COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 400 Series Aeroplanes AD/CESSNA 400/70 Elevator Horn Inboard Tip Rib - Modification Applicability: All model 441 with S/Nos. 441-0001 to -0106 and 0109. Document: Cessna Propjet SIL No. PJ79-32. 4/80 Compliance: Unless already accomplished, within 25 hours time in service after 28 February 1980. Background: Sealing of the inboard tip rib of the elevator horn is required to preclude foreign material from entering or exiting the elevator tip rib.