COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 727 Series Aeroplanes AD/B727/108 Aileron Power Control Unit 6/89 Applicability: All model 727 series. Requirement: Unless already accomplished in accordance with National Water Lift SB 27-21-1/200 or NWL SB 27-10-1/200 Revision 1; 1. In accordance with Boeing Alert SB 727-27A0220: Remove and replace any aileron PCU which has accumulated 18000 or more hours since new or since piston seal replacement, OR 2. In accordance with Boeing Alert SB 727-27A0220: Remove any aileron PCU which has accumulated 18000 or more hours since new or since piston seal replacement and perform a hydraulic bench internal leakage check. Replace any aileron PCU which fails the internal leakage test. Note 1: Compliance to National Water Lift SB 27-21-1/200 or NWL SB 27-10-1/200 Revision 1 constitutes terminating action for this AD. NOTE 2. FAA AD 89-07-05 Amdt 39-6163 refers. Compliance: 1. Within the next 3000 hours time in service on the PCU, after 15 June 1989 and thereafter at intervals not exceeding 18,000 hours. 2. Within the next 3,000 hours time in service on the PCU after 15 June 1989 and thereafter at intervals not exceeding 2,500 flight cycles. Background: Incidents of aileron control wheel binding have been attributed to internal damage in the aileron power control unit. This damage was due to deterioration of the piston primary seals. Service experience indicates that significant seal deterioration can be anticipated on units that have accumulated 18,000 hours or more since new or last overhaul.