COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Eurocopter BK 117 Series Helicopters AD/GBK 117/12 Transmission and Engine Cowling Hook System 13/99 Applicability: All Model MBB BK-117 helicopters with serial numbers 7001 through 7253, and 7500 through 7523. Requirement: Action in accordance with Eurocopter Deutschland Service Bulletin MBB BK 117- 20-109 Revision 2, dated April 30 1999. Note 1: Accomplishment of Alert Service Bulletin MBB BK 117-20-104 is a prerequisite for compliance with this Directive for certain serial number helicopters, and is addressed by AD/GBK 117/3 Amdt 1. Compliance: Before 30 June 2000, unless already accomplished. This Airworthiness Directive becomes effective on 30 December 1999. Background: The LBA requires installation of a hook system to the doors of the transmission and engine cowlings to prevent the doors from opening fully during flight; in the event of the door fasteners not being correctly latched during pre-flight check.