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/39 Introduction Of Inverter Part No. 1B350-1B1-3 (Modification Jm 7740) Applicability: All Jetstream aircraft detailed in the Requirement Document. Requirement: Action in accordance with BAe SB 24-JM 7740. Note 1: Compliance with this SB is considered mandatory by the CAA (UK). 3/91 Note 2: Accomplishment of modification JM 7740 (Mandatory SB 24-JM 7740) in accordance with this AD does not remove the necessity to comply with the emergency procedures of the flight manual amendment introduced by Mandatory Alert SB 24-A- JA 900443 (refer AD/JETSTREAM/38, Requirement 1). The Flight Manual emergency procedures are revised only after the accomplishment of both Mandatory SB 24-JM 7740 and optional SB 24-JA 900941. Compliance: As specified in the Requirement Document. Background: BAe have advised that investigations into recent AC power instability problems have been concluded, and the cause has been determined to be inadequate protection within the part no 1B350-1B1-2 inverters. This AD mandates compliance with BAe Mandatory SB 24-JM 7740, and advises that compliance with optional SB 24-JA 900941 as well as with SB 24-JM 7740 will allow the transfer function deleted by Alert 3/91SB 24-JA 900443 R1 (refer AD/JETSTREAM/38, Requirement 1) to be reinstated.