{"id":"F2006B02215","name":"AD/AC-SNOW/25 - MLG to Fuselage Attach Bolts","slug":"ad-ac-snow-25-mlg-to-fuselage-attach-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41445,"registerId":"commonwealth-F2006B02215-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (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.","sortOrder":0},{"sectionNumber":"AD/AC-SNOW/25 MLG to Fuselage Attach Bol","sectionType":"part","heading":"AD/AC-SNOW/25 MLG to Fuselage Attach Bolts 5/2000","content":"# AD/AC-SNOW/25 MLG to Fuselage Attach Bolts 5/2000\n\nApplicability: All models, all S/nos, with any MLG attach bolt installed which is drilled for greasing.\n\nRequirement: Replace the any MLG bolt drilled for greasing with an undrilled bolt P/N AN10-33, or NAS 6610-42D, or other bolt approved by the Authority; in accordance with Ayres SB No. SB-AG-42R1 dated 28 September1999.\n\nNote: FAA AD 2000-05-23 refers, but references the initial issue of the Requirement document.\n\nCompliance: Within 100 hours’ time in service after the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 18 May 2000.\n\nBackground: Bolts modified by drilling to enable better lubrication of the MLG attachment have been found cracked. This could lead to main landing gear collapse and possible rupture of a fuel tank.\n\n![](image.003.png)  \n\nBernard Malcolm Hole\n\nDelegate of the Civil Aviation Safety Authority 7 April 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 19 April 2000.","sortOrder":1}],"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":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in landing gear bolts. It has not expanded beyond its initial safety purpose."},"complexity_factors":["Very short document (approximately 250 words)","Only 3 substantive sections: Applicability, Requirement, and Compliance","Minimal defined terms (only standard aviation abbreviations like MLG, P/N)","No cross-references to other legislation beyond a single note about FAA AD 2000-05-23","Simple conditional logic: 'if drilled bolt installed → must replace'","Single compliance deadline with clear trigger (100 hours time in service after effective date)"],"plain_english_summary":"CASA orders Ayres aircraft owners/operators to replace any main landing gear attach bolt drilled for lubrication with an undrilled bolt (AN10-33, NAS 6610-42D or CASA‑approved equivalent) per Ayres Service Bulletin SB-AG-42R1.\n\nComplete the replacement within 100 flight hours after 18 May 2000. Drilled bolts have cracked; failure could cause MLG collapse, fuel tank rupture, fire, or serious injury."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive stays within the original safety purpose: remove a known structural weakness (drilled MLG attach bolts) by mandating replacement with undrilled, approved bolts. There is no expansion of scope beyond addressing the drilled bolts (Applicability; Requirement). The allowance for Authority‑approved alternative bolts preserves limited flexibility but does not broaden the safety objective."},"complexity_factors":["Very short instrument (single-page AD)","Clear single safety action: replace drilled MLG bolts with specified undrilled parts","Few defined items: two part numbers listed and a catch‑all for Authority‑approved alternatives","Single compliance condition: within 100 hours’ time in service","References one external service bulletin (Ayres SB-AG-42R1) and one FAA AD (informational)","No nested exceptions, conditional logic, or multiple compliance pathways"],"plain_english_summary":"**What this directive requires (mechanics first)**\n\n- **Who it covers:** Any aircraft (all models and serial numbers) that currently has a main landing gear (MLG) attachment bolt which has been drilled for greasing (Applicability).\n\n- **What to do:** Replace any MLG bolt that has been drilled for greasing with an undrilled bolt specified as P/N AN10-33, or NAS 6610-42D, or another bolt that has been approved by the aviation safety authority. The replacement must follow the instructions of Ayres Service Bulletin SB-AG-42R1 dated 28 September 1999 (Requirement).\n\n- **When to do it:** The replacement must be completed within 100 hours’ time in service after the directive’s effective date (Compliance). The directive became effective 18 May 2000.\n\n- **Why it matters (stated safety reason):** Bolts that were modified by drilling to allow greasing were found to have cracked. Cracked MLG attach bolts can lead to main landing gear collapse and could possibly rupture a fuel tank (Background).\n\n**Who pays and who decides**\n\n- The aircraft owner/operator is responsible for arranging and paying for the replacement (parts and labour). A maintenance organisation or licensed mechanic will normally carry out the work in accordance with the Service Bulletin (Requirement).\n\n- The Civil Aviation Safety Authority (CASA) delegate issued the directive and approves any alternative bolt (Requirement).\n\n**Practical effects and implementation considerations**\n\n- Direct costs: purchase of undrilled bolts (AN/NAS parts listed) and labour/downtime to replace the bolts. The AN and NAS part numbers listed are common standard hardware, so parts should be purchasable from the market (Requirement).\n\n- Operational impact: aircraft will need to be taken into maintenance within the 100‑hour window; operators must schedule the work to avoid disrupting operations (Compliance).\n\n- Flexibility: the directive allows an alternative bolt if it is approved by the Authority, which provides a path for engineering alternatives but requires regulatory approval (Requirement).\n\n- Compliance paperwork: maintenance logs and records must reflect the AD compliance and parts used. Organisations may need to follow Ayres SB-AG-42R1 for specific installation steps (Requirement).\n\n- Risks and trade-offs: immediate cost and downtime are the principal trade-offs to reduce risk of landing gear collapse. Supply shortages of the specified part numbers or delays in obtaining Authority approval for alternatives would increase implementation risk and potentially extend downtime.\n\n**Market and competition effects (briefly)**\n\n- Parts listed (AN and NAS standards) are industry-standard hardware, so multiple suppliers are likely; this limits the risk of a single-source monopoly on parts (Requirement).\n\n- Independent maintenance providers can perform the replacement under ordinary maintenance rules, preserving competitive service provision, subject to their ability to follow the Ayres service bulletin and meet regulatory record-keeping (Requirement).\n\n**Notes and cross-references**\n\n- The directive references a related FAA AD (FAA AD 2000-05-23) but points out the FAA document refers to the initial issue of the Requirement document; operators should check the Ayres Service Bulletin SB-AG-42R1 (dated 28 Sep 1999) for the exact instructions to follow (Note).\n\n**Bottom line**\n\n- If your aircraft has an MLG attach bolt that was drilled for greasing, you must replace it with an undrilled approved bolt within 100 hours’ flying time. The stated purpose is to eliminate a cracking failure mode that can cause landing gear collapse and possible fuel-tank damage (Applicability; Requirement; Compliance; Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-snow-25-mlg-to-fuselage-attach-bolts","history":"/api/acts/ad-ac-snow-25-mlg-to-fuselage-attach-bolts/history","analysis":"/api/acts/ad-ac-snow-25-mlg-to-fuselage-attach-bolts/analysis","conflicts":"/api/acts/ad-ac-snow-25-mlg-to-fuselage-attach-bolts/conflicts","importantCases":"/api/acts/ad-ac-snow-25-mlg-to-fuselage-attach-bolts/important-cases","documents":"/api/acts/ad-ac-snow-25-mlg-to-fuselage-attach-bolts/documents"}}