COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Kawasaki BK 117 Series Helicopters AD/JBK 117/13 Engine Mount Truss Supports 4/99 Applicability: Kawasaki model BK-117, BK-117A-3, BK-117A-4, BK-117B-1, and BK-117B2 helicopters. Requirement: Action in accordance with Kawasaki Service Bulletin KSB -117-127. Note: JCAB AD TCD-4930-99 refers. Compliance: For helicopters with less than 1,200 total flight hours: Unless already accomplished, at the first 1,200 inspection. For helicopters with more than 1,200 total flight hours: Unless already accomplished, at the next 600 hour inspection or next engine removal after 22 April 1999, whichever occurs first. This Airworthiness Directive becomes effective on 22 April 1999. Background: Cracks caused by grain boundary corrosion were detected on the engine mounting sideward link. This Directive requires an inspection for corrosion on the engine truss supports which are fabricated with an identical material and installed in the same environment as the sideward link.