COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 550 (Citation II) Series Aeroplanes AD/CESSNA 550/9 Airframe Ice Protection System Proportioning Units Applicability: All model S550 with unit numbers -0001 to -0075. 2/86 Requirement: 1. Install the following placard on the instrument panel in full view of the pilot using letters of at least 5mm in height: "Flight into Known or Forecast Icing Prohibited". 2. Perform the requirements of FAA AD 85-24-04 paragraphs B.1, 2, 3 and 4. Compliance: 1. Prior to further flight after 20 December 1985 until the actions of paragraph 2 of the Requirement have been complied with. 2. Within 100 hours time in service after 28 February 1986. Background: The manufacturer has identified a production error resulting in incorrect installation of fluid ice protection system proportioning units. This Directive removes approval for flight into icing conditions and requires inspection and replacement, as necessary, of the fluid protection system proportioning units.