{"id":"F2006B02434","name":"AD/APU/16 - T-62T APU Compressor Wheel Replacement","slug":"ad-apu-16-t-62t-apu-compressor-wheel-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41690,"registerId":"commonwealth-F2006B02434-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\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.\n\n![](image.001.png)\n\nAuxiliary Power Units","sortOrder":0},{"sectionNumber":"AD/APU/16 T-62T APU Compressor Wheel Rep","sectionType":"part","heading":"AD/APU/16 T-62T APU Compressor Wheel Replacement 11/2002","content":"# AD/APU/16 T-62T APU Compressor Wheel Replacement 11/2002\n\nApplicability: Hamilton Standard Power Systems (formerly Sundstrand Power Systems, Turbomach, and Solar) models T-62T-2C, T-62T-25, T-62T-29 and T-62T-39 Auxiliary Power Units (APU) that have compressor wheel part number 100636-1 installed.\n\nRequirement: 1. Replace cast steel (see Note 1) compressor wheels Part Number (P/N) 100636-1 with compressor wheel P/N 4503164, 4504174, or M4504174.\n\n2. Replace wrought steel (see Note 2) compressor wheels P/N 100636-1 with compressor wheel P/N 4503164, 4504174, or M4504174.\n\nNote 1: Cast steel compressor wheels are identifiable by a four digit casting lot vendor identification number used as a prefix to the serial number.\n\nNote 2: Wrought steel compressor wheel is identifiable by a serial number beginning with the letter “W”.\n\nNote: FAA AD 2002-15-02, Amdt 39-12830 refers.\n\nCompliance: Requirement 1: a. Cycles since new greater than 2.350; within 250 cycles in service\n\n(CIS) after the effective date of this directive.\n\nb. Cycles since new less than 2,350; prior to 2600 cycles.\n\nRequirement 2: a. Cycles since new greater than 3,600; within 500 CIS after the effective date of this directive.\n\nb. Cycles since new less than 3,600; prior to 4,100 cycles.\n\nThis Airworthiness Directive becomes effective on 31 October 2002.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD remains narrowly focused on correcting an identified unsafe condition for compressor wheels P/N 100636-1 on the listed T-62T APU models. It prescribes specific replacement parts and time-in-service windows. There is no indication in this text that the AD expands beyond that original corrective purpose (no additional systems, parts or wider applicability are added)."},"complexity_factors":["Limited scope: applies to 4 APU models and a single installed part number (P/N 100636-1).","Two material/identification paths (cast vs wrought) with distinct identification methods (four‑digit casting lot prefix vs serial starting with 'W').","Different compliance windows depending on cycles-since-new with two threshold branches for each material type (total 4 conditional paths).","Specified replacement part numbers (three acceptable P/Ns), limiting substitution logic.","Cross-reference to FAA AD 2002-15-02 (external document dependency).","Short text but operationally consequential timing (effective date and short CIS windows)."],"plain_english_summary":"**What this rule does (mechanically)**\n\n- This is an Airworthiness Directive (AD) that requires specific compressor wheels in certain Auxiliary Power Units (APUs) to be replaced.  It applies to Hamilton Standard Power Systems models T-62T-2C, T-62T-25, T-62T-29 and T-62T-39 APUs that currently have compressor wheel part number (P/N) 100636-1 installed (Applicability).\n\n- There are two replacement rules depending on the material/identification of the existing wheel:\n  - If the installed wheel is a cast-steel wheel (identified by a four‑digit casting lot vendor prefix to the serial number), replace P/N 100636-1 with P/N 4503164, 4504174 or M4504174 (Requirement 1 and Note 1).\n  - If the installed wheel is a wrought-steel wheel (identified by a serial number starting with the letter \"W\"), replace P/N 100636-1 with P/N 4503164, 4504174 or M4504174 (Requirement 2 and Note 2).\n\n- The AD sets different deadlines (compliance times) depending on how many cycles the wheel has accumulated since new (Cycles Since New, CIS):\n  - Cast wheels: if CIS > 2,350 then replacement is required within 250 cycles in service (CIS) after the AD’s effective date; if CIS < 2,350 then replacement before 2,600 CIS (Compliance for Requirement 1).\n  - Wrought wheels: if CIS > 3,600 then replacement is required within 500 CIS after the AD’s effective date; if CIS < 3,600 then replacement before 4,100 CIS (Compliance for Requirement 2).\n\n- The AD became effective 31 October 2002 and explicitly refers to a corresponding FAA AD as a related document (Note / FAA AD 2002-15-02).\n\n**Who this affects and who decides**\n\n- Affected parties: operators and owners of aircraft fitted with the listed T-62T APU models that have the specified compressor wheel P/N 100636-1 installed. Also affected are maintenance organisations and parts suppliers who perform and supply the replacement.\n\n- Decision authority: the CASA delegate issued the AD under the airworthiness regulation cited; compliance is mandatory under that regulatory scheme.\n\n**Why the AD is issued (stated purpose) and how that maps to costs and incentives**\n\n- Stated purpose: the AD mandates the replacement to correct an \"unsafe condition\" identified for the compressor wheel part P/N 100636-1 (background/rationale section referenced in the AD). That is a safety-driven regulatory intervention: remove or replace a part that regulators consider to pose an unacceptable risk of failure if left in service beyond set life limits.\n\n- Who pays: aircraft owners/operators bear the direct cost of procuring replacement parts and paying for labour, downtime, and any associated inspections. Maintenance providers incur the operational burden of scheduling and performing replacements. Parts suppliers designated by P/N benefit from sales of the listed replacement wheels.\n\n- Behavioural effect: operators must track cycles-since-new for applicable APUs, identify whether wheels are cast or wrought, and schedule replacements within the specified cycle windows. Until replacement, operators may face operational constraints to avoid exceeding mandated cycle limits.\n\n**Implementation, compliance and practical trade-offs**\n\n- Compliance burden: requires accurate records of cycles-since-new and serial number checks to determine whether a wheel is cast or wrought. If records are incomplete, operators will need inspections or paperwork recovery to establish CIS and serial number format.\n\n- Parts choice and competition: the AD prescribes specific P/Ns for replacement. That limits replacement options to the specified parts (unless an alternative approved via separate authority), which concentrates demand on suppliers able to provide those P/Ns and may affect price and lead times.\n\n- Downtime and operational cost: replacement windows (some as short as 250 CIS after the AD takes effect for higher‑used cast wheels) can require unscheduled maintenance or out‑of‑phase shop visits, generating direct costs and potential aircraft or fleet availability impacts.\n\n- Risk and ambiguity: identifying cast versus wrought wheels depends on serial/lot notation rules (four‑digit vendor prefix vs serial beginning with \"W\"). Mis-identification risks non‑compliance or premature removal of safe wheels; conversely, ambiguity can lead to conservative early replacements.\n\n- Regulatory cross-reference: the AD references an FAA AD (2002-15-02), which may be used as supporting technical material; operators with international fleets routinely track such cross-references but must comply with CASA's AD as issued.\n\n**Concrete trade-offs and opportunity costs**\n\n- The AD transfers safety risk mitigation costs from the regulator to operators (parts, labour, downtime). It reduces the chance of in-service compressor-wheel failures (the safety benefit claimed) at the expense of those costs.\n\n- Specifying exact replacement P/Ns reduces choice for operators and can increase short-term procurement risk (lead times/prices) but simplifies uniformity of corrective action and inspection acceptance by regulators.\n\n- The directive is targeted (specific models, part number, and cycle windows). That focuses costs on a subset of operators rather than imposing fleet-wide measures.\n\n**Where to look in the AD for specifics**\n\n- Applicability: model and part-number scope.\n- Requirement and Notes: which parts to fit and how to identify the old parts (cast vs wrought).\n- Compliance: cycle thresholds and deadlines for replacement.\n\n"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete safety directive with a single, focused purpose: mandating replacement of a specific defective part. The scope remains tightly constrained to the identified compressor wheel issue without expansion into broader operational or maintenance requirements."},"complexity_factors":["Multiple compliance pathways based on two material types (cast vs wrought steel) and two usage thresholds each (4 separate deadline calculations)","Requires visual identification of manufacturing method through serial number patterns (4-digit prefix vs 'W' prefix)","Cross-reference to FAA AD 2002-15-02 for additional context","Technical aviation terminology (cycles in service, part numbers, APU) assumes specialised knowledge","Nested conditional logic: material type → usage threshold → compliance deadline"],"plain_english_summary":"This CASA safety order requires owners/operators of Hamilton Standard T‑62T APUs fitted with compressor wheel P/N 100636‑1 to replace it with redesigned wheels (P/N 4503164, 4504174, or M4504174) before it fails. The original cast or wrought steel wheels can crack and disintegrate, risking APU damage and flight/ground incidents. Affected operators must replace cast‑steel wheels by specified cycle limits (about 2,350–2,600 cycles) and wrought‑steel wheels by their own cycle limits (about 3,600–4,100 cycles)."},"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-apu-16-t-62t-apu-compressor-wheel-replacement","history":"/api/acts/ad-apu-16-t-62t-apu-compressor-wheel-replacement/history","analysis":"/api/acts/ad-apu-16-t-62t-apu-compressor-wheel-replacement/analysis","conflicts":"/api/acts/ad-apu-16-t-62t-apu-compressor-wheel-replacement/conflicts","importantCases":"/api/acts/ad-apu-16-t-62t-apu-compressor-wheel-replacement/important-cases","documents":"/api/acts/ad-apu-16-t-62t-apu-compressor-wheel-replacement/documents"}}