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/PC-6/51 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. Pilatus Porter PC-6 Series Aeroplanes AD/PC-6/51 Amdt 1 Stabiliser-Trim Attachment 8/2005 Components - Inspection/Replacement Applicability: All Model PC-6 Series aircraft, all serial numbers up to and including MSN 946. All Model PC-6 Series aircraft, manufactured by Fairchild Industries, MSN 2001 through MSN 2092. Requirement: Perform an inspection for crack damage in the applicable stabiliser-trim attachment and structural components, in accordance with Pilatus Aircraft Service Bulletin No. 53-001 Revision 1, dated 1 June 2005. If are cracks are found during the Requirement 1 inspection, before further flight, replace any crack damaged components. Replace without inspection any Fairchild type connecting pieces part number 6232.0026.xx installed in Config. 2 aircraft with Pilatus type connecting pieces. Replace without inspection any fittings part number 116.40.06.033 without an index after the part number with new fittings part number 116.40.06.033 with an index after the part number or with new fittings part number 116.40.06.112. Note: FOCA AD HB-2005-263 refers. Compliance: At the next 100 hour inspection or 3 months after 4 August 2005. This Amendment becomes effective on 4 August 2005. Background: This Directive is prompted by an occurrence where a PC-6 aircraft had to make an emergency landing outside an airport after the failure of the lower attachment bracket of the horizontal stabiliser. This type of failure could result in loss of control of the aircraft. Amendment 1 is issued in response to a new FOCA AD, which supersedes existing ADs HB-86-042 (AD/PC-6/40) and HB-2005-080. The AD mandates the replacement of certain part number fittings which provides terminating action for the repetitive inspections required by HB-86-042. Furthermore, the new AD introduces Revision 1 of the Requirement document, which includes a correction of the tolerance of the actuator attachment hole diameters in fitting part number 116.40.06.033 of Config. 1 aircraft; and extends and specifies aircraft applicability. David Villiers Delegate of the Civil Aviation Safety Authority 21 June 2005