COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes
AD/DHC-8/68 Beta Backup Test Switches 1/2000
TX
Applicability: DHC-8 aeroplanes Models 102, 103, 106, 201, 202, 301, 311, 314 and 315 Serial Numbers 003 up to and including 538.
Requirement: 1. Inspect the two beta back-up test switches in accordance with Bombardier Alert Service Bulletin A8-61-30 Revision B dated 6 December 1999 to ensure switches are Part Number (P/N) MS27407-6.
2. If, during the Requirement 1 inspection, a switch with other than P/N MS27407-6 is found to be fitted, replace the switch with a P/N MS27407-6 switch.
Note: Transport Canada Emergency AD CF-99-30 refers.
Compliance: 1. Within 50 hours time in service from the effective date of this Directive.
2. Before further flight.
This Airworthiness Directive becomes effective on 17 December 1999.
Background: An incorrect switch (P/N MS24524-27) is wrongly identified in the wiring diagram manuals as an allowable replacement for the Beta back-up test switch. This switch is used elsewhere on the aircraft and is physically interchangeable with the correct switch (P/N MS27407-6). However, the internal contacts are different, preventing the Beta back-up system from functioning correctly. Mechanical failure of the propeller control system with incorrect switches installed may result in the loss of automatic overspeed protection, allowing the propeller to go into an overspeed condition, resulting in possible engine and propeller damage.
This Directive requires that all Beta back-up switches be inspected to ensure that correct switches are fitted.
Overview
The Civil Aviation Regulations 1998 (Cth), specifically Part 39 - 105, introduced the Civil Aviation Safety Authority Schedule of Airworthiness Directives to address the safety concerns associated with the Bombardier (Boeing Canada/De Havilland) DHC-8 Series aeroplanes. Enacted by the Parliament of Australia, this legislation was introduced to ensure the safety of civil aviation by providing specific directives for maintaining and inspecting aircraft. One such directive, AD/DHC-8/68, was created in response to the problem of incorrect switches being identified in wiring diagrams, which could lead to mechanical failures and potential loss of automatic overspeed protection in the propeller control system.
This Airworthiness Directive, effective from 17 December 1999, aims to ensure that the two beta back-up test switches in certain DHC-8 aeroplane models are correctly identified and replaced if necessary. The directive mandates that inspections be carried out to verify that the switches are of the correct part number (P/N MS27407-6) and require compliance within 50 hours of service from the directive's effective date or before further flight. The objective is to eliminate the risk of mechanical failure due to incorrect switches, thereby enhancing the overall safety of the aircraft in operation.
Scope and Application
The Civil Aviation Regulations 1998, specifically under PART 39 - 105, detail the Civil Aviation Safety Authority's Airworthiness Directives, which apply to specific models of aircraft within Australia's jurisdiction. This particular directive, AD/DHC-8/68, pertains to Bombardier (Boeing Canada/De Havilland) DHC-8 series aeroplanes, namely models 102, 103, 106, 201, 202, 301, 311, 314, and 315, with serial numbers ranging from 003 up to and including 538. The directive mandates that all affected aircraft undergo an inspection of the two beta backup test switches to ensure they are of the correct part number MS27407-6. If any switch is found to be of a different part number during the inspection, it must be replaced with the correct part number MS27407-6 switch. The directive requires compliance within 50 hours of the directive's effective date and before any further flight. The directive became effective on 17 December 1999, referencing an emergency directive from Transport Canada. This directive is a critical safety measure designed to prevent mechanical failures in the propeller control system that could lead to overspeed conditions, potentially causing engine and propeller damage.
Key Provisions
The Civil Aviation Regulations 1998, specifically Part 39 - 105, contain an Airworthiness Directive (AD) aimed at ensuring the safety of Bombardier (Boeing Canada/De Havilland) DHC-8 Series aeroplanes. The directive, AD/DHC-8/68, focuses on the installation and inspection of beta backup test switches on certain models and serial numbers of DHC-8 aircraft. Section 1 of the directive (AD/DHC-8/68) mandates that two specific beta backup test switches must be inspected to ensure they are the correct part number (P/N MS27407-6). This inspection is to be conducted in accordance with Bombardier Alert Service Bulletin A8-61-30 Revision B dated 6 December 1999.
If, during the inspection, any switches other than the specified part number are found, they must be replaced with the correct P/N MS27407-6 switches. This requirement is critical to prevent mechanical failure of the propeller control system, which can lead to an overspeed condition of the propeller and consequent damage to the engine and propeller. The directive applies to DHC-8 aeroplanes models 102, 103, 106, 201, 202, 301, 311, 314, and 315, with serial numbers ranging from 003 to 538 inclusive.
Compliance with this directive is mandatory and must be achieved within 50 hours of time in service from the effective date of the directive or before further flight. The directive became effective on 17 December 1999. Failure to comply with this AD can lead to severe safety risks, including the potential for mechanical failure in the propeller control system. This directive is a response to an issue where an incorrect switch (P/N MS24524-27) was mistakenly identified as an allowable replacement for the beta backup test switch, which led to potential safety hazards.
The AD imposes specific obligations on aircraft operators and maintenance personnel to inspect and, if necessary, replace the beta backup test switches with the correct part number. It is crucial for operators to ensure that their maintenance teams are aware of this directive and that the necessary inspections and replacements are carried out promptly to maintain airworthiness. The consequences of non-compliance can include severe safety risks, potential mechanical failures, and significant damage to the aircraft, which could result in grounding or further regulatory actions.