{"id":"F2006L00672","name":"AD/AS 355/90 - Main Servo-Controls","slug":"ad-as-355-90-main-servo-controls","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":136675,"registerId":"commonwealth-F2006L00672-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Eurocopter AS 355 (Twin Ecureuil) Series","sectionType":"division","heading":"Eurocopter AS 355 (Twin Ecureuil) Series Helicopters","content":"### Eurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\n| AD/AS 355/90 | Main Servo-Controls | 4/2006 TX |\n| ------------ | ------------------- | --------- |\n\n| Applicability: | Models AS 355 E helicopters, equipped with main servo-controls, all part numbers, not modified per MOD 073343, and on which the tightening torque of the nut that secures the upper ball-end has been increased following:- embodiment of MOD 073191; or,- compliance with MET Work Card 67.30.00.402 since MET Revision 04-08.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Check the tapered housings of the main servo-controls for cracks, in accordance with paragraph 2.B.2.of Eurocopter AS 355 Alert Service Bulletin (ASB) No. 05.00.48.a. If no crack is evident, comply once with paragraph 2.B.3. of ASB No. 05.00.48, then resume flights.b. If there is a vertical crack (along the servo-control axis) that is less than 20 mm long:(i) Comply once with paragraph 2.B.3. of ASB No. 05.00.48, and identify the end of the crack using an indelible ink marker and resume flights.(ii) Comply with paragraph 2.B.4. of ASB No. 05.00.48.2. Replace the servo-control in accordance with paragraph 2.A. of ASB No. 05.00.48, in the following cases if:- a vertical crack is found (along the servo-control axis) that is 20 mm long or longer,- the crack has grown by more than 5mm,- there is an oblique or a horizontal crack,- there are several cracks.For main servo-controls held as spares: |\n\n|             | 3. Accomplish paragraph 2.B.2.b. of ASB No. 05.00.48.If no crack is evident, comply once with paragraph 2.B.3. of ASB No. 05.00.48.If a crack is evident, return the servo-control for repair.Note: EASA AD 2006-0055-E refers.                                                                                                                                                                                                                                                                   |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | 1. Within 10 flight hours or 10 days after 6 March 2006, whichever occurs first.1.b.(ii) During the check after the last flight of the day, without exceeding 10 flight hours between two inspections, pending replacement of the servo-control (in accordance with paragraph 2.A. of ASB No. 05.00.48) no later than within 150 flight hours without exceeding 3 months.2. Before further flight.3. Within 10 days after 6 March 2006, or before installing a main servo-control held as spares. |\n|             | This Airworthiness Directive becomes effective on 6 March 2006.                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| Background: | The European Aviation Safety Agency received reports of cracks discovered in the tapered housings of main servo-controls during scheduled inspections. Undetected cracking in the tapered housing of a main servo-control could lead to the loss of attachment of the affected servo-control to the non-rotating swashplate, and consequent loss of control of the helicopter.                                                                                                                    |\n\n![](image.001.png)  \nDavid Punshon  \nDelegate of the Civil Aviation Safety Authority\n\n3 March 2006","sortOrder":0},{"sectionNumber":"AD/AS 355/90","sectionType":"part","heading":"AD/AS 355/90","content":"## AD/AS 355/90","sortOrder":1},{"sectionNumber":"Main Servo-Controls","sectionType":"part","heading":"Main Servo-Controls","content":"## Main Servo-Controls","sortOrder":2},{"sectionNumber":"4/2006 TX","sectionType":"part","heading":"4/2006 TX","content":"## 4/2006 TX","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with focused scope. It addresses a specific safety-critical component (main servo-controls) on a specific helicopter model (AS 355 E) with specific modification history. The scope remains tightly constrained to the identified safety defect without expansion into unrelated systems or operational areas."},"complexity_factors":["Multiple conditional pathways based on crack type, size, orientation, and growth (vertical <20mm, vertical ≥20mm, horizontal/oblique, multiple cracks, crack growth >5mm)","Cross-references to external technical documents: Eurocopter ASB No. 05.00.48 (specific paragraphs 2.A, 2.B.2, 2.B.3, 2.B.4), MOD 073343, MOD 073191, MET Work Card 67.30.00.402, MET Revision 04-08, and EASA AD 2006-0055-E","Applicability criteria involve three technical modification states that must be verified (embodiment of MOD 073191, compliance with specific MET Work Card, exclusion of MOD 073343)","Tiered compliance deadlines: 10 flight hours/10 days for initial inspection; 10 flight hours between ongoing inspections for small cracks; 150 flight hours/3 months for replacement; immediate grounding for serious cracks; 10 days for spares","Specific measurement thresholds (20mm crack length, 5mm growth) requiring precise technical assessment","Nested requirements: Requirement 1.b.(ii) references back to paragraph 2.B.4 while also imposing additional inspection frequency constraints"],"plain_english_summary":"Owners/operators of Eurocopter AS 355 E helicopters with certain torque-modified main servo-controls must urgently inspect those servo-control housings for cracking. Cracks can lead to servo detachment and complete loss of flight control, so inspections and prompt replacement or protective measures are required within tight deadlines. This mandatory AD targets aircraft with a specific mod history and reflects an immediate safety threat to flight integrity."},"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"},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"No. The AD confines its scope to the safety problem described in the Background (cracking in tapered housings of main servo-controls) and applies only to AS 355 E helicopters meeting the specific modification/torque history and not modified per MOD 073343 (Applicability). It mandates inspection, marking, repair or replacement actions specified by Eurocopter ASB No. 05.00.48 and sets time limits for compliance; the financial and operational burden falls to operators and maintenance organisations (Requirement; Compliance)."},"complexity_factors":["Applicability is narrowly tailored: only AS 355 E helicopters with main servo-controls not modified per MOD 073343 and with increased tightening torque following embodiment of MOD 073191 or MET Work Card compliance (Applicability).","Multiple conditional inspection and corrective paths depending on crack orientation and length (no crack; vertical crack <20 mm; vertical crack ≥20 mm; crack growth >5 mm; oblique/horizontal cracks; multiple cracks) (Requirement 1, 2).","Cross-references to detailed procedures in Eurocopter ASB No. 05.00.48 paragraphs 2.A and 2.B.2–2.B.4 required to perform actions and replacements (Requirement 1, 2; note in Requirement).","Different rules for in-service units versus spares, including return-for-repair requirement for cracked spares (Requirement 3; Compliance 3).","Staged and tight compliance timelines: initial inspection within 10 flight hours or 10 days after 6 March 2006; daily/last-flight checks not exceeding 10 flight hours between inspections while awaiting replacement; mandatory replacement no later than 150 flight hours or 3 months if limited continued operation allowed (Compliance 1, 1.b.(ii)).","Operational constraint to conduct certain inspections during last flight of the day and limits on flight hours between inspections create scheduling and maintenance-planning burdens (Compliance 1.b.(ii)).","Operator actions include identifying crack ends with indelible ink, tracking crack growth, and deciding when to replace — adding monitoring burdens and reliance on maintenance judgement (Requirement 1.b.(i), 1.b.(ii)).","Reference to EASA AD 2006-0055-E and European Aviation Safety Agency reports ties this AD to external findings, requiring alignment with referenced certification material (Requirement note; Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of Eurocopter AS 355 E helicopters (with main servo-controls meeting specific modification/torque histories) to inspect the tapered housings of main servo-controls for cracks and to mark, repair or replace servo-controls per Eurocopter ASB No. 05.00.48. It imposes short inspection deadlines, limits on continued operation pending replacement, and applies different rules for installed units and spares; operators and maintenance organisations bear inspection, repair and replacement costs (Applicability; Requirement; Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-90-main-servo-controls","history":"/api/acts/ad-as-355-90-main-servo-controls/history","analysis":"/api/acts/ad-as-355-90-main-servo-controls/analysis","conflicts":"/api/acts/ad-as-355-90-main-servo-controls/conflicts","importantCases":"/api/acts/ad-as-355-90-main-servo-controls/important-cases","documents":"/api/acts/ad-as-355-90-main-servo-controls/documents"}}