AD/CA21/1 - Air Filter Box Rear Mounting Bracket

The central concept in this instrument is the Airworthiness Directive itself, a regulatory mechanism under Civil Aviation Regulations 1998 Part 39-105 that mandates specific corrective actions on designated aircraft types to maintain airworthiness. The directive distinguishes between pop rivets, which are susceptible to loosening, and solid rivets of the MS20470AD4-4 and MS20470AD5-4 specifications, which provide a more secure fastening method.

Another key concept is the Maintenance Release, referenced in the compliance requirement for the second action. This document certifies that the aircraft is airworthy for a defined period and must reflect completion of the required work. Time in service (TIS) is used as an alternative compliance trigger measured in hours of aircraft operation, providing a usage-based deadline independent of calendar inspections.

The instrument also incorporates reference to an external service bulletin, Skyfox Aviation Service Bulletin 9 Issue 2, as a source of supplementary instructions. This creates a layered compliance obligation where the directive sets the mandatory outcome while the bulletin supplies the detailed method. Applicability is narrowly drawn to CA 22A aircraft within the broader CA21 and CA22A series, requiring precise identification of the individual airframe before any action is taken.

The background statement introduces the safety rationale of preventing foreign object ingestion into the engine, linking the mechanical defect directly to potential loss of propulsion. These concepts operate together to create a prescriptive maintenance regime that overrides normal operator discretion on timing and method of repair.

This directive directly affects owners and operators of CA 22A aircraft. Any person or entity holding legal title to or operational control of such an aircraft must ensure the required inspection and replacement actions are performed within the stated time frames. Maintenance organisations and licensed aircraft maintenance engineers who perform work on these aircraft are also affected, as they must carry out the visual inspection, rivet replacement and air filter box removal in accordance with the directive and the referenced service bulletin.

Pilots in command of CA 22A aircraft bear responsibility for confirming that the aircraft has complied with Requirement 1 before flight after 4 January 1996. The directive therefore influences pre-flight checks and operational decision-making. Organisations holding Air Operator Certificates that include CA 22A aircraft in their fleet must incorporate the directive into their maintenance control manuals and ensure that continuing airworthiness records demonstrate compliance.

Because the instrument forms part of the safety regulatory framework, it indirectly affects insurers, financiers and lessors who rely on the aircraft maintaining valid airworthiness status. The narrow applicability to CA 22A aircraft means that operators of other variants in the CA21 and CA22A series are not subject to these specific requirements, although they may need to verify model designation carefully to avoid misapplication.

The directive creates a clear duty on the owner or operator of a CA 22A aircraft to perform the visual inspection of the rivets securing the air filter box rear mounting bracket before the next flight after 4 January 1996. Where defects are identified, there is a further duty to replace the affected rivets with MS20470AD4-4 solid rivets. Separately, there is a duty to remove the air filter box and replace all pop rivets with MS20470AD4-4 or MS20470AD5-4 solid rivets at the next Maintenance Release inspection or within 100 hours time in service, whichever occurs first.

These duties must be discharged by authorised personnel and recorded in the aircraft's maintenance documentation. The directive does not confer express rights on operators, but it implicitly preserves the right to operate the aircraft once the required actions are completed and certified. Compliance with the directive is a precondition for the aircraft remaining in a state where a Maintenance Release can be issued.

The reference to Skyfox Aviation Service Bulletin 9 Issue 2 creates an ancillary duty to consult that document for procedural details, although the directive itself sets the minimum mandatory standard. Failure to meet the compliance deadlines renders the aircraft non-compliant with the airworthiness requirements embedded in the Civil Aviation Regulations 1998.

The source text of the directive does not set out specific penalties. However, the instrument operates within the regulatory structure established by the Civil Aviation Act 1988, section 98, which authorises regulations prescribing matters necessary or convenient for carrying out or giving effect to the Act, including safety of air navigation. Non-compliance with an Airworthiness Directive issued under Part 39-105 of the Civil Aviation Regulations 1998 can result in the aircraft being treated as unairworthy.

Enforcement may occur through CASA action under provisions relating to Air Operator Certificates, such as the power in section 27AC of the Civil Aviation Act 1988 to require information and inspections to ensure compliance with safety requirements. Where an aircraft is operated without completing the mandated actions, the operator risks suspension or cancellation of certificates and potential prosecution for breaches of the regulations. The background statement concerning rivet ingestion into the engine underscores the safety basis for enforcement, as continued operation with defective rivets could constitute a breach of the general duty to maintain airworthiness.

In the context of international operations, section 16 of the Air Navigation Act 1920 imposes a condition on licences, permissions or approvals that the owner, operator, hirer, pilot in command and other pilots must comply with all applicable Commonwealth, State or Territory laws. This includes the requirements of this directive, so non-compliance could also affect international flight permissions.

This directive interacts with the Civil Aviation Act 1988, particularly section 98, which empowers the making of regulations for safety of air navigation, including those relating to air navigation within a Territory or to or from a Territory, and regulations with respect to trade and commerce. The directive itself is an exercise of that power through Part 39-105 of the Civil Aviation Regulations 1998.

It also connects to section 27AC of the Civil Aviation Act 1988, under which CASA may require information or documents from an applicant for an Air Operator Certificate to ensure compliance with safety obligations, including personal injury liability insurance requirements for operations covered by the certificate. Completion of the actions required by the directive forms part of demonstrating that the aircraft meets the safety standards necessary for certificate issue or continuation.

Section 16 of the Air Navigation Act 1920 further links the directive to international operations. It provides that it is a condition of any licence, permission or approval that, for aircraft arriving from or departing to places outside Australian territory, the owner, operator, hirer, pilot in command and other pilots must comply with all applicable laws of the Commonwealth or of a State or Territory. The directive constitutes such an applicable law, meaning that CA 22A aircraft engaged in international flights must have completed the required rivet inspection and replacement to satisfy this condition.

The directive does not override or amend these provisions but operates as a specific application of the safety regulation powers they contain. Compliance with the directive is therefore necessary to satisfy the broader obligations imposed by the Civil Aviation Act 1988 and the Air Navigation Act 1920.

The source text of the directive records its issue date as 1/96, with compliance tied to 4 January 1996. No amendments or revisions are noted in the provided instrument. The directive therefore remains in the form originally promulgated, requiring the inspection and solid rivet replacement actions as set out.

The absence of recorded changes means that operators must continue to treat the original compliance times and rivet specifications as current. Any subsequent directive that cancels or supersedes AD/CA21/1 would need to be checked separately, but the source text itself contains no indication of later modification. The original promulgation was driven by the identified risk of pop rivet loosening and engine ingestion, and the lack of amendment suggests that the safety concern has not been resolved through design changes or alternative means of compliance within the instrument's own terms.

The source text of the directive does not reference any court challenges, litigation or controversies arising from its requirements. No judicial decisions or disputes are recorded in the instrument. The directive presents a straightforward technical requirement based on the background statement concerning rivet security and the risk of ingestion into the engine.

In the absence of any indicated controversy within the source material, the instrument stands as an uncontested regulatory measure. Practitioners should nevertheless be aware that disputes could arise in practice over the precise identification of CA 22A aircraft, the interpretation of "loose, broken or missing" rivets during visual inspection, or the adequacy of documentation when relying on the referenced service bulletin. Such matters would be resolved through administrative processes with CASA rather than through the court challenges noted in the source text, which records none.

Several practical considerations arise from the precise wording of the directive. First, applicability is limited to CA 22A aircraft; operators must verify the exact model designation before assuming the requirements apply, as the broader CA21 and CA22A series is mentioned only in the title. Second, Requirement 1 creates an immediate pre-flight obligation after 4 January 1996, meaning that any aircraft not inspected by that point cannot legally fly until the visual check and any conditional replacement are completed.

Third, the two requirements are cumulative rather than alternative. Even if no defects are found during the initial inspection, Requirement 2 still mandates removal of the air filter box and replacement of all pop rivets at the next Maintenance Release inspection or within 100 hours time in service. Fourth, the rivet specifications are exact: MS20470AD4-4 for conditional replacements under Requirement 1, and either MS20470AD4-4 or MS20470AD5-4 for the full replacement under Requirement 2. Use of incorrect rivets would constitute non-compliance.

Fifth, the reference to Skyfox Aviation Service Bulletin 9 Issue 2 means that the bulletin forms part of the compliance pathway, and failure to follow its procedures could expose the maintainer to regulatory risk even if the broad outcome of fitting solid rivets is achieved. Finally, all work must be recorded in a manner that supports the issue of a Maintenance Release; incomplete or ambiguous entries could prevent lawful operation regardless of the physical work having been performed.

To achieve compliance, the first step is to confirm that the aircraft is a CA 22A model within the Skyfox Aviation (Calair/Hedaro) CA21 and CA22A Series Aeroplanes. Once confirmed, arrange for a visual inspection of the rivets securing the air filter box rear mounting bracket to be conducted before the next flight after 4 January 1996. This inspection must be performed by an appropriately authorised person.

If any rivets are found to be loose, broken or missing during the inspection, replace them immediately with MS20470AD4-4 solid rivets. Regardless of the inspection outcome, proceed to Requirement 2 by removing the air filter box at the next scheduled inspection for issue of a Maintenance Release or within 100 hours time in service, whichever occurs first. At that time, replace the pop rivets securing the rear mounting bracket with MS20470AD4-4 or MS20470AD5-4 solid rivets.

Throughout the process, consult Skyfox Aviation Service Bulletin 9 Issue 2 for detailed removal, inspection and installation procedures, including any diagrams or torque specifications that may be required. All work must be certified in the aircraft maintenance records, and the Maintenance Release must be updated to reflect completion of both requirements. Operators should retain copies of the work order, rivet part numbers used and any associated documentation to demonstrate compliance during audits or inspections by CASA.

For organisations holding Air Operator Certificates, the actions should be incorporated into the approved maintenance program and any continuing airworthiness management procedures. Where the aircraft is used on international flights, confirmation of compliance should also be available to satisfy the conditions imposed by section 16 of the Air Navigation Act 1920. Regular review of the aircraft's status against the directive's requirements will prevent inadvertent operation outside the compliance windows.