AD/DHC-8/51 - Horizontal Stabiliser Skin Disbonding

Overview

The Civil Aviation Regulations 1998, which were enacted by the Parliament of Australia, aim to ensure the safety of civil aviation. Part 39, specifically, addresses airworthiness directives, with the 1998 Regulations providing a legal framework for maintaining the airworthiness of aircraft through safety directives. One such directive is AD/DHC-8/51, which was introduced to address the problem of disbonding in the horizontal stabiliser skin of Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes, particularly for models 102 and 103 within specified serial numbers. This directive mandates a one-time ultrasonic bond inspection and repair if necessary to ensure the structural integrity of the horizontal stabiliser, thereby preventing potential loss of control due to disbonding. The policy objective is to enhance flight safety by mitigating the risks associated with structural failures in aircraft components.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, apply to Bombardier (Boeing Canada/De Havilland) DHC-8 series aeroplanes, particularly models 102 and 103, with serial numbers ranging from 003 to 050. This regulation is pertinent to the maintenance and safety standards of these aircraft and falls under the jurisdiction of the Civil Aviation Safety Authority (CASA). The directive mandates a one-time ultrasonic bond inspection of the upper and lower skin panels of the horizontal stabiliser to detect any disbonds as per the guidelines outlined in de Havilland Document PSM 1-8-7A. Compliance with this directive is critical to ensuring the structural integrity of the aircraft, and failure to adhere to the specified inspection and repair protocols could lead to significant safety risks. The directive also references Transport Canada AD CF-98-01 and Bombardier AOM 469 for additional context. The compliance timeframes vary based on the aircraft's serial number, with certain aircraft requiring inspections within 20 flight cycles or 7 calendar days after 25 February 1998, while others must comply within 60 flight cycles or the same 7-day period. Any detected disbonds beyond the specified limits must be repaired before the aircraft can be flown again.

Key Provisions

The Civil Aviation Regulations 1998, Part 39 - 105, outlines the Civil Aviation Safety Authority's (CASA) Schedule of Airworthiness Directives, specifically for Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes under AD/DHC-8/51 (Section 1). This directive pertains to the horizontal stabiliser skin disbonding issue identified in DHC-8 aircraft, models 102 and 103, with serial numbers 003 through 050 (Section 2). The requirement is to perform a one-time ultrasonic bond inspection of the upper and lower skin panels (part numbers 85510025 and 85510026) of the horizontal stabiliser for disbond as per de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01 (Section 3). Reference documents include Transport Canada AD CF-98-01 and Bombardier AOM 469 (Section 3). Compliance with this directive is time-sensitive. For aircraft serial numbers 010 through 040, the inspection must be conducted within 20 flight cycles or 7 calendar days after 25 February 1998, whichever occurs first, unless the inspection has already been completed within the last 6 months (Section 4). For aircraft serial numbers 003 through 009, and 041 through 050, the compliance period extends to 60 flight cycles or 7 calendar days after 25 February 1998, again unless the inspection has already been completed within the last 6 months (Section 4). Any disbonds identified that exceed the local disbond limits defined in de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01 must be repaired before further flight (Section 4). Failure to comply with the requirements of this airworthiness directive could result in serious safety hazards. The directive became effective on 25 February 1998, following two reports of disbonding of the doubler and stringers on the upper and lower skin panels of the horizontal stabiliser on two separate aircraft (Section 5). This condition, if not detected and corrected, could lead to structural failure of the horizontal stabiliser and possible loss of control of the aircraft (Section 5). The directive is a critical measure to ensure the continued airworthiness and safety of the affected DHC-8 aircraft models.