COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES British Aerospace BAe 146 Series Aeroplanes AD/BAe 146/25 Freight Door Torque Shaft 3/91 Applicability: Model 146 with Constructor's numbers listed in BAe SB 52-81-56012A Rev 1. Requirement: Action in accordance with BAe Mandatory SB 52-81-56012A Rev 1. Compliance: As specified in the Requirement Document with revised effective date 31 March 1991. Background: This Directive is raised to introduce a modification that adds two spring struts to the torque shaft detents to provide additional locking torque. This will ensure that the vent door does not open under any circumstances other than normal freight door operation.