COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Propellers - Variable Pitch - McCauley
AD/PMC/35
Amdt 1
Propeller Blade Butt Retention Thread - Eddy Current Inspection
13/88
Applicability: All threaded blade McCauley propellers.
Requirement: In addition to the dye penetrant inspection described in the appropriate McCauley Propeller Service Manual, conduct an eddy current inspection of the tapered thread butt section of the propeller blade in accordance with technique approved by the Secretary.
Eddy Current Technique ATG/NDI/EC/5 constitutes one such technique. Copies of this technique, and test samples may be obtained through regional offices of the Authority.
Compliance: 1. Each time propeller is overhauled.
2. Whenever propeller disassembly will allow inspection of the blade butt retention threads.
Background: Two recent local failures have occurred at the butt thread section of McCauley propeller blades. One other cracked blade has been detected using eddy current equipment. All subject blades had shot peened and truncated threads. Laboratory tests indicate that the compressive surface formed by the shot peening process may prevent detection of substantial cracks when inspecting with dye penetrants.
This Amendment raised to clarify reinspection requirements.
Overview
The Civil Aviation Regulations 1998, as amended by the Civil Aviation (Airworthiness) Regulations 1998 (F2006B06290), introduce specific safety measures for the inspection of McCauley propeller blades used in aircraft. The legislation was enacted to address the problem of recent failures in the blade butt retention threads of McCauley propellers, where traditional dye penetrant inspections had proven inadequate. This safety amendment mandates an additional eddy current inspection for these blades to ensure any substantial cracks are detected, thereby enhancing aviation safety. The Australian Government, through the Civil Aviation Safety Authority, established this policy to mitigate the risk of in-flight failures by ensuring more reliable inspection techniques are employed. The objective is to prevent failures and enhance the safety of civil aviation by requiring a more comprehensive inspection process for critical components of aircraft propellers.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 107, under the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, mandate the application of AD/PMC/35 Amendment 1 for McCauley propellers. This directive applies to all threaded blade McCauley propellers used in civil aviation. The requirement stipulates that an eddy current inspection of the tapered thread butt section of the propeller blade must be conducted, in addition to the dye penetrant inspection described in the applicable McCauley Propeller Service Manual. The eddy current inspection must comply with a technique approved by the Secretary, with Eddy Current Technique ATG/NDI/EC/5 being one such approved method. This amendment was necessitated by recent local failures at the butt thread section of McCauley propeller blades, which were shot peened and had truncated threads, potentially hindering the detection of substantial cracks using dye penetrants alone. Compliance with this directive is mandatory each time a propeller is overhauled and whenever propeller disassembly permits inspection of the blade butt retention threads.
Key Provisions
The Civil Aviation Regulations 1998, specifically Part 39 - 107, under the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, mandate certain requirements for the inspection of propellers. The directive AD/PMC/35Amdt 1 pertains to the eddy current inspection of the tapered thread butt section of McCauley propeller blades (section 1). The primary requirement is that in addition to the dye penetrant inspection, an eddy current inspection must be conducted as specified in the applicable McCauley Propeller Service Manual and approved by the Secretary (section 2). The approved technique for such inspections is Eddy Current Technique ATG/NDI/EC/5, which is available from regional offices of CASA (section 3).
These requirements are intended to ensure the airworthiness of the propellers by detecting any potential defects that might not be visible through dye penetrant inspection alone. The directive applies to all threaded blade McCauley propellers (section 4). The inspections must be carried out each time the propeller is overhauled and whenever the propeller is disassembled in a manner that allows inspection of the blade butt retention threads (section 5). This directive was issued following incidents where failures occurred at the butt thread section of McCauley propeller blades, with laboratory tests suggesting that the shot peening process might mask substantial cracks when using dye penetrants (section 6).
Failing to comply with these airworthiness directives can result in significant legal and operational repercussions. Operators must ensure adherence to these inspection requirements to maintain compliance with CASA regulations. Non-compliance can lead to severe consequences, including grounding of the aircraft, enforcement actions by CASA, and potential civil or criminal penalties depending on the severity and intent of the breach. The specific penalties for non-compliance are not detailed in the directive but may include fines and other sanctions as prescribed by the Civil Aviation Act 1988.