{"id":"F2006L03410","name":"AD/SF340/99 - MLG Shock Strut and Axle Adaptors","slug":"ad-sf340-99-mlg-shock-strut-and-axle-adaptors","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":60860,"registerId":"commonwealth-F2006L03410-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"SAAB SF340 Series Aeroplanes","sectionType":"division","heading":"SAAB SF340 Series Aeroplanes","content":"### SAAB SF340 Series Aeroplanes\n\n| AD/SF340/99 | MLG Shock Strut and Axle Adaptors | 11/2006 |\n| ----------- | --------------------------------- | ------- |\n\n| Applicability: | Model SF340A aircraft, serial numbers SF340A-004 through -159, unless equipped with main landing gear (MLG) shock struts modified in accordance with APPH Ltd. Service Bulletin (SB) AIR83022-32-32 or SB AIR83064-32-12.Model 340B aircraft, serial numbers 340B-160 through -459, unless equipped with MLG shock struts modified in accordance with APPH Ltd. SB AIR83064-32-12.              |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Inspect the MLG in accordance with SAAB SB 340-32-133 original issue, or at latest EASA approved revision.2. Inspect and modify the MLG shock strut and axle adaptors in accordance with Attachment 1 to SAAB SB 340-32-133 original issue, or at latest EASA approved revision, (APPH Ltd. SB AIR83022-32-32) or Attachment 2 (APPH Ltd. SB AIR83604-32-12).Note: EASA AD 2006-0263 refers. |\n| Compliance:    | 1. Within 8,000 flight cycles since the last MLG overhaul, or within 1,500 flight cycles or 6 months after 26 October 2006, whichever occurs later. Inspect thereafter at intervals not to exceed 2,000 flight cycles, until Requirement 2 is accomplished.2. At the next MLG overhaul after 26 October 2006.                                                                                   |\n|                | This Airworthiness Directive becomes effective on 26 October 2006.                                                                                                                                                                                                                                                                                                                              |\n| Background:    | A crack was detected in an MLG axle adaptor during fatigue testing. Investigation revealed the internal edges of the dowel holes did not have the correct radius, and the crack had propagated from the edge of one of the dowel holes. Failure of the axle adaptor could lead to wheel separation and total loss of brake capability.                                                          |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n14 September 2006","sortOrder":0},{"sectionNumber":"AD/SF340/99","sectionType":"part","heading":"AD/SF340/99","content":"## AD/SF340/99","sortOrder":1},{"sectionNumber":"MLG Shock Strut and Axle Adaptors","sectionType":"part","heading":"MLG Shock Strut and Axle Adaptors","content":"## MLG Shock Strut and Axle Adaptors","sortOrder":2},{"sectionNumber":"11/2006","sectionType":"part","heading":"11/2006","content":"## 11/2006","sortOrder":3}],"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"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The directive remains focused on a single, clearly identified safety issue: cracking in MLG axle adaptors caused by incorrect dowel hole edge radii. The requirements (inspect until modified; perform the modification at next overhaul) are corrective and narrowly targeted at the affected serial ranges. There is no material expansion beyond that original corrective purpose: it does not create ongoing new regulatory programmes, new categories of regulated entities, or additional unrelated obligations."},"complexity_factors":["Applicability limited to two model/serial‑number ranges with an exception for aircraft already modified per specific service bulletins","Multiple external cross‑references: SAAB SB 340‑32‑133, APPH Ltd. SB AIR83022‑32‑32, APPH Ltd. SB AIR83064‑32‑12, and EASA AD 2006‑0263","Two distinct mandatory actions (inspection and modification) with different triggering events","Several timing conditions expressed in flight cycles and calendar time (8,000 flight cycles since last overhaul vs. 1,500 cycles or 6 months after a date, and recurring 2,000‑cycle inspection intervals)","Modification required at next MLG overhaul (event‑based compliance) in addition to cycle/time‑based inspections","References to 'original issue or latest EASA approved revision' introduce dependency on externally updated documents","Technical attachments (Attachment 1 / Attachment 2) provide alternative procedures depending on which APPH SB applies"],"plain_english_summary":"**What this directive does (mechanically)\n\n- Requires operators of certain SAAB SF340A and SF340B aeroplanes to inspect their main landing gear (MLG) and to modify the MLG shock strut and axle adaptors according to specified service bulletin procedures. (See: Requirement.)\n- Inspections must be done on a defined schedule measured in flight cycles and months, and modification must be completed at the next MLG overhaul if not done earlier. (See: Compliance.)\n\nWho is affected\n\n- Airlines, operators and maintenance organisations that own or maintain SAAB SF340A aeroplanes serial numbers SF340A‑004 through SF340A‑159, and SAAB SF340B aeroplanes serial numbers 340B‑160 through 340B‑459, unless their aircraft already have the specified MLG shock strut modifications. (Applicability.)\n\nWhy the rule exists (stated purpose)\n\n- During fatigue testing a crack was found running from the edge of a dowel hole in an MLG axle adaptor. The investigation showed the internal edge radius of the dowel holes was incorrect, and this could allow crack initiation and propagation. Failure of the axle adaptor could lead to wheel separation and complete loss of brakes. The directive requires inspection and a modification intended to remove that risk. (Background; Requirement.)\n\nKey mechanical details and timing\n\n- Operators must inspect the MLG in line with SAAB Service Bulletin SB 340‑32‑133 (original issue or latest EASA‑approved revision). (Requirement.)\n- Operators must inspect and modify the shock strut and axle adaptor per the attachments to SAAB SB 340‑32‑133, which reference APPH Ltd. service bulletins AIR83022‑32‑32 or AIR83064‑32‑12. (Requirement.)\n- Initial inspection timing: within 8,000 flight cycles since last MLG overhaul, or within 1,500 flight cycles or 6 months after 26 October 2006 (whichever is later). After that, re‑inspect every 2,000 flight cycles until the modification is done. (Compliance.)\n- Modification timing: must be completed at the next MLG overhaul after 26 October 2006 if not done earlier. (Compliance.)\n\nStated cross‑references\n\n- The directive references SAAB service bulletins (SB 340‑32‑133), APPH Ltd. service bulletins (AIR83022‑32‑32 and AIR83064‑32‑12), and an EASA airworthiness directive (EASA AD 2006‑0263). Operators must follow the latest EASA‑approved revisions where applicable. (Requirement; Note.)\n\nPractical effects, incentives and costs (analyst's note)\n\n- Who pays: operators bear the direct costs — labour for inspections, parts and labour for the modification, and aircraft downtime while work is done. (Requirement; Compliance.)\n- Behavioural incentives: operators may accelerate an MLG overhaul to complete the mandated modification rather than continue recurring inspections, especially if inspections are frequent or logistically costly. (Compliance.)\n- Concentrated benefits and suppliers: the modification is specified via APPH Ltd. service bulletins. That fact means APPH (or organisations authorised to supply parts/procedures in those SBs) is the technical source for the corrective method; consequently, APPH is likely to derive the bulk of aftermarket revenue from the required work. The directive does not itself ban other maintenance providers from performing the work, but required compliance with those SBs can channel demand toward suppliers who can meet the SB specifications. (Requirement.)\n- Compliance burden and operational risk: the directive creates recurring inspection obligations (until modification) which raise maintenance planning and recordkeeping needs. If parts or approved procedures are delayed, operators face either repeated inspections (with their attendant cost) or grounding/overhaul scheduling pressure. (Compliance.)\n- Trade‑offs and opportunity cost: funds and shop hours spent on this mandated work are not available for other maintenance or upgrades. Operators choosing to defer modification remain exposed to the inspection schedule and the marginal risk of undetected cracking between inspections. (Compliance; Background.)\n- Implementation risk and enforcement: effective compliance requires accurate tracking of flight cycles and overhaul histories, access to the specified service bulletin revisions, and competent implementation of the modification details. Regulators will monitor compliance under normal airworthiness enforcement mechanisms. (Applicability; Requirement.)\n\nNet mechanical effect\n\n- The directive reduces the probability of axle adaptor failure by requiring a one‑time modification (plus interim inspections until that modification is completed). It transforms an identified manufacturing/design tolerance issue (dowel hole edge radius) into a mandatory maintenance/modification obligation for a defined fleet subset. (Background; Requirement.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with focused, original scope. It addresses a specific safety defect in specific aircraft models without expansion into broader regulatory areas."},"complexity_factors":["Short, single-purpose document (1 page)","Limited conditional logic: only two applicability categories (SF340A vs 340B) with straightforward serial number ranges","Three defined technical terms (MLG, SB, EASA) that are standard aviation abbreviations","Clear two-step compliance structure with specific but simple time-based triggers (flight cycles, calendar dates, overhaul events)","No nested exceptions or cross-references to other legislation — only references to manufacturer service bulletins","Single background issue with direct causal chain (manufacturing defect → crack → failure mode)"],"plain_english_summary":"This AD requires owners/operators of specified SAAB SF340A (s/n 004–159) and 340B (s/n 160–459) to inspect and repair main landing gear shock struts and axle adaptors after fatigue testing found cracks from a manufacturing defect. If unchecked, adaptor failure could cause wheel separation and total brake loss. Initial and recurring inspections are mandated until the parts are modified/ repaired at the next overhaul per SAAB service instructions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sf340-99-mlg-shock-strut-and-axle-adaptors","history":"/api/acts/ad-sf340-99-mlg-shock-strut-and-axle-adaptors/history","analysis":"/api/acts/ad-sf340-99-mlg-shock-strut-and-axle-adaptors/analysis","conflicts":"/api/acts/ad-sf340-99-mlg-shock-strut-and-axle-adaptors/conflicts","importantCases":"/api/acts/ad-sf340-99-mlg-shock-strut-and-axle-adaptors/important-cases","documents":"/api/acts/ad-sf340-99-mlg-shock-strut-and-axle-adaptors/documents"}}