Civil Aviation Order 108.29 Instrument 2007

The core regulatory concepts in the Order are specification, measurement, minimums, permitted imperfections, testing, and traceability.

Specification: The instrument operates as a technical specification for material selection , it applies to “timber for use in the manufacture of laminated wooden propellers” (Schedule 1, para 1). It identifies acceptable species in Appendix I and sets numerical thresholds for physical properties (density, moisture content, Izod impact energy).

Measurement and minimums: The Order converts physical attributes into measured thresholds. Moisture content must be between 10% and 15% measured at three points per plank with intra-plank variance limits and inter-plank average limits (para 5). Density minima are specified species-by-species in Appendix I and are conditional on moisture content being within the prescribed band (para 6). Brittleness is measured by Izod impact test with a minimum of 6.5 joules for the standard specimen (para 7 and Appendix II D).

Permitted imperfections: The Order lists a wide set of defects that must be absent (para 3.3) but carves out narrowly defined allowances (pin-knots, pin-holes, and small isolated imperfections) with quantitative limits (para 3.3(a)-(c)) and a slope-of-grain tolerance not exceeding 1 in 12 (para 3.2). The specification makes an explicit trade-off between absolute absence of defects and limited, quantified imperfections.

Testing and alternative methods: The Order prescribes test methods and allows specific alternative methods outlined in Appendix II. Para 5 prescribes an electrical resistance moisture meter or “other approved method”; Appendix II supplies an oven-drying alternative for moisture, a density calculation method, and a simple field method for grain slope. The Izod test method is described in Appendix II D, including specimen geometry and orientation of impact relative to growth rings.

Traceability and marking: Each accepted plank must be ink-stamped with the standard timber name and the CAO number (para 8), creating a basic traceability/identification requirement for materials entering propeller manufacture.

Administrative discretion and approvals: The Director may approve additional timber types (para 2) and may approve the propeller manufacturer to perform Izod testing (para 7 note), creating a route for case-by-case regulatory adjustments and for regulated entities to internalise some testing functions subject to approval.

Direct regulated parties: The instrument directly binds persons and entities involved in the manufacture of laminated wooden aircraft propellers because it prescribes the requirements “to be observed in the selection of timber for use in the manufacture of laminated wooden propellers” (Schedule 1, para 1). That includes propeller manufacturers, timber suppliers who provide planks prepped for propeller manufacture, and any workshop that assembles laminated propellers from planks.

Downstream parties: Aircraft owners and operators using laminated wooden propellers are indirectly affected because their propeller procurement and maintenance will need to ensure that timber, and any repairs that involve replacement lamina, meet the CAO’s measurement and marking requirements. Inspectors and maintenance organisations that certify propellers will need to confirm compliance with the plank-level requirements (paras 3-8 and Appendices).

Government and regulator: The Director of Aviation Safety and CASA have decision-making roles. The instrument was made by the Director under subregulation 36A(2) of the Civil Aviation Regulations 1988 (preamble), and the Director retains explicit approval powers for additional timber species (para 2) and for allowing in-house Izod testing by manufacturers (para 7 note). These delegation points create administrative workload and discretionary decision-making tasks for the Director and CASA.

Laboratories and third-party testers: The Order’s test prescriptions (electrical resistance moisture meter, oven-drying method in Appendix II B, density determination in Appendix II C, Izod test in Appendix II D) create demand for calibrated equipment or accredited test services. Where a manufacturer does not have capacity or Director approval to run an Izod machine, an external testing laboratory will be needed to provide the required impact testing.

Timber suppliers and foresters: Suppliers who produce planks for propeller lamination must meet identification, origin documentation and physical property requirements (para 3.1 and para 5-6), which can affect harvesting, drying, storage, and inventory practices. For mountain/alpine ash suppliers there is an extra reconditioning requirement after seasoning (para 4), which specifically changes processing steps for those species.

Traceability/system operators: Ink-stamping requirement (para 8) imposes a marking step and an associated record-keeping/quality-control process on suppliers or manufacturers who accept planks as complying with the specification.

Duties established by the instrument are procedural and substantive, expressed at the plank-selection, testing and marking levels.

Duty to use approved species or secure Director approval: Timber for laminated propellers must be an approved type listed in Appendix I unless the Director approves additional types upon satisfactory evidence of suitability (para 2). The duty is therefore to either source from Appendix I or secure the Director’s approval beforehand.

Duty to identify and verify origin: Each plank “must be clearly identified with respect of species and must be of known origin” (para 3.1). That is a duty of provenance and labelling prior to use in manufacture.

Duty to meet physical-quality requirements: Planks must be free from warp, conform to slope-of-grain limits (not exceeding 1 in 12, para 3.2), be free from an extensive list of defects (para 3.3), and only contain specific minor permissible imperfections within quantified limits (para 3.3(a)-(c)). The duty is materially expressed as a pass/fail for those enumerated characteristics.

Duty to season and, for certain species, recondition: Timber must be air- or kiln-dried to a moisture-content band specified in para 5. Mountain and alpine ash require an additional reconditioning step of 6 hours at 100°C under saturated conditions before drying back to the moisture requirement (para 4).

Measurement duties: Moisture content must be measured at three specified points per plank via an electrical resistance moisture meter or other approved method, with numeric intra-plank and inter-plank variance constraints (para 5). Density must be measured when moisture content is within limits and meet minimum species-specific values in Appendix I (para 6). Brittleness must be evaluated by Izod impact tests with the specified minimum (para 7 and Appendix II D). The Order requires adherence to specific measurement procedures or approved alternatives in Appendix II.

Duty to mark compliant planks: Each plank accepted as complying must be ink stamped with the standard timber name and “CAO 108.29” (para 8).

Rights and administrative pathways: Rights are limited and procedural. The Director retains a discretionary right to approve additional timber types (para 2), and to approve manufacturer-performed Izod testing (para 7 note). Parties therefore have the procedural right to apply for approvals and to submit “satisfactory evidence” in support of additional species (para 2), and to seek operational approval for in-house Izod testing (para 7 note).

Record-keeping implication: While the instrument does not prescribe retention periods or a formal documentary record requirement beyond the ink stamp (para 8) and the “known origin” requirement (para 3.1), the specified tests and measurements imply a need to retain measurement data to demonstrate compliance in practice. The Order does not itself set explicit documentary or audit obligations.

The instrument text itself does not specify criminal or civil penalties, nor does it set out a bespoke enforcement regime within its clauses. It is a Civil Aviation Order made under subregulation 36A(2) of the Civil Aviation Regulations 1988 (preamble), and enforcement mechanisms (including sanctions for non‑compliance) will therefore arise from the parent regulations and the broader regulatory framework, rather than from this Order’s text.

What the instrument does prescribe are mandatory technical requirements. Non‑compliance with the CAO’s mandatory specifications would, as a matter of regulatory practice, expose the regulated party to enforcement action under the Civil Aviation Regulations or other applicable statutory provisions, but the instrument does not enumerate specific penalty amounts, infringement notices, or administrative remedies. Because the CAO replaces a prior CAO (clause 3), any enforcement approach will operate against the new text from commencement (clause 2).

Enforcement implications that follow from the instrument’s content include: inspectors or assigned regulatory officers assessing planks and propellers against the fixed numerics and defect lists (paras 3-7); challengeable administrative decisions when the Director exercises approval powers (para 2 and para 7 note); and the potential for regulatory action where timber lacks required marking (para 8), fails moisture/density/Izod thresholds (paras 5-7), or is of an unapproved species. The Order’s specification of measurement points and testing methods gives enforcement authorities precise, repeatable tests to rely on when assessing compliance (para 5 and Appendix II).

Because the instrument itself is silent on penalties, parties should look to the Civil Aviation Regulations 1988 and related enforcement instruments for the applicable contraventions and sanctions. The absence of penalties in the Order means the CAO depends on the enforcement architecture and sanctioning provisions of the parent statute and regulations.

The instrument is a subordinate legislative instrument made under subregulation 36A(2) of the Civil Aviation Regulations 1988 (preamble). That means its legal force and enforcement mechanisms flow from the Regulations; the Order supplies technical mandatory detail within the regulatory regime for civil aviation safety. Mechanically, the CAO operates as a specification that fills out the technical content expected by the Regulations for materials used in propeller manufacture.

There are explicit cross‑links internal to the instrument. It repeals and substitutes the prior Civil Aviation Order 108.29 (clause 3), so it sits in continuity with prior CAO numbering and likely interacts with any other regulatory provisions that reference CAO 108.29 by number. The ink-stamping requirement (para 8) ties CAO compliance to traceability and identification obligations within the broader maintenance and airworthiness ecosystem, which often requires material traceability for parts and assemblies; however, the Order itself does not prescribe how its stamping must be recorded in maintenance logs or aircraft certification documentation.

Administrative interaction arises from the Director’s approval powers. The Director may approve additional timber species on provision of “satisfactory evidence regarding their suitability for use in propellers” (para 2) and may approve a propeller manufacturer to carry out Izod testing (para 7 note). Those approval functions will be exercised under the administrative law framework that governs CASA and the Director, such as procedural fairness and record‑keeping expectations that apply to administrative decisions. The Order does not set administrative procedures or standards of evidence; it only creates the approval pathway.

Laboratory and standardisation interaction: Appendix II prescribes methods that mirror standard test techniques (moisture via oven-drying, density calculation, Izod specimen and orientation). Where industry or national testing standards exist, regulated parties would need to map the Appendix II methods against those standards where testing is conducted by external labs. The instrument, however, specifies its own methods and permits “other approved methods” where indicated (paras 5 and Appendix II), meaning conformity can be demonstrated by adherence to the CAO or by Director-approved alternatives.

Limitations and absence: The CAO does not address certification of finished propellers, continuing airworthiness procedures, record-keeping duration, or explicit interactions with consumer protection, building codes for sawmills, or export controls. Any such interactions must be resolved by reading this CAO alongside the Civil Aviation Regulations and other applicable statutory instruments.

The instrument itself is the amendment event: it repeals and substitutes Civil Aviation Order 108.29 (clause 3) and provides a new Schedule 1 containing the full specification and Appendices. The instrument is dated 19 December 2007 (preamble and signature) and commences the day after registration (clause 2). No other amendments, prior versions, dates of earlier CAO 108.29 text, or incremental amendment notes appear within the instrument text supplied.

Operationally, the instrument creates a single-point replacement: the text instructs that “Civil Aviation Order 108.29 is repealed and a new Civil Aviation Order 108.29 substituted as set out in Schedule 1” (clause 3), meaning this document is self-contained as the new operative CAO. The instrument does not include transitional provisions, savings clauses, or grandfathering mechanisms in relation to planks already in inventory or propellers already certified under the previous CAO. Because no transitional text is included, parties must assume the new specification applies from the instrument’s commencement unless the parent Regulations or CASA guidance supplies transitional arrangements outside the CAO text.

The instrument records the legal basis for its making , subregulation 36A(2) of the Civil Aviation Regulations 1988 , but does not record any prior amendment timeline or consultative history inside the text. Therefore, the amendment history within this source is limited to: instrument made on 19 December 2007, commences day after registration, and substitutes the former CAO with the Schedule 1 technical specification.

The supplied text contains no litigation history, judicial references, or citations to court decisions. The instrument includes only the making authority, signature of the Director of Aviation Safety, commencement clause (clause 2) and the full replacement CAO text in Schedule 1 with Appendix I and Appendix II. There are no cases, appeals, tribunal decisions or judicial interpretations recorded in the document.

As a result, within this source there is no recorded precedent, no recorded legal challenge to the instrument, and no adjudicated construction guidance. Any questions about legal interpretation, enforcement disputes, or judicial review of Director approvals, testing methods, or the instrument’s scope would need to be assessed against decisions external to this document. The instrument itself does not provide that litigation context.

Readers should therefore treat the CAO’s technical provisions as the starting point for compliance and administrative action, while recognising that absence of litigation history in the text leaves open potential interpretative questions (for example, meaning of “known origin” or the scope of “satisfactory evidence” for additional species) that would be resolved only by administrative decision or court process not captured here.

The instrument contains precise numeric thresholds and procedural points that create specific points of potential non‑compliance if overlooked.

Moisture measurement specifics: Moisture content must be measured at three specific points approximately 300 mm from each end and at mid-length (para 5). The three readings must all lie between 10% and 15%; an individual reading must not vary more than 2% within any one plank; and average moisture content must not vary more than 3% between planks (para 5). Failure to take readings at the specified points or to observe the intra- and inter-plank tolerances will render a plank non‑compliant even if the general moisture level appears acceptable.

Izod testing orientation and specimen preparation: The Izod test must be conducted on specimens with the blow applied in the tangential direction to growth rings and with a specific notched specimen geometry as shown in Figure 1 of Appendix II D. Two samples from each plank must be tested from diagonally opposite edges at one end of the plank (Appendix II D). The CAO gives a numerical pass threshold of not less than 6.5 joules (para 7). Incorrect specimen orientation, incorrect notch geometry, or insufficient sample location will generate invalid results.

Mountain/alpine ash special step: Mountain ash and alpine ash require a reconditioning step of 6 hours at 100°C “(saturated conditions)” following seasoning and before final drying to the moisture content requirement (para 4). Misunderstanding this as optional, or omitting the reconditioning before final drying, would breach the specification for those species.

Slope of grain measurement: The permitted slope-of-grain limit is 1 in 12 determined by splitting test or the Appendix II methods (para 3.2). Appendix II A offers simple field checks (splinters, ink drop, swivel-handled scribe) but those methods can be subjective; reliance on a subjective field check without consistent recordable procedure may create disputes about compliance.

Pin-hole and pin-knot numeric limits: The Order allows pin-knots up to 3 mm diameter and pin-holes up to 1.5 mm, but imposes spacing rules (not closer than 50 mm and no more than 3 pin-holes in any 10 000 sq mm) (para 3.3(a)-(b)). These are precise constraints; counting and area calculations are required to verify compliance.

Marking and traceability: Each accepted plank must be ink stamped with the timber standard name and the number “CAO 108.29” (para 8). Lack of appropriate stamping removes the prescribed traceability and can be interpreted as non‑compliance even where the plank otherwise meets physical tests.

Director approval dependencies: The Director’s discretion to approve additional species (para 2) and to approve in-house Izod testing (para 7 note) means parties cannot unilaterally adopt non‑listed species or internal testing until approvals are obtained. Operating with an unapproved species or unapproved in-house test procedure risks later non‑conformity findings.

Apparent silence on documentation retention and transitional graduates: The CAO does not set out required record-keeping or transitional arrangements for stock harvested or tested before commencement. That silence creates a compliance gap that may require administrative clarification from the regulator.

Compliance requires a blend of sourcing, process controls, measurement, marking and, where necessary, seeking Director approvals. The CAO’s requirements are plank-level and species-specific.

1. Confirm species eligibility: Source timber from the species listed in Appendix I. If a supplier proposes a species not listed, apply to the Director for approval supplying “satisfactory evidence regarding their suitability for use in propellers” (para 2). Do not assume unlisted species are acceptable without written Director approval.

2. Identification and provenance: Ensure each plank is clearly identified as to species and origin before it is accepted for propeller manufacture (para 3.1). Implement incoming-material checks to verify species, origin documentation and to ensure labelling aligns with the future ink-stamp requirement (para 8).

3. Visual and dimensional inspection: Reject planks with warp (para 3.2), or with prohibited defects listed in para 3.3. Tolerate only the permitted pin-knots, pin-holes and small isolated imperfections within the numeric limits (para 3.3(a)-(c)). Measure slope-of-grain by either the splitting test or the Appendix II A techniques and ensure slope does not exceed 1 in 12 (para 3.2 and Appendix II A).

4. Seasoning and special reconditioning: Dry timber by air-drying or kiln-drying to achieve the moisture band required in para 5. For mountain ash and alpine ash, after seasoning to 12% recondition for 6 hours at 100°C under saturated conditions, then re-dry to meet para 5 requirements (para 4).

5. Measure moisture content correctly: Use an electrical resistance type moisture meter or an approved alternative method (para 5). Take readings approximately 300 mm from each end and at mid-length for each plank (three readings). Ensure all readings fall between 10% and 15%; intra-plank variance does not exceed 2% and average moisture content variance between planks does not exceed 3% (para 5). If relying on oven-drying, follow Appendix II B precisely for sample handling and calculation. Maintain records of measurements to demonstrate compliance.

6. Measure density: With moisture in the correct band, determine density per Appendix II C and confirm the measured density for each plank meets or exceeds the species minimum in Appendix I (para 6 and Appendix II C). Record calculations (W and V), and ensure samples are cut cleanly from each end clear of weathering per Appendix II C.

7. Conduct Izod brittleness testing: For brittleness, prepare the standard notched specimens in the geometry specified in Appendix II D, take two samples from each plank as described, and perform Izod impact tests with the blow applied tangential to growth rings. Ensure Izod values for the standard specimen are not less than 6.5 joules (para 7 and Appendix II D). If the manufacturer intends to carry out Izod testing in-house, obtain Director approval as noted in para 7.

8. Mark compliant planks: Once a plank passes required inspections and tests, ink-stamp it with the standard timber name and “CAO 108.29” (para 8). Retain records showing test results, measurement data and the correspondence or approvals from the Director where applicable.

9. Administrative steps for approvals: Prepare evidence supporting suitability when applying for Director approval of additional timber species (para 2). For in-house Izod testing, prepare method details, equipment calibration and quality assurance procedures to submit for Director approval (para 7 note).

10. Quality management and record retention: Although the CAO does not prescribe document-retention periods, implement a record-keeping regime that retains species origin documentation, moisture and density readings, Izod test results, and stamping records sufficient to demonstrate compliance for the life of the plank and the finished propeller. Maintain calibration certificates for moisture meters and Izod equipment where used.

11. External testing where required: If in-house capability is lacking or Director approval is not sought/obtained, engage accredited laboratories to perform oven-dry moisture determination, density calculation and Izod testing in accordance with Appendix II methods. Ensure specimen preparation and test orientation are precisely followed to match the CAO procedures.

12. Ongoing liaison with regulator: Where there is any uncertainty about interpretation (for example, what constitutes “satisfactory evidence” for species approval, or the acceptability of an alternative measurement method), seek clarification or approval from the Director rather than unilaterally adopting alternate practices (para 2 and para 7 note).

Following these steps aligns procurement and manufacturing workflows with the CAO’s plank-level specification, the numerical tolerances in paras 3-7, the species minima in Appendix I, and the test methods in Appendix II.