COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Propellers - Variable Pitch - Hartzell AD/PHZL/8 Hub Spider - Replacement NK Applicability: All HC12X20 models. Requirement: 1. Replace all Hartzell hub spiders having S/Nos. as follows: 1 to 4303, 4307 to 4316, 4318, 4319, 4321, 4323, 4324, 4325, 4328, 4329, 4332 to 4336 and 4341. 2. Hub spiders with S/nos. other than those listed above may be used as replacements; or FAA AD 59-26-1; or ANO 107.1.11.0.1.7. Compliance: Before installation in an aircraft.