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-6/35
Amdt 2
Wing Rear Spar Attachment Fittings 3/92
Applicability: Model DHC-6, all series, with serial numbers 1 through 330 inclusive, not incorporating modification 6/1301 or 6/1630.
Requirement: 1. Action in accordance with de Havilland Service Bulletin 6/295 Revision B; subject to the following changes:
(a) Inspection Method A.1 (Radiographic) is to have the exposure time of 60 seconds increased to 120 seconds for the inboard X-ray tube location; and
(b) The X-ray beam angle of approximately 10 degrees is to be changed to approximately 5 degrees for all of the X-ray locations.
2. Incorporate de Havilland modification 6/1301.
Note: Transport Canada AD CF-73-03 R1 refers.
Compliance: 1. At intervals specified in the Requirement Document, until modified in accordance with Requirement 2.
2. Prior to 30 September 1993.
The compliance with paragraphs of the previous issue of this Directive were:
For Paragraph 1 - Within 200 hours time in service after 20 October 1972 and thereafter at intervals not exceeding 200 hours time in service.
For Paragraph 2 to 6 - Within the time limits as detailed in the respective paragraphs. This Amendment is effective from 6 March 1992.
Background: Inter-rivet cracking of the top flange of the attachment cap member, part number C6WM1032-1 and -2 located at the inboard end of the wing rear spar, has been found on a number of aircraft in service. Reports have also been received that the radiographic inspection set out in the de Havilland Service Bulletin 6/295 is not locating all the cracks.
Amendment 2 is issued to align this Directive with a revision of the related Country of Origin AD, which requires terminating action in lieu of ongoing inspections.
Overview
The Civil Aviation Regulations 1998, enacted by the Parliament of the Commonwealth of Australia, are designed to ensure the safety of civil aviation in Australia. The specific regulation in focus here is Part 39 - 105, which pertains to the Civil Aviation Safety Authority's Schedule of Airworthiness Directives for DHC-6 (Twin Otter) Series Aeroplanes, as amended. This legislation was introduced to address the identified issue of inter-rivet cracking in the wing rear spar attachment fittings of certain DHC-6 aircraft models, which could compromise the structural integrity and safety of the aircraft. The policy objective of this amendment is to enhance the inspection and modification processes to ensure the ongoing airworthiness of these aircraft, in line with international standards and recommendations from authorities such as Transport Canada.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 105, pertains to the Civil Aviation Safety Authority's (CASA) Schedule of Airworthiness Directives, targeting the DHC-6 (Twin Otter) Series Aeroplanes. The Act applies to all DHC-6 aircraft models across all series, with serial numbers ranging from 1 to 330 inclusive, unless they have already incorporated modifications 6/1301 or 6/1630. This regulation is jurisdictional across the Commonwealth of Australia, enforcing safety standards set forth by CASA. The primary requirement of this directive is for aircraft operators to comply with the updated de Havilland Service Bulletin 6/295 Revision B, which includes specific changes to the inspection methodology and angles for radiographic inspection to ensure the detection of inter-rivet cracking on the wing rear spar attachment fittings. Compliance must be achieved in intervals specified within the Requirement Document until the aircraft is modified in accordance with the second requirement. The directive mandates that modifications be completed prior to 30 September 1993, thereby establishing a clear timeframe for operators to adhere to the outlined safety measures. This legislative instrument ensures that the aircraft meet the necessary safety standards, thus maintaining operational airworthiness within the Australian airspace.
Key Provisions
The Civil Aviation Regulations 1998, specifically Part 39 - 105, include an Airworthiness Directive (AD) pertaining to the DHC-6 (Twin Otter) Series Aeroplanes, which addresses wing rear spar attachment fittings (AD/DHC-6/35 Amendment 2). This directive applies to all DHC-6 series models with serial numbers ranging from 1 to 330, excluding those that have already incorporated modification 6/1301 or 6/1630. The directive mandates compliance with de Havilland Service Bulletin 6/295 Revision B, with specific adjustments to the inspection method. Specifically, the radiographic inspection method, as described in Inspection Method A.1, requires an increase in exposure time from 60 seconds to 120 seconds for the inboard X-ray tube location, and a reduction in the X-ray beam angle from approximately 10 degrees to approximately 5 degrees across all X-ray locations. Additionally, the directive requires the incorporation of de Havilland modification 6/1301.
Compliance with this AD involves two key elements. Firstly, inspections must be carried out in accordance with the specified requirements until the aircraft are modified as per Requirement 2. Secondly, the modifications must be completed by 30 September 1993. The previous compliance criteria required inspections within 200 hours of time in service after 20 October 1972 and subsequently at intervals not exceeding 200 hours of time in service. This amendment to the AD is effective from 6 March 1992.
Entities governed by this AD must ensure that their DHC-6 series aircraft meet the specified requirements, which include performing the adjusted radiographic inspections and incorporating the required modification. The directive aims to address the issue of inter-rivet cracking in the wing rear spar attachment fittings, which has been identified as a safety concern. Failure to comply with the AD could result in non-airworthiness of the affected aircraft, which could in turn lead to serious safety implications. The Civil Aviation Safety Authority (CASA) enforces these regulations, and non-compliance could result in enforcement actions, including potential penalties or grounding of the aircraft until compliance is achieved.