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.
Overview
The Civil Aviation Safety Authority (CASA) issued Airworthiness Directive (AD) DHC-8/84 for Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes in 2002 to address the potential safety issue of angle of attack (AOA) sensor vane sticking. The AD was introduced to ensure that the AOA sensors on these aircraft models (301, 311, 314, and 315) are functioning correctly to provide accurate stall warning readings. The directive mandates specific actions to be taken, such as checking the modification status of the sensors, conducting tests to evaluate vane sticking, and replacing any faulty vanes. The objective is to prevent any unsafe conditions that may arise from incorrect angle of attack readings, which could potentially compromise flight safety. The AD became effective on 21 February 2002, and compliance is required according to specified time intervals and flight hour limits.
Scope and Application
The Airworthiness Directive issued under the Civil Aviation Regulations 1998 (CAR 1998) applies specifically to Bombardier (Boeing Canada/de Havilland) DHC-8 Series aeroplanes, which include models 301, 311, 314, and 315 with serial numbers ranging from 100 to 583. The directive mandates actions to address potential unsafe conditions related to the angle of attack (AOA) sensors, specifically concerning the possible sticking of the AOA sensor vane, which could lead to incorrect angle of attack readings. The AD requires that certain inspections and modifications be undertaken by the relevant parties, such as aircraft operators or maintenance organisations, to ensure the safety of these aircraft. The directive is effective from 21 February 2002 and applies throughout the Commonwealth of Australia, as it is notified in the Commonwealth of Australia Gazette. There are no stated exclusions or exemptions in the directive itself; however, compliance timelines are specified for each requirement, ranging from immediate actions post-inspection to longer-term intervals based on flight hours or months of service. The AD extends its application through specific instructions and tests detailed in Bombardier Alert Service Bulletin A8-27-94.
Key Provisions
The Airworthiness Directive (AD) under the Civil Aviation Regulations 1998 mandates specific actions to ensure the airworthiness of Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes. Section 1 of the AD requires an initial check (section 1) to ascertain if the Modification 'J' (MOD 'J') has been incorporated in both the right and left angle of attack (AOA) sensors, part number 861CAB. If MOD 'J' is present, no further action is necessary. If MOD 'J' is not present, an AOA sensor vane movement test must be conducted on each AOA sensor (section 2) to evaluate sticking against the upper and lower vane travel end stops, following the instructions of Bombardier Alert Service Bulletin (ASB) A8-27-94 dated 25 October 2001. Based on the test results, the vane may need to be replaced if the gram gauge reading is either less than 110 grams or exceeds 170 grams (sections 3 and 4). If the reading falls between 110 and 170 grams, the AOA sensor must be replaced (section 5). A repeat test must then be conducted (section 6) and the vane replaced if the readings again fall outside the specified range (sections 7 and 8).
The AD imposes several obligations on the operators of the DHC-8 aircraft. Operators must ensure that the specified inspections and tests are conducted within the prescribed timeframes. For example, the initial inspection and any necessary modifications must be completed before the aircraft accumulates 1000 hours of time in service (TIS) or six months, whichever comes first, following the AD's effective date (section 1). The vane movement test must be completed before further flight, immediately after the initial inspection (section 2). Replacement of any non-compliant vanes must occur within five days of the test (sections 3 and 4) or within 1000 hours TIS or six months from the initial test (section 5). A repeat test must be conducted before the aircraft accumulates 5000 hours TIS or 24 months from the initial test (section 6), with any necessary replacements completed within five days of the repeat test (sections 7 and 8). Furthermore, pre-MOD 'J' status AOA sensors (P/N 861CAB) must not be installed on any aircraft as of the effective date of this directive (section 8).
Failure to comply with the requirements of this AD may result in civil or criminal penalties. The AD is issued under the authority of the Civil Aviation Safety Authority (CASA) delegate, and non-compliance could be considered a breach of civil aviation regulations. While the AD does not explicitly state penalties, non-compliance with CASA directives can result in enforcement actions, including fines, aircraft grounding, and other regulatory sanctions. Operators are expected to adhere strictly to the specified timelines and actions to avoid potential penalties and ensure the continued airworthiness of their aircraft.