AD/AS 355/95 - Fuselage Centre Cross-Member under Cabin Floor

The AD concentrates on a narrow structural-failure risk and prescribes three interlocking concepts: applicability, inspection with interim operational limits, and mandatory modification. The applicability rule is precise: Model AS355 E, F, F1, F2 and N helicopters, all serial numbers, delivered before 1 January 2007, and equipped with collective-to-yaw control coupling, with or without an Automatic Flight Control System (AFCS). This limits the population to airframes delivered before the 2007 cut-off and to those having the specified coupling; airframes delivered on or after 1 January 2007, or without the coupling, are excluded by the AD’s own applicability statement.

The inspection-and-modify sequence is the AD’s core control logic. First, operators must confirm whether the mitigating structure (cross-member and doublers) already exists; if it does, the AD imposes no further obligations. If the structure is absent, a non‑destructive inspection (visual or dye-penetrant) of a specific area (centre cross-member at station X 2325, around the attachment point of the tail rotor directional ball-type control sheath stop) is required. That inspection is both a safety check and an interim risk-control measure. If the inspection finds no crack, the operator must perform a tail rotor control rigging check before further flight and commence a recurring inspection regime (repeat Requirement 2 at intervals not exceeding 55 flight hours) until the permanent modification is fitted. If a crack is found, the AD states “Flight is prohibited,” making detection an immediate operational constraint.

The permanent remedy is installation of the cross-member and doublers (stations X 2165, X 2325, Y 269) according to the Appendix of ASB 53.00.23 (original issue or later EASA-approved revision). The AD defers details of the modification and inspection techniques to the manufacturer’s alert service bulletin text and any subsequent EASA-approved revisions of that ASB. The AD also references an EASA Emergency AD (2007-0139-E) as relevant material.

Finally, timing and sequencing are explicit: short-term inspections within 10 flight hours or 1 month, recurring inspections every ≤55 flight hours until modification, and full installation within 12 months. The AD therefore uses a three-tiered control regime: immediate verification, interim inspection plus operational check, and a mandated retrofit within a longer window.

The AD applies only to a subset of the Eurocopter AS 355 fleet. Specifically it names Model AS355 E, F, F1, F2 and N helicopters, all serial numbers, provided they were delivered before 1 January 2007 and are equipped with collective-to-yaw control coupling, with or without an Automatic Flight Control System. The key points for affected parties are:

• Operators/owners of AS355 E/F/F1/F2/N helicopters delivered before 1 January 2007, if those helicopters have the collective-to-yaw control coupling. The AD does not apply to frames delivered on or after 1 January 2007 according to the applicability statement.
• Maintenance organisations and engineers who perform inspections, rigging checks, non-destructive testing (visual or dye-penetrant inspections), and the structural installation work required by the Appendix of ASB 53.00.23.
• Pilots and flight operations managers: the AD requires a tail rotor control rigging check before further flight when an inspection shows no crack but the modification is not yet fitted; where a crack is detected, the AD explicitly prohibits flight.
• Registrars and airworthiness authorities at operator level: the AD becomes effective on 18 May 2007 and must be recorded and complied with insofar as the operator’s helicopters meet the applicability criteria.
• Parts suppliers and the manufacturer: they are implicated because the AD requires installation of specific structural doublers and a cross-member as per the ASB Appendix.

The AD excludes helicopters not meeting the delivery date cut-off or not equipped with the collective-to-yaw control coupling. The background notes that the cracking was reported on a Model AS355 N helicopter fitted with the coupling, and that the cracked helicopter lacked the structure doublers which are “combined with the collective-to-yaw control coupling installation.” Thus the presence of the coupling is a gating criterion: only helicopters with that installation risk the particular failure mode described in the AD.

Who pays: the document itself does not state cost-shifting arrangements. Practically, the operator or owner who is responsible for maintaining airworthiness will bear the direct cost of inspections, rigging checks, recurring inspections, and the eventual installation of the cross-member and doublers, plus any downtime imposed by inspections, rigging checks or grounding if a crack is found. The AD does not set compensatory mechanisms or provide parts or labour; it instead references the manufacturer’s ASB for technical instructions.

The AD creates clear duties for applicable operators and maintenance personnel. Those duties, drawn directly from the AD text, are:

• Duty to determine applicability and confirm installation (Requirement 1): Operators must confirm whether the cross-member at station X 2165 and doublers at stations X 2325 and Y 269 are installed, using the Accomplishment Instructions of Eurocopter ASB 53.00.23 or a later EASA-approved revision. If those parts are installed, the AD places no further obligation on the helicopter.
• Duty to inspect when parts are absent (Requirement 2): If the cross-member and/or doublers are not installed, operators must inspect for cracks at the specified location (centre cross-member at X 2325, around the attachment point of the tail rotor directional ball-type control sheath stop) by visual or dye-penetrant methods as detailed in ASB 53.00.23. If no crack is detected, the operator must check tail rotor control rigging before further flight and repeat the crack inspection at intervals not exceeding 55 flight hours until Requirement 3 is done.
• Duty to ground if crack detected: If any crack is detected during inspection, the AD states explicitly that flight is prohibited. That is a direct operational duty: aircraft with a detected crack cannot be flown until the condition is rectified, per the AD.
• Duty to modify (Requirement 3): Within 12 months after 18 May 2007, operators whose helicopters lack the cross-member and doublers must install them as per the Appendix paragraph of ASB 53.00.23 original issue, or a later EASA-approved revision.

Rights, as implied by the AD text:

• Right to rely on the ASB text: The AD explicitly permits use of ASB 53.00.23 original issue or a later EASA-approved revision for accomplishment instructions and installation details. That gives operators a compliance document to follow.
• Right to avoid further obligations if parts already fitted: If the cross-member and doublers are already installed at the specified stations, the AD states “no further action is required.” That is a direct relief of burden for compliant airframes.

Timing duties are specific: Requirements 1 and 2 must be complied with within 10 flight hours or 1 month after the AD’s effective date (18 May 2007), whichever occurs first. Requirement 2 inspections are to be repeated at intervals not to exceed 55 flight hours until Requirement 3 is accomplished. Requirement 3 must be completed within 12 months after 18 May 2007.

The AD delegates technical details to the manufacturer’s ASB and to any later EASA-approved revision. The AD does not provide alternative methods of compliance (AMOC) text within the document itself; it instructs compliance with the ASB or later EASA-approved revisions.

The AD text declares the directive to be effective from 18 May 2007 and specifies operational prohibitions in certain conditions, but it does not include a penalty schedule or explicit enforcement procedures in the body of the document. The only operational enforcement measure stated on the face of the AD is the immediate prohibition on flight if a crack is detected during the required inspection (Requirement 2: “If any crack is detected: Flight is prohibited”). The AD is issued by the Civil Aviation Safety Authority (CASA) delegate (David Punshon), which signals its regulatory force as an airworthiness directive, but the document itself does not set out sanctions, administrative penalties, or criminal offences for non-compliance.

From the document’s structure and wording the enforcement implications that can be drawn directly from the source are limited to the following, source-grounded points:

• Mandatory status and effective date: The directive “becomes effective on 18 May 2007.” An AD’s effective date is the point from which the stated compliance timelines run: Requirements 1 and 2 within 10 flight hours or 1 month after that effective date; Requirement 3 within 12 months after that date.
• Operational prohibition where crack is found: The AD mandates grounding in the event of crack detection by stating “Flight is prohibited” in Requirement 2. That is a direct operational restriction contained in the directive.
• Delegation: The document bears the signature of the CASA delegate, indicating the issuing authority within the Civil Aviation Safety Authority.

The AD does not itself describe CASA enforcement processes, certificate actions, or penalties for failing to comply with an AD, nor does it specify administrative review or appeal mechanisms. The AD also does not specify who is responsible for verifying compliance records or certifying accomplishment, though it expects compliance with the ASB’s Accomplishment Instructions and Appendix. Any enforcement action, sanctions or regulatory follow-up beyond the AD’s text would be a matter of applicable aviation regulatory enforcement practice, which the AD does not enumerate.

Operators should therefore treat the AD’s prohibitions and compliance windows as mandatory and record their compliance steps according to the Accomplishment Instructions and the ASB referenced, because the AD establishes binding technical requirements and immediate operational limitations (grounding) where cracking is found.

The AD references and integrates two distinct sources of technical and regulatory authority: the Eurocopter Alert Service Bulletin (ASB 53.00.23 original issue, or later EASA-approved revision) and an EASA Emergency AD (2007-0139-E). Those cross-references define the AD’s interaction with other regulatory or technical instruments in the following ways:

• Deference to manufacturer ASB and EASA approvals: The AD requires that inspections and installations be carried out “as detailed in the Accomplishment Instructions paragraph of Eurocopter ASB 53.00.23 original issue, or later EASA approved revision,” and that the installation be performed “in accordance with the Appendix paragraph of ASB 53.00.23 original issue, or later EASA approved revision.” Practically, the AD therefore operates by mandating compliance with the manufacturer’s service bulletin as approved by the European aviation authority (EASA). The ASB is the technical execution document; the AD is the regulatory compulsion to follow it.
• Reference to EASA Emergency AD: The AD notes “Note: EASA Emergency AD 2007-0139-E refers.” That indicates the CASA AD is aligned with or follows an EASA emergency directive addressing the same unsafe condition. The CASA AD does not restate the EASA AD’s content but directs operators to the ASB processes that EASA has approved.
• Applicability cut-off and coupling installation: The AD’s applicability criterion (delivery before 1 January 2007 and equipped with collective-to-yaw control coupling) sets a boundary where other airworthiness requirements or modifications (for example, incorporation of the cross-member and doublers as part of some modification) remove the AD’s applicability. If the structural doublers and cross-member are already installed, the AD says “no further action is required.” This establishes an interaction with prior modifications or earlier supplemental type certificates or manufacturer retrofits that may have already addressed the condition.

The AD does not expressly reference national civil aviation law provisions such as enforcement processes, continuing airworthiness responsibilities, or maintenance records duties. Those legal obligations are not restated in the AD text; rather, the AD imposes a specific technical and operational obligation within the broader airworthiness regime. The AD’s reliance on ASB and EASA approvals situates it within a transnational compliance framework where manufacturer instructions and EASA approvals inform domestic regulatory directives.

Because the AD directs compliance through an existing ASB and acknowledges an EASA Emergency AD, operators are required to follow those documents in performing inspections and modifications; thereby the AD functions as the domestic enforcement mechanism for an unsafe condition identified at the EASA/manufacturer level. Any interplay with other laws, such as certification rules or enforcement procedures, is not described in the AD itself.

The document supplied is self-contained and indicates a single issuance: AD/AS 355/95 dated 16 May 2007 with an effective date of 18 May 2007. Within the AD it invites use of ASB 53.00.23 original issue, or later EASA-approved revisions, for the Accomplishment Instructions and Appendix. The specific amendment-history points that can be drawn from the AD text are:

• Single AD issuance: The AD text appears as a single directive dated 16 May 2007 and noting effectiveness from 18 May 2007. There is no amendment sequence or later CASA revision recorded within the supplied text.
• Delegation and signature: The AD is signed by David Punshon as Delegate of the Civil Aviation Safety Authority, dated 16 May 2007, which is the execution date recorded in the document.
• Deference to future ASB revisions: The AD explicitly allows operators to use ASB 53.00.23 original issue or “later EASA approved revision.” That language leaves open the possibility of future technical updates being incorporated by reference, but it does not itself record any later or prior amendments to the AD.
• Cross-reference to EASA Emergency AD 2007-0139-E: The AD notes that EASA Emergency AD 2007-0139-E refers, which situates the AD alongside an EASA-level emergency directive. The AD text does not list any earlier CASA AD numbers or prior amendments to this particular AD.

The multiple repeated header lines and formatting anomalies in the supplied document (for example repetitions of “AD/AS 355/95” and “Fuselage Centre Cross-Member under Cabin Floor”) appear to be artefacts of the published page design rather than substantive amendments. There is no statement in the supplied AD text that it supersedes or replaces a prior CASA AD on the same topic.

Because the AD permits the use of later EASA-approved revisions of ASB 53.00.23 for accomplishment instructions and installation, any future amendments to the ASB that receive EASA approval would be acceptable methods to comply with the AD’s inspection and modification requirements. However, the supplied AD text itself contains no subsequent amendment history or re-issuances beyond the 16 May 2007 issue and 18 May 2007 effective date.

The supplied document does not record any litigation history. The AD is an administrative regulatory instrument and includes no references to judicial proceedings, appeals, or contested enforcement actions. The text contains:

• No case citations.
• No references to appeals to courts or tribunals.
• No administrative review statements within the AD text.

Thus, based solely on the supplied AD text, there is no recorded litigation history, no precedent cited, and no publicised challenges or court decisions related to this AD. The AD does reference EASA Emergency AD 2007-0139-E and Eurocopter ASB 53.00.23 (original issue or later EASA-approved revision) as technical and regulatory materials, but it does not reference any adjudicative outcomes or legal disputes. Any litigation or administrative review that may have occurred is not included in the supplied document.

The AD contains specific technical and timing traps that operators and maintenance organisations must note precisely to avoid non-compliance. These are concrete, source-based “gotchas” drawn from the text:

• Applicability is delivery-date dependent. The AD applies only to helicopters delivered before 1 January 2007. A frame delivered 2 January 2007 is outside the AD’s applicability even if it otherwise matches the model and coupling criteria. Operators must verify delivery date records to determine applicability.
• Applicability requires the collective-to-yaw control coupling. The AD applies only to helicopters “equipped with collective-to-yaw control coupling with or without an Automatic Flight Control System.” Helicopters without that coupling, even if delivered before 1 January 2007, are not covered by this AD.
• The “no further action” relief is narrow. If the cross-member at station X 2165 and doublers at X 2325 and Y 269 are installed, the AD says “no further action is required.” That relief depends on verification in accordance with ASB 53.00.23 Accomplishment Instructions; mere belief or informal inspection may be insufficient for compliance records.
• Inspection method restrictions. Requirement 2 specifies the inspection method as “visual or a dye penetrant inspection” at the centre cross-member at station X 2325 around the attachment point of the tail rotor directional ball-type control sheath stop. If operators use other NDT methods, the AD text does not authorise them; compliance should follow the ASB’s instructions or a later EASA-approved revision.
• Immediate grounding on crack detection. The AD is explicit: “If any crack is detected: Flight is prohibited.” That is an immediate operational consequence that may strand passengers, cargo or create commercial disruption.
• Interim operational duty to rig the control before flight. When an inspection reveals no crack but the modification has not yet been installed, the AD requires the operator to “check the tail rotor control rigging in accordance with the Accomplishment Instructions paragraph of ASB 53.00.23 … Before further flight.” That is an operational step that must be documented and performed before resuming flight after the inspection.
• Recurrent inspection burden until modification. Requirement 2 inspections must be repeated “until Requirement 3 is accomplished” and at intervals “not to exceed 55 flight hours.” This creates a continuing maintenance burden and scheduling consideration for operators who have not yet completed the installation.
• Time windows. Requirements 1 and 2 have a short compliance window: within 10 flight hours or 1 month after 18 May 2007, whichever occurs first. Requirement 3 has a longer but finite window: within 12 months after 18 May 2007. Operators who do not plan installations promptly will be subject to recurring inspections in the interim.
• Reliance on ASB and EASA-approved revision language. The AD repeatedly defers specifics to ASB 53.00.23 original issue or later EASA-approved revisions. Operators must ensure they are working from the ASB revision that is EASA-approved; an unapproved revision or an ASB with different wording might not satisfy the AD’s requirements.
• Location specificity. The AD lists precise structural stations X 2165, X 2325 and Y 269. Misidentifying stations or misstating the location of inspection/installation could render an operator’s actions non-compliant.
• Cross-reference to an EASA Emergency AD. The AD notes “EASA Emergency AD 2007-0139-E refers.” Operators should review that EASA AD and the ASB to confirm there are no additional instructions or variations in methodology required by EASA that complement the CASA AD.
• Documentation expectations (implicit). While the AD does not spell out recordkeeping requirements, the nature of AD compliance implies the need to retain proof of inspections, rigging checks, and installation per the ASB. Operators should ensure their maintenance records clearly reference the ASB paragraphs used to satisfy the AD.

Each of these items is grounded in the AD text. Missing any one of them risks non-compliance , either by failing to apply the AD when it applies, by using the wrong inspection method or ASB revision, by flying a cracked aircraft, or by failing to meet the AD’s strict timing and recurrence rules.

The AD sets a specific, stepwise compliance pathway. To comply consistently with the AD text, operators and maintainers should follow the steps below, using the Eurocopter ASB 53.00.23 original issue or a later EASA-approved revision for technical instructions and record references, and observing the AD’s timing requirements measured from 18 May 2007:

1. Confirm applicability:

   • Check the helicopter model (AS355 E, F, F1, F2 or N) and delivery date (the AD applies to helicopters delivered before 1 January 2007).
   • Confirm whether the helicopter is equipped with collective-to-yaw control coupling (with or without AFCS). If the helicopter lacks that coupling or was delivered on or after 1 January 2007, the AD does not apply.

2. Requirement 1 , verify presence of parts:

   • Within 10 flight hours or 1 month after 18 May 2007 (whichever occurs first), confirm whether the cross-member at station X 2165 and doublers at stations X 2325 and Y 269 are installed, in accordance with the Accomplishment Instructions paragraph of ASB 53.00.23 (original issue or later EASA-approved revision).
   • If the cross-member and doublers are present and installed as per the ASB instructions, document the verification in the aircraft’s maintenance records and no further action is required under the AD.

3. Requirement 2 , inspect if parts are absent:

   • If the cross-member and/or doublers are not installed, perform the specified inspection without delay. The inspection method specified by the AD is a visual inspection or a dye penetrant inspection of the centre cross-member at station X 2325, focusing on the area around the attachment point of the tail rotor directional ball-type control sheath stop, as detailed in the ASB.
   • If the inspection finds no cracking:
     • Before further flight, perform a tail rotor control rigging check in accordance with the ASB’s Accomplishment Instructions paragraph.
     • Commence a recurring inspection regime: repeat the Requirement 2 inspection at intervals not to exceed 55 flight hours until the modification (Requirement 3) is carried out.
     • Record the inspection, rigging check and next inspection due date/flight-hour counter in the maintenance log, citing ASB 53.00.23 as the source.
   • If the inspection finds any cracking:
     • Do not fly the helicopter. The AD explicitly states “Flight is prohibited” when a crack is detected. Take the helicopter out of service and make arrangements to effect repair or modification per Requirement 3, following the ASB Appendix instructions and any instructions from the manufacturer or EASA-approved revisions.

4. Requirement 3 , install the modification:

   • Within 12 months after 18 May 2007, install the cross-member at station X 2165 and the doublers at stations X 2325 and Y 269 in accordance with the Appendix paragraph of ASB 53.00.23 (original issue or later EASA-approved revision).
   • Use the ASB-approved procedures for any necessary part procurement, structural work, fasteners, torque values, and post-installation rigging and checks as specified in the Appendix.
   • After installation, ensure any post‑installation inspections or tests required by the ASB are completed and documented.

5. Documentation and recordkeeping:

   • Record Requirement 1 verification, Requirement 2 inspections and rigging checks, any findings of cracking and resultant grounding, and the completion of Requirement 3 installation in the maintenance records, referencing ASB 53.00.23 and the AD number (AD/AS 355/95).
   • Maintain records of the EASA-approved ASB revision used to accomplish inspections and installations, and retain evidence that the ASB revision was EASA-approved at the time of use, as the AD permits use of the original ASB or later EASA-approved revisions.

6. Coordinate with relevant authorities and resources:

   • Consult the ASB 53.00.23 original issue and any later EASA-approved revisions for detailed procedures and tool/part lists. The AD defers technical specifics to those ASB paragraphs.
   • Consider reviewing EASA Emergency AD 2007-0139-E (not fully reproduced in this AD) for any EASA-level requirements that refer to the same unsafe condition.

7. Operational planning:

   • Arrange scheduling to accommodate the short initial compliance window (10 flight hours or 1 month after 18 May 2007) and the potential for recurrent inspections every 55 flight hours if installation cannot be completed immediately.
   • Prepare contingency plans for grounding and parts procurement in the event a crack is found to avoid prolonged downtime and to ensure safe handling of the aircraft while out of service.

Following these steps will meet the AD’s explicit instructions. The AD’s technical execution language requires strict adherence to ASB 53.00.23 original issue or a later EASA-approved revision for both inspection detail and the installation Appendix; any deviation should be considered only if accompanied by an alternative method of compliance that is EASA-approved and acceptable to the national regulator. The AD itself contains no alternative method of compliance text; it relies on the ASB and EASA-approved revisions to provide the validated technical path.