{"id":"F2005L00233","name":"AD/APU/18 - Fuel Leaks on Hamilton Sundstrand APU Models T-62T-46C12 and T-62T-40C14","slug":"ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":33791,"registerId":"commonwealth-F2005L00233-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Auxiliary Power Units","sectionType":"division","heading":"Auxiliary Power Units","content":"### Auxiliary Power Units\n\n| AD/APU/18 | Fuel Leaks on Hamilton Sundstrand APU Models T-62T-46C12 and T-62T-40C14 | 3/2005 |\n| --------- | ------------------------------------------------------------------------ | ------ |\n\n| Applicability: | Hamilton Sundstrand Power Systems Models T-62T-46C12 and T-62T-40C14 (APS 500R) auxiliary power units (APUs) with fuel filter housing assemblies, part numbers (P/Ns) 4951627, 4951960, or 4952039 installed.Note 1: These APUs are installed on, but not limited to, Bombardier DHC-8-400 airplanes and Empresa Brasileira de Aeronautica S.A. (EMBRAER) EMB-135 and-145 series aircraft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | APU Model T-62T-46C12Install a bracket onto the fuel filter housing assembly on APU Model T-62T-46C12 as per provisions of Hamilton Sundstrand Alert Service Bulletin (ASB) No. ASB-4503067-49-9 dated 2 December 2003.APU Model T-62T-40C14 (APS 500R)Unless previously installed, install a bracket onto the fuel filter housing assembly on APU Model T-62T-40C14 (APS 500R) as per provisions of Hamilton Sundstrand ASB- 4504112-49-22 Revision 2 dated 4 October 2004.For brackets previously installed using Original Issue of the ASB-4504112-49-22, dated 2 December 2003, perform a one-time inspection for proper gap and if necessary, adjust the gap between the bracket and bypass button. Use paragraph 2.B. and 2.D. (1) of the Accomplishment Instructions of ASB-4504112-49-22 Revision 2 dated 4 October 2004 to inspect and adjust the gap.Note 2: For APU Model T-62T-40C14 (APS 500R), installation of a part number fuel filter assembly that is not listed in this AD constitutes optional terminating action to the requirements of this AD.Note 3: FAA Airworthiness Directive 2004-24-03 Amendment 39-13879 refers. |\n| Compliance:    | Unless accomplished earlier, within 500 hours time-in-service or 6 months after the effective date of this AD, whichever occurs earlier.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |\n|                | This Airworthiness Directive becomes effective on 17 March 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |\n\n| Background: | There have been reports of failed / cracked fuel bypass button on the fuel filter housing, protruding beyond internal o-ring seal and causing fuel leak.This AD addresses the identified unsafe condition caused by leaking fuel and resultant fire or explosion. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n4 February 2005","sortOrder":0},{"sectionNumber":"AD/APU/18","sectionType":"part","heading":"AD/APU/18","content":"## AD/APU/18","sortOrder":1},{"sectionNumber":"Fuel Leaks on Hamilton Sundstrand APU Mo","sectionType":"part","heading":"Fuel Leaks on Hamilton Sundstrand APU Models T-62T-46C12 and T-62T-40C14","content":"## Fuel Leaks on Hamilton Sundstrand APU Models T-62T-46C12 and T-62T-40C14","sortOrder":2},{"sectionNumber":"3/2005","sectionType":"part","heading":"3/2005","content":"## 3/2005","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":3,"scope_assessment":{"changed":false,"description":"This AD maintains focused scope on the specific fuel leak hazard identified in the background. The optional terminating action and conditional inspection for previously modified units represent standard aviation safety practice rather than scope creep."},"complexity_factors":["Single-issue directive with narrow, specific applicability (2 APU models, 3 part numbers)","Clear bifurcated requirements for two different APU models with distinct service bulletins","One conditional requirement (inspection only if bracket previously installed under original issue)","Optional terminating action provided (alternative part number installation)","Standard compliance timeframe formula (hours or months, whichever earlier)","Minimal cross-referencing (one FAA AD reference, two Hamilton Sundstrand service bulletins)","No defined terms section — technical terms (APU, P/N, ASB) are industry standard","Background section provides clear causal explanation (failed button → leak → fire risk)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires airlines and aircraft operators to fix a dangerous fuel leak problem in specific aircraft engines.\n\n**What it does:**\n- Orders operators to install a protective bracket on the fuel filter housing of two specific models of **Auxiliary Power Units (APUs)** — small engines that provide power to aircraft when the main engines are off\n- The affected models are **Hamilton Sundstrand T-62T-46C12** and **T-62T-40C14 (APS 500R)**\n- These APUs are commonly found on **Bombardier Q400** and **Embraer EMB-135/145** regional aircraft\n\n**Why it matters:**\n- **The safety risk:** The fuel filter housing has a bypass button that can crack or fail, causing fuel to leak past an internal seal\n- **The danger:** Leaking fuel near a hot engine creates risk of **fire or explosion**\n- **The fix:** Install a bracket to prevent the bypass button from protruding and leaking; for some units, check the gap between bracket and button\n\n**Who must comply:**\n- Aircraft operators with these specific APU models installed\n- Must complete the work within **500 flight hours or 6 months** (whichever comes first) from 17 March 2005\n\n**Key detail:** Operators can permanently end their obligations under this directive by installing a different, improved fuel filter assembly not listed in this AD."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD stays within its original safety purpose: removing an unsafe condition caused by fuel leaking past a failed bypass button on specified APU fuel filter housings. It imposes a corrective hardware installation (or replacement) and a limited, one‑time inspection/adjustment in narrowly defined circumstances. The instrument does not broaden obligations beyond that technical remedy or extend into unrelated operational areas."},"complexity_factors":["Short, single‑issue AD focused on a hardware retrofit/inspection","Two APU models covered (T‑62T‑46C12 and T‑62T‑40C14) with three listed fuel filter housing part numbers","References to two specific Hamilton Sundstrand Alert Service Bulletins (one with a revision) that contain detailed instructions","One conditional path: inspection/adjustment required only if bracket was previously installed under original ASB","Optional terminating action (replacement with a fuel filter assembly P/N not listed) creates an alternative compliance route","Compliance window expressed as either 500 hours time‑in‑service or 6 months (whichever earlier)","Cross‑reference to an FAA Airworthiness Directive"],"plain_english_summary":"This AD requires installing a small metal bracket on specified Hamilton Sundstrand APUs (certain T‑62T‑46C12 and T‑62T‑40C14 units with listed fuel‑filter housing P/Ns), with a one‑time inspection/adjustment where an earlier bracket was fitted. Replacing the fuel‑filter assembly with an approved alternative P/N can terminate the AD for that unit. Compliance is within 500 flight hours or six months.\n\nIt affects operators/maintenance organisations that own or service the listed APUs and aims to prevent fuel‑bypass button damage and fuel leaks that could cause fire."}},"importantCases":[],"_links":{"self":"/api/acts/ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14","history":"/api/acts/ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14/history","analysis":"/api/acts/ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14/analysis","conflicts":"/api/acts/ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14/conflicts","importantCases":"/api/acts/ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14/important-cases","documents":"/api/acts/ad-apu-18-fuel-leaks-on-hamilton-sundstrand-apu-models-t-62t-46c12-and-t-62t-40c14/documents"}}