AD/Robin/21 Amdt 3 - Stabilator Spar and Attachment Brackets

The AD is built around a small set of technical and procedural concepts drawn from the aircraft’s structure and established inspection practice.

• Structural locus. The focal structural elements are the rear fuselage bulkhead that supports the stabilator hinge brackets, the stabilator hinge brackets themselves, and the stabilator spar where the hinge bracket bolts and nut plate rivets are located. The directive identifies particular geometric areas of interest: outboard of the hinge bracket bolt holes and the balance weight cutout on the bulkhead, and around the bolt holes and nut plate rivets in the stabilator spar (Requirement 1, Requirement 2, Requirement 3).
• Inspection modes. Two inspection modes are prescribed. One is a visual inspection aided by strong lighting directed at the forward face of the bulkhead (Requirement 1). The other is a non-destructive penetrant inspection using the fluorescent dye penetrant method, as detailed in Civil Aviation Order 108.10, applied to the forward and aft faces of the bulkhead and to the stabilator spar (Requirement 2, Requirement 3). The AD distinguishes the simpler, quicker visual check from a more invasive penetrant inspection that requires removal of the stabilator.
• Access method. The AD requires removal of the stabilator to gain access for the penetrant inspections; the method for removal is specified as paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual (Requirement 2, Requirement 3). Removal is therefore a mandatory step before performing the penetrant inspections.
• Timing and recurrence. The AD sets initial compliance triggers using a later-of formulation, combining a time-in-service hours trigger with a date trigger tied to 22 February 1995 (Compliance). Recurrent inspections are specified with maximum intervals varying by inspection type: 100 hours for the visual inspection (Requirement 1) and 750 hours for the penetrant inspections (Requirement 2 and Requirement 3).
• Mod 79 exemption. The directive recognises a structural modification, Major Mod 79, that reinforces the rear bulkhead. The AD excludes aircraft with Major Mod 79 embodied from some inspection obligations (Requirement 1, Note; Background). The amendment history explains that Amendment 2 and Amendment 3 progressively alleviated obligations for Mod 79-equipped aircraft, including removal of the need to inspect the forward face repetitively and removal of the requirement to inspect the aft face of the bulkhead for those aircraft (Background).
• Manufacturer and authority references. The AD binds operators to use two external documents by reference for method and procedure: the Avions Pierre Robin R2000 Service Manual (for stabilator removal) and Civil Aviation Order 108.10 (for fluorescent dye penetrant inspection) (Requirement 2, Requirement 3). The AD itself is an instrument issued by CASA’s delegate, with an effective date specified (effective date; signature).

These concepts combine to make the AD an access- and procedure-driven safety instrument, where the central operational consequences are removal of the stabilator to permit dye-penetrant inspection and an ongoing schedule of repetitive inspections unless Major Mod 79 is embodied.

The AD explicitly applies to all Model R2000 series aircraft (Applicability). Therefore the principal parties affected are:

• Registered owners and operators of Avions Pierre Robin R2000 series aeroplanes. They are the entities responsible for ensuring required inspections occur within the AD’s specified time frames (Compliance; Requirement 1-3).
• Maintenance organisations and maintenance personnel responsible for carrying out inspections and for removal and reinstallation of the stabilator. The AD mandates specific methods for removal (Avions Pierre Robin R2000 Service Manual, para 4.4.1) and the use of fluorescent dye penetrant methods as detailed in Civil Aviation Order 108.10 (Requirement 2, Requirement 3). Those organisations must have the skills, procedures and equipment to comply with these specified methods.
• Aircraft that have Major Mod 79 bulkhead reinforcement embodied. The AD draws a distinction for such aircraft in the inspection obligations. The AD notes that Alpha Aviation models R2160, R2160i and R2120U are manufactured with Major Mod 79 embodied, which directly affects owners or operators of those variants (Note). Amendment 2 and Amendment 3 progressively alleviated some inspection obligations applicable to aircraft with Major Mod 79 embodied (Background), meaning owners/operators of Mod 79-equipped aircraft must determine whether their aircraft are relieved from specified inspections.
• Safety regulators and CASA-appointed inspectors. CASA issued the AD and a CASA delegate signed it; therefore CASA is the issuing authority that will be monitoring compliance in its regulatory capacity (signature; effective date). The AD does not itself describe enforcement steps in the text supplied, but CASA’s role as issuer makes it the relevant oversight actor for implementation.
• Suppliers and repair stations that provide dye-penetrant inspection services or assist with stabilator removal and repair. The AD requires fluorescent dye penetrant inspection per Civil Aviation Order 108.10, meaning external providers that offer penetrant inspection services will be engaged where operators do not have in-house capability.

Practical implications for these affected parties arise from the access requirement. Because Requirements 2 and 3 require removal of the stabilator, affected operators will incur aircraft downtime, need to use the service manual procedure, secure equipment for dye-penetrant inspection, and record inspection results. Operators of Mod 79-equipped aircraft need to verify embodiment of the modification in maintenance records to determine which parts of the AD still apply to their fleet. The AD’s timing formulation referencing 22 February 1995 requires operators to compute compliance against either an hours-based trigger or a historic date-based trigger, whichever is later, which may complicate compliance scheduling for older aircraft.

The AD prescribes mandatory duties; it does not set out express “rights” language. The key duties are:

• Duty to inspect the forward face of the rear fuselage bulkhead (Requirement 1). For aircraft not embodying Major Mod 79, operators must visually inspect the forward face with strong lighting for cracks and corrosion, focusing outboard of hinge bracket bolt holes and around the balance weight cutout. The initial compliance window is the later of before 1 000 hours time in service or before further flight after 22 February 1995; thereafter the inspection must be repeated at intervals not exceeding 100 hours (Compliance; Requirement 1).
• Duty to remove stabilator and perform dye-penetrant inspection of the rear bulkhead faces (Requirement 2). For aircraft not embodied with Major Mod 79 (subject to the amendment history), operators must remove the stabilator per paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual, remove hinge brackets from the rear fuselage bulkhead and apply the fluorescent dye penetrant method to the forward and aft bulkhead faces following Civil Aviation Order 108.10. The initial compliance provision is the later of before 2 000 hours time in service or before 25 hours time in service after 22 February 1995; thereafter repeat at intervals not exceeding 750 hours (Compliance; Requirement 2).
• Duty to remove stabilator and perform dye-penetrant inspection of stabilator spar (Requirement 3). For all aircraft, operators must remove the stabilator per the same manual paragraph, remove the stabilator hinge brackets from the stabilator spar and inspect around the bolt holes and nut plate rivets using the fluorescent dye penetrant method per Civil Aviation Order 108.10. The initial compliance is the later of before 2 000 hours time in service or before 25 hours time in service after 22 February 1995; thereafter repeat at intervals not exceeding 750 hours (Compliance; Requirement 3).
• Duty to use nominated procedures and standards. The AD requires that stabilator removal follow the Avions Pierre Robin R2000 Service Manual para 4.4.1 and that penetrant inspections follow Civil Aviation Order 108.10. Those method specifications are duties imposed by the AD text (Requirement 2; Requirement 3).

The AD does not specify corrective or repair instructions within the supplied text. It identifies that during a precautionary inspection multiple cracks were found and that removal of the stabilator revealed widespread cracking (Background). It records laboratory findings that fatigue cracks in the stabilator spar had initiated from fretting damage due to free movement of hinge fittings and balance weight attachment. That background information describes the hazard the AD addresses but does not itself create procedural rights for operators beyond the inspection duties.

The document does not expressly state any operator "right" to an exemption process, nor does it include referral or appeal mechanisms in the text supplied. However, the AD’s amendment history indicates that CASA has previously altered the scope of obligations for aircraft with Major Mod 79 embodied (Amendment 1, Amendment 2, Amendment 3). Practically, operators’ capacity to rely on an exemption depends on verifying the embodiment of Major Mod 79 in the aircraft’s maintenance logbook and records (Note; Background). The AD imposes explicit methods, timing and recurrence duties; absent further text in this document, it neither elaborates nor prescribes a repair standard or alternate compliance procedure.

The text of AD/ROBIN/21 Amdt 3 supplied does not contain explicit penalty provisions, infringement notice schedules or prosecutorial mechanisms. The document is an airworthiness directive issued by a CASA delegate (signature) with an effective date (8 June 2015), and it sets mandatory inspection actions and compliance intervals (Requirement 1-3; Compliance; effective date). The AD therefore functions as a regulatory instrument commanding specific maintenance actions; the instrument itself does not, in its text, set out enforcement sanctions or administrative fine schedules.

From the material provided, the identifiable enforcement elements are limited to the directive form and the prescriptive compliance timings. The AD’s structure implies that compliance is required by the effective date and that CASA is the issuing regulator, but the AD does not specify how CASA will monitor compliance, how non-compliance will be treated administratively or criminally, or whether failure to comply will be treated as an airworthiness certificate matter. Those enforcement relationships are not described in this document.

Operators should note two points that arise from the AD text itself. First, the AD links method and standard references: it prescribes particular inspection techniques (visual with strong lighting, and fluorescent dye penetrant per Civil Aviation Order 108.10) and a particular service manual paragraph for stabilator removal. Compliance therefore requires adherence to both the AD and the referenced documents. Second, the AD contains precise timing requirements, expressed as initial compliance triggers and maximum intervals; the AD makes those times mandatory in the text supplied.

Given the absence of explicit penalty language in this document, any questions about administrative consequences or enforcement practice,such as certificate suspension, grounding, directions to rectify, or civil penalties,are not answerable from this AD alone. The AD should be read alongside the broader regulatory framework administered by CASA and the applicable civil aviation legislation and enforcement procedures, which are not reproduced in the supplied text.

Within the supplied text, the AD interacts directly with two specified regulatory or technical documents and with previous AD amendments:

• Civil Aviation Order 108.10. The AD mandates the fluorescent dye penetrant inspection method "as detailed in Civil Aviation Order 108.10" for the penetrant inspections of both the bulkhead faces and the stabilator spar (Requirement 2, Requirement 3). That reference makes a procedural standard outside the AD normative for the required penetrant inspections.
• Avions Pierre Robin R2000 Service Manual. The AD requires that removal of the stabilator be performed in accordance with paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual (Requirement 2, Requirement 3). That embeds a manufacturer maintenance procedure into the compliance pathway.
• Major Mod 79. Major Mod 79 is a structural modification to the rear bulkhead. The AD’s applicability and requirements are qualified by whether Major Mod 79 has been embodied in an aircraft’s structure. The AD explicitly notes that Alpha Aviation models R2160, R2160i and R2120U are manufactured with Major Mod 79 embodied (Note). The amendment history explains that embodiments of Major Mod 79 have been treated differently across amendments, progressively alleviating some inspection obligations for aircraft with the modification (Background).

The AD is itself an amendment (Amendment 3) to an earlier AD. The Background paragraph summarises past changes and how they affect current obligations: Amendment 1 introduced repeat inspections of the stabilator spar; Amendment 2 relieved aircraft with Major Mod 79 from repetitive inspections to the forward face of the rear bulkhead; Amendment 3 extended the relief for Major Mod 79-equipped aircraft to include the aft face of the bulkhead. Therefore the AD modifies prior regulatory obligations for certain aircraft based on the presence of a structural modification and the manufacturer's information.

The AD also situates its measures in relation to the aircraft’s maintenance schedule: the Background states that the cracks were found during a "precautionary inspection, not required by the maintenance schedule", implying that the AD imposes inspections outside what the standard maintenance schedule required at the time of discovery. That relationship between the AD-imposed inspections and the aircraft maintenance schedule is explicit in the Background and in the Requirements.

The supplied text does not cite or state interaction with broader criminal, civil or administrative statutes, nor does it incorporate other legislative instruments aside from Civil Aviation Order 108.10 and the Avions Pierre Robin service manual. Where a practitioner needs information on enforcement consequences, certification effects, or appeals, those matters are not contained within this AD and must be sought in the wider CASA regulatory framework and relevant legislation, which are not reproduced in the supplied document.

The document is AD/ROBIN/21 Amdt 3; the Background paragraph provides a concise amendment history and the reason for each change.

• Original AD and discovery. The Background records that cracks were discovered during a precautionary inspection not mandated by the maintenance schedule, and that removal of the stabilator revealed widespread cracking of the rear fuselage bulkhead and cracking of the stabilator spar near hinge bracket bolts. The Background states that the stabilator attachment’s structural integrity is critical to flight safety. This is the hazard basis for the initial directive (Background).
• Amendment 1. According to the Background, Amendment 1 included repeat inspections of the stabilator spar. The Basis recorded in the Background includes laboratory findings that the stabilator spar fatigue cracks initiated from fretting damage due to free movement of the stabilator hinge fittings and the balance weight attachment fitting. Amendment 1 therefore expanded the directive to include ongoing inspections of the stabilator spar to detect such fatigue cracks early (Background).
• Amendment 2. Amendment 2 altered the scope of the repetitive inspection obligations by relieving R2000 aircraft that have the rear bulkhead strengthening modification Major Mod 79 embodied from the requirement for repetitive inspections to the forward face of the rear bulkhead structure. That is, following Amendment 2, aircraft with Major Mod 79 were no longer required to perform the repetitive forward-face inspections that Requirement 1 had previously mandated (Background).
• Amendment 3 (this Amendment). Amendment 3 further alleviates aircraft with Major Mod 79 from the requirement to inspect the aft face of the bulkhead. The Background explains the rationale: the modification covers the area of interest and the manufacturer advised they have not received reports of cracking in models with the modification installed. Consequently, Amendment 3 extends exemption relief for Mod 79-equipped aircraft to the aft face inspections that were previously required under Requirement 2 (Background).

The AD’s Note identifies specific aircraft models that are manufactured with Major Mod 79 embodied: Alpha Aviation models R2160, R2160i and R2120U. That clarifies which aircraft are typically subject to the alleviation by default, though operators must still verify embodiment in their own maintenance records (Note).

The effective date for the AD as amended is 8 June 2015 and the document is signed by Mike Higgins as CASA delegate on 1 June 2015 (effective date; signature). The amendment history in the Background therefore documents a migration from broader inspection obligations to targeted inspections with exemptions for Mod 79 embodiments, reflecting a narrowed scope where the modification provides coverage for the previously identified area of interest and where manufacturer experience showed no reports of cracking for the modified configuration.

The supplied AD text contains no information about litigation, court proceedings, appeals or disputes arising from the directive. It names no cases and records no judicial or administrative challenges in the document. The Background refers to laboratory examination of cracked parts and to manufacturer advice about reports of cracking, but it does not indicate any legal proceedings.

Consequently, from the material provided there is no litigation history to report. Practitioners needing to know whether this AD has been the subject of review or legal challenge must consult external case law databases, administrative appeal records or CASA correspondence, none of which are contained in this AD document.

The absence of litigation information in the AD itself means that any legal or judicial developments related to compliance, enforcement or contested interpretation are outside this text. If an operator or adviser needs to understand precedent or case-law interpretation concerning airworthiness directives generally or this AD specifically, that information must be sourced from judicial and tribunal records and CASA publications that are not reproduced in the supplied AD.

This AD contains several points that can cause implementation pitfalls if not read closely.

• Exemption by Major Mod 79 is contextual and phased. The AD’s exemptions for aircraft with Major Mod 79 are not a blanket early exemption in all historical formulations of the AD. The Background shows Amendment 2 and Amendment 3 progressively relieved Mod 79-equipped aircraft from repetitive inspections to the forward face and later the aft face of the rear bulkhead respectively (Background). Operators must verify whether Major Mod 79 is actually embodied in their specific airframe maintenance logbook before assuming exemption. The AD’s Note identifies Alpha Aviation R2160, R2160i and R2120U models as manufactured with Major Mod 79 embodied, but manufacturing origin does not replace a record-based determination for a given aircraft (Note).
• Different inspection techniques and access requirements. Requirement 1 is a visual inspection with strong lighting but Requirement 2 and Requirement 3 require removal of the stabilator and dye-penetrant inspection. The penetrant inspections require more maintenance time, access, and specialised equipment compliant with Civil Aviation Order 108.10 (Requirement 1; Requirement 2; Requirement 3). Operators who read only the visual-inspection clause risk missing the requirement to perform deeper inspections that mandate removal of the stabilator.
• Timing formula uses later-of triggers with a historic date. The initial compliance triggers are framed as "the later of" a time-in-service hours threshold or a date-based deadline anchored to 22 February 1995 (Compliance). For older aircraft and for aircraft with complex time-in-service histories, computing the applicable initial trigger correctly can be non-trivial. The "later of" construction can mean an aircraft that has accumulated many hours still must inspect by a historic date, or conversely a low-hours aircraft might need to wait until it reaches the hours threshold. Miscomputing the later-of can lead to non-compliance.
• Multiple recurring-interval regimes. The AD imposes different recurrent intervals: 100 hours for the visual inspection (Requirement 1) and 750 hours for the penetrant inspections (Requirement 2 and 3). Operators must track three distinct recurring schedules across the fleet and ensure appropriate maintenance windows for the penetrant inspections that require stabilator removal.
• Documentation references matter. The AD requires that the stabilator be removed "in accordance with paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual" and that the fluorescent dye penetrant method be used as detailed in Civil Aviation Order 108.10 (Requirement 2; Requirement 3). If an operator does not have access to or is not using the exact referenced documents or revisions, procedural non-conformance may arise. The AD does not specify acceptable alternate procedures within the supplied text.
• No repair instructions in the AD text. The supplied AD sets inspection obligations but does not state specific corrective action steps or repair specifications in the event cracks are discovered. The Background notes that removal of the stabilator revealed widespread cracking and laboratory analysis identified fretting as an initiating mechanism, but the AD text does not direct a particular repair method, part replacement or further action. Practitioners must be prepared to consult the manufacturer’s approved repair data or CASA for direction if cracking is found.
• Effective date versus signed date. The AD is signed by the CASA delegate on 1 June 2015 and has an effective date of 8 June 2015. Operators should not assume immediate effective force on the signature date; the AD’s stated effective date is the operative date (signature; effective date).
• Manufacturer advice underpins relief. Amendment 3’s relief for Mod 79-equipped aircraft from inspecting the aft face rests partly on the manufacturer advising it has not received reports of cracking in models with the modification installed (Background). That relief therefore depends on the continued absence of reports; changes in manufacturer data or incident reporting could affect future ADs.

These "gotchas" are concrete reading and compliance traps deriving from the AD’s text and amendment history. Each requires operators to verify physical modification embodiment, maintain accurate time-in-service records, hold the referenced technical publications, and prepare for stabilator removal and dye-penetrant inspection logistics.

The AD establishes a clear, document-tied compliance pathway; the following steps, grounded in the AD text, are practical for operators and maintenance providers:

1. Verify applicability and modification embodiment. Confirm that the aircraft is a Model R2000 series (Applicability). Check maintenance records to determine whether Major Mod 79 rear bulkhead reinforcement has been embodied. Note that Alpha Aviation R2160, R2160i and R2120U are manufactured with Major Mod 79 embodied, but verification must be aircraft-specific (Note; Background).

2. Schedule and perform Requirement 1 (for aircraft not relieved by Major Mod 79). If the aircraft does not have Major Mod 79 embodied, perform a visual inspection, with the aid of strong lighting, of the forward face of the rear fuselage bulkhead supporting the stabilator hinge brackets. Focus on outboard regions of the stabilator hinge bracket bolt holes and around the stabilator balance weight cutout (Requirement 1). Ensure the inspection occurs at the later of before 1 000 hours time in service or before further flight after 22 February 1995. Thereafter, repeat at intervals not exceeding 100 hours (Compliance).

3. Schedule and perform Requirement 2 (for aircraft not relieved by Major Mod 79). For aircraft not relieved from this obligation by Major Mod 79, remove the stabilator in accordance with paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual, remove the stabilator hinge brackets from the rear fuselage bulkhead, and inspect the forward and aft faces of the bulkhead using the fluorescent dye penetrant method detailed in Civil Aviation Order 108.10 (Requirement 2). Perform the first such inspection at the later of before 2 000 hours time in service or before 25 hours time in service after 22 February 1995 and thereafter at intervals not exceeding 750 hours (Compliance).

4. Schedule and perform Requirement 3 (for all aircraft). For all Model R2000 series aircraft, remove the stabilator in accordance with paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual and remove the stabilator hinge brackets from the stabilator spar. Using the fluorescent dye penetrant method as detailed in Civil Aviation Order 108.10, inspect around the bolt holes and nut plate rivets in the stabilator spar (Requirement 3). The initial compliance is the later of before 2 000 hours time in service or before 25 hours time in service after 22 February 1995; repeat at intervals not exceeding 750 hours (Compliance).

5. Use specified methods and documentation. Ensure personnel performing stabilator removal use paragraph 4.4.1 of the Avions Pierre Robin R2000 Service Manual. Ensure the dye penetrant inspection follows Civil Aviation Order 108.10. Maintain copies or access to those documents for procedural fidelity and auditability (Requirement 2; Requirement 3).

6. Ensure competency and equipment. Ensure the inspection team has appropriate lighting for the visual inspection and the equipment, chemicals and expertise necessary to perform fluorescent dye penetrant inspection per Civil Aviation Order 108.10. Because penetrant inspection requires controlled processes for surface preparation, application, dwell time, removal and fluorescence inspection, use qualified personnel or an approved inspection provider (Requirement 1-3).

7. Record and log inspections. Document initial and repeat inspections in the aircraft maintenance logbook and record whether Major Mod 79 is embodied. Track inspection intervals and schedule future removal-based inspections sufficiently in advance to account for access and downtime (Compliance).

8. Prepare for findings. The AD does not specify repair procedures in the supplied text. If cracks or corrosion are found, consult the Avions Pierre Robin R2000 Service Manual for repair instructions where available, and consult the manufacturer or CASA for approved repair data if the manual does not contain prescriptive repairs. The Background records that fretting-induced fatigue initiated the spar cracks; be prepared to examine hinge fittings and balance weight attachment fittings for fretting and free movement that could require correction (Background).

9. Verify effective date and amendment status. Note that this instrument is AD/ROBIN/21 Amdt 3, effective 8 June 2015, signed by the CASA delegate on 1 June 2015. Ensure that no later AD supersedes or modifies these obligations before acting (effective date; signature; Background).

10. Where in doubt, seek confirmation. Because the AD incorporates external documents and refers to a modification embodiment that affects compliance scope, operators should, if uncertain, confirm interpretation with CASA or the manufacturer. The AD’s amendment history shows CASA has altered obligations in the past based on technical information; if there are novel circumstances or missing repair instructions, seek written approval or clarification before returning the aircraft to service.

In sum, compliance requires verifying Mod 79 embodiment, scheduling and performing the specified visual and penetrant inspections at the stated initial triggers and intervals, using the specified manual and Civil Aviation Order procedures for removal and penetrant testing, documenting results, and consulting manufacturer-approved repair data or CASA guidance where inspection discovers cracking.