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-6/69
Amdt 1
Corrosion Prevention and Control 13/99
Applicability: All Model DHC-6 aircraft.
Requirement: To maintain corrosion to Level 1 or better, accomplish the following:
- Develop a schedule for accomplishing the Corrosion Tasks in accordance with Requirement 2 of this Directive.
2. In accordance with the following schedule, accomplish all Corrosion Tasks specified in Part 3 of the de Havilland DHC-6 Twin Otter Corrosion Prevention and Control Manual, PSM 1-6-5, Revision 1, dated 16 December 1998 (hereafter referred to as “the Manual”), by performing the seven basic tasks defined at paragraph 3.0 of the Manual.
The final deadline and rate of initial complete aircraft inspections are specified in the following table:
Applicable Aircraft Serial Numbers
Accomplishment Deadline for All Aircraft in Applicable S/N Range
Minimum Rate of Initial Inspections of Aircraft in Applicable S/N Range
001 to 199 31 December 1995 All aircraft
200 to 439 31 December 1996 50% or one (1) aircraft per calendar
year, whichever is greater
440 to 659 31 December 1998 25% or one (1) aircraft per calendar
year, whichever is greater
660 to 819 31 December 1999 20% or one (1) aircraft per calendar
year, whichever is greater
820 to 844 31 December 2002 Commencing 1 January 1999, 25% or
one (1) aircraft per calendar year, whichever is greater
Once the first CT commences, the aircraft is not to be returned to service until all CTs, excluding the float inspections, have been completed and any resulting rework and parts replacement have been completed. Floats that were on an aircraft just prior to the aircraft being inspected in accordance with the Manual do not have to be inspected simultaneously with that same aircraft; however, the aircraft cannot be returned to service with floats that have not had their applicable CTs completed and any resulting rework and parts replacement completed.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
When performing CTs with less than a five year Repeat Interval (R) after the initial inspection of the aircraft, all CTs with the same R interval are to be completed during one maintenance visit and any resulting rework and parts replacement must be performed before returning the aircraft or floats to service.
Corrosion is to be addressed in accordance with the references specified in paragraph
4.0 of Part 3 of the Manual.
Corrosion level determinations are to be based on the definitions contained in Part 1 of the Manual.
Corrosion classified as Level 1 need not be reported.
Level 2 corrosion may be consolidated with a quarterly report of corrective action, and submitted to the Authority District (Airport) Office under cover of a single MDR.
Level 3 corrosion shall be reported by MDR.
Note: Transport Canada AD CF-94-12R1 refers.
Compliance: 1. Prior to 31 January 1995.
2. Commencing 1 February 1995.
The compliance of the original issue of this Directive remains unchanged. This Amendment becomes effective on 30 December 1999.
Background: As aircraft become older, they are more likely to exhibit indications of corrosion.
Transport Canada Aviation, in conjunction with other airworthiness authorities, has committed itself to ensuring that additional maintenance programs for older aircraft are developed and implemented to minimise and control corrosive deterioration that could jeopardise airworthiness.
Amendment 1 is issued in response to revision of the related Transport Canada AD which introduces Revision 1 of the CPC Manual which deletes the requirement for repetitive inspections after initial compliance. Transport Canada AD CF-99-11 (AD/DHC-6/72) now provides for the requirement to perform the inspections a second time, but on a more flexible schedule than required by the original issue of this Directive.
The original issue of this Directive became effective on 8 December 1994.
Overview
The Civil Aviation Regulations 1998 were enacted to ensure the safety and efficiency of civil aviation in Australia. The Civil Aviation Safety Authority (CASA) under this Act issues Airworthiness Directives (ADs) to address specific safety issues, ensuring aircraft meet safety standards. AD/DHC-6/69 Amendment 1, introduced in 1999, is one such directive aimed at preventing and controlling corrosion in DHC-6 (Twin Otter) Series Aeroplanes. This amendment was necessary to align with the updated Transport Canada AD CF-99-11, which revised the Corrosion Prevention and Control Manual. The policy objective is to ensure that all DHC-6 aircraft maintain a corrosion level of 1 or better by adhering to a specified inspection and maintenance schedule. This schedule aims to prevent corrosive deterioration that could compromise the airworthiness of these aircraft.
Scope and Application
The Civil Aviation Safety Authority Schedule of Airworthiness Directives (AD) for DHC-6 (Twin Otter) Series Aeroplanes applies to all Model DHC-6 aircraft. This legislative instrument mandates that these aircraft must maintain corrosion at Level 1 or better, requiring operators to develop a schedule for accomplishing Corrosion Tasks in accordance with specific requirements detailed in the de Havilland DHC-6 Twin Otter Corrosion Prevention and Control Manual. The schedule for initial complete aircraft inspections is set out in a table within the AD, with deadlines based on the applicable aircraft serial numbers and rates of inspection specified for different ranges. Once the first Corrosion Task (CT) commences, the aircraft cannot be returned to service until all specified tasks are completed, excluding float inspections, and any resulting rework and parts replacement are finished. This AD applies nationally within Australia, administered under the Civil Aviation Regulations 1998, and its provisions extend through subordinate instruments as necessary to ensure compliance.
Key Provisions
The Civil Aviation Regulations 1998, particularly Part 39, outlines the Airworthiness Directives (AD) concerning DHC-6 (Twin Otter) series aeroplanes, specifically addressing corrosion prevention and control as per AD/DHC-6/69 Amendment 1 (sections 13/99). The directive mandates that all Model DHC-6 aircraft must maintain corrosion at Level 1 or better, which necessitates a systematic approach to corrosion tasks. The directive requires operators to develop a schedule for accomplishing the Corrosion Tasks as specified in Part 3 of the de Havilland DHC-6 Twin Otter Corrosion Prevention and Control Manual (PSM 1-6-5, Revision 1). This involves performing the seven basic corrosion tasks outlined in the Manual, ensuring that the inspections and any necessary rework or parts replacement are completed before the aircraft is returned to service.
The obligations imposed by the Act require operators to adhere to the specified deadlines and inspection rates for the initial complete aircraft inspections. For instance, aircraft with serial numbers 001 to 199 must complete all inspections by 31 December 1995, while those with serial numbers 200 to 439 must adhere to a deadline of 31 December 1996, with a minimum inspection rate of 50% or one aircraft per calendar year, whichever is greater. Similarly, other serial number ranges have specified deadlines and inspection rates, with the aim of ensuring that all aircraft are inspected and maintained to the required standard by the stipulated dates. Additionally, operators must ensure that floats are not returned to service unless all corrosion tasks have been completed, including any necessary rework and parts replacement.
Failure to comply with these directives can result in significant consequences. While the regulations do not explicitly state penalties, non-compliance can lead to safety issues that may result in enforcement actions by the Civil Aviation Safety Authority (CASA). Such actions could include grounding of aircraft, fines, and other regulatory sanctions. The overarching goal of these regulations is to ensure the continued airworthiness of DHC-6 series aeroplanes by mitigating the risk of corrosion, thereby maintaining high safety standards within the aviation industry.