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/77 Stall Warning - Removal of Ground Inhibit Switch 4/98 Applicability: All BAe Regional Aircraft Jetstream 3100 and 3200 Series aircraft with Modification JM7813A (SB 27-JM7813A) or Modification JM7813B embodied. Requirement: Unless previously accomplished, remove the ground inhibit function of the stall warning system in accordance with BAe Alert Service Bulletin 27-A-JM7847. Note: CAA UK AD 003-12-97 refers. Compliance: No later than 26 June 1998. This airworthiness directive becomes effective on 26 March 1998. Background: Modification JM7813 installed a ground inhibit relay and ground test relay to prevent the operation of the stall warning system until the aircraft has been airborne for at least three seconds. Investigation by BAe has shown that a failure of the ground test relay in the energised position would cause a failure in the stall warning system with no indication to the crew of the malfunction.