AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/LJ45/4 and issues the following AD under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. Learjet 45 Series Aeroplanes AD/LJ45/4 Amdt 1 Cockpit Foot Warmer 3/2004 Applicability: Model 45 aeroplanes, serial numbers 45-005 through 45-213 inclusive. Requirement: 1. Unless already accomplished in accordance with AD/LJ45/4 original issue, pull (open) the FOOT WARM circuit breaker, located on the copilot's circuit breaker panel, and install a collar on the FOOT WARM circuit breaker, per Bombardier Aerospace Learjet Alert Service Bulletin SB A45-21-14, dated 3 May 2002. 2. Reactivate the foot warmer system by removing the collar and closing the FOOT WARM circuit breaker. Note 1: FAA AD 2002-17-01 Amdt 39-12866 and FAA Small Airplane Directorate Alternate Method of Compliance (AMOC) letter dated 5 November 2003 refer. The FAA AMOC letter is included in Bombardier Aerospace Advisory Wire 21-006. Compliance: For Requirement 1 - As of the effective date of this Amendment. For Requirement 2 - Following the optional replacement/modification of the pilot and co-pilot heel plate assemblies in accordance with Bombardier Aerospace Learjet Service Bulletin SB 45-21-15. Note 2: SB 45-21-15 requires either concurrent or prior incorporation of SB45-21-2 on aeroplanes serial numbers 45-001 through 45-119. This Amendment becomes effective on 18 March 2004. Background: The United States Federal Aviation Administration has received reports of smoke in the cockpit caused by electrical short circuits between the pilot's and copilot's foot warmers and the composite floorboards. A short circuit in a foot warmer causes electrical current to flow through the metal heelplate of the foot warmer to the composite floorboards. Due to the high resistance of the composite floorboards, the circuit breaker may not open, or the opening could be significantly delayed, which could result in outgassing of the faceply material of the composite floorboards, and consequent smoke in the cockpit. The original issue of this Directive required pulling the FOOT WARM circuit breaker and installing a collar on that circuit breaker. Learjet 45 Series Aeroplanes AD/LJ45/4 Amdt 1 (continued) This amendment introduces an optional terminating action to the deactivation of the cockpit foot warmer system. ` The original issue of this Airworthiness Directive became effective on 18 September 2002. James Coyne Delegate of the Civil Aviation Safety Authority 22 January 2004 The above AD is notified in the Commonwealth of Australia Gazette on 25 February 2004.