COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
DHC-6 (Twin Otter) Series Aeroplanes
AD/DHC-6/50 Main Landing Gear Legs - Inspection 5/80
Applicability: All model DHC-6 which do not have De Havilland Aircraft of Canada Ltd.
Modification 6/1660 incorporated.
Requirement: 1. Inspect as necessary the main landing gear legs in accordance with either Schedule No. 1 or Schedule No. 2 of the De Havilland Aircraft of Canada Ltd. SB No.
6/380. In lieu of the visual external inspections required by paragraph (a) of Schedule No. 1 or Schedule No. 2, refer to the Accomplishment Instructions and Figure 1 of the referenced Service Bulletin, remove the external finish from the Inspection Area and inspect using a dye penetrant method. If no cracks are observed, reprotect the stripped area, and proceed in accordance with paragraph (b) of the appropriate Schedule. If cracks are found, proceed in accordance with Schedule No. 1 paragraph (e), (f) and (g) as appropriate.
2. Perform a Check D inspection in accordance with the Accomplishment Instructions of the De Havilland Aircraft of Canada Ltd. SB No. 6/380.
Note: Transport Canada Airworthiness Directive CF-80-06 De Havilland refers.
Compliance: Para. 1 - Within 50 hours time in service after 15 May 1980, unless already accomplished.
Para. 2 - Within 2400 hours flight time or before 21 December 1980 whichever comes first, unless already accomplished within the last 9600 hours flight time or 4 years, and thereafter at intervals not to exceed 12000 hours flight time or 5 years whichever comes first.
Background: Advice from overseas indicated failures of the Main Landing Gear Legs originated from corrosion pockets in the Y-joint weld.
Overview
The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia and administered by the Civil Aviation Safety Authority, includes Part 39 - 105 which contains Airworthiness Directives (AD) aimed at maintaining the safety and airworthiness of aircraft. One such AD, AD/DHC-6/50, pertains specifically to the DHC-6 (Twin Otter) series aeroplanes and mandates inspections of the main landing gear legs to address issues identified with corrosion pockets in the Y-joint weld, which could potentially lead to failures. The directive was introduced to ensure that any identified structural weaknesses are rectified to maintain the safety of air operations.
This AD requires inspections to be conducted in accordance with either Schedule No. 1 or Schedule No. 2 of the De Havilland Aircraft of Canada Ltd. Service Bulletin No. 6/380. The inspections are to be carried out within specific timeframes after certain milestones, such as the aeroplane's service hours or calendar dates, unless the inspections have already been performed within the preceding period. The objective of this AD is to proactively identify and address potential structural issues that could compromise the safety of the aircraft in service.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 105, encompasses Airworthiness Directives pertinent to various aircraft types, including the DHC-6 (Twin Otter) series aeroplanes. AD/DHC-6/50 mandates that all model DHC-6 aircraft, excluding those that have incorporated De Havilland Aircraft of Canada Ltd. Modification 6/1660, undergo mandatory inspections of the main landing gear legs. This requirement is designed to address corrosion issues identified in the Y-joint weld of the landing gear legs, a defect reported to originate from corrosion pockets. The inspections must be conducted in accordance with either Schedule No. 1 or Schedule No. 2 of the De Havilland Aircraft of Canada Ltd. Service Bulletin No. 6/380. Compliance timelines are stringent, with initial inspections mandated within 50 hours of time in service post 15 May 1980 unless previously accomplished, and a subsequent Check D inspection required within 2400 flight hours or before 21 December 1980, unless completed within the last 9600 hours of flight time or 4 years, with subsequent inspections at intervals not exceeding 12000 hours of flight time or 5 years. These directives apply nationally, ensuring uniformity in aircraft maintenance standards across the Commonwealth of Australia.
Key Provisions
The Civil Aviation Regulations 1998, under Part 39 - 105, specifically address the airworthiness directives for the DHC-6 (Twin Otter) Series Aeroplanes. The regulation AD/DHC-6/50 mandates the inspection of the main landing gear legs, referencing the De Havilland Aircraft of Canada Ltd. Service Bulletin No. 6/380 (sections 1 and 2). The directive requires that inspections be conducted in accordance with either Schedule No. 1 or Schedule No. 2 of the referenced service bulletin. The regulation permits an alternative to the visual external inspection by using a dye penetrant method, provided certain conditions are met (section 1). Furthermore, it requires a Check D inspection as per the Accomplishment Instructions of the same service bulletin (section 2).
The obligations imposed by this regulation on the parties or entities it governs are stringent and specific. Operators must inspect the main landing gear legs within 50 hours of the aircraft's time in service after 15 May 1980, unless these inspections have already been performed. Additionally, a Check D inspection must be conducted within 2400 hours of flight time or before 21 December 1980, whichever comes first. This inspection must also be performed if it has not already been done within the last 9600 hours of flight time or four years, and subsequently, at intervals not exceeding 12000 hours of flight time or five years, whichever comes first. These requirements are designed to ensure the ongoing airworthiness of the aircraft by preventing failures originating from corrosion pockets in the Y-joint weld of the landing gear legs.
Failure to comply with these regulations can result in severe consequences. Although the specific civil or criminal penalties for non-compliance are not detailed in the legislative instrument, it is implied that non-adherence could lead to the aircraft being deemed unairworthy. This could result in the aircraft being grounded until the necessary inspections and repairs are performed, potentially incurring significant financial and operational costs for the operator. The regulation’s focus on specific inspection intervals underscores the importance of compliance to maintain safety standards in aviation.