{"id":"F2006B10259","name":"AD/GBK 117/12 - Transmission and Engine Cowling Hook System","slug":"ad-gbk-117-12-transmission-and-engine-cowling-hook-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55930,"registerId":"commonwealth-F2006B10259-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/GBK 117/12 - Transmission and Engine Cowling Hook System","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 117/12 Transmission and Engine Cowling Hook System\n\n  \n13/99\n\nApplicability: All Model MBB BK-117 helicopters with serial numbers 7001 through 7253, and 7500 through 7523.\n\nRequirement: Action in accordance with Eurocopter Deutschland Service Bulletin MBB BK 117- 20-109 Revision 2, dated April 30 1999.\n\nNote 1: Accomplishment of Alert Service Bulletin MBB BK 117-20-104 is a prerequisite for compliance with this Directive for certain serial number helicopters, and is addressed by AD/GBK 117/3 Amdt 1.\n\nCompliance: Before 30 June 2000, unless already accomplished.\n\nThis Airworthiness Directive becomes effective on 30 December 1999.\n\nBackground: The LBA requires installation of a hook system to the doors of the transmission and engine cowlings to prevent the doors from opening fully during flight; in the event of the door fasteners not being correctly latched during pre-flight check.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope remains focused on the specified BK‑117 serial numbers and requires installation per the referenced Eurocopter service bulletin (Applicability; Requirement). The only scope nuance is the conditional prerequisite for some serial numbers (Note 1), which is managed by a prior AD; there is no indication in the text that the scope has been broadened or narrowed from the stated requirement."},"complexity_factors":["Narrow, serial‑numbered applicability reduces interpretive complexity (Applicability).","Requirement cross‑references an external technical document (Service Bulletin MBB BK 117‑20‑109 Rev 2), creating a dependency on that material (Requirement).","A conditional prerequisite (Alert Service Bulletin MBB BK 117‑20‑104) applies to some serial numbers, adding conditional compliance steps (Note 1).","Fixed compliance deadline imposes scheduling pressure but does not add legal or procedural complexity beyond meeting the date (Compliance).","Text is concise and prescriptive with no discretionary exemptions or multiple compliance pathways, limiting legal complexity."],"plain_english_summary":"### What this directive does\n\nThis Airworthiness Directive (AD/GBK 117/12) requires installation of a hook system on the transmission and engine cowling doors of certain Eurocopter MBB BK‑117 helicopters. The installation must be carried out in accordance with Eurocopter Deutschland Service Bulletin MBB BK 117‑20‑109 Revision 2 (Requirement). The AD applies to helicopters with serial numbers 7001–7253 and 7500–7523 (Applicability).\n\n### Who it affects\n\n- Owners and operators of the specific BK‑117 helicopters listed by serial number (Applicability).\n- Maintenance organisations that perform work to the Eurocopter service standard (Requirement).\n\n### Why it matters (stated purpose and mechanical effect)\n\n- The stated reason for the requirement is that the LBA (German authority) requires the hook installation to prevent the transmission and engine cowling doors from opening fully in flight if their fasteners were not correctly latched during pre‑flight checks (Background).\n- Mechanically, compliance means having the hook system fitted to those doors according to the technical steps in the referenced service bulletin (Requirement).\n\n### Timing and related actions\n\n- The AD became effective on 30 December 1999 and sets a compliance deadline of before 30 June 2000 unless the work has already been done (Compliance).\n- For some serial numbers, accomplishing Alert Service Bulletin MBB BK 117‑20‑104 is a prerequisite. That prerequisite is addressed by a separate directive (Note 1).\n\n### Who pays, who decides, and what must change\n\n- The directive creates an obligation to perform the specified modification by the stated deadline (Compliance). Practically, that obligation will be discharged by having maintenance personnel or an approved organisation carry out the installation in accordance with the Eurocopter service bulletin (Requirement). The text does not state who pays, but the compliance obligation falls on the owners/operators of the affected helicopters (Applicability; Requirement).\n\n### Implementation and administrative points to note\n\n- The AD cross‑references an external technical document (the Eurocopter service bulletin). Complying exactly requires access to and follow‑through of that external document (Requirement).\n- A conditional prerequisite (Alert Service Bulletin MBB BK 117‑20‑104) applies to certain serial numbers and is handled under a different AD; operators of those helicopters must ensure that prerequisite work is completed before or alongside this AD (Note 1).\n\n### Trade‑offs, incentives and practical risks (source‑grounded)\n\n- Benefit claimed by the authority: reduction in risk of an in‑flight door opening if fasteners are not correctly latched (Background).\n- Concrete cost and effort implications implied by the directive: owners/operators must arrange for the specified installation and meet the compliance deadline, which will require scheduling maintenance resources and following the service bulletin instructions (Requirement; Compliance). The AD text itself does not quantify costs, downtime, or where the work must be performed.\n- The cross‑reference to Eurocopter technical material concentrates the technical specification outside the AD text; compliance therefore depends on that external material being available and followed precisely (Requirement).\n\n### Summary in one line\n\nOwners/operators of Eurocopter MBB BK‑117 helicopters with serial numbers 7001–7253 and 7500–7523 must have a transmission and engine cowling hook system installed in accordance with Eurocopter Service Bulletin MBB BK 117‑20‑109 Rev 2 by 30 June 2000 to address the LBA's requirement that doors be prevented from opening fully in flight if fasteners are not correctly latched (Applicability; Requirement; Background; Compliance)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive addressing a specific mechanical safety concern. It has not expanded beyond its original purpose of mandating cowling hook installation."},"complexity_factors":["Single, specific technical requirement (install hook system)","Limited applicability (defined by two serial number ranges)","One cross-reference to prerequisite directive (AD/GBK 117/3 Amdt 1)","No defined terms section","Single compliance deadline with standard exception clause ('unless already accomplished')","Short document (under 200 words)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopters.\n\n**What it does:**\nOrders owners and operators of certain Eurocopter BK 117 helicopters to install a hook system on the transmission and engine cowling doors. This safety fix prevents the cowling doors from swinging fully open during flight if the ground crew forgets to properly latch them before takeoff.\n\n**Who it affects:**\n- Owners and operators of MBB BK-117 helicopters with serial numbers 7001–7253 and 7500–7523\n- Maintenance organisations servicing these aircraft\n\n**Why it matters:**\nAn unlatched cowling door opening in flight could damage the helicopter, cause loss of control, or lead to an accident. The German aviation authority (LBA) identified this risk and mandated the fix. Australian operators must comply by 30 June 2000 (or earlier if already done).\n\n**Key requirement:**\nFollow the manufacturer's instructions in Eurocopter Service Bulletin MBB BK 117-20-109 Revision 2 (dated 30 April 1999). Some helicopters first need a different fix (Alert Service Bulletin 117-20-104) before they can comply with this one."}},"importantCases":[],"_links":{"self":"/api/acts/ad-gbk-117-12-transmission-and-engine-cowling-hook-system","history":"/api/acts/ad-gbk-117-12-transmission-and-engine-cowling-hook-system/history","analysis":"/api/acts/ad-gbk-117-12-transmission-and-engine-cowling-hook-system/analysis","conflicts":"/api/acts/ad-gbk-117-12-transmission-and-engine-cowling-hook-system/conflicts","importantCases":"/api/acts/ad-gbk-117-12-transmission-and-engine-cowling-hook-system/important-cases","documents":"/api/acts/ad-gbk-117-12-transmission-and-engine-cowling-hook-system/documents"}}