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 146/30 Lower Wing Skin 4/91 Applicability: Model 146 with Constructor's Numbers: E2133, E3134, E3135, E3137, E2139, E3141, E3142, E3145, E2148, E3151 and E3155. Requirement: Action in accordance with Mandatory BAe 146 SB 57-36. Compliance: As specified in the Requirement Document but with a revised effectivity date of 18 April 1991 for Australian registered aircraft. Background: Production inspection records cannot confirm that chamfering of the edge of the inner skin was carried out during aircraft build. Fretting of an unchamfered skin edge against the inner face of the outer butt strap could lead to an increase in stresses on the butt strap.