COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES De Havilland DHC-1 (Chipmunk) Series Aeroplanes AD/DHC-1/30 Amdt 1 Applicability: All models. Engine Mount Upper Attachment Points/Reinforcing Plates 10/86 DM Requirement: Action in accordance with: 1. British Aerospace TNS Chipmunk (C1) No. 180 Issue 1, and b. British Aerospace Modification Chipmunk H358. Compliance: Prior to 1 August 1986. Aircraft which have been modified to a different engine installation are affected by this Directive. Some of these aircraft have external reinforcing doublers which may not be sufficient to meet the requirements of this Directive. If there are no doublers present or if they do not cover the vertical and horizontal extent of Mod. H358, or are not of the required thickness, the aircraft will need further evaluation and/or modification in accordance with a scheme approved by the Secretary. For these aircraft only, the compliance date is extended to 31 December 1986. Background: External reinforcing plates are introduced on the forward fuselage skin adjacent to the two engine upper mounting attachment points, together with an access hole for periodic inspection of the upper deck plate and adjacent internal structure. This amendment clarifies the position with regard to re-engined aircraft such as the DHC- 1/A1 and DHC-1/A2.