{"id":"F2007L04903","name":"Civil Aviation Order 108.29 Instrument 2007","slug":"civil-aviation-order-108-29-instrument-2007","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":71732,"registerId":"commonwealth-F2007L04903-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"Civil Aviation Order 108.29 Instrument 2007","content":"I, WILLIAM BRUCE BYRON, Director of Aviation Safety, on behalf of CASA, make this instrument under subregulation 36A (2) of the Civil Aviation Regulations 1988.\n\n\\[Signed Bruce Byron\\]\n\nBruce Byron  \nDirector of Aviation Safety and  \nChief Executive Officer\n\n19 December 2007\n\nCivil Aviation Order 108.29 Instrument 2007\n\n1 Name of instrument\n\nThis instrument is the Civil Aviation Order 108.29 Instrument 2007.\n\n2 Commencement\n\nThis instrument commences on the day after it is registered.\n\n3 New Civil Aviation Order 108.29\n\nCivil Aviation Order 108.29 is repealed and a new Civil Aviation Order 108.29 substituted as set out in Schedule 1.\n\nSchedule 1 Civil Aviation Order 108.29\n\nSpecification — timber for use in aircraft propellers\n\n1 Application\n\nThis Civil Aviation Order specifies the requirements to be observed in the selection of timber for use in the manufacture of laminated wooden propellers.\n\n2 Approved timbers\n\nApproved types of timber are listed in Appendix I. The Director may approve additional types on the provision of satisfactory evidence regarding their suitability for use in propellers.\n\n3 Quality\n\n3.1The timber must be clearly identified with respect of species and must be of known origin.\n\n3.2The timber must be in the form of selected planks which must be free from warp. Sloping grain is permitted but not exceeding 1 in 12, as determined by the splitting test or alternatively as described in Appendix II.\n\n> Note Deviation of grain due to knots of permissible size may be disregarded.\n\n3.3The timber must be clean and free from obvious and incipient decay and from knots, shakes, splits, seasoning checks, internal checks, fractures, brittle heart, compression failures, bark pockets, gum pockets or gum veins, callus tissue, insect attack, wane or want, but the following imperfections are permitted:\n\n(a) pin-knots not exceeding 3 mm diameter and not closer than 50 mm;\n\n(b) pin-holes not exceeding 1.5 mm diameter, not more than 3 in any 10 000 sq mm of surface area and no 2 of which are closer than 50 mm to each other;\n\n(c) small, isolated imperfections which do not significantly affect the strength of the timber, such as wavy grain, interlocked grain, flecks, spots, fine drying checks and blemishes.\n\n4 Seasoning\n\nThe timber must have been either air-dried or kiln-dried to a moisture content within the limits specified in subsection 5. Mountain ash and alpine ash after seasoning to 12% moisture content must be reconditioned for 6 hours at 100C (saturated conditions) following which the material must be air or kiln dried to the requirements of subsection 5.\n\n5 Moisture content\n\nThe moisture content of each plank must be determined by means of an electrical resistance type moisture meter or other approved method. Tests must be made at points approximately 300 mm from each end and at the mid length. The 3 readings must lie between 10% and 15% and the individual readings must not vary more than 2% moisture content in any 1 plank. The average moisture content must not vary more than 3% between planks.\n\n> Note An acceptable alternative method of determining moisture content is given in Appendix II.\n\n6 Density\n\nWith a moisture content within the limits specified in subsection 5, the measured density of each plank must not be less than the value given in Appendix I for the particular timber.\n\n> Note An acceptable method for determining density is given in Appendix II.\n\n7 Brittleness\n\nIn order to detect brittleness, 2 samples from each plank must be tested for impact resistance in an Izod testing machine. The Izod values obtained for the standard specimen shown in Figure I of Appendix II must not be less than 6.5 joules.\n\n> Note Details of the Izod test method are given in Appendix II. This test may be carried out by the propeller manufacturer subject to approval by the Director.\n\n8 Marking\n\nEach plank accepted as complying with this specification must be ink stamped with the following particulars:\n\n(a) the standard name of the timber (i.e. Maple, Queensland, Coachwood,  \nMahogany, Honduras etc);\n\n(b) the number — CAO 108.29.\n\nAppendix I\n\nTimbers approved for use in aircraft propellers\n\n| Timbers                                                                 | Minimum densityKilograms/cubic metre |\n| ----------------------------------------------------------------------- | ------------------------------------ |\n| 1 Ash, Mountain/Ash Alpine(Eucalyptus regnans/(Eucalyptus delegatensis) | 601                                  |\n| 2 Ash, Silver, Northern(Flindersia pubescens)                           | 633                                  |\n| 3 Ash, Silver Queensland(Flindersia bourjotiana)                        | 577                                  |\n| 4 Beech, Myrtle(Nothofagus cunninghamii)                                | 671                                  |\n| 5 Birch, White(Schizomeria ovata)                                       | 604                                  |\n| 6 Bollywood(Litsea reticulata)                                          | 449                                  |\n| 7 Coachwood(Ceratopetalum apetalum)                                     | 577                                  |\n| 8 Mahogany Honduras(Swietenia macrophylia)                              | 513                                  |\n| 9 Maple, Queensland(Flindersia brayleyana/pimenteliana)                 | 513                                  |\n| 10 Oak, Silky Southern(Grevillea robusta)                               | 615                                  |\n| 11 Pine, Bunya(Araucaria bidwillii)                                     | 420                                  |\n| 12 Pine, Hoop(Araucaria cunninghamii)                                   | 455                                  |\n| 13 Pine, Klinki(Araucaria hunsteinii)                                   | 385                                  |\n| 14 Sassafras(Doryphora sassafras)                                       | 543                                  |\n| 15 Spruce, Sitka(Picea sitchensis)                                      | 384                                  |\n\nAppendix II\n\nA — Alternative method for the determination of slope of grain\n\nThe direction of splitting is probably the best guide to the slope of the grain. Splinters prised out from the surface of a piece of wood with a pocket knife will also reveal the grain direction and a drop of ink placed on a face of the piece of wood will spread most readily in the direction of the grain. A swivel handled scribe may also be used to determine the slope of grain in wood.\n\nB — Alternative method for the determination of moisture content\n\nTake a small sample of the timber from the appropriate position, weigh it (W1) to an accuracy of 1% of its weight and then desiccate it in an oven at a temperature of 100C\\-105C until the weight is constant (WO), taking great care to prevent any change in moisture content between the cutting of the sample and the first weighing and also between removal from the oven and the subsequent weighing.\n\nCalculate the moisture content as follows:\n\nMoisture content, per cent = ![](image.001.png)\n\nC — Method for the determination of density\n\nCleanly cut a sample, approximately 2.5 cm long and of the full cross-section of the board or plank, from each end of the piece at a position clear of weathering, where the moisture content is known or is about to be determined.\n\nMake a series of measurements of the length, width and thickness of each sample, obtain the arithmetic mean of each dimension and calculate the volume (V) of the samples in cubic centimetres. From each sample take the weight (W) in grams to an accuracy of ± 1% of its weight.\n\nCalculate the density as follows:\n\nDensity = ![](image.002.png) kilograms per cubic metre\n\nwhere: — W is in grams\n\nV is in cubic centimetres.\n\nD — Brittleness (Izod) test\n\nTest specimens\n\nTwo samples must be cut from diagonally opposite edges from 1 end of the plank.\n\nA notched specimen, the sides of which are cut radially and tangentially, of the form and dimensions shown in Figure 1 must be prepared from each of the samples.\n\nProcedure\n\nThe test specimens must be broken in an Izod impact testing machine, the blow being applied in the direction tangential to the growth rings. The testing machine must be of a type which will permit the test results being determined to within 0.3 joule.\n\n![](image.003.png)\n\nFigure 1 — Impact test specimen","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The instrument repeals and substitutes CAO 108.29 but retains the same subject matter: specification of timber for laminated propellers. It provides more-prescriptive testing, sampling and marking procedures and confirms Director discretion to approve additional timbers (s.2), but does not extend regulation to other materials or aircraft components."},"complexity_factors":["Technical testing requirements: moisture content measurement, density calculation and Izod impact (brittleness) test (ss.5-7, Appendix II)","Tight numeric tolerances and sampling rules (e.g. 10–15% moisture, ≤2% variation per plank, sampling points at ends and mid-length) (s.5)","Detailed acceptability criteria for surface defects and permitted imperfections (s.3.3)","List of approved species with minimum densities (Appendix I) plus Director discretion to approve additional species (s.2)","Procedural requirements for seasoning, reconditioning and specific oven conditions for certain timbers (s.4)","Marking and traceability obligation requiring ink stamping of each accepted plank (s.8)","Multiple acceptable and alternative test methods with prescribed sample preparation and calculation formulas (Appendix II)"],"plain_english_summary":"This instrument repeals and replaces Civil Aviation Order 108.29 and sets mandatory specifications for timber used in laminated aircraft propellers. It tells propeller manufacturers, timber suppliers and maintenance organisations which species are acceptable, what physical and moisture tests to perform, how planks must be marked, and that the Director may approve additional timbers (s.2). Compliance requires sampling, testing (moisture, density, Izod impact) and stamping, creating equipment, testing and record-keeping costs for businesses."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"The legislation maintains its original narrow scope: technical specifications for timber selection in aircraft propeller manufacturing. The 2007 instrument is a straightforward remake/repeal and substitution of the previous CAO 108.29, updating the regulatory instrument without expanding beyond its original purpose of ensuring airworthiness of wooden propellers through material specifications."},"complexity_factors":["Technical specifications dominate: detailed requirements for moisture content (10-15%), grain slope (not exceeding 1 in 12), and density minimums for 15 specific timber species","Precise measurement protocols: requires specific testing equipment (electrical resistance moisture meters, Izod impact testing machines) with defined accuracy tolerances (±1% for weight, ±0.3 joule for impact tests)","Mathematical calculations required: formulas provided for moisture content percentage and density calculations","Conditional exceptions: nested permitted imperfections (pin-knots, pin-holes, small isolated imperfections) with specific dimensional and spatial constraints (e.g., 'not closer than 50 mm')","Alternative methods provided: Appendix II offers alternative testing methods for grain slope, moisture content, density, and brittleness","Limited cross-referencing: primarily self-contained, though references to 'the Director' (Director of Aviation Safety) for approvals and oversight","Special reconditioning requirement: specific 6-hour heat treatment at 100°C for Mountain Ash and Alpine Ash after initial seasoning"],"plain_english_summary":"This technical safety standard tells Australian manufacturers how to select, dry, test and mark wood for laminated aircraft propellers. It limits usable species, requires moisture control, impact-strength testing and quality inspection so planks are free of harmful defects, and mandates identification stamping.\n\nBecause propeller wood failure can be catastrophic, the order ensures only properly prepared, tested timber is used to keep aircraft safe."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/civil-aviation-order-108-29-instrument-2007","history":"/api/acts/civil-aviation-order-108-29-instrument-2007/history","analysis":"/api/acts/civil-aviation-order-108-29-instrument-2007/analysis","conflicts":"/api/acts/civil-aviation-order-108-29-instrument-2007/conflicts","importantCases":"/api/acts/civil-aviation-order-108-29-instrument-2007/important-cases","documents":"/api/acts/civil-aviation-order-108-29-instrument-2007/documents"}}