COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Gates Learjet 24 & 25 Series Aeroplanes AD/LEARJET/37 Outflow/Safety Valve 3/96 Applicability: Learjet 24/25 series aircraft as identified in Learjet Service Bulletin SB 24/25-21-4. Requirement: 1. Unless previously carried out, revise the Aircraft Flight Manual to amend the aircraft maximum operating altitude to 41,000 feet by; (a) inserting a CASA 'green page' amendment issued under CASA approval number "24 Initial" or "25 Initial" or, (b) inserting Learjet Temporary Flight Manual Change 94-15 dated 9 January 1995. 2. Unless previously carried out, action in accordance with paragraph 2B and 2C of Learjet Service Bulletin 24/25-21-4 dated 3 January 1995. 3. Remove the aircraft flight manual change introduced in Requirement 1 by application through the CASA District Airworthiness Office responsible for the aircraft. Note: FAA AD 95-20-03 Amdt 39-9381 refers and supersedes FAA AD 94-26-01 Amdt 39-9097. Compliance: Requirement 1. Prior to 1 April 1996. Requirement 2. Prior to 28 February 1997. Requirement 3. On compliance with Requirement 2. Background: The manufacturer has advised that valves identified in Allied Signal Service Bulletin 130406-21-A4011 Revision 3 or 102850-21-4021 Revision 2 may experience fracture or cracking of the poppet valve which could cause rapid decompression of the aircraft. Until affected valves can be replaced a flight manual amendment has been inserted in the Australian flight manual.