{"id":"F2006B02523","name":"AD/AS 355/73 Amdt 1 - Flight Control Stop Screws","slug":"ad-as-355-73-amdt-1-flight-control-stop-screws","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41779,"registerId":"commonwealth-F2006B02523-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/73 Amdt 1 - Flight Control Stop Screws","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nOn the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AS 355/73 and issues the following 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\n\nAD/AS 355/73\n\nAmdt 1\n\n  \nFlight Control Stop Screws 9/2004\n\nApplicability: Models AS 355 E, F, F1, F2, and N helicopters; without MOD 073206 or MOD 073102 incorporated.\n\nComponents affected: roll, pitch, and collective flight control stops.\n\nRequirement: 1. Action in accordance with paragraph 2.B.1. of Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1.\n\n2. Action in accordance with paragraph 2.B.2. of Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1.\n\nNote: DGAC AD F-2003-322 R1 refers.\n\nCompliance: 1. Within 100 flight hours after 30 October 2003, unless already accomplished.\n\n2. Within 500 flight hours or 1 year after 30 October 2003, whichever occurs first. The compliance time remains unchanged by this issue.\n\nThis Amendment becomes effective on 2 September 2004.\n\nBackground: A report was received of an incident during a ground run-up with a Model EC 120 helicopter, where it was possible to push the collective lever downward beyond it’s normal position. Investigation revealed that the locknut of the low pitch stop had come loose and that the stop was out of adjustment. The worst case scenario is that of collective low pitch stop maladjustment, which can result in rotor under-speed in an auto-rotation situation.\n\nAmendment 1 is issued in response to a revision of the related DGAC AD, which introduces additional applicability information and revised Requirement document, with no change to the technical content.\n\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\nAD/AS 355/73 Amdt 1 (continued)\n\nThe original issue of this Airworthiness Directive became effective on 30 October 2003.\n\n![](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 13 July 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 11 August 2004.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This Amendment (Amendment 1) does not materially broaden the AD’s technical scope. The instrument states it introduces additional applicability information and a revised Requirement document tied to the Eurocopter service bulletin, but expressly says there is no change to the technical content of the corrective actions. The amendment therefore clarifies and slightly expands applicability language (who is covered) and updates the referenced service bulletin paragraph numbers, rather than adding new safety obligations or new affected components."},"complexity_factors":["Short standalone Airworthiness Directive (AD) text (single-page length).","One external technical cross-reference: Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1 (paragraphs 2.B.1 and 2.B.2) — technical steps not reproduced in the AD.","Reference to another regulator's AD (DGAC AD F-2003-322 R1) and a stated linkage to a DGAC revision.","Applicability condition excludes aircraft with two specific MODs (MOD 073206 or MOD 073102), adding a binary eligibility check.","Two separate compliance windows (100 flight hours; 500 flight hours or 1 year) measured from a historical date (30 October 2003), creating dual timing rules.","Revocation and replacement of a prior AD: administrative cross-reference to earlier legal instrument.","Limited conditionality — few nested exceptions or definitions within the AD itself (most technical definitions are in the external bulletin)."],"plain_english_summary":"**What this instrument does (mechanically)\n\n- Revokes the previous Airworthiness Directive AD/AS 355/73 and replaces it with Amendment 1. (See heading and first paragraph.)\n- Requires operators of certain Eurocopter AS 355 (Twin Ecureuil) helicopters to carry out the inspection and adjustment actions set out in specified paragraphs (2.B.1 and 2.B.2) of Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1. (See \"Requirement\".)\n- Applies only to Models AS 355 E, F, F1, F2 and N that have not had MOD 073206 or MOD 073102 installed. (See \"Applicability\".)\n- Sets two mandatory compliance windows measured from 30 October 2003: one action within 100 flight hours, the other within 500 flight hours or 1 year (whichever is sooner). (See \"Compliance\".)\n\nWho is affected\n\n- Operators and owners of Eurocopter AS 355 E/F/F1/F2/N helicopters that do not have modification MOD 073206 or MOD 073102 incorporated. (Applicability.)\n- Maintenance organisations, licensed engineers and technicians who must perform the inspections, adjustments or corrective work required by the referenced Eurocopter service bulletin. (Requirement.)\n\nWhy the rule exists (official rationale and mechanical risk)\n\n- The background explains the safety concern: a report from an EC 120 helicopter ground run-up found the collective lever could be pushed downward beyond its normal stop because a locknut on the low-pitch stop had come loose. If a low-pitch stop is maladjusted, the rotor can go below safe speed during autorotation. (See \"Background\".)\n- The AD’s stated purpose is to correct that unsafe condition on AS 355 helicopters by ensuring flight control stop screws and their locknuts are correctly set and secured, per the Eurocopter instructions. (Requirement + Background.)\n\nHow it works in practice (who pays, who decides, and what changes)\n\n- Who pays: aircraft owners/operators fund the inspections, labour, and any corrective work or parts required by the service bulletin. If an operator chooses to install the MODs listed (073206 or 073102) to remove applicability, that installation also costs the operator. (Applicability + Requirement.)\n- Who decides: the Civil Aviation Safety Authority (CASA) delegate issues and enforces the AD; operators decide how to schedule compliance within the specified timeframes and which maintenance provider to use. Maintenance must follow Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1 (paragraphs 2.B.1 and 2.B.2) to meet the AD. (First paragraph + Requirement.)\n- Behaviour change required: affected helicopters must be inspected and any adjustment or corrective action performed to secure flight control stop screws and locknuts. Operators must track flight hours or calendar time to meet the compliance windows. (Compliance.)\n\nImplementation, costs and trade-offs (practical considerations)\n\n- Compliance burden: the AD imposes short-to-medium term maintenance actions (inspection/adjustment) within a specified number of flight hours or time. That creates scheduling demands and maintenance labour costs for operators. (Compliance + Requirement.)\n- Opportunity cost: time spent in maintenance is aircraft downtime; there may be logistical costs if aircraft must be grounded or moved for work. If parts or further corrective work are needed, extra cost and lead time can arise. (Requirement + Compliance.)\n- Compliance paths: aircraft already fitted with MOD 073206 or MOD 073102 are outside the AD’s applicability, which gives operators the option (at cost) to install those mods to avoid repeated AD requirements on the same issue. (Applicability.)\n- Implementation risk: the AD relies on an external service bulletin for technical steps. Operators must correctly interpret and follow the bulletin paragraphs cited (2.B.1 and 2.B.2). Misinterpretation or incomplete work risks residual unsafe condition and possible enforcement action. (Requirement.)\n- Enforcement and discretion: CASA enforces AD compliance under CASR subregulation 39.1(1); the AD itself specifies compliance windows but delegates technical detail to the Eurocopter bulletin, limiting CASA’s technical prescription to that document. (First paragraph + Requirement.)\n\nOther notes\n\n- This amendment (Amendment 1) was issued after a revision of the related French DGAC AD; the document states the amendment adds applicability information and a revised requirement document but did not change the technical content of the corrective actions. (See \"Amendment 1\" in Background.)\n\nSources in the instrument: Applicability; Components affected; Requirement (paragraphs 2.B.1 and 2.B.2 of Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1); Compliance; Background; Amendment note."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment explicitly states it introduces 'no change to the technical content' and only updates applicability information and requirement document references in response to a revised French aviation directive. The scope remains limited to flight control stop screw inspections on specific AS 355 helicopter models."},"complexity_factors":["Multiple cross-references to external technical documents (Eurocopter Alert Service Bulletin AS 355 No. 67.00.25 R1, DGAC AD F-2003-322 R1)","Conditional applicability based on aircraft model and modification status (MOD 073206 or MOD 073102)","Dual compliance timelines with 'whichever occurs first' logic","Nested regulatory references (subregulation 39.1(1) of CASR 1998)","Amendment structure requires understanding of previous directive version"],"plain_english_summary":"This safety order updates a previous CASA directive for Eurocopter AS355 E/F/F1/F2/N helicopters (unless fitted with MOD 073206 or 073102). It requires inspection and corrective action on the collective control stop screws to prevent a loose locknut allowing excessive collective travel, which could reduce rotor speed during an autorotation after engine failure. Initial checks are mandated within 100 flight hours and follow‑up work within 500 flight hours or one year after 30 October 2003."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-73-amdt-1-flight-control-stop-screws","history":"/api/acts/ad-as-355-73-amdt-1-flight-control-stop-screws/history","analysis":"/api/acts/ad-as-355-73-amdt-1-flight-control-stop-screws/analysis","conflicts":"/api/acts/ad-as-355-73-amdt-1-flight-control-stop-screws/conflicts","importantCases":"/api/acts/ad-as-355-73-amdt-1-flight-control-stop-screws/important-cases","documents":"/api/acts/ad-as-355-73-amdt-1-flight-control-stop-screws/documents"}}