COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Aerospatiale (Socata) TB9 and TB10 (Tobago) Series Aeroplanes AD/TB10/16 Lower Engine Cowl Carburettor Air Supply 3/91 Applicability: All TB9 & TB10 series aircraft from S/No's 1 to 944 inclusive fitted with lower cowling carburettor air supply. Requirement: Action in accordance with the technical requirements of DGAC AD 90-240 (A). Compliance: As specified in the Requirement Document with revised effective date of 31 March 1991. Background: The lower engine cowl `NACA' fitting can be damaged if the supply hose clamp is overtightened. If the fitting is damaged the intake hose could come loose possibly restricting engine operation.