AD/DHC-1/12 Amdt 7 - Fatigue Life Limitations

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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-1/12 Amdt 6 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.
De Havilland DHC-1 (Chipmunk) Series Aeroplanes
AD/DHC-1/12 Amdt 7
Fatigue Life Limitations
All models except English and Portuguese built.

Incorporate into the aircrafts maintenance schedule, life limitations and/or inspections of critical structure determined from a fatigue assessment approved by the Authority.
Note 1:  The fatigue life assessment may involve retirement lives of components and/or an inspection scheme that manages fatigue through detection of fatigue cracks in critical structure using damage tolerance methodology.
Note 2:  Consideration should be given to the operational usage and severity of the aircraft’s historical and future operations.

This Amendment becomes effective on 14 May 2012.

State of Design Airworthiness Directive G-2012-0001 dated 15 March 2012 has been issued by the UK CAA.  The UK directive supersedes requirements for British and Portuguese built aircraft and mandates information contained in TNS CT(C1) No 138 Issue 6 for those aircraft.
This Amendment remains applicable to Canadian built Chipmunks and recognises that Canadian built Chipmunks are structurally different to the English and Portuguese built models and in some cases to each other.
De Havilland aircraft of Canada have advised that they have not carried out a fatigue assessment of the Canadian Chipmunk models and have no immediate intention to do so.  The previous issue of this directive required Canadian Chipmunk models to have a fatigue assessment carried out and this requirement remains unchanged in this directive.

Mike Higgins
Delegate of the Civil Aviation Safety Authority
8 May 2012

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