{"id":"F2006B09243","name":"AD/DHC-8/84 - Angle of Attack Sensor","slug":"ad-dhc-8-84-angle-of-attack-sensor","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53149,"registerId":"commonwealth-F2006B09243-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor 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.\n\n![](image.001.png)\n\nBombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/DHC-8/84 Angle of Attack Sensor 2/200","sectionType":"part","heading":"AD/DHC-8/84 Angle of Attack Sensor 2/2002","content":"# AD/DHC-8/84 Angle of Attack Sensor 2/2002\n\nApplicability: DHC-8 Aircraft Models 301, 311, 314 and 315, Serial Numbers 100 through 583 inclusive.\n\nRequirement: 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.\n\n    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.\n\nIf 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.\n\n    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.\n\n    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.\n\n    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.\n\nIf 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.\n\n    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.\n\n    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.","sortOrder":1},{"sectionNumber":"Bombardier (Boeing Canada/de Havilland) ","sectionType":"part","heading":"Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes","content":"## Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes\n\nAD/DHC-8/84 (continued)\n\n    8. Pre-Mod ‘J’ status AOA sensor (P/N 861CAB) may not be installed on any aircraft.\n\nNote: Transport Canada CF-2001-46 refers.\n\nCompliance: 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.\n\nFor Requirement 2 - Before further flight, immediately following Requirement 1. For Requirement 3 - Within five days after completing the Requirement 2 test.\n\nFor Requirement 4 - Within 1000 hours TIS or six months, whichever occurs first, from the date of the Requirement 2 test.\n\nFor Requirement 5 - Prior to accumulating 5000 hours TIS or 24 months, whichever occurs first, from the date of the initial Requirement 2 test.\n\nFor Requirement 6 \\- Within five days after completing the Requirement 5 repeat test.\n\nFor Requirement 7 - Within 1000 hours TIS or six months, whichever occurs first, from the date of the Requirement 5 repeat test.\n\nFor Requirement 8 \\- As of the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 21 February 2002.\n\nBackground: 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.\n\nAlthough 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.","sortOrder":2}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The AD confines action to DHC‑8 models 301/311/314/315, S/N 100–583 and prescribes inspection, test, replacement and a ban on pre‑Mod 'J' sensors. Those measures align with the directive’s stated safety objective (addressing viscous damper leakage and vane sticking) and do not expand applicability or duties beyond the manufacturer‑identified defect and the aircraft population specified in the text."},"complexity_factors":["Multiple force thresholds (gram‑gauge) trigger different actions: <110g (no replace), 110–170g (replace sensor), >170g (replace vane/sensor) — Requirements 2–7","Repeat-test logic with conditional escalation (initial test, then mandatory repeat and outcome-dependent replacements) — Requirements 5–7","Several distinct compliance timeframes (e.g. before further flight; within 5 days; within 1000 hours TIS or 6 months; prior to 5000 hours TIS or 24 months) creating scheduling complexity — Compliance section","Applicability limited to specific aircraft models and serial numbers (DHC‑8 301/311/314/315, S/N 100–583) — Applicability","Procedural reliance on an external document (Bombardier Alert Service Bulletin A8‑27‑94) for test method and replacement instructions — Requirement 2","Immediate operational constraint banning installation of pre‑Mod 'J' AOA sensors as of the effective date — Requirement 8 / Compliance","Measurement‑based compliance (use of a gram gauge) requires calibrated tools and correct interpretation of readings — Requirement 2","Risk assessment tied to flight regime (sticking expected below ~110 kt) which narrows hazard but affects when sticking matters operationally — Background"],"plain_english_summary":"Requires owners/operators of Bombardier DHC‑8 models 301, 311, 314 and 315 (S/N 100–583) to confirm whether Angle of Attack (AOA) sensors have Mod 'J'. If not, mechanics must perform gram‑gauge vane movement tests, replace vanes or sensors according to measured force thresholds, and pre‑Mod 'J' sensors are prohibited from installation. The AD's stated purpose is to prevent incorrect stall warnings from AOA vanes that may stick; operators pay for inspections, tests and any replacements and must follow Bombardier’s service bulletin."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original scope as a targeted safety directive addressing a specific mechanical defect in identified aircraft models. The requirements follow the standard AD structure (applicability, requirement, compliance, background) without expansion beyond the original safety purpose of addressing AOA sensor sticking issues."},"complexity_factors":["Multiple conditional branches (7 distinct requirements with interdependent logic)","Nested decision tree: initial check → test → conditional replacement → retest → further conditional replacement","Precise technical thresholds (110g and 170g gram gauge readings) with different compliance timeframes","Cross-reference to external technical document (Bombardier Alert Service Bulletin A8-27-94)","Multiple compliance timeframes varying by requirement (immediate, 5 days, 6 months/1000 hours, 24 months/5000 hours)","Specific aircraft serial number range applicability (100–583 inclusive)","Technical terminology requiring aviation engineering knowledge (TIS = Time In Service, Mod 'J', P/N 861CAB, viscous damper)"],"plain_english_summary":"This Airworthiness Directive mandates inspection and, if needed, replacement of angle-of-attack (AOA) sensors on specified Bombardier DHC‑8 (models 301/311/314/315, S/N 100–583) because a faulty viscous damper can leak and cause the vane to stick. Sticking AOA sensors can give false or missing stall warnings at low airspeeds, risking loss of control.\n\nIt affects owners, operators and maintenance organisations and bans reinstalling the older unmodified sensors."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-84-angle-of-attack-sensor","history":"/api/acts/ad-dhc-8-84-angle-of-attack-sensor/history","analysis":"/api/acts/ad-dhc-8-84-angle-of-attack-sensor/analysis","conflicts":"/api/acts/ad-dhc-8-84-angle-of-attack-sensor/conflicts","importantCases":"/api/acts/ad-dhc-8-84-angle-of-attack-sensor/important-cases","documents":"/api/acts/ad-dhc-8-84-angle-of-attack-sensor/documents"}}