AD/AS 355/96 - Main & Tail Rotors Servo Controls

This AD revolves around a short, concrete set of technical and procedural concepts that determine scope, detection, remediation, and installation control.

Applicability is defined tightly by aircraft type, component type, part number, serial number and an identification-plate marking condition. The covered aircraft are EUROCOPTER AS 355 models E, F, F1, F2 and N equipped with Goodrich main and tail rotor servo-controls that have no letter “C” marked in the inspection box of the servo-control identification plate. The AD then enumerates specific P/N and S/N combinations for main rotor servo-controls (P/N SC5083 with S/N 270M, 272M, 409M, 423M, 452M or 1573; P/N SC5083-1 with S/N from 2902 to 2921 inclusive; P/N SC5084 with S/N 30, 84, 104, 186, 438, 575 or 695; P/N SC5084-1 with S/N from 1462 to 1481 inclusive) and tail rotor servo-controls (P/N SC5072 with S/N 222M, 306M or 309) (Applicability). That specificity confines the AD to a recognisable set of units rather than to an undifferentiated fleet.

Detection mechanics are central. The unsafe condition is an internal surplus of play in the input lever bearing that can produce an off-centred lever/distributor slide valve and possibly jam the distributor slide valve in its sleeve, which could reduce rotor controllability. The AD states a jammed distributor slide valve “would be detected during the pre-flight hydraulic check by a ‘hard point’ in the flight controls” (Background). The operational detection method is therefore the pre-flight hydraulic check described in Rotorcraft Flight Manual section 4; the AD mandates that pre-flight tests be performed during each pre-flight and until required replacements are effected (Compliance 2a).

Remediation mechanics are threefold. If an affected P/N/S/N is present, the operator must (a) check thoroughly for any “hard point,” (b) if a hard point is detected, replace the defective servo-control(s) before further flight as instructed in paragraph 2.B. of the EUROCOPTER ASB, and (c) replace all listed servo-controls as instructed in paragraph 2.B. of the ASB (Requirement 2a-2c). The AD cross-references the ASB for the replacement procedure; the AD does not itself reproduce the replacement steps, but makes those steps mandatory by reference.

Installation control is explicit. The AD forbids installation of servo-controls with the listed P/N/S/N on any EUROCOPTER AS 355 unless the equipment manufacturer has previously returned them to conformity as indicated in paragraph 2 of EUROCOPTER ASB No. 01.00.53 Revision 1 or a later NAA approved revision (Requirement 3). This prevents reuse of affected units unless manufacturer remediation and certification has occurred.

Process flexibility is limited but present. Instead of a physical inspection of the rotorcraft to establish P/N/S/N the AD allows a review of maintenance records and other applicable data (rotorcraft logbook, component lists) if each P/N and S/N can be positively determined from that review (Requirement 1). This permits reliance on documentation for initial identification.

Temporal constraints are explicit. The AD prescribes that checks for hard points be carried out during each pre-flight test until replacements are completed; replacement of all affected servo-controls must be done within 50 flight hours or four months from the AD effective date, whichever comes first; any replacement required due to a detected hard point must be effected before further flight after the detection (Compliance).

Cross-references situate the AD within a broader regulatory and manufacturer framework. The AD references EUROCOPTER ASB No. 01.00.53 Revision 1, permits later NAA approved revisions to be used, and notes EASA Emergency AD 2007-0141-E as related (Requirement; Note). The AD’s implementation therefore depends on the ASB content and any national aviation authority approvals of revised ASBs.

Together, these concepts define the AD’s intervention space: targeted identification, monitoring via the pre-flight hydraulic check, mandatory remediation per manufacturer procedures, time-limited replacement, and a ban on installation of unremediated affected units.

The AD’s applicability clause identifies the affected population precisely. It targets EUROCOPTER helicopters models AS 355 E, F, F1, F2 and N that are fitted with Goodrich main rotor servo-controls and tail rotor servo-controls that lack a letter “C” in the inspection box of the servo-control identification plate and that have one of the enumerated part and serial numbers (Applicability). This ties regulatory obligation to the aircraft operator and their fitted components.

Primary affected parties are aircraft operators, owners, maintenance organisations, and maintenance personnel responsible for pre-flight checks and component replacement. The directive requires verification of P/N and S/N and allows verification either by physical inspection of the helicopter or by a documented review of maintenance records, rotorcraft logbook and component lists if each P/N and S/N can be positively determined from that review (Requirement 1). Whoever holds the helicopter’s maintenance records or who conducts the pre-flight hydraulic check must therefore act on the AD.

Goodrich as the supplier of the servo-controls, and EUROCOPTER as the manufacturer issuing the Alert Service Bulletin referenced by the AD, are also implicated. The AD requires replacement and the ASB’s paragraph 2.B. provides the replacement instructions; the AD further requires that listed servo-controls not be reinstalled unless they have been “previously returned to conformity by the equipment manufacturer as indicated in paragraph 2. of EUROCOPTER ASB No. 01.00.53 Revision 1 or later NAA approved revision” (Requirement 3). That creates an operational dependency on the equipment manufacturer to perform and certify conformity returns for units that might otherwise be re-used.

Regulatory actors are named in the document. The AD is issued under the auspices of the Civil Aviation Safety Authority, signed by a delegate, Charles Lenarcic, with an effective date. The AD text itself does not set out further enforcement agencies or penalty provisions, but the document is the instrument of action requiring immediate operator response (signature and effective date).

Organisations that provide or source spare parts and repair services for these servo-controls are indirectly affected. The prohibition on installing listed P/N/S/N units unless returned to conformity by the manufacturer (Requirement 3) means that businesses supplying spares must confirm the conformity status of supplied units and may need to coordinate with the equipment manufacturer or maintain records proving conformity returns.

Aircraft operators who rely on short-term or second-hand parts are affected by availability constraints. The AD’s installation ban unless manufacturer-returned-to-conformity will limit ability to source used servo-controls that match the listed P/N/S/N unless those units have been remediated and certified by the manufacturer.

Flight crews and maintenance personnel who perform the pre-flight hydraulic check are affected operationally because the AD requires that the pre-flight hydraulic check be carried out during each pre-flight test and that a “hard point” be treated as an immediate ground-to-maintenance condition requiring replacement before further flight (Requirement 2a-2b; Compliance 2a-2b). This modifies pre-flight behaviour until the mandated replacements are done.

Finally, the AD affects scheduling and operational planning for operators of the listed AS 355 aircraft. The requirement to replace all listed servo-controls within 50 flight hours or four months (whichever is sooner) generates a planning and cost impact for owners and operators that must be managed within that window (Compliance 2c).

The AD imposes specific duties and establishes procedural options; it does not enumerate statutory rights or penalties within the text provided.

Duties (explicit):

• Identification duty: Operators must verify the P/N and S/N of main and tail rotor servo-controls in accordance with paragraph 1.E.2. of EUROCOPTER ASB No. 01.00.53 Revision 1 or a later NAA approved revision. The AD expressly allows a records-based alternative: “Instead of inspecting the rotorcraft, a review of the helicopter maintenance records along with any other applicable data (rotorcraft logbook, Components list, etc...) is acceptable if each P/N and S/N can be positively determined from that review” (Requirement 1). That duty is an initial triage to find whether affected units are present.

• Pre-flight check duty: If an affected servo-control is identified, the operator must “check thoroughly that no ‘hard point’ exists in the flight controls” (Requirement 2a). The AD ties this duty to the Rotorcraft Flight Manual pre-flight test (see Rotorcraft Flight Manual section 4) and specifies that such checks are required “during each pre-flight test … and until accomplishment of requirement 2c … is completed” which creates an ongoing monitoring duty until replacement (Compliance 2a).

• Immediate remediation duty: Upon detection of any hard point, the defective servo-control(s) must be replaced as instructed in paragraph 2.B. of the EUROCOPTER ASB and before further flight (Requirement 2b; Compliance 2b). This creates a strict “no further flight” condition until the defective unit is replaced.

• Replacement duty: All servo-controls identified in the AD’s applicability must be replaced as instructed in paragraph 2.B. of the ASB within the time window set in the AD, specifically within the next 50 flight hours or 4 months after the effective date of the AD, whichever occurs first (Requirement 2c; Compliance 2c).

• Installation restriction duty: No listed servo-controls are to be installed on any EUROCOPTER AS 355 helicopter unless they have been previously returned to conformity by the equipment manufacturer as indicated in paragraph 2 of the ASB (Requirement 3). This duty controls component sourcing and installation.

Rights and procedural latitude provided by the AD:

• Documentation alternative: Operators have the right to determine applicability by documented review rather than by physical inspection, if records can positively determine each P/N and S/N (Requirement 1). This reduces immediate physical inspection burden where accurate records exist.

• Use of later NAA-approved ASB revisions: The AD allows compliance with EUROCOPTER ASB No. 01.00.53 Revision 1 or “later NAA approved revision”, granting operators and maintenance organisations the ability to use updated ASB versions once nationally approved (Requirement cross-references). This provides procedural latitude in the methods for replacement and conformity processes as long as the relevant NAA has approved the revision.

• Time-bound compliance flexibility: The replacement duty for all affected servo-controls is not immediate for those units not showing a hard point but instead gives a finite compliance window of 50 flight hours or 4 months (Compliance 2c). Where no hard point is detected, operators can continue to operate subject to the ongoing pre-flight checks.

Matters the AD does not specify within its text:

• The AD text does not describe penalties, civil enforcement mechanisms or inspection powers in the body of the document. It prescribes actions and timings but does not, in the text provided, state what sanctions apply for non-compliance or which authority will enforce the AD beyond being issued by the Civil Aviation Safety Authority (signature and effective date).

• The AD delegates replacement methodology and “return to conformity” criteria to EUROCOPTER’s ASB and to what that ASB indicates in paragraph 2.B. and paragraph 2, respectively. The AD therefore relies on the ASB to specify the technical steps and any certification statements that constitute a return to conformity.

Who decides compliance decisions in practice from the instrument alone:

• The operator/owner or their maintenance organisation must determine applicability (by inspection or by records review per Requirement 1), must carry out the pre-flight checks (Compliance 2a), must initiate and complete replacements (Requirement 2b-2c), and must ensure no listed parts are installed unless manufacturer-return-to-conformity is evidenced (Requirement 3). The equipment manufacturer is tasked implicitly with performing and certifying any return to conformity.

In short, the AD imposes identification, monitoring, replacement and installation-control duties on operators and maintenance organisations, while delegating the technical remediation details and standards for “return to conformity” to the EUROCOPTER ASB and the equipment manufacturer.

The AD text supplied prescribes mandatory actions and compliance timings but does not set out penalties, specific enforcement procedures, inspection powers, or civil or criminal consequences for non-compliance within its own text. The document’s operative content is the identification of affected servo-controls, the mandatory pre-flight checks and replacement obligations (Requirement; Compliance), and the effective date (This Airworthiness Directive becomes effective on 25 May 2007). The AD is signed by a CASA delegate, Charles Lenarcic, which indicates the issuing authority (signature block and date).

What the AD does specify concerning enforceable requirements:

• Timing and pre-flight conditions. The AD obliges operators to perform the identification step prior to flight activities and to conduct pre-flight hydraulic checks during each pre-flight test until replacements are completed (Compliance 1 and 2a). It requires immediate replacement before further flight if a “hard point” is detected during a check (Requirement 2b; Compliance 2b). Replacement of all affected servo-controls is required within a specific window: 50 flight hours or four months after the AD’s effective date, whichever occurs first (Compliance 2c). Those temporal conditions set clear, enforceable milestones.

• An installation prohibition. The AD explicitly prohibits installation of the listed P/N/S/N servo-controls on AS 355 helicopters unless they have been returned to conformity by the equipment manufacturer as indicated in the referenced ASB (Requirement 3). That prohibition creates an installation control that can be examined by maintenance records and parts traceability.

Absent material in the AD text:

• The AD does not, within this text, specify the mechanisms by which the Civil Aviation Safety Authority or any other body will monitor or assess compliance, nor does it state the sanctions, fines, or legal consequences that will apply to operators who fail to comply. The AD also does not state procedures for reporting compliance, for obtaining explicit acceptance or relief, or for interaction with continuing airworthiness management documentation beyond the records-based identification option.

• The AD does not describe inspection or auditing routines, nor does it prescribe post-action reporting requirements to the issuing authority in the text provided.

Implication for operators and advisers:

• Although penalties and enforcement steps are not stated in the AD text, operators should treat the AD as a mandatory safety requirement with clear temporal and operational constraints. The AD’s explicit duties and the presence of an effective date and CASA delegate signature indicate that the operator’s failure to adhere would expose the operator to the regulatory regime that governs airworthiness directives in the relevant jurisdiction. The AD itself, however, does not enumerate those follow-on regulatory sanctions within its issued text.

• Practical enforcement will be tested by available documentary proof (maintenance records, parts traceability, service bulletin compliance records) and by the physical condition of components uncovered during checks. Because the AD allows records-based identification and defers technical replacement details to the EUROCOPTER ASB, enforcement will hinge on traceable evidence that the ASB instructions were followed and that any returned-to-conformity parts have manufacturer evidence as required by the AD.

Operators should therefore assume that the AD’s timing and replacement obligations are intended to be adhered to and that compliance evidence should be prepared and retained, even though explicit penalty provisions are not included in the AD text provided.

The AD explicitly cross-references other regulatory and manufacturer instruments and therefore operates in a networked administrative-technical context rather than in isolation.

Primary cross-reference: EUROCOPTER Alert Service Bulletin No. 01.00.53 Revision 1. The AD requires identification and replacement actions “in accordance with paragraph 1.E.2. of EUROCOPTER Alert Service Bulletin (ASB) No. 01.00.53 Revision 1 or later NAA approved revision” and instructs replacement as per paragraph 2.B. of the ASB (Requirement 1; Requirement 2.B). The AD also references paragraph 2 of the ASB for the manufacturer’s “return to conformity” process (Requirement 3). That means the AD’s technical content is functionally dependent on the ASB’s content: the AD supplies the mandatory regulatory force and timing, while the ASB supplies the technical procedures and the formal criteria for conformity returns. Operators must therefore use the ASB as the procedural manual to meet the AD’s obligations.

Interaction with national aviation authority approvals. The AD allows use of “later NAA approved revision” of the ASB. That connects the AD to the processes of the relevant National Aviation Authority for approving ASB revisions. The AD’s operative flexibility therefore depends on national approval decisions; a later ASB revision is acceptable only once it is NAA approved (Requirement cross-reference).

Reference to foreign regulator: EASA Emergency AD 2007-0141-E. The AD contains a note: “EASA Emergency AD 2007-0141-E dated 21 May 2007 refers.” That links the CASA-issued AD to a contemporaneous EASA emergency AD, indicating that the same technical concern was the subject of urgent action by the European authority. The AD therefore aligns with, and may be responsive to, international regulatory activity on the same technical issue.

Operational interaction with Rotorcraft Flight Manual requirements. The AD ties detection procedures to the pre-flight hydraulic check contained in Rotorcraft Flight Manual section 4: “During each pre-flight test (see Rotorcraft Flight Manual section 4) …” (Compliance 2a). That means operators must integrate the AD’s monitoring duty into their existing flight manual compliance routines.

Relationship to manufacturer obligations. The AD requires that unremediated listed servo-controls not be installed unless they have been “previously returned to conformity by the equipment manufacturer as indicated in paragraph 2. of EUROCOPTER ASB No. 01.00.53 Revision 1” (Requirement 3). This creates a normative link between manufacturer remediation and the operator’s legal ability to install parts.

What the AD does not say about interactions with other statutes or regulations within its own text. The AD does not set out how it interacts with the broader administrative or criminal statutes that govern non-compliance with airworthiness directives in the issuing jurisdiction, nor does it include cross-references to particular sections of national aviation legislation or civil aviation regulations. Nor does it specify reporting obligations to CASA beyond the replacement and inspection activities mandated. The AD presumes the standard regulatory overlay that attaches to airworthiness directives but does not detail it in the AD text.

Practical consequences of these interactions:

• Compliance will require documentary coordination across at least three artefacts: the AD itself, EUROCOPTER ASB No. 01.00.53 Revision 1 (or later NAA approved revision) and the operator’s Rotorcraft Flight Manual. Operators must ensure consistency among these documents when scheduling inspections and replacements.

• The AD’s reference to EASA Emergency AD 2007-0141-E indicates that the same technical issue has been subject to international regulatory attention, which supports the AD’s requirement but also suggests that operators operating under other jurisdictions may be subject to simultaneous parallel directives.

• Because the AD defers technical remediation standards and the definition of “returned to conformity” to the ASB, any dispute about whether a remediation meets the AD will turn on the ASB text and any NAA approvals. That makes the ASB and NAA approval decisions operationally determinative.

The AD text provides a limited amendment trail within itself and key cross-references that indicate where substantive revisions to process might arise, but it does not contain a multi-version amendment log.

Key dates and document references contained in the text:

• Effective date. The AD states that it “becomes effective on 25 May 2007” and is signed by Charles Lenarcic, Delegate of the Civil Aviation Safety Authority, dated 22 May 2007 (signature block). That provides the AD’s point of legal effect in time.

• EUROCOPTER ASB reference and revision point. The AD prescribes compliance “in accordance with paragraph 1.E.2. of EUROCOPTER Alert Service Bulletin (ASB) No. 01.00.53 Revision 1 or later NAA approved revision” and directs replacements as instructed in paragraph 2.B. of that ASB (Requirement 1; Requirement 2). It also permits later NAA approved revisions. This gives an explicit mechanism for the AD’s technical prescriptions to be amended indirectly by the ASB subject to NAA approval. In other words, technical amendments arise via later ASB revisions that are NAA approved rather than by direct amendment of the AD text. The AD therefore anticipates updates to the ASB and defers to the NAA approval process for substantive technical change.

• Reference to external regulatory action. The AD’s note states that “EASA Emergency AD 2007-0141-E dated 21 May 2007 refers.” This indicates contemporaneous action by EASA and can serve as a cross-jurisdictional indicator of the event prompting the AD. It also functions as a reference point for related directives and any subsequent updates issued by EASA.

What is not recorded here:

• The AD text does not list previous amendments to the AD itself. It appears as a single instrument issued in May 2007, referencing ASB Revision 1 and allowing subsequent NAA approved ASB revisions. The document provides no later amendment dates or versions within the supplied text.

• There is no explicit stated process in this AD for seeking exemptions, extensions or alternative means of compliance contained in the AD text itself. Any such mechanisms, if available, would need to be located in the broader regulatory framework or in national procedures for alternatives to AD compliance; the AD text itself does not set them out.

Practical implications for operators tracking amendments:

• Operators should monitor EUROCOPTER ASB No. 01.00.53 for any later revisions and track NAA approval notices that would validate the use of a later ASB revision under the AD’s terms. Because the AD permits use of a “later NAA approved revision,” such approvals will effectively modify the acceptable technical procedures for replacement and return to conformity without the AD text requiring direct amendment.

• Operators should also observe EASA publications, in particular Emergency AD 2007-0141-E referenced in the AD, for any follow-up action or clarifying material that may be relevant to international fleets or to the manufacturer’s remedial programmes.

In sum, the AD contains a single effective date and a reliance on the ASB revision mechanism plus NAA approvals as the channel for technical amendment rather than containing an internal amendment log.

The supplied AD text contains no record of litigation, appeals, injunctions or judicial review relating to this AD. There are no case names, court decisions, or dispute records referenced in the document. The text is a regulatory safety instrument describing applicability, required actions, compliance timing and background of the technical issue, and it does not summarise or reference any legal challenges.

Potential areas where disputes might arise, drawn from the AD’s content and structure:

• Interpretation of applicability. The AD uses a combination of aircraft models, component P/Ns, S/Ns, and an inspection-plate marking condition (“no letter ‘C’ marked in the inspection box of the servo-control identification plate”) to define applicability. Dispute could arise over whether a particular unit falls within the listed serial numbers, over how to treat unclear identification-plate markings, or over records that are incomplete or ambiguous. Because the AD allows records-based verification in lieu of inspection, disagreements over whether records “positively determine” each P/N and S/N could produce administrative disputes.

• Adequacy of compliance periods. The AD provides a replacement window for all listed servo-controls of “within the next 50 Flight Hours or 4 months after the effective date … whichever occurs first.” Disagreements could occur about how flight hours are counted, whether maintenance scheduling or operational constraints make this window impossible, and whether an operator could obtain relief or an alternative means of compliance. The AD text does not describe a relief mechanism within itself.

• Determination of a “hard point.” The AD instructs that a jammed distributor slide valve would be “detected during the pre-flight hydraulic check by a ‘hard point’ in the flight controls” and mandates replacement before further flight if a hard point is found. Operators and regulators might disagree over what constitutes a hard point for purposes of the AD, how subjective the assessment is, and whether minor stiffness that does not compromise controllability should be treated as a disqualifying hard point.

• Conformity return sufficiency. The AD bars the installation of listed servo-controls unless they have been “previously returned to conformity by the equipment manufacturer as indicated in paragraph 2. of EUROCOPTER ASB No. 01.00.53 Revision 1.” Litigation or administrative dispute could focus on whether the manufacturer’s return-to-conformity documentation is sufficient, especially where replacement parts have been refurbished by third parties or where records are incomplete.

• Enforcement and sanctioning. Because the AD itself does not set out penalties or enforcement mechanisms in the text provided, any enforcement action taken by the regulator could give rise to procedural challenges. Operators might contest the legal basis for enforcement action or the proportionality of sanctions applied, but any such litigation would depend on the broader statutory framework outside the AD text.

In the absence of recorded litigation in the AD itself, advisers should treat the above as plausible dispute loci rather than as documented litigation history. Any actual litigation records, appeals, or decisions would need to be sought outside the AD text, for example in regulatory enforcement records, court dockets or administrative tribunal files.

This AD contains several specificity and procedural traps that can cause non-compliance or operational friction if missed. These are drawn from the AD text and the way it cross-references the EUROCOPTER ASB.

1. Narrow applicability by marking. The AD excludes servo-controls that have a letter “C” marked in the inspection box of the servo-control identification plate. That means a unit with the same P/N and S/N but with the letter “C” marked may not be covered. Operators must therefore check the identification-plate marking as well as P/N and S/N; failing to do so can cause misclassification (Applicability). Do not assume part number alone determines applicability.

2. Records-based verification can produce false negatives. The AD permits reliance on maintenance records, rotorcraft logbooks and component lists “if each P/N and S/N can be positively determined” (Requirement 1). If records are incomplete, ambiguous, or incorrectly transcribed, an affected unit might not be identified. Operators who rely on records must ensure those records provide positive identification and maintain traceability.

3. Multiple discrete serial numbers and ranges. The AD lists discrete S/Ns and ranges across four P/Ns for main rotor servo-controls and three discrete S/Ns for tail rotor servo-controls. It is easy to overlook a discrete serial number among the ranges, or to misread inclusive ranges. A careful inventory check is required.

4. Reliance on Rotorcraft Flight Manual for detection. The AD ties detection of a potential jam to a “hard point” identified during the pre-flight hydraulic check in Rotorcraft Flight Manual section 4 (Background; Compliance 2a). If a flight crew or maintenance team uses a different pre-flight checklist or omits components of the hydraulic check, a jam could go undetected. Operators must align their pre-flight procedures with the Rotorcraft Flight Manual and the AD’s monitoring duty.

5. Operational disruption on detection. The AD requires replacement “before further flight” if a hard point is detected (Requirement 2b; Compliance 2b). This can ground the aircraft until a replacement is available or until the defect is rectified per the ASB. Operators should plan for logistic contingencies, especially for aircraft on short notice operations.

6. Time-bound full replacement. Replacing all affected servo-controls must occur within the earlier of 50 flight hours or four months after the effective date (Requirement 2c; Compliance 2c). Operators that push compliance to the limit may face resource and scheduling pressure, especially if replacement parts are scarce.

7. Installation prohibition and manufacturer conformity requirement. The AD forbids installation of listed P/N/S/N units unless they are “previously returned to conformity by the equipment manufacturer as indicated in paragraph 2. of EUROCOPTER ASB No. 01.00.53 Revision 1 or later NAA approved revision” (Requirement 3). Operators cannot lawfully install units that have been repaired by third parties unless the manufacturer has performed and certified the return to conformity according to the ASB. This restricts the market for used or third-party refurbished parts.

8. Technical instructions are external to the AD. The AD references paragraph 2.B. of the EUROCOPTER ASB for replacement instructions and paragraph 1.E.2. for verification procedures. The AD does not reproduce those steps. Operators must obtain and follow the ASB and confirm any later NAA approved revisions. Failure to consult the ASB can lead to incomplete or incorrect remediation.

9. Cross-jurisdictional references. The AD notes EASA Emergency AD 2007-0141-E, implying related actions in other jurisdictions. Operators that operate internationally must ensure compliance both with this AD and with any foreign directives applicable to their operations. Differences in wording or timing between ADs in other jurisdictions can create complexity.

10. Documentation and evidentiary burdens. Because the AD allows records-based verification and delegates technical remediation evidence to ASB processes and manufacturer conformity statements, operators must maintain clear contemporaneous records showing identification, checks, detection events, replacements, and any manufacturer return-to-conformity certificates. Failure to retain or produce this documentation can raise enforcement exposure.

In short, the AD’s specificity, reliance on records, contingency on the ASB and manufacturer remediation, and firm timing requirements create a set of potential operational pitfalls for aircraft operators, maintenance organisations and parts suppliers.

The AD sets out a clear sequence of compliance actions tied to timing. Below is a stepwise compliance checklist that follows the AD’s text and references, with notes on documentary practice and dependence on the EUROCOPTER ASB.

Step 1 , Determine applicability without delay

• Identify all EUROCOPTER AS 355 E, F, F1, F2 and N helicopters in your fleet that may be fitted with Goodrich main or tail rotor servo-controls. The AD applies only to servo-controls “with no letter ‘C’ marked in the inspection box of the servo-control identification plate” and then only to the listed P/N and S/N combinations (Applicability).
• Verify each servo-control’s P/N and S/N in accordance with paragraph 1.E.2. of EUROCOPTER ASB No. 01.00.53 Revision 1 or later NAA approved revision. If a physical inspection is impractical, a records-based review (rotorcraft logbooks, component lists, maintenance records) is acceptable provided each P/N and S/N can be positively determined (Requirement 1). Maintain copies of the records used to demonstrate this step.

Step 2 , If any listed servo-control is present, begin increased pre-flight scrutiny

• For any helicopter with an affected servo-control identified, require that the pre-flight hydraulic check (Rotorcraft Flight Manual section 4) be performed during each pre-flight test until the full replacement obligation is met (Requirement 2a; Compliance 2a).
• Document each pre-flight test and its findings in the aircraft’s maintenance log and the flight release documentation. Note explicitly that the pre-flight hydraulic check was performed pursuant to AD/AS 355/96.

Step 3 , Act immediately on detection of a hard point

• If a pre-flight hydraulic check reveals any “hard point” in the flight controls, do not permit further flight. The AD mandates replacement of the defective servo-control(s) before further flight as instructed in paragraph 2.B. of EUROCOPTER ASB No. 01.00.53 Revision 1 (Requirement 2b; Compliance 2b).
• Arrange for replacement per paragraph 2.B. of the ASB. Ensure the replacement is performed by appropriately authorised maintenance personnel and that the replacement action is recorded in the maintenance records, including reference to the ASB paragraph relied upon.

Step 4 , Replace all affected servo-controls within the specified window

• Replace all servo-controls identified in the AD’s applicability within the earlier of 50 flight hours or 4 months from the AD’s effective date (Requirement 2c; Compliance 2c). If parts are scarce, prioritise scheduling replacement while continuing mandatory pre-flight checks until replacements are completed.
• Ensure that replacements are performed “as instructed in paragraph 2.B. of EUROCOPTER ASB No. 01.00.53 Revision 1 or later NAA approved revision.” Keep records that demonstrate conformance to the ASB instructions.

Step 5 , Ensure any re-installation is backed by manufacturer conformity

• Do not install servo-controls with any P/N/S/N listed in the applicability unless they have been “previously returned to conformity by the equipment manufacturer as indicated in paragraph 2. of EUROCOPTER ASB No. 01.00.53 Revision 1 or later NAA approved revision” (Requirement 3). If presented with a candidate replacement part that matches listed P/N/S/N, obtain and retain manufacturer documentation proving the return-to-conformity and its conformity with the ASB paragraph referenced by the AD.

Step 6 , Recordkeeping and documentary evidence

• Keep clear records demonstrating verification of P/N and S/N (inspection or records-based review), pre-flight hydraulic checks, any detection of hard points and resulting grounding actions, replacement work orders and parts traceability, and manufacturer return-to-conformity certificates where used. The AD’s reliance on records for identification and on ASB instructions for remediation makes documentary evidence the primary proof of compliance.
• Where a records-based verification was used instead of physical inspection, ensure the records are contemporaneous, legible, and collectively provide “positive determination” of each P/N and S/N, as required by the AD.

Step 7 , Coordinate with manufacturer and monitor ASB revisions

• Obtain and retain EUROCOPTER ASB No. 01.00.53 Revision 1 and monitor for later NAA approved revisions. The AD explicitly allows use of later NAA approved ASB revisions, which may contain updated instructions for replacement and for return-to-conformity processes.
• Contact the equipment manufacturer (Goodrich or the authorised service centre specified by EUROCOPTER) to coordinate return-to-conformity actions for affected servo-controls and to obtain the necessary conformity documentation in line with paragraph 2 of the ASB.

Step 8 , Plan operations and logistics

• Prepare contingency plans for aircraft that may be grounded upon detection of a hard point. Evaluate spare parts inventory, cannibalisation options only if parts have been properly returned to conformity by the manufacturer, and maintenance scheduling to meet the 50 flight hour/4 month deadline.
• Inform flight crew and dispatch of the requirement to perform pre-flight hydraulic checks in accordance with Rotorcraft Flight Manual section 4 and the AD, and ensure they understand that detection of a hard point requires immediate grounding.

Step 9 , Cross-jurisdictional coordination for international operations

• Note the AD’s reference to EASA Emergency AD 2007-0141-E dated 21 May 2007. If the aircraft operate internationally, verify whether corresponding directives apply in other jurisdictions and ensure any actions taken meet all applicable directives.

Step 10 , Seek clarification or relief if necessary

• The AD text does not include a mechanism for exemptions, alternative means of compliance, or an appeal process. Where practical impossibility, supply constraints, or ambiguous applicability arise, operators should engage with the issuing authority, the Civil Aviation Safety Authority delegate or the relevant NAA to seek guidance, relief or approval of an alternative means of compliance in accordance with the regulatory processes outside the AD text.

In all steps, refer to the AD text for precise wording and to the EUROCOPTER ASB for technical instructions and the manufacturer’s definition of “returned to conformity.” Keep records that explicitly cross-reference the AD, ASB paragraph numbers and the dates of action to create an auditable compliance trail.