{"id":"F2006B02537","name":"AD/AT 800/1 - Main Landing Gear P/N 40091-2","slug":"ad-at-800-1-main-landing-gear-p-n-40091-2","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41793,"registerId":"commonwealth-F2006B02537-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AT 800/1 - Main Landing Gear P/N 40091-2","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 800 Series Aeroplanes\n\nAD/AT 800/1 Main Landing Gear P/N 40091-2 6/96\n\nDM\n\nApplicability: Models AT-802 and AT802A all serial numbers with P/N 40091-2 main landing gear legs.\n\nRequirement: Replace the main landing gear legs in accordance with Snow Engineering Co.\n\nSL 104A.\n\nNote: FAA AD 96-04-08 refers.\n\nCompliance: Prior to achieving 3001 landings, or within 25 landings after 27 March 1996, whichever occurs last.\n\nWhere the total number of landings is not recorded, calculate by using three landings per one hour time in service.\n\nBackground: A combination of heat treatment for higher UTS and inadequate leg thickness has resulted in the failure of a main landing gear leg. This Directive is issued to prevent possible failure of the main landing gear leg which could result in the loss of control during landing or take off.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in a specific aircraft part. It has not expanded beyond its original purpose of preventing main landing gear failure."},"complexity_factors":["Single, specific mechanical part affected (P/N 40091-2 main landing gear legs)","Only two aircraft models covered (AT-802 and AT-802A)","Clear compliance deadline with simple alternative calculation method for operators without landing records","No cross-references to other legislation beyond a single FAA reference for context","No defined terms section — uses plain technical language","Single requirement: replace the part per manufacturer's service letter"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a compulsory recall notice, but for aircraft parts rather than cars.\n\n**What it does:** It orders owners and operators of specific Air Tractor 800 series agricultural aircraft (models AT-802 and AT-802A) to replace their main landing gear legs (part number 40091-2) before they reach 3,001 landings.\n\n**Why it matters:** The original landing gear legs have a dangerous flaw. They were heat-treated to be extra strong (higher UTS = Ultimate Tensile Strength), but this made them too thin and brittle. One has already failed. If another fails during takeoff or landing, the pilot could lose control and crash.\n\n**Who must comply:** Anyone operating these specific aircraft models with the affected part number.\n\n**When to act:**\n- **If you track landings:** Replace before the 3,001st landing, or within 25 landings after 27 March 1996 — whichever comes *later* (so you get the full 3,001 landings if you haven't reached them yet).\n- **If you don't track landings:** Calculate using 3 landings per hour of flight time, then apply the same deadline.\n\n**How to fix it:** Follow the instructions in Snow Engineering Service Letter 104A. The FAA (American regulator) issued a similar order (AD 96-04-08), which is referenced for additional guidance."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's operative scope is limited to replacing a specific part (main landing gear legs P/N 40091-2) on specified Airtractor models and prescribes how and when that replacement must occur (Applicability; Requirement; Compliance). Those actions match the stated background purpose of preventing possible gear-leg failure and resulting loss of control during landing or takeoff (Background). The text does not expand or narrow the stated safety purpose beyond the mechanical mandate to replace the parts according to SL 104A within the specified compliance window."},"complexity_factors":["Narrow applicability: only AT-802 and AT802A with P/N 40091-2 main landing gear legs (Applicability) — limits scope of affected fleet.","Single, discrete technical action: mandatory replacement following a specified service letter (SL 104A) (Requirement) — low procedural complexity for what to do.","Fixed compliance metric with fallback calculation: 3,001 landings or within 25 landings after 27 March 1996, with a prescribed conversion of three landings per flight hour if landing counts are not recorded (Compliance) — introduces record-keeping and calculation tasks.","Dependency on an external document for the technical method (Snow Engineering Co. SL 104A) — requires access to and interpretation of that service letter (Requirement).","Operational risks and supply-chain considerations (parts availability, maintenance capacity) that are not resolved in the AD text — practical complexity for implementation, though not legal complexity in the instrument itself (Requirement; Compliance)."],"plain_english_summary":"This AD mandates replacement of main landing gear legs (P/N 40091-2) on Airtractor AT‑802 and AT802A aircraft, installed per Snow Engineering Service Letter SL‑104A, before 3,001 recorded landings (or within 25 landings after 27 Mar 1996), treating each flight hour as three landings if counts are missing.  \n\nIssued after a reported gear‑leg failure linked to heat treatment and thin material, it aims to prevent loss of control; owners/operators bear parts, labour and downtime costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-at-800-1-main-landing-gear-p-n-40091-2","history":"/api/acts/ad-at-800-1-main-landing-gear-p-n-40091-2/history","analysis":"/api/acts/ad-at-800-1-main-landing-gear-p-n-40091-2/analysis","conflicts":"/api/acts/ad-at-800-1-main-landing-gear-p-n-40091-2/conflicts","importantCases":"/api/acts/ad-at-800-1-main-landing-gear-p-n-40091-2/important-cases","documents":"/api/acts/ad-at-800-1-main-landing-gear-p-n-40091-2/documents"}}