{"id":"F2006B06466","name":"AD/R44/16 - Vertical-to-Horizontal Stabiliser Attach Channel","slug":"ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47952,"registerId":"commonwealth-F2006B06466-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 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.","sortOrder":0},{"sectionNumber":"AD/R44/16 Vertical-to-Horizontal Stabili","sectionType":"part","heading":"AD/R44/16 Vertical-to-Horizontal Stabiliser Attach Channel 13/2001","content":"# ![](image.003.png)AD/R44/16 Vertical-to-Horizontal Stabiliser Attach Channel 13/2001\n\nDM\n\nApplicability: Model R44 helicopters, with horizontal stabiliser assembly part number C044-1; horizontal stabiliser serial number 0009 through 0224, except 0018, 0090, 0094,\n\n0111, 0129, 0144, 0161, 0178, 0201, and 0223, installed.\n\nRequirement: Remove the vertical stabiliser to inspect the nutplate on channels, part number D283- 1 and -2 in accordance with Robinson Helicopter Company Service Bulletin SB-39.\n\nIf the nutplates are part number MS21086L4, no further action is required by this Directive.\n\nIf the nutplates are part number NAS697A4, replace the channels with serviceable channels, part number D296-1 or -2.\n\nThis AD revises the Limitations section of the maintenance manual by establishing a retirement life of 2,200 time in service for horizontal stabiliser assembly, part number C044-1, with channels part number D283-1 or -2, with nutplates, part number NAS697A4, installed.\n\nNote: FAA AD 2001-20-18 Amdt 39-12466 refers.\n\nCompliance: Before accumulating 2,200 hours time in service on the horizontal stabiliser assembly.\n\nThis Airworthiness Directive becomes effective on 19 November 2001.","sortOrder":1}],"analysis":{"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 AD maintains its original narrow scope — addressing a specific unsafe condition in a specific helicopter part. It has not expanded beyond its initial safety purpose."},"complexity_factors":["Single, specific aircraft model and limited serial number range with explicit exclusions","Simple binary decision tree (two possible nutplate types, two corresponding actions)","Only one cross-reference (to FAA AD 2001-20-18)","Clear, single compliance deadline (2,200 hours time in service)","No nested exceptions or conditional sub-clauses","Straightforward mechanical inspection and replacement procedure"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of certain Robinson R44 helicopters with a specific horizontal stabiliser assembly to inspect the vertical‑to‑horizontal stabiliser attachment for unsafe nutplates and, if found, replace the affected channels and limit that stabiliser assembly to 2,200 flight hours.  \n\nIt addresses a risk of structural failure at the stabiliser connection that could cause loss of control."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD stays within the original safety-correction scope: it identifies an unsafe condition for a defined set of stabiliser assemblies, mandates inspection and remedial action, and sets a retirement life for the affected parts combination. The main substantive change relative to a simple inspection/remedy approach is the explicit addition of a 2,200-hour retirement life for assemblies with D283 channels combined with NAS697A4 nutplates; that is an extension of remedies (a time limit on continued use) but does not expand the class of aircraft affected or introduce unrelated regulatory obligations."},"complexity_factors":["Applicability tied to a narrow model and a range of serial numbers with 10 listed exclusions","Two alternative nutplate part numbers (MS21086L4 vs NAS697A4) produce different mandatory outcomes","Action requires removal of a major component (vertical stabiliser) to access inspection area","Conditional replacement: only channels with a particular nutplate type must be replaced with specified part numbers (D296-1 or -2)","Imposes a new retirement life (2,200 hours TIS) for a specific parts combination, requiring maintenance manual and record updates","Cross-reference to an FAA AD and to manufacturer Service Bulletin SB-39 (external-doc dependency)","Compliance timing is a before-threshold rule (before accumulating 2,200 hours), not a simple immediate deadline"],"plain_english_summary":"**What this directive does (mechanically):**\n\n- Applies to Robinson R44 helicopters that have horizontal stabiliser assembly part number C044-1 with serial numbers 0009 through 0224, except for serial numbers 0018, 0090, 0094, 0111, 0129, 0144, 0161, 0178, 0201 and 0223 (Applicability).  \n- Requires removal of the vertical stabiliser so a mechanic can inspect the nutplates on the attach channels (channels part numbers D283-1 and D283-2), following Robinson Service Bulletin SB-39 (Requirement).  \n- If the nutplates are part number MS21086L4, no further work is required.  \n- If the nutplates are part number NAS697A4, the directive requires replacing the D283 channels with serviceable channels part number D296-1 or D296-2 (Requirement).  \n- Revises the maintenance manual limitations by imposing a retirement life of 2,200 hours time-in-service (TIS) for the horizontal stabiliser assembly C044-1 when it has D283-1 or D283-2 channels fitted together with NAS697A4 nutplates (Requirement / Limitations).  \n- Compliance timing: the replacement/inspection and retirement-life rule must be complied with before the horizontal stabiliser assembly reaches 2,200 hours TIS (Compliance).  \n\n**Who this affects:**\n\n- Owners and operators of Robinson R44 helicopters that match the listed stabiliser serial numbers.  \n- Licensed maintenance organisations and engineers who will perform the removal, inspection and any required channel replacement.  \n- Aircraft record-keeping personnel, because the maintenance manual limitation (retirement life) must be recorded and tracked.  \n\n**Why it matters (stated purpose and mechanical effect):**\n\n- The stated reason is to correct an unsafe condition relating to the attach channels and nutplates between the vertical and horizontal stabilisers. Mechanically, the AD prevents continued service of a stabiliser assembly combination (D283 channels + NAS697A4 nutplates) beyond 2,200 hours, and requires replacement of channels where the nutplates are the NAS697A4 type. This aims to remove a potentially unsafe parts combination from service and to ensure the alternative (MS21086L4 nutplates) does not require corrective action (Requirement / Compliance).\n\n**Costs, incentives and trade-offs (practical implications):**\n\n- Who pays: the helicopter owner/operator pays for the removal, inspection, any replacements, and for associated downtime and record-keeping.  \n- Direct costs: labour to remove the vertical stabiliser, inspect nutplates, and replace channels if required; cost of replacement channels D296-1 or D296-2 where NAS697A4 nutplates are found.  \n- Opportunity cost: aircraft will be out of service for the inspection/repair; operators may need to schedule maintenance earlier than planned to meet the retirement-life limit.  \n- Incentives: owners have an incentive to identify assemblies with MS21086L4 nutplates (no further action) and to replace D283 channels proactively with D296 channels to avoid the 2,200‑hour retirement clock where appropriate.  \n- Substitution effects: operators may choose to replace channels with the D296-1/-2 configuration (if available and compatible) to avoid the retirement requirement associated with the D283/NAS697A4 combination.  \n\n**Implementation and compliance risks:**\n\n- Parts identification risk: correct identification of nutplate part numbers (MS21086L4 vs NAS697A4) is a factual step; misidentification could lead to unnecessary replacements or missed hazards (Requirement).  \n- Supply risk: availability of replacement channels (D296-1/-2) could affect how quickly operators can comply.  \n- Maintenance burden: the required removal of the vertical stabiliser is non-trivial maintenance work and requires appropriately authorised personnel and facilities.  \n- Administrative burden: maintenance manuals and aircraft logbooks must be updated to reflect the new retirement life and any parts changes.\n\n**Who decides and what changes:**\n\n- The CASA delegate issued the AD under the relevant aviation regulation (noted at top of the directive). The delegate sets the mandatory requirement and compliance date (top matter / Compliance).  \n- Behaviour change required: operators must inspect, replace if necessary, and ensure that C044-1 stabiliser assemblies with the specified parts do not remain in service past 2,200 hours TIS.  \n\n**Cross-references and alignment:**\n\n- The AD references FAA AD 2001-20-18 (Note), indicating alignment with a corresponding FAA airworthiness action; it also mandates following Robinson Service Bulletin SB-39 for the inspection procedure (Requirement).  \n\n**Net effect (summary):**\n\n- The AD imposes a specific inspection and conditional replacement rule for a subset of R44 stabiliser assemblies, and it creates a fixed retirement life (2,200 hours TIS) for assemblies that combine D283 channels with NAS697A4 nutplates. This creates a clear, time-limited requirement for operators to inspect and, where necessary, replace parts to mitigate the identified unsafe condition (Applicability / Requirement / Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel","history":"/api/acts/ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel/history","analysis":"/api/acts/ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel/analysis","conflicts":"/api/acts/ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel/conflicts","importantCases":"/api/acts/ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel/important-cases","documents":"/api/acts/ad-r44-16-vertical-to-horizontal-stabiliser-attach-channel/documents"}}