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. Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes AD/DHC-8/84 Angle of Attack Sensor 2/2002 Applicability: DHC-8 Aircraft Models 301, 311, 314 and 315, Serial Numbers 100 through 583 inclusive. Requirement: 1. Determine if MOD 'J' has been incorporated in both right and left angle of attack (AOA) sensors, Part Number (P/N) 861CAB. If Mod 'J' has been incorporated in both AOA sensors, no further action is required. 2. Conduct an AOA sensor vane movement test, on each AOA sensor that does not have Mod 'J' installed, to evaluate sticking against both the upper and the lower vane travel end stops. Conduct the tests in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin (ASB) A8-27-94 dated 25 October 2001. If the gram gauge readings from both the upper and lower AOA sensor vane positions are less than 110 grams, the applicable AOA sensor vane does not require replacement. 3. If the test results of the gram gauge reading from either the upper or the lower vane position exceeds 170 grams, replace the applicable AOA vane in accordance with the above-referenced ASB. 4. If the test results of the gram gauge reading from either the upper or the lower vane position is between 110 and 170 grams, replace the applicable AOA sensor in accordance with the above-referenced ASB. 5. Repeat the Requirement 2, AOA sensor vane movement test, on those AOA vanes that are not Mod 'J' and were not replaced in accordance with either Requirements 3 or 4. If both the gram gauge readings from the repeat AOA sensor vane movement test are again less than 110 grams, the applicable AOA sensor does not require replacement and no further tests are required. 6. If either of the gram gauge readings from the repeat AOA sensor vane movement tests exceed 170 grams, replace the AOA sensor in accordance with the above- referenced ASB. 7. If gram gauge reading from the repeat AOA sensor vane movement test is between 110 and 170 grams, replace the AOA sensor in accordance with the above-referenced ASB. Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes AD/DHC-8/84 (continued) 8. Pre-Mod 'J' status AOA sensor (P/N 861CAB) may not be installed on any aircraft. Note: Transport Canada CF-2001-46 refers. Compliance: For Requirement 1 - Initially, prior to 1000 hours time in service (TIS), or 6 months whichever occurs first, after the effective date of this Directive. For Requirement 2 - Before further flight, immediately following Requirement 1. For Requirement 3 - Within five days after completing the Requirement 2 test. For Requirement 4 - Within 1000 hours TIS or six months, whichever occurs first, from the date of the Requirement 2 test. For Requirement 5 - Prior to accumulating 5000 hours TIS or 24 months, whichever occurs first, from the date of the initial Requirement 2 test. For Requirement 6 - Within five days after completing the Requirement 5 repeat test. For Requirement 7 - Within 1000 hours TIS or six months, whichever occurs first, from the date of the Requirement 5 repeat test. For Requirement 8 - As of the effective date of this Directive. This Airworthiness Directive becomes effective on 21 February 2002. Background: The manufacturer of the AOA vane has determined that viscous damper leakage in some vanes can cause the vane to stick against the upper or the lower vane travel stop. Although no problems with sticking AOA vanes have been reported on the DHC-8 aircraft, a sticking vane would provide the stall warning system with an incorrect angle of attack reading. This would be expected to occur at airspeeds below approximately 110 kts. Above 110 kts, the airflow would unstick the vane. Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes AD/DHC-8/84 (continued) This Directive requires an initial inspection to determine the modification status of the AOA sensors and, if necessary, a sensor vane movement test together with the replacement of any sensor vane that fails the test. Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority 14 January 2002 The above AD is notified in the Commonwealth of Australia Gazette on 30 January 2002.