COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES British Aerospace BAe 3100 (Jetstream) Series Aeroplanes AD/JETSTREAM/81 Nose Wheel Steering Jack Seal Change 1/99 Applicability: All British Aerospace Regional Aircraft HP137 Mk 1 Jetstream Series 200, 3100 and 3200 series aircraft. Requirement: Modify the nose wheel steering jack in accordance with British Aerospace Regional Aircraft Service Bulletin 32-JA900942 Revision 5 and the Landing Gear manufacturer's Service Bulletin, APPH Limited SB32-51 Revision 5. Note: UK CAA AD 003-09-98 dated 22 Oct 98 refers. Compliance: At the next scheduled overhaul of the nose wheel steering jack but no later than 30 September 1999. This Airworthiness Directive becomes effective on 28 January 1999. Background: Following a recent serious incident it was discovered that the nose wheel steering jack seals were deteriorating and contaminating the jack to the extent of causing steering lock up. This Directive mandates the incorporation of a modified, improved seal to prevent steering jack lock up.