AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 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. Boeing 767 Series Aeroplanes AD/B767/144 Warning Electronics Unit 8/2001 DM Applicability: Model 767-200 -300 and -300F series aeroplanes, line numbers 668 through 723 inclusive, equipped with a warning electronics unit (WEU) power supply Part Number (P/N) 285T0035-201. Requirement: 1. If not previously accomplished in accordance with AD/B767/113 Requirement 1, check the status page of the engine indication and crew alerting system (EICAS) for any WEU failure; and perform Work Instructions in Section 3, Part 1 of Boeing Service Bulletin (SB) 767-31-0106 Revision 1 dated 17 December 1998 or Revision 2 dated 18 November 1999 to detect loss of any visual, aural, or tactile alert. 2. If a WEU failure or loss of any visual, aural, or tactile alert is not detected. 1. Repeat the Requirement 1 EICAS status page check. b. Repeat the Requirement 1 Work Instructions. Note 1: The EICAS status page check and performance of the Work Instructions in Section 3, Part 1 of the Service Bulletin are maintenance functions that require an aircraft log book entry and maintenance release prior to flight. 3. If any failure of the WEU, or the loss of any visual, aural, or tactile alert is detected during any Requirement 1, 2.a or 2.b test replace the power supplies with new, modified, or serviceable power supplies having P/N 285T0035-202 Mod A, P/N 285T0035-9, P/N 285T0035-10, or P/N 285T0035-11, in accordance with SB 767-31-0106, Revision 2. 4. Replace WEU power supplies having P/N 285T0035-201, with new or modified power supplies having P/N 285T0035-202 Mod A; or new, modified, or serviceable power supplies having P/N 285T0035-9, P/N 285T0035-10, or P/N 285T0035-11; in accordance with SB 767-31-0106, Revision 2. Boeing 767 Series Aeroplanes AD/B767/144 (Continued) Replacement of the WEU power supplies with new or modified power supplies having P/N 285T0035-202 Mod A, in accordance with SB 767-31-0106 Revision 1, is an acceptable means of compliance if carried out prior to the effective date of this Directive. 5. WEU power supply P/N 285T0035-201 may not be installed on any aeroplane as a replacement part. Note 2: FAA AD 2001-11-08 Amdt 39-12250 refers. Compliance: For Requirement 1 - Initially, within 15 days of the effective date of this Directive and thereafter in accordance with Requirements 2.a and 2.b. For Requirement 2.a - Before each flight until either Requirement 3 or 4 is accomplished. For Requirement 2.b - At intervals not to exceed every "A" check or 45 days, whichever occurs first until either Requirement 3 or 4 is accomplished. For Requirement 3 - Before further flight. For Requirement 4 - Before 16 July 2002. For Requirement 5 - As of the effective date of this Directive. This Airworthiness Directive becomes effective on 27 June 2001. Background: The Federal Aviation Administration received a report advising that during a production test flight of a Model 747-400 series aeroplane the flight test crew noticed a power supply failure on the status page of the EICAS. Investigation revealed the automatic bench test procedure for the modular avionics warning electronic assembly (MAWEA) overstressed the 5.7 volt over-voltage clamp circuit which resulted in failure of the circuit to protect the warning cards in the MAWEA. A slow failure of the MAWEA power supply could result in the gradual degradation of available visual, aural and tactile alerts, which could result in flight crew not being aware of and not taking immediate or appropriate action, in the event of an unsafe condition occurring. The WEU power supply units on some Boeing 767-200 and -300 series aeroplanes are identical to those on the MAWEA on the affected Model 747-400 aeroplanes. Therefore, all of these aeroplanes may be subject to the same unsafe condition. Boeing 767 Series Aeroplanes AD/B767/144 (Continued) This Directive requires repetitive checks to detect failures of the WEU power supply and if necessary, corrective action. The Directive also provides for terminating action. This Airworthiness Directive supersedes AD/B767/113. Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority 20 June 2001 The above AD is notified in the Commonwealth of Australia Gazette on 27 June 2001.