COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Pratt and Whitney Turbine Engines - JT9D Series AD/JT9D/21 Drain Tube Replacement 5/90 Applicability: JT9D-7R4 engines fitted to Boeing 767 aircraft. Requirement: Replace three existing drain tubes and a tee fitting as detailed in Boeing Service Bulletin 767-71A0057. Compliance: Prior to 31 December 1990. Background: This Directive requires replacement of certain drain lines and a tee fitting to prevent possible oil loss due to chafing of the number three oil pressure line against a drain tube tee fitting.