COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F50 (F27 Mk 50) Series Aeroplanes AD/F50/75 Aft Fuselage Skin Joint 6/97 Applicability: All Serial numbers F27 Mk 050. Requirement: Inspect in accordance with Fokker Service Bulletin F50-53-053. Note: Netherlands AD 1997-022(A) refers. Compliance: Before accumulating 10 000 flight cycles from new, or within 6 months after 22 May 1997, whichever occurs last. This Airworthiness Directive becomes effective on 22 May 1997. Background: Fatigue cracking has been discovered on the LH side of the fuselage between STA 15375 and STA 16275 following investigation of pressurisation problems. Such cracking could lead to an unsafe condition, and thus requires an inspection to detect any problem, and to take any necessary corrective action.