{"id":"F2006B06743","name":"AD/S-76/67 - Attitude and Heading Reference Warning","slug":"ad-s-76-67-attitude-and-heading-reference-warning","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114570,"registerId":"commonwealth-F2006B06743-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \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\nSikorsky S-76 Series Helicopters","sortOrder":0},{"sectionNumber":"AD/S-76/67 Attitude and Heading Referenc","sectionType":"part","heading":"AD/S-76/67 Attitude and Heading Reference Warning 3/2002","content":"# AD/S-76/67 Attitude and Heading Reference Warning 3/2002\n\nApplicability: Model S-76B helicopters, serial numbers (S/N) 760430, 760441 through 760445, 760448 through 760452, 760454, 760455, 760458, 760462, and 760465.\n\nModel S-76C helicopters, S/N 760420, 760436, 760438, 760440, 760453, 760456,\n\n760457, 760459, 760460, 760461 760463, 760464, 760466 through 760487.\n\nRequirement: Modify the number 1 and 2 AHRS WARN circuits in accordance with the Accomplishment Instructions, paragraphs 3.A. through 3.D, of Sikorsky Aircraft Corporation Alert Service Bulletin 76-34-7A (320A), Revision A, dated 17 September 2001.\n\nNote: FAA AD 2001-25-06 refers.\n\nCompliance: No later than 21 April 2002.\n\nThis Airworthiness Directive becomes effective on 21 March 2002.\n\nBackground: The United States Federal Aviation Administration has advised that during a ground test simulating loss of the essential bus, both autopilots went off-line.\n\nThis Directive requires modification of the electrical power distribution system to change the source of the 28 volts supplied to Nos. 1 and 2 attitude and heading reference system (AHRS) WARN circuits. These actions are intended to prevent an AHRS fail signal to both autopilots due to a failure of the essential bus, loss of autopilot functions, and subsequent loss of control of the helicopter.\n\n![Signature of Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 7 February 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 27 February 2002.","sortOrder":1}],"analysis":{"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"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The AD applies to the listed S‑76B and S‑76C serial numbers and requires modification per the Sikorsky service bulletin; the document contains no indication that the applicability or required actions differ from the stated intent to prevent dual autopilot loss after essential-bus failure."},"complexity_factors":["Technical electrical change to aircraft power distribution (affects AHRS WARN circuits).","Mandates following manufacturer Alert Service Bulletin (paragraphs 3.A–3.D) for accomplishment details.","Applicability limited to specific serial numbers across two S‑76 variants, requiring record checks per helicopter.","Safety‑critical nature with a firm compliance date (operational downtime and direct cost to owners/operators).","Cross-reference to a related FAA AD (2001‑25‑06), indicating international regulatory alignment.","Regulatory directive issued by CASA delegate — limited regulatory discretion in the AD text; operators must comply as required."],"plain_english_summary":"**What it does:** This Airworthiness Directive requires owners/operators of specified Sikorsky S‑76B and S‑76C helicopters to modify the No.1 and No.2 AHRS WARN electrical circuits so the 28‑volt supply is changed, following Sikorsky Alert Service Bulletin 76‑34‑7A Rev A. **Who it affects and why it matters:** CASA issued the directive to prevent simultaneous AHRS fail warnings that could disable both autopilots after an essential-bus failure; compliance was required by 21 April 2002."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope. It addresses a specific electrical fault in specific helicopter models identified by serial number. There is no evidence of scope creep; the directive targets exactly the unsafe condition described in the background section with no expansion into unrelated systems or aircraft types."},"complexity_factors":["Very short document (under 400 words)","Only 3 defined applicability criteria (aircraft models and serial numbers)","Single, unambiguous requirement referencing an external technical standard (Sikorsky service bulletin)","No nested exceptions or conditional logic — compliance is mandatory for all listed aircraft","Simple, fixed compliance deadline with no alternative methods or phased implementation","Minimal cross-referencing (only one FAA AD mentioned in a note, not incorporated by complex reference)"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of certain Sikorsky S-76B and S-76C helicopters (about 40–50 aircraft) to rewire the electrical supply to the AHRS warning circuits in accordance with Sikorsky Service Bulletin 76-34-7A.\n\nThe modification prevents both autopilots from shutting down if the essential bus loses power—avoiding a potential loss of control—and must be completed by 21 April 2002."}},"importantCases":[],"_links":{"self":"/api/acts/ad-s-76-67-attitude-and-heading-reference-warning","history":"/api/acts/ad-s-76-67-attitude-and-heading-reference-warning/history","analysis":"/api/acts/ad-s-76-67-attitude-and-heading-reference-warning/analysis","conflicts":"/api/acts/ad-s-76-67-attitude-and-heading-reference-warning/conflicts","importantCases":"/api/acts/ad-s-76-67-attitude-and-heading-reference-warning/important-cases","documents":"/api/acts/ad-s-76-67-attitude-and-heading-reference-warning/documents"}}