{"id":"F2006B10258","name":"AD/GBK 117/11 Amdt 1 - Tension-Torsion Straps","slug":"ad-gbk-117-11-amdt-1-tension-torsion-straps","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55929,"registerId":"commonwealth-F2006B10258-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/GBK 117/11 Amdt 1 - Tension-Torsion Straps","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nEurocopter BK 117 Series Helicopters\n\nAD/GBK 117/11\n\nAmdt 1\n\n  \nTension-Torsion Straps 11/99\n\nApplicability: All Eurocopter MBB-BK 117 helicopters.\n\nRequirement: Action in accordance with Eurocopter Alert Service Bulletin ASB-MBB-BK 117-10- 120 Revision 1, dated August 31 1999.\n\nNote 1: The calendar time in service commences with date of issue of the initial certificate of airworthiness issued for the aircraft, or date of first installation for any replacement tension-torsion straps fitted, and is continuous from that date.\n\nNote 2: LBA AD 1999-284/2 dated 1 September 1999 refers.\n\nCompliance: At the times or number of flights stated in Eurocopter Alert Service Bulletin ASB- MBB-BK 117-10-120 Revision 1, dated 31 August 1999. For the purpose of section\n\n1.D.3 a date of 18 August 1999 must be used as the reference date. Return to service of tension-torsion straps in accordance with section 1.D.4 applies only to parts which exceed 10 years calendar time in service on 18 August 1999.\n\nThis Amendment becomes effective on 4 November 1999.\n\nBackground: Failure of a tension-torsion strap installed in a US registered BK-117 helicopter caused a fatal crash of the aircraft. The actions of the Eurocopter Service Bulletin have been taken as a precautionary measure. The service limit placed on the tension- torsion strap is presently 10 years (since installation) or 25000 flights, whichever occurs first. Limited return to service of tension torsion straps following inspection is permitted for parts installed for less than 15 years, provided an inspection of the part is made.\n\nAmendment 1 is issued in response to minor amendments of the Eurocopter Service Bulletin. As the amendments are for clarification, the initial compliance date is unchanged from the initial issue of this Directive.\n\nThe original issue of this Airworthiness Directive became effective on 18 August 1999.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — mandating inspection/replacement of tension-torsion straps on BK-117 helicopters following a fatal accident. Amendment 1 explicitly states it only makes minor clarifications without changing compliance dates or substantive requirements."},"complexity_factors":["Single specific technical requirement referencing an external document (Eurocopter Service Bulletin)","Two-tier compliance structure (calendar time vs. flight cycles)","Conditional logic for parts exceeding 10 years service life as of reference date","Cross-reference to German aviation authority document (LBA AD 1999-284/2)","No defined terms section — relies entirely on external technical documentation","Short document (approximately 250 words) with single purpose"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and replacement of tension‑torsion straps on all Eurocopter MBB‑BK 117 helicopters, requiring compliance with Eurocopter Alert Service Bulletin ASB‑MBB‑BK 117‑10‑120 Rev 1. Straps must be removed from service after 10 years or 25,000 flights (with special rules for parts already older as of 18 Aug 1999).\n\nPrompted by a US fatal crash from strap failure, the AD is precautionary and grounding applies if not complied with."},"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":3,"scope_assessment":{"changed":false,"description":"Amendment 1 makes minor clarifications to the Eurocopter Service Bulletin and does not change applicability, compliance dates or the existing service limits (10 years or 25,000 flights). The Directive’s practical scope and obligations remain the same as the original AD effective 18 August 1999."},"complexity_factors":["Narrow applicability (all Eurocopter MBB‑BK 117 helicopters) reduces scope complexity","Normative reliance on an external Eurocopter Alert Service Bulletin for technical actions","Dual service limits (calendar time and flight cycles) require operators to track two metrics","Historic reference date (18 Aug 1999) and age-based return‑to‑service exceptions add record-keeping detail","Safety-critical part with a known failure history motivates urgent compliance but limits regulatory discretion","Administrative burden on operators for inspections, parts replacement and aircraft downtime"],"plain_english_summary":"This Directive requires operators of all Eurocopter MBB‑BK 117 helicopters to carry out the inspections, repairs and any replacements set out in Eurocopter Alert Service Bulletin ASB‑MBB‑BK 117‑10‑120 Rev 1 (31 Aug 1999). It enforces a service limit of 10 years or 25,000 flights for tension‑torsion straps, uses 18 Aug 1999 as the compliance reference date, and allows limited return‑to‑service for parts under 15 years after inspection. CASA enforces the AD; operators pay inspection, replacement and downtime costs. The action follows a fatal strap failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-gbk-117-11-amdt-1-tension-torsion-straps","history":"/api/acts/ad-gbk-117-11-amdt-1-tension-torsion-straps/history","analysis":"/api/acts/ad-gbk-117-11-amdt-1-tension-torsion-straps/analysis","conflicts":"/api/acts/ad-gbk-117-11-amdt-1-tension-torsion-straps/conflicts","importantCases":"/api/acts/ad-gbk-117-11-amdt-1-tension-torsion-straps/important-cases","documents":"/api/acts/ad-gbk-117-11-amdt-1-tension-torsion-straps/documents"}}