COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Propellers - Fixed Pitch AD/PFP/18 Hoffman Propeller Bolt Replacement 11/98 Applicability: All Hoffman HO 27 ( ) and HO4 27 ( ) model propellers using propeller mounting bolts P/N FP20-147. If the part number of the installed bolts cannot be positively established, assume they are P/N FP20-147 and are, therefore, subject to the requirements of this Directive. Requirement: 1. Inspect propeller installation in accordance with Hoffman Propeller Service Bulletin SB 61-11-03 E10 Revision A dated 28/7/98. 2. Replace the propeller mounting bolts, P/N FP20-147 with serviceable bolts that feature a "V" marking in accordance with Hoffman Propeller Service Bulletin SB 61-11-03 E10 Revision A dated 28/7/98. Note 1: LBA AD 1998-322 also refers. Note 2: Refer to AD/PFP/1 Amdt3 (or later amendment) for ongoing torque requirements for fixed pitch wooden propellers. Compliance: 1. Within 30 days of the effective date of this Directive. 2. At the next occasion the propeller is removed from the aircraft, but no later than 1 April 1999. This Airworthiness Directive becomes effective on 8 October 1998. Background: After an accident investigation it was found that the strength values of the propeller mounting bolts were below design specifications. The lower design specifications of the bolts could lead to premature failure of the bolts and subsequent separation of the propeller in flight.