{"id":"F2006B11075","name":"AD/LA-4/26 Amdt 1 - Wing Upper and Lower Spar Doublers","slug":"ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56713,"registerId":"commonwealth-F2006B11075-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LA-4/26 Amdt 1 - Wing Upper and Lower Spar Doublers","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/LA \\-4/26 and issues the following 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.\n\n![](image.001.png)\n\nConsolidated Aeronautics, Colonial and LA-4 Series Aeroplanes\n\nAD/LA-4/26\n\nAmdt 1\n\n  \nWing Upper and Lower Spar Doublers 7/2002\n\nApplicability: Affected aircraft with wing spar part numbers incorporated as specified below:\n\n| Model          | Serial Numbers                                                |\n| -------------- | ------------------------------------------------------------- |\n| Lake LA-4      | 246 through 421, 423 through 429, 445, and 446                |\n| Lake LA-4A     | 244 and 245                                                   |\n| Lake LA-4P     | 121                                                           |\n| Lake LA-4-200  | 422, 430 through 444, 446, and all subsequent serial numbers. |\n| Lake Model 250 | 1 through 232                                                 |\n\n| Wing Spar Parts       | Part Numbers                             |\n| --------------------- | ---------------------------------------- |\n| Upper Spar Cap Angles | 2-1610-015 and 2-1610-016                |\n| Lower Spar Cap Angles | 2-1610-075 and 2-1610-076                |\n| Upper Spar Doublers   | 2-1610-061 and 2-1610-081 and 2-1610-065 |\n| Lower Spar Doublers   | 2-1610-063 and 2-1610-083                |\n\nRequirement: 1. Inspect the left and right wing upper and lower spar doublers for cracks in accordance with the Inspection section of Revo Incorporated Service Bulletin B- 79 R1, Revised 5 January 2000.\n\nConsolidated Aeronautics, Colonial and LA-4 Series Aeroplanes\n\nAD/LA-4/26 Amdt 1 (continued)\n\nReplace any cracked wing spar doubler, before further flight, with a new part that incorporates the same part number (or FAA-approved equivalent part number), in accordance with the applicable maintenance manual.\n\n2A. Incorporate Modification Kit B-79 in accordance with the Kit Installation section of Revo Incorporated Service Bulletin B-79 R1.\n\nOR\n\n2B. Incorporate STC ASA052ML.\n\nNote: FAA AD 2000-10-22 Amdt 39-11746 refers.\n\nCompliance: 1. Within 50 hours time in service after 10 August 2000, or before 10 August 2001, whichever occurs first.\n\n2. Before further flight after Requirement 1 is accomplished. Also, if 2B, inspect regularly in accordance with the STC instructions.\n\nThis amendment becomes effective on 11 July 2002.\n\nThe original issue of this Airworthiness Directive became effective on 10 August 2000.\n\nBackground: The FAA received a report of a fatigue crack found at the second most inboard wing attachment bolt hole on one of the affected aircraft. Similar fatigue cracking has since been reported on seven more of the affected aircraft, including incidents where the fatigue cracking occurred on aircraft with less than 500 hours time in service.\n\nSuch cracking could result in wing separation from the aircraft with consequent loss of control.\n\nAmendment 1 adds an alternative modification.\n\n![Signature of David Alan Villiers Delegate of the Civil Aviation Safety Authority](image.002.jpeg)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 31 May 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 19 June 2002.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing AD. The amendment adds an alternative modification option (STC ASA052ML) to the original requirement, but does not expand the scope beyond the original safety purpose of addressing wing spar fatigue cracking in the specified Lake aircraft models."},"complexity_factors":["Single-purpose document with clear applicability table (5 aircraft models, specific serial number ranges)","Straightforward two-part requirement structure (inspect/replace, then modify)","Simple compliance timeline with 'whichever occurs first' logic","Limited cross-referencing (one FAA AD mentioned in a note, one service bulletin)","Two alternative modification paths (2A or 2B) with conditional note for ongoing inspections if 2B chosen","No nested definitions or extensive interpretation sections"],"plain_english_summary":"This CASA Airworthiness Directive mandates owners/operators of certain Consolidated Aeronautics/Lake amphibious models to inspect left and right upper/lower wing spar doublers for cracking, replace any cracked doublers before further flight, and install an approved reinforcement/modification to prevent recurrence.\n\nIt addresses fatigue cracks found even on low-hour aircraft that could lead to wing separation and catastrophic loss of control."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 expanded the original AD by adding an alternative modification route (Requirement 2B: incorporate STC ASA052ML) in addition to the existing requirement to install Modification Kit B-79 (Requirement 2A). That change broadens the methods by which operators can comply (potentially changing cost, installation logistics, and ongoing inspection schedules) but does not alter the core safety purpose (detect and correct spar-doubler cracking). The amendment therefore increases compliance option scope without changing the AD’s stated safety objective."},"complexity_factors":["Applicability defined by multiple model/serial-number ranges (table of models and serial ranges).","List of specific wing spar part numbers to check (four part categories with multiple part numbers).","Dependence on external technical documents: Revo Service Bulletin B-79 R1 (inspection and kit installation); STC ASA052ML; cross-reference to FAA AD 2000-10-22.","Two alternative compliance routes (2A: kit installation; 2B: STC incorporation) with different ongoing obligations (STC requires regular inspections).","Time-limited compliance window for initial inspection (50 hours TIS after 10 Aug 2000 or before 10 Aug 2001).","Clear mandatory action on discovery of cracked parts (replace before further flight)."],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- This Airworthiness Directive (AD) applies to specified Consolidated/Colonial/Lake LA-4 series aircraft identified by model and serial-number ranges, and to wings that include certain spar part numbers (see Applicability table).\n- It requires two steps: 1) inspect both left and right upper and lower wing spar doublers for cracks using the inspection procedure in Revo Incorporated Service Bulletin B-79 R1 (Inspection section); and 2) either install Modification Kit B-79 (per the Kit Installation section of the same service bulletin) or incorporate STC ASA052ML (a Supplemental Type Certificate) as an alternative modification.\n- Any cracked doubler discovered must be replaced with a new part (same part number or FAA‑approved equivalent) before the aircraft is flown again.\n- Timing: the inspection must be done within 50 hours time-in-service after 10 August 2000 or before 10 August 2001, whichever is earlier. The chosen modification (kit or STC) must be fitted before further flight after the inspection. If the STC option is used, the STC’s inspection schedule must be followed thereafter.\n\n**Who is affected**\n\n- Registered owners and operators of the listed Lake LA-4 family aeroplanes that have the specified wing spar parts installed. That includes a defined set of serial numbers for each model.\n- Maintenance organisations and licensed engineers who perform the inspection, replacement and modification work.\n\n**Why it matters (official rationale and how that translates into action)**\n\n- The AD was issued because fatigue cracking was found in the wing spar doublers at an attachment-bolt hole on a number of affected aircraft. The stated safety concern is that such cracking could lead to wing separation and loss of control.\n- The AD’s mechanical remedy is to detect existing cracks (inspect), remove any cracked parts immediately (replace before flight), and fit a modification that addresses the weakness (install kit B-79 or apply STC ASA052ML).\n\n**Who pays, who decides, and what behaviour changes**\n\n- Owners/operators pay for the inspection, any replacements, and the chosen modification (kit installation or STC incorporation). Maintenance providers and parts suppliers receive the work and supply the parts.\n- The CASA delegate issued the AD (enforcement decision). Affected operators decide which modification route to take (Kit B-79 or STC ASA052ML) subject to the AD’s requirements and any STC instructions.\n- Behaviour changes: operators must prioritise and schedule an inspection within the specified time window; they must not return an aircraft with a cracked doubler to service; and they must ensure the chosen modification is installed before further flight. If using the STC, operators must comply with its ongoing inspection regime.\n\n**Costs, incentives, trade-offs and implementation risks**\n\n- Direct costs: inspection labour and time, parts cost for replacements, cost of purchasing and installing Modification Kit B-79 (if chosen) or complying with STC ASA052ML (which may include parts and modification fees). Aircraft downtime is an opportunity cost while work is done.\n- Incentives: owners have a clear safety and legal incentive to comply (airworthiness/legal requirement). Operators with low utilisation may face a fixed-cost burden (inspection and possible modification) that is large relative to flight hours.\n- Trade-offs: kit installation likely raises short-term costs but may reduce future inspection frequency; the STC is offered as an alternative and may impose a different inspection cadence (the AD requires following the STC’s inspection schedule). The AD allows either route, so operators can choose based on cost, availability, or maintenance capability.\n- Implementation risks: availability of kits or qualified installers, lead times for replacement parts, and scheduling constraints at approved maintenance facilities could delay compliance. Recordkeeping and demonstrating compliance to regulators is required.\n- Effects on market participants: maintenance organisations and parts suppliers are likely to gain work; aircraft owners bear the expense. The AD does not change ownership rights or operating privileges other than imposing mandatory maintenance actions.\n\n**Cross-references and dependency on external documents (practical note)**\n\n- Compliance depends on following Revo Incorporated Service Bulletin B-79 R1 (Inspection and Kit Installation sections) and, if chosen, STC ASA052ML instructions. The AD also refers to FAA AD 2000-10-22. Those documents contain the detailed procedures and any additional limitations.\n\n(References: Requirement 1 and Requirement 2A/2B; Compliance section.)"},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers","history":"/api/acts/ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers/history","analysis":"/api/acts/ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers/analysis","conflicts":"/api/acts/ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers/conflicts","importantCases":"/api/acts/ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers/important-cases","documents":"/api/acts/ad-la-4-26-amdt-1-wing-upper-and-lower-spar-doublers/documents"}}