COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Aircraft - General
AD/GENERAL/29 Wooden Aircraft - Airframe NK
Structural Inspection
Applicability: All aeroplanes and rotorcraft having wooden stressed shell structures or wooden box spars, except Proctor and Vega Gull series.
Note: This does not apply to wings with routed laminated or solid spars and fabric coverings.
Requirement: 1. Preparation: Prepare the aeroplane for inspection by removing all removable equipment, cabin linings, seats, inspection and access panels, fairings, fabric patches, tape sealing and sufficient fabric and secondary structure to enable an inspection of the airframe in accordance with these requirements.
2. Inspection Procedure:
2.1 Inspect all fabricated structural components such as box spars, wooden ribs, stringer struts and braces, and all glued connections between these components for the following defects:
(a) Cracks, cuts, splits, bruises, compression shakes, warping, contamination by foreign matter, attack by fungus in the wood, shrinkage of the timber at bolt holes.
(b) Separation or sponginess in the glued joints and plywood. A O.10 mm or
0.005 in. feeler gauge should be used to determine separation of glued joints and the depth of glue failure.
2.2 Inspect all plywood skin for the following defects:
(a) Cracks, splits, cuts, bruises and shakes in the surface of the wood, deterioration and contamination by foreign matter.
(b) Separation of the glue where skin connects to the skeletal structure beneath.
Note: Load carrying wooden skin becomes inefficient and the complete structure loses strength when adhesion to the structure beneath has failed. Consequently, all structural connections and joints must be thoroughly inspected for deterioration and defects. In carrying out an inspection the following notes may prove helpful in detecting defects. Separation from the structure is often detectable from the exterior in several ways. It is likely to appear as a local discontinuity in the skin contour which can be pressed down without the immediate firm resistance anticipated. When the structure is flexed the skin will tend to take up waves. If these waves do not pass across lines of gluing to the structure beneath, adhesion may be taken as sound.
Oblique lighting of the surface will be found helpful in studying surface waves and contour discontinuities. Timber shakes appear as thin lines across the timber of the
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
varnish layer. By sponging ink on the varnish and subsequently wiping it off, a line where a shake exits should show. Where there are signs of failure in the protective coating on surfaces it should be removed to inspect the wood beneath. Special attention is to be paid to points in the structure where the lodgement of liquids is possible. Wherever possible the inspection should be made from the interior.
However, in wings initial inspection may have to be made from the exterior. When inspecting the interior structure of the wings it may be necessary to cut holes in load carrying covering. In such instances reference should be made to the Authority for an approved scheme of inspection holes.
3. Repairs:
Any repairs necessary are to be carried out in accordance with the methods laid down in structural repair manuals or by a method approved by the Authority.
or A.N.O. 105.1.0.2.17.
Compliance: Before issue of C of A and thereafter at intervals not exceeding 3 years.
Overview
The Civil Aviation Regulations 1998 were enacted by the Parliament of Australia to regulate civil aviation safety, and specifically address the safety of wooden aircraft structures. The regulations aim to ensure that wooden aircraft maintain airworthiness by implementing regular structural inspections and repairs. Part 39, Division 105 of the regulations outlines specific Airworthiness Directives, including AD/GENERAL/29, which mandates detailed inspections for wooden aircraft to detect and address structural issues. The policy objective is to mitigate the risks associated with wooden airframes by ensuring regular and thorough inspections, thereby maintaining the safety and integrity of these aircraft in operation. The Civil Aviation Safety Authority oversees the compliance with these directives to uphold the highest safety standards in civil aviation.
Scope and Application
The Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998, specifically within Part 39 - 105 Schedule of Airworthiness Directives, mandates a structural inspection for all aeroplanes and rotorcraft with wooden stressed shell structures or wooden box spars, excluding the Proctor and Vega Gull series. This regulation does not apply to wings featuring routed laminated or solid spars and fabric coverings. The geographic and jurisdictional reach of this legislation is national, applying across the Commonwealth of Australia. The directive requires that aircraft be prepared for inspection by removing various components to enable thorough examination of the airframe. Inspectors must check for structural defects such as cracks, splits, and warping, particularly in fabricated components and glued joints, using specified tools and methods to detect separation and other issues. Additionally, plywood skin must be inspected for surface defects and separation from the underlying structure. Repairs must adhere to methods outlined in structural repair manuals or be approved by CASA. Compliance with these airworthiness directives is mandatory before the issuance of a Certificate of Airworthiness and at intervals not exceeding three years.
Key Provisions
The Civil Aviation Regulations 1998, specifically under Part 39 - 105, mandate certain procedures for the inspection and repair of wooden aircraft structures. Section (29) details the requirements for conducting a structural inspection on all aeroplanes and rotorcraft with wooden stressed shell structures or wooden box spars, except for Proctor and Vega Gull series, and explicitly excludes wings with routed laminated or solid spars and fabric coverings. The preparation for inspection involves removing all removable equipment, cabin linings, seats, and other structural components to enable a thorough examination of the airframe (Section 1). The inspection procedure requires checking all fabricated structural components, including box spars, wooden ribs, stringer struts, and braces, for defects such as cracks, cuts, splits, and warping (Section 2.1). Additionally, the plywood skin must be inspected for cracks, splits, and separation of glue joints (Section 2.2). Detailed guidance is provided for detecting these defects, such as using oblique lighting and ink sponging to highlight surface waves and separations.
Compliance with these regulations is critical and must be met before issuing a Certificate of Airworthiness (C of A) and thereafter at intervals not exceeding three years (Compliance). The regulations impose strict obligations on aircraft owners and operators to ensure that all wooden structural components are inspected and any necessary repairs are performed in accordance with approved methods. This includes ensuring that all removable equipment and structural components are adequately secured and that inspections are conducted by qualified personnel.
Failure to comply with these requirements can result in significant consequences. If an aircraft is found to be non-compliant, it may be subject to enforcement actions by the Civil Aviation Safety Authority (CASA). This could include the grounding of the aircraft until the necessary repairs and inspections are completed. In severe cases, CASA may impose fines or other penalties for non-compliance. The exact penalties and consequences for non-compliance are detailed in the Civil Aviation Act 1988, which provides for both administrative and criminal sanctions. It is important for aircraft operators to adhere to these regulations to ensure the safety and airworthiness of their aircraft.