COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES GAF N22 and N24 Series Aeroplanes AD/GAF-N22/66 Amdt 2 Stub Fin Ribs 12/98 Applicability: All Nomad N22 series and N24 series aircraft. Requirement: Action in accordance with ASTA Nomad Alert Service Bulletin ANMD-53-16 Revision 2. Compliance: Within 100 hours time in service after 5 November 1998 or before 10 February 1999, whichever occurs first; thereafter at intervals not to exceed 300 hours time in service or 12 calendar months, whichever occurs first. This Amendment becomes effective on 5 November 1998. Background: Cracks have been found in the stub fins of the Nomad tail section fatigue test article. Failure of the ribs would result in loss of structural stiffness in the stub fin, and possible loss of aircraft control. Amendment 1 increased the scope of the inspection to other areas of the stub fin structure. Amendment 2 is issued in response to revision 2 of the Requirement document which was prompted by a report from an operator of a crack at the forward end of the stub fin lower diaphragm. Tailplane resonance testing also indicated possible cracking of the stub fin front corner posts below the stub fin lower diaphragm. Amendment 1 of this Airworthiness Directive became effective on 14 September 1995. The original issue of this Airworthiness Directive became effective on 16 September 1993.