{"id":"F2006L03877","name":"AD/AT 600/5 - Wing Main Spar Lower Cap Fastener Hole","slug":"ad-at-600-5-wing-main-spar-lower-cap-fastener-hole","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":60807,"registerId":"commonwealth-F2006L03877-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Airtractor 600 Series Aeroplanes","sectionType":"division","heading":"Airtractor 600 Series Aeroplanes","content":"### Airtractor 600 Series Aeroplanes\n\n| AD/AT 600/5 | Wing Main Spar Lower Cap Fastener Hole | 1/2007 |\n| ----------- | -------------------------------------- | ------ |\n\n| Applicability: | Model AT-602 aircraft, serial numbers 602-0337 and subsequent. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement: | 1. Unless already accomplished, before accomplishment of the initial eddy current inspection, gain access for the inspection by cutting inspection holes, modify the vent tube, and install cover plates, in accordance with Snow Engineering Co. Service Letter No. 204 Revised 26 March 2001, and Drawing titled “602 Spar Inspection Holes and Vent Tube Mod.,” dated 13 November 2003.2. Eddy current inspect the wing centre splice joint outboard two fastener holes in both the left and right wing main spar lower spar caps for cracks, in accordance with Snow Engineering Co. Process Specification 197 Revised 4 June 2002. For the following aircraft, use the wing spar lower cap hours time in service in the compliance section and accomplish the initial and repetitive inspections:a. For aircraft with serial numbers 602-0337 through 602-0584, as manufactured, inspect at the times specified in the compliance section.b. For aircraft with serial numbers 602-0337 through 602-0584, modified with cold-worked fastener holes in accordance with Snow Engineering Co. Service Letter (SL) No. 244 dated 25 April 2005; if performing the cold working procedure in SL No. 244, it includes the eddy current inspection.Accomplish an eddy current inspection as part of the cold working procedure in SL No. 244 even if the wing spar was previously inspected.3. For aircraft with serial numbers 602-0337 through 602-0584, terminating action for the inspection requirements may be achieved by modification of the wing with installation of part number 20996-2 steel web plate and part number20985-1/2 8-bolt splice blocks in accordance with Snow Engineering Co. Drawing 20998 Revision B, dated 28 September 2004, and cold work of the lower spar cap two outboard fastener holes at the wing centre section splice connection in accordance with Snow Engineering Co. Service Letter No. 240 dated 30 September 2004.4. For aircraft with serial numbers 602-0337 through 602-0584, repair or replace a cracked spar cap found during any inspection, by accomplishing one of the following: |\n\n| | a. For cracks that can be removed by performing the terminating action listed in Requirement 3, accomplish the action specified in Requirement 3.b. For cracks that cannot be removed by performing the terminating action listed in Requirement 3, replace the lower spar caps and associated parts listed in Requirement 5 before continued flight.5. For all Model AT-602 aircraft, replace the wing lower spar caps, splice blocks and hardware, wing attach angles and hardware, and install the steel web plate part number 20996-2, if not already installed, in accordance with Snow Engineering Co. Drawing 20776, Sheet 2, Revision A dated 30 August 2004. This Requirement terminates the inspection requirements of Requirement 2.Note: FAA AD 2006-23-09 Amdt 39-14798 refers. |\n| ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | 1. As specified in Requirement 1.2.a. Unless the initial inspection is already accomplished, inspect upon the accumulation of 2,000 hours time in service or within 50 hours time in service after 18 January 2007, whichever occurs later. Inspect thereafter at intervals not to exceed 1,000 hours time in service.2.b. Repetitively inspect thereafter at intervals not to exceed 2,000 hours time in service.3. As specified in Requirement 3.4. Before further flight.5. Upon the accumulation of 6,500 hours time in service on the wing spar lower caps or within 50 hours time in service after 18 January 2007, whichever occurs later. |\n| | This Airworthiness Directive becomes effective on 18 January 2007. |\n| Background: | The FAA received reports of fatigue cracking at the wing centre splice joint outboard fastener hole in one of the wing main spar lower caps. Such cracking, unless detected and corrected, could result in failure of the spar cap and lead to wing separation and loss of control of the aircraft. |\n\n![](image.001.png) \nDavid Villiers \nDelegate of the Civil Aviation Safety Authority\n\n23 November 2006","sortOrder":0},{"sectionNumber":"AD/AT 600/5","sectionType":"part","heading":"AD/AT 600/5","content":"## AD/AT 600/5","sortOrder":1},{"sectionNumber":"Wing Main Spar Lower Cap Fastener Hole","sectionType":"part","heading":"Wing Main Spar Lower Cap Fastener Hole","content":"## Wing Main Spar Lower Cap Fastener Hole","sortOrder":2},{"sectionNumber":"1/2007","sectionType":"part","heading":"1/2007","content":"## 1/2007","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"},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":false,"description":"This appears to be the original issuance of AD/AT 600/5 (version 1/2007). The scope is appropriately focused on the specific safety defect in the wing spar lower cap fastener holes. The directive maintains a tight focus on the identified fatigue cracking issue and provides multiple compliance pathways (inspection, modification, or replacement) that are all directly related to addressing this specific airworthiness concern."},"complexity_factors":["Multiple serial number ranges with different requirements (602-0337 through 602-0584 vs. 'subsequent' aircraft)","Cross-references to external technical documents (Snow Engineering Co. Service Letters No. 204, 240, 244; Process Specification 197; Drawings 20776 and 20998)","Conditional logic based on whether specific modifications have already been performed","Alternative compliance paths (inspection regime vs. terminating action via modification vs. full replacement)","Nested time-based triggers (whichever occurs later clauses combining flight hours with calendar dates)","Different inspection intervals depending on modification status (1,000 vs. 2,000 hours)","Requirement 5 applies to 'all Model AT-602 aircraft' while Requirements 2-4 apply only to specific serial ranges, creating a split applicability structure"],"plain_english_summary":"This Airworthiness Directive imposes mandatory inspections and corrective actions on Air Tractor AT-602 aircraft (serial 602-0337 and later) after fatigue cracking was found at fastener holes in the main wing spar lower cap. It requires access modifications and periodic eddy‑current inspections, plus either steel reinforcement with cold‑working or eventual lower spar cap replacement.\n\nIt affects owners/operators (notably crop‑duster and firefighting operators in Australia) because compliance is essential to prevent catastrophic wing failure and to keep affected aircraft legal to fly."},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"The AD remains focused on the original safety objective: preventing fatigue cracking and possible spar failure at the wing centre splice joint outboard fastener holes. It preserves that mechanical remit while adding a fleet‑wide terminating replacement requirement (Requirement 5) that applies to all Model AT‑602 aircraft, not only the serial range initially singled out for the inspection regime. That broadening is consistent with the same safety objective (removing the need for repetitive inspection by mandating replacement/modification) rather than a material change of purpose beyond addressing the identified structural fatigue risk."},"complexity_factors":["Five main numbered Requirements with interlocking effects (inspection access, inspection, terminating action, repair options, fleet replacement).","Conditional branches based on serial number ranges (602‑0337 through 602‑0584) and whether a cold‑work modification (SL No. 244) has been applied.","Multiple cross‑references to external technical documents: at least three Snow Engineering Service Letters (SL No. 204, 240, 244), a Process Specification (197), and multiple dated drawings (e.g. 20776 Sheet 2 Rev A, 20998 Rev B).","Different compliance intervals depending on condition: initial inspection at 2,000 hours or within 50 hours after a calendar date; repetitive intervals of 1,000 hours or 2,000 hours TIS; terminating replacement by 6,500 hours or within 50 hours after a date.","A terminating action path that both cancels inspection obligations and requires specific parts and cold‑working procedures.","Operationally critical \"before further flight\" requirement for detected cracks (creates immediate grounding decisions).","Reference to an external regulator's AD (FAA AD 2006‑23‑09) as contextual material.","Specialist procedures required (eddy‑current NDT and cold‑work of holes) increase procedural and competence complexity."],"plain_english_summary":"**What the directive does (mechanics first)**\n\n- This Airworthiness Directive (AD) requires owners/operators of Airtractor Model AT-602 aeroplanes (serial numbers 602-0337 and later) to inspect, and in many cases modify or replace, parts of the wing main spar lower cap where fatigue cracking has been reported.\n\n- Required actions (summary of the numbered Requirements):\n - Gain access to the inspection area by cutting inspection holes, modify the vent tube, and fit cover plates, following Snow Engineering Service Letter No. 204 and the named drawing (Requirement 1).\n - Perform eddy-current (non‑destructive) inspections of the two outboard fastener holes at the wing centre splice joint on both left and right lower spar caps, following Snow Engineering Process Specification 197 (Requirement 2). How and when you inspect depends on aircraft serial number and whether a cold‑work modification has already been done:\n - For serials 602‑0337 through 602‑0584 \"as manufactured\": follow the time-in-service inspection schedule in the Compliance section.\n - For those same serials if modified with cold‑worked fastener holes per Snow SL No. 244, the cold‑work procedure includes the eddy‑current inspection; you must do the inspection as part of that procedure even if the spar was previously inspected.\n - You may permanently end the repetitive inspection requirement for serials 602‑0337 through 602‑0584 by installing a steel web plate and 8‑bolt splice blocks and cold‑working the two outboard fastener holes, using the specified Snow Engineering drawing and service letter (Requirement 3).\n - If a crack is found during any inspection, you must either accomplish the terminating modification (if that will remove the crack) or replace the lower spar caps and associated parts listed in Requirement 5 before further flight (Requirement 4).\n - For all Model AT‑602 aircraft (not just the serial range above), replace the wing lower spar caps, splice blocks and hardware, wing attach angles and hardware, and install the steel web plate (part number 20996‑2) per Snow Engineering Drawing 20776 Sheet 2 Rev A. Doing this is a terminating action for the inspection requirements (Requirement 5).\n\n- Compliance timing (key points):\n - Initial inspections (if not already done): at 2,000 hours time-in-service (TIS) on the wing spar lower caps, or within 50 hours TIS after 18 January 2007, whichever is later; repeat inspections at intervals not to exceed 1,000 hours TIS (per the relevant clause).\n - For some aircraft modified under SL No. 244, repetitive inspections are at intervals not to exceed 2,000 hours TIS.\n - The full replacement/terminating modification in Requirement 5 must be done by 6,500 hours TIS on the wing spar lower caps or within 50 hours TIS after 18 January 2007, whichever is later.\n - Any crack found must be repaired or the aircraft grounded until the required replacement or terminating modification is done (repairs must be completed before further flight).\n\n- Source documents and procedures you must follow:\n - Multiple Snow Engineering Company service letters, process specifications and drawings are normatively referenced (SL No. 204, SL No. 240, SL No. 244, Process Spec 197, Drawings 20776, 20998, 20996‑2, 20985‑1/2 etc.). The AD requires compliance with those documents as written.\n - The AD also notes a related FAA AD (2006‑23‑09).\n\n**Who is affected and who pays**\n\n- Aircraft owners/operators of Airtractor AT‑602 serials 602‑0337 onward are directly affected. Requirement 5 extends a mandatory parts replacement to all AT‑602 aircraft.\n- Costs fall to the owners/operators: labour to cut inspection access holes, NDT (eddy current) inspection fees, possible recurring inspection labour and downtime, and parts and installation costs if performing the terminating modification or full replacement of spar caps and associated hardware.\n\n**Why it matters (official rationale and a practical test of that rationale)**\n\n- Officially: the AD responds to reported fatigue cracking in the wing centre splice joint outboard fastener holes of the lower spar cap. If undetected, that cracking could lead to spar cap failure and wing separation.\n\n- Practical implications and trade-offs:\n - Detection vs replacement: recurring eddy‑current inspections are an ongoing maintenance burden and cause aircraft downtime; the AD therefore offers a one‑time terminating modification (installation of steel web plate, splice blocks and cold work on holes) that ends repetitive inspections but requires parts, shop time and likely higher immediate cost.\n - Technical competence and equipment: eddy‑current inspection and cold‑working fastener holes require qualified non‑destructive testing and structural modification capability; operators without those capabilities will need to use approved maintenance organisations, increasing cost and aircraft out‑of‑service time.\n - Supply and scheduling risk: the AD mandates specific part numbers and dated engineering documents; availability of parts, drawing revisions, or maintenance capacity will affect how quickly operators can accomplish terminating action.\n - Concentration of costs and benefits: immediate costs (parts, labour, downtime) are concentrated on individual owners/operators. The safety benefit (reduced risk of catastrophic structural failure) is collective and diffuse, but directly protects the affected aircraft.\n - Administrative clarity: the AD is prescriptive — it mandates compliance with particular service letters and drawings. That reduces discretionary interpretation but increases dependence on the availability and clarity of those referenced engineering documents.\n\n**Concrete behavioural effects**\n\n- Operators will need to schedule and pay for eddy‑current inspections at the specified intervals unless they elect to install the terminating modification or do the full replacement required by Requirement 5.\n- Maintenance providers that supply the specified parts, or who perform cold‑working and eddy‑current inspections, will see demand for those services.\n\n**Immediate operational constraints**\n\n- A cracked spar cap found in inspection must be repaired or replaced before further flight.\n\n(References in text correspond to the AD's numbered Requirements and the Compliance timing given in the AD.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-at-600-5-wing-main-spar-lower-cap-fastener-hole","history":"/api/acts/ad-at-600-5-wing-main-spar-lower-cap-fastener-hole/history","analysis":"/api/acts/ad-at-600-5-wing-main-spar-lower-cap-fastener-hole/analysis","conflicts":"/api/acts/ad-at-600-5-wing-main-spar-lower-cap-fastener-hole/conflicts","importantCases":"/api/acts/ad-at-600-5-wing-main-spar-lower-cap-fastener-hole/important-cases","documents":"/api/acts/ad-at-600-5-wing-main-spar-lower-cap-fastener-hole/documents"}}