AD/PHS/21 Amdt 1 - Blade Spar Taper Bore

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 107, was enacted by the Commonwealth of Australia to establish and maintain standards for civil aviation safety, addressing the need for consistent and stringent regulations to safeguard the aviation industry. The 1998 Regulations were developed to address safety gaps identified in the aviation sector, ensuring the highest standards of airworthiness and operational safety for aircraft within Australia. This legislative instrument, administered by the Civil Aviation Safety Authority, aims to prevent accidents and incidents by enforcing specific safety directives, such as those outlined in AD/PHS/21 Amendment 1. This amendment was introduced in response to a significant accident involving an Embraer EMB-120 aircraft, which was linked to fatigue cracking in the blade taper bore area, leading to a blade liberation during flight. The policy objective is to enhance the safety of aircraft operations by mandating rigorous inspections and repair procedures for specified propeller models.

Scope and Application

The Civil Aviation Regulations 1998, specifically PART 39 - 107, applies to all model 14RF, 14SF, and 6/5500/F Series propellers with blade and pin assemblies with a manufacturing serial number less than 885718, fitted to various aircraft types including Embraer EMB-120, DHC-8-100 and 300, Aerospatiale ATR42, CASA CN-235, SAAB SF340, BAe ATP, and Canadair CL215T/CL415T Series. The regulations mandate that the ultrasonic shear wave inspections required by this directive must be conducted by an appropriately qualified NDT Authority holder in accordance with the technical requirements of FAA AD 96-08-02 Amendment 39-9568. The directive became effective on 29 May 1996, following a recent accident involving an Embraer EMB-120 aircraft where fatigue cracking in the blade taper bore area led to the liberation of a blade during flight. Compliance with this directive is crucial to ensure the airworthiness and safety of the specified propellers and aircraft.

Key Provisions

The Civil Aviation Regulations 1998, Part 39 - 107, includes specific provisions in the Civil Aviation Safety Authority Schedule of Airworthiness Directives concerning variable pitch propellers, particularly those manufactured by Hamilton Standard. The relevant section is AD/PHS/21 Amendment 1, which pertains to the blade spar taper bore of certain propeller models (section 1). This directive applies to all model 14RF, 14SF, and 6/5500/F series propellers with blade and pin assemblies having manufacturing serial numbers less than 885718. These propellers are commonly fitted to various aircraft types, including Embraer EMB-120, DHC-8-100 and 300, Aerospatiale ATR42, CASA CN-235, SAAB SF340, BAe ATP, and Canadair CL215T/CL415T Series aircraft (section 2). The directive requires compliance with the technical requirements outlined in FAA AD 96-08-02 Amendment 39-9568, which mandates ultrasonic shear wave inspections to be conducted by an appropriately qualified NDT Authority holder (section 3). This requirement aims to address issues such as fatigue cracking in the blade taper bore area, which has been linked to in-flight blade separation incidents. Notably, any blade and pin assemblies previously inspected under AD/PHS/17 Amendment 2, AD/PHS/19 Amendment 1, or AD/PHS/21 must be re-inspected under this directive (section 4). Additionally, the directive specifies that a blade repair constituting terminating action exempts the propeller from the repetitive taper bore ultrasonic inspection requirement (section 5). Entities and individuals governed by this directive bear specific obligations to ensure compliance. These include conducting the required ultrasonic shear wave inspections by qualified personnel and ensuring that all inspections are carried out according to the stipulated technical requirements (section 6). Furthermore, any blade and pin assemblies previously inspected under older directives must be re-inspected in accordance with the current directive, ensuring no prior inspections are overlooked (section 7). Non-compliance with these obligations may have serious repercussions, given the potential safety implications of undetected fatigue cracking. Failure to comply with the requirements of this Airworthiness Directive may result in serious consequences. The directive emphasises the critical nature of adhering to the specified inspection protocols to mitigate risks associated with propeller failure. Any breach of the directive's requirements could lead to safety hazards, potentially resulting in accidents or other severe consequences. The specific penalties for non-compliance are not detailed within the directive itself, but non-compliance with Civil Aviation Regulations can generally lead to enforcement actions, including fines and other regulatory sanctions. These penalties aim to enforce adherence to safety standards and protect the public from potential aviation risks.