COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Short SD3-60 Series Aeroplanes AD/SD3-60/21 Landing Gear Warning Horn 12/86 Applicability: All models SD3-60 aeroplanes with S/Nos. SH3601 through SH3689. Requirement: 1. Upon replacement of Lucas horn P/No V.0603L with Keystone horn P/No. AC155F, relocate mounting of horn according to the requirements of Shorts SD3- 60 Service Bulletin SD360-32-23. 2. For aeroplanes previously fitted with Keystone horn P/No. AC155F, relocate mounting of horn according to the requirements of the document referenced in Para 1 above. Compliance: For Para 1: Upon replacement. For Para 2: Within 30 hours time in service after 31 January 1987. Background: Reports have been received that the Keystone P/No. AC155F landing gear warning horn is inaudible when located between Station 3 and 13.45 on the aircraft top centre line.