COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Rolls Royce Turbine Engines - Viper Series AD/VIPER/8 Oil Tank and Oil Pump Drain Valves 9/90 DM Applicability: Viper Mk 520, 521 and 522 engines. Requirement: Inspect oil tank and oil pump drain valve assemblies in accordance with Rolls Royce Viper Mks 520, 521 and 522 Service Bulletin No 72-A381. Note: CAA UK Airworthiness Directive 030-04-90 refers. Compliance: (1) Engines in service - Prior to 6 August 1990. (2) Uninstalled engines - Prior to installation in an aircraft. Background: Failure to detect oil leakage at the oil tank drain valve may result in total loss of oil pressure. Investigation of a total loss of oil pressure on a test flight following engine installation revealed that the oil tank drain valve cap was not in position and the drain valve was stuck open allowing a rapid loss of oil tank contents.