COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Porsche Piston Engines AD/PORSCHE/2 Engine - Output Shaft Bearing 4/89 DM Applicability: Porsche 930/67 (Skyship 600) and 930/01 (Skyship 500). Requirement: Replace bell housing, complete with output shaft, bearing, bearing housing, sealing ring and retaining nut in accordance with, For Skyship 500, Airship Industries SB 500-72-A297 and For Skyship 600, Airship Industries SB 600-72-A297 Note 1: CAA(UK) Airworthiness Directive 057-12-88 refers. Note 2: Compliance with this Directive: for 930/01 engines is Mod 25 (embodiment of kit No 5-877) and, for 930/67 MK 1 engines - Mod 24 and 930/67 MK2 engines Mod 4. Compliance: Unless already accomplished; For installed engines within 75 operating hours, For uninstalled engines prior to installation, After 17 February 1989. Background: This Directive is issued following further investigation by the manufacturer after the issue of Inspection Service Bulletin 500-72-297 on 24-10-88, revealed the cause of bearing failure. All known failures were on bearings having a heat stabilised polyamide bearing cage with a limiting speed of 3200 rpm.. This has resulted in the necessity to replace the bearing with an improved item with a higher limiting speed.