{"id":"F2006B01802","name":"AD/A109/18 Amdt 3 - Upper Transmission Mount Fitting","slug":"ad-a109-18-amdt-3-upper-transmission-mount-fitting","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41000,"registerId":"commonwealth-F2006B01802-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/A109/18 Amdt 3 - Upper Transmission Mount Fitting","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)  \nAgusta A109 Series Helicopters\n\nAD/A109/18\n\nAmdt 3\n\n  \nUpper Transmission Mount Fitting 8/91\n\nApplicability: All model A109A and A109AII series helicopters and A109C series helicopters up to S/N 7628; equipped with upper transmission mount fitting P/N 109-0402-27-11.\n\nRequirement: 1. Visually inspect the aft lugs of the upper right and left transmission mount fittings, in the visible area, for integrity, without removal of any components.\n\n    2. Manufacture and install a placard with the following instructions: VNE=140 kts sl to 3000 ft.\n\nAbove 3000 ft decrease\n\nAll placarded VNE by 20 kts.\n\nAvoid rough manoeuvres and rough flares.\n\n    3. Replace the upper transmission mount fittings in accordance with BT No 109-80 revision B.\n\nNote: RAI AD 91-202 refers.\n\nCompliance: 1. Prior to each flight.\n\n    2. Unless already accomplished; on receipt of this Airworthiness Directive.\n\n    3. Unless already accomplished; Prior to 31 October 1991.\n\nNote: Compliance with Requirement 3 cancels Requirement 1 and 2 for all models.\n\nBackground: Original AD was issued in response to a report of a cracked transmission mount fitting on a A109C model, in the area of the left hand aft support leg connection.\n\nAmendment 1 expanded the AD Requirement to include all A109 models, in response to a similar case of cracking on a A109 II model in the area of the right hand aft support leg connection.\n\nAmendment 2 introduced an improved mount fitting for the A109C model, which constituted terminating action for the repetitive inspection and flight limitations.\n\nAmendment 3 is raised in response to the Country of Origin AD which requires terminating action to be incorporated on models A109A and A109A II.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original AD (1991) targeted only the A109C model after one incident. Amendment 1 expanded it to all A109 models after a second incident on a different model. Amendment 2 added a terminating action for the A109C specifically. Amendment 3 now extends that terminating action to the A109A and A109AII models. The scope has grown from a single-model fix to a fleet-wide safety mandate across multiple variants, though the core safety issue (faulty transmission mount fittings) remains consistent."},"complexity_factors":["Short, single-purpose document (1 page)","Only 3 substantive requirements with clear compliance deadlines","Minimal defined terms (only standard aviation abbreviations: VNE, P/N, S/N, RAI, BT)","Simple conditional logic (Requirement 3 cancels Requirements 1 and 2)","Clear applicability section limiting scope to specific models and serial numbers","Historical amendments clearly explained in Background section rather than embedded in operative text"],"plain_english_summary":"This CASA Airworthiness Directive targets Agusta A109 (A, AII and early A109C up to S/N 7628) helicopters fitted with upper transmission mount fitting P/N 109-0402-27-11. It mandates preflight visual checks of the aft lugs, a cockpit placard imposing reduced speed/flight handling limits, and replacement of the fittings per BT No 109-80 Rev B by 31 Oct 1991. The actions prevent catastrophic transmission separation caused by cracked fittings; replacement cancels the inspections and placard."},"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":true,"description":"This amendment broadened the terminating-action coverage compared to earlier versions. The original AD responded to a cracked fitting on an A109C and initially required inspections and limitations for that model. Subsequent amendments expanded the repetitive-inspection requirement to additional A109 models. Amendment 3 specifically requires that the terminating action (replacement with the improved mount fitting per BT No. 109-80 rev B) be incorporated on A109A and A109AII models as well, thereby extending the scope of the definitive remedy (replacement) across more variants rather than leaving those models subject only to inspections and placarded limitations."},"complexity_factors":["Three discrete Requirements (inspection, placard/limitations, replacement) with a clear terminating-action conditionality (Requirement 3 cancels Requirements 1 and 2).","Narrow applicability clause (specific models, serial-number cut-off for A109C, and specific part number), which reduces scope complexity but requires careful aircraft/parts identification.","Cross-reference to external document for terminating action: BT No. 109-80 revision B (requires consulting another technical document for full implementation).","Operational conditionality tied to altitude for speed limitation (VNE 140 kts SL–3000 ft; above 3000 ft reduce by 20 kts).","Repeated/ongoing compliance element (inspect prior to each flight) creates operational complexity though not legal complexity.","Minor interpretive ambiguity in phrases like \"visible area\" and \"avoid rough manoeuvres and rough flares\", which rely on operator judgement rather than strict definitional rules.","Historic compliance timing (deadline date listed) but otherwise short and procedural rather than heavily conditional or heavily cross-referenced."],"plain_english_summary":"**What this instrument does (mechanics)\n\n- Applies to: Agusta A109A and A109AII helicopters, and A109C helicopters up to serial number 7628, when fitted with upper transmission mount fitting P/N 109-0402-27-11 (see \"Applicability\").\n\n- Immediate actions required:\n  - Requirement 1: Before each flight, visually inspect the aft lugs of the upper right and left transmission mount fittings in the visible area for any loss of integrity (no removal of components allowed).\n  - Requirement 2: As soon as you receive the AD, manufacture and install a cockpit/airframe placard giving a VNE (never-exceed speed) of 140 knots at sea level to 3,000 ft; instruct that above 3,000 ft the placarded VNE is reduced by 20 knots; and warn crews to avoid rough manoeuvres and rough flares.\n  - Requirement 3 (terminating action): Replace the upper transmission mount fittings in accordance with Bollettino Tecnico (BT) No. 109-80 revision B. If Requirement 3 is completed, Requirements 1 and 2 are cancelled for all affected models.\n\n- Timing: Inspections (Req.1) are prior to each flight; the placard (Req.2) is required on receipt of the AD (unless already done); the replacement (Req.3) must be done unless already accomplished, and in this instrument had a specified deadline (Prior to 31 October 1991).\n\n**Why it exists (official rationale and practical effect)\n\n- Stated reason: The AD responds to reports of cracked upper transmission mount fittings on A109 variants (cracking found on A109C and A109 II in the aft support-leg connection area). The AD requires repetitive inspection and flight restrictions as interim risk controls, and provides a terminating action (replace with an improved fitting) to remove the recurring inspection and speed/handling limits.\n\n**Who it affects and who pays\n\n- Affected parties: Owners and operators of the specified A109 helicopters fitted with the identified mount part number, and maintenance organisations that service them.\n- Who decides / enforces: The Civil Aviation Safety Authority (as issuer) requires compliance; operators and authorised maintenance organisations carry out inspections, placard installation and the replacement action.\n- Who bears the cost: Operators (or their insurers) pay for the extra pre-flight inspection time, producing/installing the placard, any flight restrictions' operational impacts, and the cost of parts and labour to replace the mount fittings per BT No. 109-80 rev B.\n\n**Practical incentives and trade-offs (implementation, costs and operational effects)\n\n- Short-term risk mitigation: Daily (pre-flight) inspections and immediate placarding reduce the short-term risk of undetected cracking by limiting speeds and certain manoeuvres.\n- Medium-term/long-term trade-off: Replacing the fittings under the BT terminates the recurring inspections and operating limits, but requires acquisition of replacement fittings and maintenance hours (downtime and direct cost). The operator trades recurring labour/operational constraints for a one-off parts-and-labour expense and associated downtime.\n- Compliance burden: Repetitive inspections prior to each flight increase pre-flight workload for pilots/technicians; placard manufacture/installation is low-cost; replacement requires certified maintenance and specific BT instructions to be followed.\n- Implementation risks and supply-side issues: The AD cross-references BT No. 109-80 rev B for the terminating action. If only the OEM supplies the improved fittings or special tooling, replacement costs and lead times could be material and may temporarily reduce aircraft availability. The AD does not itself specify authorised suppliers, so operators must follow the BT and standard approval paths.\n\n**Effects on private enterprise and operating choices\n\n- Operators must either accept the ongoing inspection and speed/handling limits (affecting payload/scheduling and pilot handling choices) or incur the replacement cost to remove those constraints.\n- Maintenance organisations gain work from inspections and replacements; if replacement parts are restricted to certain suppliers, costs may be concentrated for operators while benefits (maintenance revenue) are concentrated among suppliers/repairers.\n\n**Concentrated benefits and diffuse costs\n\n- Safety benefit (concentrated on individual aircraft and passengers) is direct and concentrated for operators who replace fittings; costs (inspection time, replacement parts, downtime) are concentrated on affected aircraft owners/operators.\n\n**Notes on wording and potential ambiguities\n\n- The AD uses practical phrases such as \"in the visible area\" and \"avoid rough manoeuvres and rough flares\" that require operator judgment and standard maintenance/pilot practice to implement. The terminating action is specified by reference to a maintenance bulletin (BT No. 109-80 rev B), so full compliance detail requires consulting that document (see Requirement 3).  (Requirements cited: Requirement 1, Requirement 2, Requirement 3, Applicability, Compliance, Background.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-a109-18-amdt-3-upper-transmission-mount-fitting","history":"/api/acts/ad-a109-18-amdt-3-upper-transmission-mount-fitting/history","analysis":"/api/acts/ad-a109-18-amdt-3-upper-transmission-mount-fitting/analysis","conflicts":"/api/acts/ad-a109-18-amdt-3-upper-transmission-mount-fitting/conflicts","importantCases":"/api/acts/ad-a109-18-amdt-3-upper-transmission-mount-fitting/important-cases","documents":"/api/acts/ad-a109-18-amdt-3-upper-transmission-mount-fitting/documents"}}