COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F28 Series Aeroplanes AD/F28/54 Horizontal Stabilizer Control Unit Bolts 4/88 Applicability: All aircraft. Requirement: Ensure that the horizontal stabilizer control unit has been modified to incorporate the NAS 1303 bolts required by Menasco Service Bulletin No 27-76 Rev 3, rather than AN 3 bolts. Note: Fokker F28 S B No 27-168 Rev 1, RLD AD 86-08, DGAC AD 86-111-IMP(B) and FAA AD 87-18-01 all refer. Compliance: Not later than 7 October 1988 and on each occasion on which the lock washer P/No 25011-1 is disturbed. Note: Aircraft equipped with horizontal Stabilizer control units P/No 11100 (all dash numbers) which do not have S B 27-76 stamped on the nameplate are most likely to be affected. At delivery this included aircraft S/Nos 1003 to 11195, 11991 and 11992. Background: Fatigue failures of certain bolts in the horizontal stabilizer control unit have occurred in service. This condition, combined with an in-flight hydraulic system failure, could add to uncontrolled movement of the horizontal stabilizer. Therefore a modification has been introduced which replaces the affected AN 3H3A bolts with stronger NAS 1303-2H bolt.