{"id":"F2006B02552","name":"AD/AT/3 Amdt 5 - Landing Gear","slug":"ad-at-3-amdt-5-landing-gear","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41808,"registerId":"commonwealth-F2006B02552-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AT/3 Amdt 5 - Landing Gear","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)  \nAirtractor AT-300, 400 and 500 Series Aeroplanes\n\nAD/AT/3\n\nAmdt 5\n\n  \nLanding Gear 4/97\n\nApplicability: All models fitted with main landing gear spring legs P/N 40007-2/-3, 40058-1/-2 and 40086-1.\n\nRequirement: Retire the main landing gear spring legs, the forward and aft main gear clamp block bolts and the inboard main gear large bolt.\n\nNote: Snow Engineering Service Letters #117, #119 and FAA AD 82-06-12 refer.\n\nCompliance: Retire the main landing gear spring legs at the number of landings listed in Table 1.\n\nAt the same time, retire the forward and aft main gear clamp block bolts and the inboard main gear large bolt.\n\nIf, during initial compliance with this directive, any or all of the components listed in the above Requirement are found to be outside the Table 1 lives, replace those components within 500 landings after 27 March 1997, or by 30 June 1997, whichever occurs first.\n\nTable 1 \\- Spring Retirement Lives\n\n| Spring Part # | Thickness (in) | Aircraft Fitted                   | Retire at every (#LDGs) |\n| ------------- | -------------- | --------------------------------- | ----------------------- |\n| 40007-2       | 1.0            | AT-300, -301                      | 7500                    |\n| 40007-2       | 1.0            | AT-302, -400A                     | 6000                    |\n| 40058-1       | 1.0            | AT-300, -301                      | 7500                    |\n| 40058-1       | 1.0            | AT-400, -400A                     | 6000                    |\n| 40058-2       | 1.19           | AT-400, -402, -402A, -402B        | 10000                   |\n| 40058-2       | 1.19           | AT-301, -400A, -401, -401B        | 12500                   |\n| 40007-3       | 1.12           | AT-301, -401, -401B               | 12500                   |\n| 40086-1       | 1.31           | AT-501, -502, -502A, -502B, -503A | 8000                    |\n\nWhere the total number of landings during a period of service has not been recorded, the number of landings for that period of service is to be calculated using a rate of 4 landings per hour time in service.\n\nThis Amendment becomes effective on 27 March 1997.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBackground: The original directive was written to inspect for cracking of the undercarriage springs and to publish a life limitation on the springs after a number of failures. Since initial issue of the directive and subsequent amendments, service history and the introduction of a bolt retirement life have led to a need to reassess the directive.\n\nThis amendment deletes the retirement life based on flight hours, as the cause of failure is driven by number of landings.\n\nAmendment 4 of this Airworthiness Directive became effective on 30 January 1997\\. Amendment 3 of this Airworthiness Directive became effective on 17 August 1995. The original issue of this Airworthiness Directive became effective on\n\n30 September 1982.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"The original directive focused on inspecting for cracks and setting life limitations based on flight hours. This amendment (Amendment 5) narrows and refines the scope by removing flight-hour-based retirement entirely and replacing it with landing-count-based retirement, which more precisely addresses the actual failure mode (landing cycles rather than time aloft). It also expands the scope slightly by adding bolt retirement requirements alongside the spring legs."},"complexity_factors":["Multiple part numbers with different retirement lives (8 distinct combinations in Table 1)","Cross-references to external documents (Snow Engineering Service Letters #117, #119 and FAA AD 82-06-12)","Conditional compliance deadlines (500 landings after 27 March 1997 OR 30 June 1997, whichever occurs first)","Alternative calculation method for missing records (4 landings per hour assumption)","Amendment structure requires understanding of previous versions (deletes flight-hour limits, replaces with landing-count limits)","Specific applicability criteria based on part numbers and aircraft models"],"plain_english_summary":"Owners, operators and maintenance organisations of Airtractor AT-300/400/500 crop-dusters must retire and replace specified main landing‑gear spring legs and bolts after a fixed number of landings (limits vary by model/part) to prevent fatigue failures.  \n\nIf limits are already exceeded, replacements are required within 500 landings or by 30 June 1997; missing records are calculated at 4 landings per flight hour. This amendment shifts from flight‑hour to landing‑based limits for safety."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The amendment narrows the failure driver from flight hours to number of landings and converts the AD from an inspection‑and‑life‑assessment approach into a mandatory retirement regime with specific landing counts. It also adds explicit retirement requirements for specified clamp block and inboard gear bolts (bolt retirement life), which broadened the directive's scope from only spring inspection/life limits to include associated fasteners. The Background expressly states the removal of flight‑hour retirement and the introduction of bolt retirement life as the reason for reassessment."},"complexity_factors":["Single narrow subject matter (landing gear spring retirement) with limited ancillary requirements","One table (Table 1) listing 8 distinct spring part/model/retirement combinations","Additional mandatory retirement for three bolt types linked to spring retirement","Transitional/initial compliance condition (replace within 500 landings after effective date or by a fixed calendar date)","Fallback calculation rule where landings are unrecorded (4 landings per hour)","Cross‑references to external service letters and an FAA AD for context (non‑normative)"],"plain_english_summary":"**What this rule does (mechanics)\n\n- It requires specific parts of the main landing gear on certain Airtractor AT‑300/400/500 series aeroplanes to be removed from service after a fixed number of landings (a \"retirement life\"). (Requirement; Table 1)\n- The affected parts are particular main landing‑gear spring legs (part numbers 40007‑2, 40007‑3, 40058‑1, 40058‑2 and 40086‑1), plus two clamp‑block bolts (forward and aft main gear clamp block bolts) and the inboard main‑gear large bolt. All those bolts must be retired at the same time as the springs. (Requirement)\n- The exact retirement life (number of landings) depends on the spring part number and the aircraft model; the directive sets those lives in a table. (Table 1)\n- If an operator cannot produce a recorded count of landings for a period of service, the directive instructs them to estimate landings by using a conversion factor of 4 landings per hour of time in service. (Compliance)\n- For components already beyond their listed life when the operator first checks under this AD, there is a short transitional window: replace those components within 500 landings after 27 March 1997 or by 30 June 1997, whichever comes first. The AD took effect on 27 March 1997. (Compliance)\n\nWho it affects\n\n- Operators and owners of Airtractor AT‑300, AT‑400 and AT‑500 series aeroplanes that use the listed spring part numbers. (Applicability; Table 1)\n- Aircraft maintenance organisations and approved maintenance engineers who must track landings, schedule retirements, and carry out replacements. (Requirement; Compliance)\n\nWhy it matters (stated purpose, and practical consequences)\n\n- The stated purpose is to prevent undercarriage spring failures by imposing mandatory retirement lives after service experience showed failures and to add a retirement life for certain bolts. (Background)\n- Mechanically, this converts an inspection/tracking regime into a mandatory parts‑retirement regime: operators must plan and pay for periodic replacement of springs and specified bolts once the number of landings reaches the listed limits. (Requirement; Table 1)\n\nCosts, incentives and trade‑offs (how behaviour and resources change)\n\n- Who pays: aircraft owners/operators pay for replacement parts, labour and aircraft downtime for each retirement event. (Requirement; Compliance)\n- Who decides and acts: the regulator (Civil Aviation Safety Authority via this AD) sets the rule; operators and maintenance providers implement it by scheduling retirement and replacement. (Applicability; Requirement)\n- Behavioural change: operators must (a) keep or reconstruct accurate landing counts, (b) schedule proactive replacement at the specified landing counts rather than waiting for visible cracking, and (c) replace related bolts whenever springs are retired. (Compliance; Table 1)\n- Compliance burden: tracking landings (or converting hours to landings at 4 landings per flight hour where records lack) and the cost/time of replacing springs and bolts. (Compliance)\n- Safety trade‑off claimed: the AD is premised on reducing in‑service failures by retiring components before they crack or break; the Background ties the change to service history and bolt life data. (Background)\n\nImplementation risks and practical notes\n\n- Estimation rule: using 4 landings per flight hour is a blunt conversion; operators with atypical operations (many short fields or many touch‑and‑goes) may over‑ or under‑estimate actual landings. That affects replacement timing and costs. (Compliance)\n- Transitional window: there is a short fixed window for initial compliance when components are already beyond life — that concentrates immediate replacement costs into the first few months after the AD becomes effective. (Compliance)\n- Cross‑references: the AD notes related service letters and an FAA AD which provide context or technical guidance but the mandatory requirements are those stated in this AD. (Note)\n\nSource claims versus costs and incentives\n\n- The AD states its motive as a response to failures and service history and says bolt life data prompted reassessment (Background). That justifies a retirement rule mechanically, but it shifts costs from contingent inspection/repair to scheduled part replacement paid by operators; it also creates concentrated replacement demand (parts suppliers/maintenance providers) and diffuse costs across all affected operators. (Requirement; Background)\n\nKey provisions to look up in the text\n\n- Applicability and parts by part number and model (Table 1)\n- Retirement lives and the 4 landings per hour conversion (Table 1; Compliance)\n- Transitional replacement timing (Compliance)\n- Effective date: 27 March 1997 (Compliance)\n\n(References in parentheses indicate the part of the AD where that material appears: Requirement; Table 1; Compliance; Note; Background.)"},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-at-3-amdt-5-landing-gear","history":"/api/acts/ad-at-3-amdt-5-landing-gear/history","analysis":"/api/acts/ad-at-3-amdt-5-landing-gear/analysis","conflicts":"/api/acts/ad-at-3-amdt-5-landing-gear/conflicts","importantCases":"/api/acts/ad-at-3-amdt-5-landing-gear/important-cases","documents":"/api/acts/ad-at-3-amdt-5-landing-gear/documents"}}