a substantial inspection programme.

3. Timing mismatch risk: The inspection regime is defined in flight hours (650 flight hours initial and repeat interval) (Compliance 2). Operators must correctly track flight hours allocation per aircraft and plan inspections accordingly. Failure to map the flight-hour clock used by the operator to the AD’s 650-hour timeline can lead to inadvertent late inspections.

4. Acceptable technical documents are specific: The AD mandates inspection "in accordance with the accomplishment instructions of Dowty Propellers Service Bulletin (SB) F50-61-158 dated 30 September 2005 or a later EASA-approved revision" (Requirement 2). Using an earlier or manufacturer-only revised SB that has not been EASA-approved will not meet the AD’s requirement. Similarly, replacement must comply with Dowty Propellers Specification PS 5723 (attached as Appendix 1 to the SB), latest revision (Requirement 3). The gotcha is relying on non-approved or incorrectly dated documents.

5. Immediate replacement timeframe for defective boots: If lifting or bubbling is found during an inspection, the affected overshoe must be replaced "before next flight" (Requirement 3; Compliance 3). This is operationally significant. The result can be immediate grounding or postponement of scheduled sectors, with associated costs and passenger disruption.

6. Prohibition scope on adhesive usage: The AD states "3M 1300L adhesive not to be used to fit de-icer boots to propeller blades on Fokker F27 Mark 050, 0502 and 0604 series aircraft" (Requirement 4). This is not merely a repair-time limitation; it is an express ban as of the effective date. Maintenance personnel must ensure procurement and stock control avoid accidental use of the banned adhesive.

7. Manufacturer dependency and EASA approval: The AD’s acceptance of later EASA-approved revisions creates a dependency on the manufacturer and the EASA approval process. If a maintenance organisation uses a Dowty SB revision that lacks EASA approval, the AD’s requirements are not satisfied. Tracking which revisions are EASA-approved is therefore essential.

8. Replacement method specificity: The AD requires replacement per Dowty Propellers Specification PS 5723 latest revision. The exact material, process and acceptance criteria may be detailed in that specification. Failure to use the current PS 5723 version risks non-compliance even if the boot is physically replaced.

9. Documentation proving compliance: The AD does not detail what evidence satisfies the regulator that the AD has been complied with. Operators should expect to retain records of the initial adhesive check, inspection results (including findings of lifting/bubbling), replacement records referencing PS 5723, and proof that 3M 1300L has been removed from allowed use. The gotcha is assuming the AD’s bare performance without accompanying record evidence will be sufficient for regulatory oversight.

10. Scope of the safety finding does not supply instructions for other components or aircraft: The AD is narrow in scope, focusing on de-icer overshoes and a particular adhesive. It does not require inspection of adjacent components unless the Dowty SB does so. Operators might mistakenly broaden or narrow the scope of their own inspections absent careful reading of the SB and PS 5723.

11. Misreading "no further action required" language: The AD’s exemption for Bostik 2402 applies only when it "has been positively established" that Bostik 2402 adhesive was used. A mistaken reading that any non-3M adhesive suffices would be incorrect; the AD specifically names Bostik 2402. Where records are silent or ambiguous, the operator cannot rely on the exemption.

12. International operations: The AD references a Netherlands AD and an EASA approval. Operators whose fleet is registered in other jurisdictions should not assume identical obligations in every country; conversely, international operators must ensure compliance with the AD on the aircraft while operating under the Australian AD’s authority.

These are concrete points in the AD’s text that can lead to operational non-compliance if overlooked. Addressing them requires careful record review, procurement changes, strict adherence to the cited Dowty documents and close scheduling of inspections and repairs.

This section sets out a practical, step-by-step compliance checklist derived directly from the AD’s text. Each step cites the AD provision that requires or permits the action. The checklist assumes the AD’s effective date is 16 March 2006, and that the aircraft in question are within the AD’s Applicability.

1. Confirm applicability (Applicability).

   • Identify aircraft of type Fokker F27 Mark 050, Mark 0502 or Mark 0604 in your fleet.
   • Confirm that the propellers installed are Dowty Type R.352 or R.410 series. If both aircraft type and propeller type match the Applicability, the AD applies.

2. Perform record check within 30 days (Requirement 1; Compliance 1).

   • Within 30 days after the AD effective date, examine maintenance records for each affected aircraft to determine what adhesive was used to fit the de-icer boots.
   • The AD provides a conditional exemption: if it can be positively established that Bostik 2402 adhesive was used, no further action under this AD is required for that aircraft (Requirement 1).
   • Document the inspection of records and retain evidence showing positive establishment of adhesive type. If the records are incomplete, treat the adhesive as unknown and proceed to step 3.

3. If 3M 1300L was used or records are inconclusive, schedule inspection per Dowty SB (Requirement 2; Compliance 2).

   • Obtain Dowty Propellers Service Bulletin F50-61-158 dated 30 September 2005, and check whether any later EASA-approved revision exists. The AD accepts that later EASA-approved revisions are also acceptable for compliance (Requirement 2).
   • Inspect the propeller blade de-icer assemblies in accordance with the "accomplishment instructions" of the SB. Ensure the maintenance team uses the SB revision that is either the cited revision or a later EASA-approved revision, as required.
   • Start the inspection within the next 650 flight hours after the AD effective date if 3M 1300L has been used (Compliance 2).

4. Establish and document inspection intervals (Compliance 2).

   • Where inspections are required, record the flight-hour counter at which the initial inspection occurs.
   • Plan for repeat inspections at intervals not exceeding 650 flight hours and update maintenance programmes and logs accordingly.

5. If lifting or bubbling is found, replace the boot before next flight (Requirement 3; Compliance 3).

   • If any signs of lifting or bubbling are found during the inspection, order and install replacement de-icer boots in accordance with Dowty Propellers Specification PS 5723 (attached to the SB as Appendix 1), latest revision (Requirement 3).
   • Implement the replacement before the aircraft’s next scheduled flight sector. Document the defect finding, the replacement action, the specification revision used and the personnel who performed the replacement.

6. Stop use of 3M 1300L immediately (Requirement 4; Compliance 4).

   • As of the AD’s effective date, 3M 1300L adhesive must not be used to fit de-icer boots on the affected Fokker types.
   • Update procurement approvals, stock inventories and maintenance standard procedures to prevent accidental re-use of 3M 1300L adhesive on these aircraft.

7. Retain and produce records demonstrating compliance.

   • Keep the initial records-check documentation, inspection reports that reference the Dowty SB revision used, replacement records that reference PS 5723 revision used, and evidence of removal or discontinuation of 3M 1300L from allowed materials.
   • Include flight-hour tracking showing compliance with the 650-hour inspection interval where inspections were required.

8. Coordinate with MROs and Dowty documentation (Requirement 2-3).

   • Ensure maintenance organisations authorised to perform the work have access to Dowty SB F50-61-158 and Specification PS 5723 latest revision.
   • Verify whether the SB revision in use is EASA-approved if relying on a revision later than 30 September 2005.

9. Operational contingency planning.

   • Develop contingency plans for removing aircraft from service where immediate replacement is required before the next flight due to found defects.
   • Account for possible supply lead times for replacement boots conforming to PS 5723, and consider stocking replacement parts where commercially sensible.

10. Communicate to relevant stakeholders.

• Notify flight operations, maintenance control, procurement, and inventory management of the ban on 3M 1300L and the need for inspections and replacements where records require them.
• Update maintenance manuals and internal compliance checklists to reflect the AD’s requirements.

11. Liaise with regulator if clarification needed.

• If an operator has unusual circumstances, ambiguous record evidence, or requires confirmation of acceptable SB revisions or PS 5723 versions, seek guidance from the Civil Aviation Safety Authority or the applicable regulatory body. The AD itself references CAA Netherlands AD NL-2005-016 and EASA approval No. 2005-6448, indicating cross-jurisdictional relevance (Note).

12. Track updates to Dowty SB and PS 5723.

• Because the AD accepts later EASA-approved revisions of the SB, and requires PS 5723 latest revision, implement a process to monitor manufacturer and EASA notices for relevant updates that affect compliance methods.

Following these steps, each tied to the corresponding AD requirements and compliance windows, is the practical route to satisfying AD/F50/93’s obligations as set out in the provided text.