AD/DHC-6/31 Amdt 4 Structural Component Inspection, Modification and Life Limitation (Cth)
AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DHC-6/31 Amdt 3 and issues the following AD under subregulation 39.001(1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
DHC-6 (Twin Otter) Series Aeroplanes
| AD/DHC-6/31 Amdt 4 | Structural Component Inspection, Modification and Life Limitation | 12/2006 |
Applicability: | All DHC-6 aircraft. |
Requirement: | 1. Inspect, modify, and/or retire the affected structural components as specified in Bombardier PSM 1-6-11 Revision 5, dated 11 January 2000, or later Transport Canada approved revision. 2. For aircraft that are approaching or have exceeded the threshold of the new or revised inspections introduced by PSM 1-6-11 Revision 5, compliance with the threshold inspection may be modified as detailed in Compliance 2. Note: Transport Canada AD CF-2000-14 refers. |
Compliance: | 1. As specified in the Requirement document. 2. Pre. Mod. 6/1117 Wing Assemblies a. If the previous inspection of the wing main spar, attachment lug fastener holes, conducted prior to 10 August 2000, was an eddy current inspection carried out in accordance with instructions supplied by Bombardier, conduct the repeat high frequency eddy current inspection in accordance with the schedule in PSM 1-6-11 Revision 5, or later Transport Canada approved revision. b. If the previous inspection of the wing main spar, attachment lug fastener holes, conducted prior to 10 August 2000, was an ultrasonic inspection carried out in accordance with Bombardier Service Bulletin 6/525, conduct the first high frequency eddy current inspection within 1,000 hours flight time or 2,000 flights, whichever occurs first, after the last ultrasonic inspection. Post Mod 6/1117 and Post Mod 6/1630 Wing Assemblies If the inspection threshold for the lower wing skin, stringers and aft spar lower flange WS122 TO WS263 (ribs 8 to 20) has been exceeded or will be exceeded within 6 months after 10 August 2000, conduct the initial inspection within 500 hours flight time or 1,000 flights, whichever occurs first, but not later than 6 months after 10 August 2000. |
| The compliance times remain unchanged by this issue of the Directive. | |
| This Amendment becomes effective on 23 November 2006. | |
Background: | Tests by the manufacturer established the need, endorsed by Transport Canada, for modification and retirement of items of primary structure at the periods specified in the Structural Components Service Life Limits Manual. Amendment 1 reflected the amendment status of SB 6/268 and PSM 1-6-11. Amendment 2 reflected the structural re-evaluation of the de Havilland DHC-6 airframe. This re-evaluation resulted in life extensions for some structural components and life reductions for others, as well, new structural inspections have been introduced. The most notable determination was a life limit for the aircraft structure. Amendment 3 introduced a revision of the service life information for the DHC-6 aircraft, as reflected in Structural Components Service Life Limits Manual, Amendment 4 is issued to allow use of later revisions of the Structural Components Service Life Limits Manual PSM 1-6-11. |
David Villiers
Delegate of the Civil Aviation Safety Authority
12 October 2006
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