{"id":"F2008L04478","name":"AD/EC 120/16 Amdt 1 - Engine Controls - Twist Grip Assembly","slug":"ad-ec-120-16-amdt-1-engine-controls-twist-grip-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":76497,"registerId":"commonwealth-F2008L04478-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Eurocopter EC 120 Series Helicopters","sectionType":"division","heading":"Eurocopter EC 120 Series Helicopters","content":"### Eurocopter EC 120 Series Helicopters\n\n| AD/EC 120/16 Amdt 1 | Engine Controls - Twist Grip Assembly | 13/2008 |\n| ------------------- | ------------------------------------- | ------- |\n\n| Applicability: | Eurocopter (formerly Eurocopter-France) EC 120 B helicopters, all serial numbers (S/N) fitted with:- Right Hand (RH) twist grip part number (P/N) C761A2024101 with S/N: 336 to 338 (inclusive), 342 to 353 (inclusive), 356 to 364 (inclusive) and 367 to 401 with no letter “V” marked on the lever base; and- P/N C761A2024102, P/N C761A2024103 or P/N C761A2024104 with S/N below 418 with no letter “V” marked on the lever base.- Left Hand (LH) twist grip P/N C761A2025102, P/N C761A2025103 or P/N C761A2025104 with S/N below 382 with no letter “V” marked on the lever base.                                                                                                                                                                                                                                                                                                                                        |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. On helicopters having already accomplished EUROCOPTER EC120 Service Bulletin (SB) No. 76-005 Revision 0:Identify the collective lever in accordance with paragraph 2.B.3. of EUROCOPTER EC 120 ASB No. 76A005 Revision 1.2. On helicopters not having already accomplished EUROCOPTER EC120 SBNo. 76-005 Revision 0:a. Remove the drive tube on:RH twist grips assemblies P/N C761A2024101, P/N C761A2024103 orP/N C761A2024104, S/N: 336 to 338 (inclusive), 342 to 353 (inclusive), 356 to 364 (inclusive), and 367 to 401(inclusive), having no letter “V” marked on the lever base; andLH twist grips P/N C761A2025103 or P/N C761A2025104, S/N 371 to 381 (inclusive), having no letter “V” marked on the lever base in accordance with paragraph 2.B of EUROCOPTER EC120 SB No. 76-005 Revision 1.b. In autorotation training, the manoeuvre must be carried out until the helicopter touches down (full autorotation). |\n\n|             | c. Do not install a twist grip having P/N and S/N as per Requirement 2a of this AD on a helicopter, unless the drive tube has been replaced and the collective lever marked in accordance with paragraphs 2.B.2. and 2.B.3. of EUROCOPTER EC 120 ASB No. 76A005 Revision 1.3. Do not install on a helicopter twist grip assemblies listed below not having accomplished EUROCOPTER EC120 SB No. 76-005 Revision 1, unless the correct bonding strength of the control pinion on the pilot and co-pilot collective lever drive tubes has been checked in accordance with paragraph 2.B.4 of EUROCOPTER EC 120 ASB No. 76A006 Revision 2.P/N C761A2024102 and C761A2024103 and C761A2024104 with S/N below 418; orP/N C761A2025102 and C761A2025103 and C761A2025104 with S/N below 382.The use of later approved revisions of these documents is acceptable for compliance with the requirements of this AD.Note: EASA AD 2008-0185 dated 8 October 2008 refers. This AD supersedes EASA AD 2006-0253. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | For Requirement 1 - Within 9 months after the effective date of this AD, unless previously accomplished.For Requirement 2.a. - Within 110 flight hours or 9 months after the effective date of this AD, whichever occurs first, unless previously accomplished.For Requirement 2.b. - Pending replacement of the twist grip drive tube as per Requirement 2.a. of this AD.For Requirement 2.c. - From the effective date of this AD.For Requirement 3 - From the effective date of this AD.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n|             | This Amendment becomes effective on 18 December 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n| Background: | This Airworthiness Directive is in response to a twist grip failure experienced during an autorotation training procedure during which the engine remained at idle rating although the twist grip had been turned back to the flight position. Analysis has revealed failure of the twist grip drive tube and control pinion bonded attachment due to non-compliant preparation of the bonding surfaces on the two components.Further investigation has revealed other twist grip batches potentially affected by non appropriate surface preparation prior to bonding.                                                                                                                                                                                                                                                                                                                                                                                                                               |\n\n|     | Over time, such surface preparation creates a risk of failure of the bonded attachment of the drive tube and thus a risk of losing in flight the engine fuel flow control function, which may constitute an unsafe condition.This amendment ensures that the twist grips correct bonding strength of the control pinion on the pilot and co-pilot collective lever drive tubes is achieved in accordance with the latest approved data.The original issue of this AD became effective on 26 October 2006. |\n| --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n6 November 2008","sortOrder":0},{"sectionNumber":"AD/EC 120/16 Amdt 1","sectionType":"part","heading":"AD/EC 120/16 Amdt 1","content":"## AD/EC 120/16 Amdt 1","sortOrder":1},{"sectionNumber":"Engine Controls - Twist Grip Assembly","sectionType":"part","heading":"Engine Controls - Twist Grip Assembly","content":"## Engine Controls - Twist Grip Assembly","sortOrder":2},{"sectionNumber":"13/2008","sectionType":"part","heading":"13/2008","content":"## 13/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":7,"scope_assessment":{"changed":true,"description":"This amendment supersedes the earlier EASA AD 2006-0253 and expands/clarifies corrective requirements: it identifies additional affected P/N/S/N ranges and prescribes removal/replacement of drive tubes, marking of the collective lever and bonding‑strength checks before (re)installation (\"This AD supersedes EASA AD 2006-0253\"; Applicability; Requirement 2.a–2.c). The amendment also sets staged compliance windows (Compliance) and accepts later approved revisions of referenced SB/ASB documents, which preserves administrative discretion but places the compliance and parts/repair cost burden on operators (Requirement; Note; Compliance)."},"complexity_factors":["Heavy technical specificity: multiple part numbers (P/N) and serial number (S/N) ranges for RH and LH twist grips (Applicability).","Conditional requirements depending on whether prior Service Bulletin (SB No. 76-005 Rev 0) was already accomplished (Requirement).","Multiple different mandatory actions: remove drive tube, mark collective lever, perform bonding‑strength checks, and limit autorotation training to full touchdown pending repairs (Requirement 2.a, 2.b, 2.c).","Varied and overlapping compliance timelines (within 9 months; within 110 flight hours or 9 months; immediate prohibitions from effective date) increasing scheduling and operational planning complexity (Compliance).","Cross‑references to several external documents: EUROCOPTER SBs/ASBs and EASA ADs; compliance can rely on later approved revisions, adding administrative discretion (Requirement, Note).","Installation prohibition clauses that condition future parts installation on prior corrective action or verification, creating parts‑management and supply constraints for operators (Requirement 2.c).","Root cause is a bonding/process defect (non‑compliant surface preparation), which requires both physical replacement/repair and verification of bonding strength — technical inspection/testing burden (Background).","Safety‑critical operational restriction (autorotation training must be full touchdown) that affects pilot training scheduling and regulatory reporting (Requirement 2.b)."],"plain_english_summary":"This AD requires inspection, removal, replacement and marking of specific right‑ and left‑hand twist‑grip assemblies on Eurocopter EC120 B helicopters identified by part and serial numbers. It responds to bonded drive‑tube/control‑pinion failures discovered during autorotation training and mandates corrective actions and installation prohibitions until correct bonding strength is achieved. Operators must meet staged time or flight‑hour compliance windows and follow referenced Eurocopter service documents."},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":false,"description":"This is an amendment to an existing Airworthiness Directive (AD/EC 120/16). The amendment remains tightly focused on the original safety issue (twist grip drive tube bonding failures) and does not expand beyond the EC 120 B helicopter type or the specific component defect. The amendment updates compliance requirements based on new investigation findings (additional affected batches and improved repair procedures) but stays within the original safety purpose."},"complexity_factors":["Multiple overlapping part number (P/N) and serial number (S/N) ranges with different requirements for each","Four different requirement streams (Requirements 1, 2a, 2b, 2c, and 3) with different compliance deadlines","Cross-references to three external Eurocopter documents (SB No. 76-005 Revision 0/1, ASB No. 76A005 Revision 1, ASB No. 76A006 Revision 2) without reproducing their content","Conditional logic based on whether previous service bulletins were accomplished","Distinguishing between 'V' marked and unmarked lever bases as a compliance differentiator","Nested applicability criteria: RH vs LH twist grips, specific P/Ns, specific S/N ranges, and visual marking status","Amendment structure requiring comparison with superseded EASA AD 2006-0253 and reference to EASA AD 2008-0185"],"plain_english_summary":"CASA requires operators of Eurocopter EC120B helicopters to inspect and, if needed, replace certain twist grip assemblies after a bonding defect in the drive tube that can break the mechanical link to the engine, risking loss of throttle control. It targets helicopters with affected part/serial numbers (excluding V‑marked levers) and temporarily requires autorotation training to continue to touchdown until repairs are done."},"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-ec-120-16-amdt-1-engine-controls-twist-grip-assembly","history":"/api/acts/ad-ec-120-16-amdt-1-engine-controls-twist-grip-assembly/history","analysis":"/api/acts/ad-ec-120-16-amdt-1-engine-controls-twist-grip-assembly/analysis","conflicts":"/api/acts/ad-ec-120-16-amdt-1-engine-controls-twist-grip-assembly/conflicts","importantCases":"/api/acts/ad-ec-120-16-amdt-1-engine-controls-twist-grip-assembly/important-cases","documents":"/api/acts/ad-ec-120-16-amdt-1-engine-controls-twist-grip-assembly/documents"}}