{"id":"F2006B02532","name":"AD/AS 355/83 - Tail Rotor Blade Trailing Edge Tab","slug":"ad-as-355-83-tail-rotor-blade-trailing-edge-tab","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41788,"registerId":"commonwealth-F2006B02532-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\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 CASR 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\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters","sortOrder":0},{"sectionNumber":"AD/AS 355/83 Tail Rotor Blade Trailing E","sectionType":"part","heading":"AD/AS 355/83 Tail Rotor Blade Trailing Edge Tab 1/2005","content":"# AD/AS 355/83 Tail Rotor Blade Trailing Edge Tab 1/2005\n\nApplicability: AS 355 helicopters, versions E, F, F1, F2, and N, fitted with tail rotor blades part number 355A 12.0040 all dash numbers, and part number 355A 12.0050 all dash numbers, with serial numbers from 8400 through 9224, before incorporation of Repair Sheet FR No. 238 or incorporation of Work Card 64.10.00.872 (Refer to equipment log card (FME)).\n\nNote: Eurocopter AS 355 Alert Service Bulletin No. 64.00.04 corresponds to Repair Sheet FR No. 238.\n\nRequirement: Install additional rivets on the trailing edge tab of blades in accordance with paragraph 2.B. of Eurocopter Alert Service Bulletin No.64.00.04 or later EASA approved revision.\n\nNote: DGAC AD F-2004-176 refers.\n\nCompliance: Within 100 flight hours or 3 months after 20 January 2005, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 20 January 2005.\n\nBackground: Reports were received of significant tail rotor blsade trailing edge tab debonding.\n\nReduced security of the trailing edge tab due to debonding could lead to loss of the tab if it is not monitored, and result in a significant increase in the vibration level.\n\n![](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 3 December 2004\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD addresses a specific unsafe condition (trailing edge tab debonding) for a narrowly defined set of tail rotor blades and prescribes a single corrective action (rivet installation). It does not broaden its remit beyond that original technical safety objective; therefore the scope has not been expanded beyond its original purpose."},"complexity_factors":["Single, focused technical requirement (install additional rivets on trailing edge tab).","Narrow applicability: two part numbers and a single serial number range (8400–9224).","One compliance timetable option (100 flight hours or 3 months after effective date).","Cross-reference to an external technical document (Eurocopter Alert Service Bulletin No. 64.00.04) and allowance for later EASA‑approved revisions.","Reference to prior incorporation of Repair Sheet FR No. 238 or Work Card 64.10.00.872 as an exemption condition (requires record checks).","Minor additional cross-reference to DGAC AD and to CASR 1998 subregulation 39.1(1) for authority basis."],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- This is an Airworthiness Directive (AD) that requires owners/operators of certain Eurocopter AS 355 (Twin Ecureuil) helicopters to install extra rivets on the trailing edge tab of specific tail rotor blades. (Requirement section.)\n\n- It applies only to AS 355 versions E, F, F1, F2 and N that have tail rotor blades with part numbers 355A 12.0040 or 355A 12.0050 and serial numbers 8400 through 9224, provided the blade has not already been modified by Repair Sheet FR No. 238 or Work Card 64.10.00.872. (Applicability section; Note.)\n\n- The rivet installation must follow paragraph 2.B. of Eurocopter Alert Service Bulletin No. 64.00.04 or a later EASA‑approved revision. (Requirement section.)\n\n- Compliance deadline: install the rivets within 100 flight hours or 3 months after 20 January 2005, whichever comes first. The AD became effective 20 January 2005. (Compliance section; Effective date.)\n\n**Why this action is required (stated purpose and immediate risk)**\n\n- The AD records reports of significant debonding of the trailing edge tab on affected tail rotor blades. (Background.)\n\n- The stated safety concern is that a loose or lost trailing edge tab can increase vibration levels significantly and therefore create an unsafe condition. The AD directs the rivet retrofit as the corrective action the regulator considers necessary. (Background; Requirement.)\n\n**Who pays and who decides**\n\n- Aircraft owners/operators must pay for the parts, labour, and downtime to carry out the rivet installation. The action is mandatory for affected helicopters unless the repair sheet/work card has already been incorporated. (Applicability; Requirement.)\n\n- The Civil Aviation Safety Authority (CASA) delegate issued the AD and set the compliance time; the AD prescribes following the Eurocopter Alert Service Bulletin or a later EASA‑approved revision, so the manufacturer and EASA influence the technical method. (Front matter; Requirement.)\n\n**Costs, incentives and implementation notes**\n\n- Direct costs: purchase of rivets/kit, certified maintenance labour, and aircraft out-of-service time during modification.\n\n- Administrative burden: identifying affected blades by part and serial number, verifying maintenance records (log cards) to see whether Repair Sheet FR No. 238 or Work Card 64.10.00.872 have already been incorporated, and recording compliance in maintenance logs. (Applicability; Note.)\n\n- Timing trade-off: the deadline forces operators to prioritise the retrofit within 100 flight hours or 3 months, which may displace other scheduled maintenance.\n\n- Implementation risk: incorrect identification of serial numbers or incomplete incorporation records could lead to unnecessary work or missed non-compliance. Using the manufacturer’s service bulletin (or later EASA revision) reduces technical ambiguity but depends on access to and correct application of that bulletin. (Requirement.)\n\n**Effects on market and behaviour**\n\n- Maintenance providers and authorised repair stations will perform the retrofit work, creating a short-term demand for labour and materials concentrated on affected operators.\n\n- Owners/operators face a choice: schedule modification during planned checks to reduce downtime, or incur additional visits and costs if deferred until a later opportunity (subject to the AD deadline). (Compliance.)\n\n**Trade-offs and opportunity costs**\n\n- The AD trades a one‑time retrofit cost and downtime for reduced risk of tab loss and increased vibration, which are safety hazards. The benefit (reduced safety risk) accrues to passengers, aircrew and the operator; the cost is borne by the operator(s) of affected aircraft. (Background; Requirement.)\n\n**Reference and cross-checks**\n\n- The AD points to Eurocopter Alert Service Bulletin No. 64.00.04 (which corresponds to Repair Sheet FR No. 238) as the technical instruction, and allows later EASA‑approved revisions. It also notes the related DGAC AD. (Note; Requirement.)\n\n\n"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in specific tail rotor blades on specific helicopter models. There is no evidence of scope creep; it remains a targeted safety directive for a defined unsafe condition."},"complexity_factors":["Single, specific mechanical action required (install additional rivets)","Clear applicability criteria (specific helicopter models, part numbers, serial number range)","Straightforward compliance deadline (100 flight hours or 3 months)","Only one substantive requirement with reference to external technical document","Minimal conditional logic (simple exclusion for already-repaired blades)","Short document length (approximately 250 words of substantive text)"],"plain_english_summary":"This mandatory CASA Airworthiness Directive requires owners/operators of certain Eurocopter AS355 helicopters with specified tail-rotor blades to secure the trailing-edge tab by installing additional rivets per Eurocopter Alert Service Bulletin No. 64.00.04. Carried out within 100 flight hours or three months from 20 Jan 2005, the fix prevents tab debonding and possible loss of control from severe vibration."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-83-tail-rotor-blade-trailing-edge-tab","history":"/api/acts/ad-as-355-83-tail-rotor-blade-trailing-edge-tab/history","analysis":"/api/acts/ad-as-355-83-tail-rotor-blade-trailing-edge-tab/analysis","conflicts":"/api/acts/ad-as-355-83-tail-rotor-blade-trailing-edge-tab/conflicts","importantCases":"/api/acts/ad-as-355-83-tail-rotor-blade-trailing-edge-tab/important-cases","documents":"/api/acts/ad-as-355-83-tail-rotor-blade-trailing-edge-tab/documents"}}