Safety Regulation Group 19 May 2003 Our Ref 9/97/CtAw/53 NOTIFICATION OF A CAA AIRWORTHINESS DIRECTIVE Please be advised that the Civil Aviation Authority has classified compliance with the following action as mandatory for aircraft on the United Kingdom Civil Register. Applicability British Aerospace BAe 146 aircraft with Modifications HCM30027A, HCM36019A or HCM30373A and Avro-RJ aircraft with Modifications HCM36019A or HCM30373A. Subject - Description Airborne Auxiliary Power (APU) – Introduction of improved APU inlet flexible duct Part No. DXA07175. Compliance - Requirement (Summary) Compliance is required with BAE Systems (Operations) Service Bulletin SB.49-036-36019E at Revision 4 at the next scheduled APU removal or the next aircraft ‘C’ check whichever is the sooner. The Service Bulletin introduces a rectangular metallic bellows duct incorporating an improved seal and clamp arrangement as a direct replacement for the rubber bellows duct. This action is required because the existing APU inlet duct and sealing arrangements have been found to be unreliable in service. This can result in APU bay air being ingested, which if contaminated can lead to poor cabin air quality. R J Tew Airworthiness Directive Co-ordinator