AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/EMB-120/17 and issues the following 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. Embraer EMB-120 (Brasilia) Series Aeroplanes AD/EMB-120/17 Amdt 1 Landing Gear - Door Blockage 9/2002 Applicability: Embraer EMB 120 (Brasilia) aircraft serial numbers 120003,120004, and 120006 through 120331 inclusive. Requirement: 1. Check for the correct installation of check valve P/N CKRC1875005A in landing gear wheel well door closure line as per Embraer Service Bulletin (SB) 120-32- 0077 Revision 3. 2. If the check valve is fitted correctly no further action is required. 3. If the check valve is not fitted, or fitted incorrectly, carry out correct installation as per Embraer Service Bulletin (SB) 120-32-0077 Revision 3. Note 1: Brazilian AD 97-05-03R3 refers. Note 2: Aircraft flight manual amendments detailed in AD 97-05-03 are required by CAR 55. Compliance: Unless previously accomplished; within the next 100 flight hours after the effective date of this Directive. This amendment becomes effective on 5 September 2002. Background: The original issue of this Directive was in response to investigation into aircraft incidents has shown that it is possible to lock up the landing gear doors when performing the emergency landing gear extension procedures in the event of the loss of the green hydraulic system. With the landing gear doors locked, the landing gear cannot be extended even by free fall. Installation of the check valve eliminates the possibility of the doors locking up in this situation. Embraer EMB-120 (Brasilia) Series Aeroplanes AD/EMB 120/17 Amdt 1 (continued) Amendment 1 was issued to address the possibility of incorrect installation or the non- installation of the check valve as required by the original version of this Directive. Revision 3 of Brazilian AD 97-05-03 was issued to address these problems. The original issue of this Airworthiness Directive became effective on 14 August 1997. Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority 26 July 2002 The above AD is notified in the Commonwealth of Australia Gazette on 14 August 2002.