COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/135 Potable Water Tank Pressure Relief Valve 2/95 Applicability: All Boeing 747 aircraft, line number 1 to 1013 inclusive. Requirement: Action in accordance with Boeing Alert Service Bulletin 747-38A2105. Compliance: Unless previously carried out by 1 August 1995. Background: Boeing has advised that rupture of several potable water tanks have occurred. In one incident the upper polar cap from the main body of the potable water tank separated and smashed through the cabin floor at seat row 21 striking the main deck ceiling panel and PSU area.