COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Aerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes AD/TB20/28 Amdt 1 Front Seats 13/94 Applicability: Model TB20 & TB21 aircraft front seats with a tilting back-rest, installed from February 1991 on aircraft up to S/N 1479; except aircraft S/N 1192, 1193, 1308, 1426 thru 1433, 1448, 1461, 1462, 1464 thru 1469, 1471, & 1473 thru 1477. Requirement: Action in accordance with Socata TB Service Bulletin 10-075-25 Amendment 1. Note: DGAC AD 94-114(A)R1 refers. Compliance: Unless already accomplished, within 50 hours time in service after 8 December 1994, or at the next inspection for maintenance release issue, whichever occurs first. Background: The DGAC requires reinforcement of the front seat structure. Amendment 1 is issued to reflect an amendment of the manufacturer's bulletin which clarifies applicability and weld filler material.