{"id":"F2006B04768","name":"AD/BN-2/57 Amdt 2 - Engine Air Intake Hose","slug":"ad-bn-2-57-amdt-2-engine-air-intake-hose","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44532,"registerId":"commonwealth-F2006B04768-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/57 Amdt 2 - Engine Air Intake Hose","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BN-2/57 Amdt 1 and issues the following 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\nPilatus Britten-Norman BN-2 Series Aeroplanes\n\nAD/BN-2/57\n\nAmdt 2\n\n  \nEngine Air Intake Hose 5/2002\n\nApplicability: All BN-2 series aircraft fitted with Textron Lycoming IO-540 series engines and not fully incorporating modification NB-M-1615 “Alternative Air Intake Hose”.\n\nRequirement: 1. Carry out a visual inspection of the engine air intake hose in accordance with B- N Group Ltd. Service Bulletin (SB) Number SB 95 - Issue 5.\n\n2. Replace a defective air intake hose in accordance with B-N Group Ltd. SB Number SB 95- Issue 5.\n\nNote: B-N Group Ltd Service Bulletin SB 95-Issue 5 has been declared mandatory by the CAA(UK).\n\nCompliance: 1. Unless previously accomplished in accordance with a previous issue of this Directive, within 5 hours time in service effective 16 May 2002 and thereafter at intervals not to exceed 60 hours time in service.\n\n2. Before further flight.\n\nThis Amendment becomes effective on 16 May 2002.\n\nBackground: This Directive was originally issued to require an inspection of the engine air intake hose. The requirement followed reports of engine power loss events resulting from failure of the air intake hose. This amendment reflects the aircraft manufacturer's revision of the requirement document. The revision, in part, provides a terminating action. Aircraft incorporating the alternative air intake hose on both engines are not subject to the requirements of this Directive.\n\nPilatus Britten-Norman BN-2 Series Aeroplanes\n\nAD/BN-2/57 Amdt 2 (Continued)\n\nThe original issue of this Airworthiness Directive became effective on 24 January 1996.\n\nAmendment 1 of this Directive became effective on 14 August 1996.\n\n![](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 7 April 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 24 April 2002.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly scoped to its original purpose: addressing air intake hose failures on BN-2 aircraft. The amendment merely updates the technical reference to the manufacturer's revised service bulletin and clarifies the terminating action. No expansion of aircraft types, engine models, or safety issues beyond the original 1996 intent."},"complexity_factors":["Short, single-purpose instrument (approximately 400 words)","Only 4 defined elements: applicability (aircraft type/engine/modification), requirement (inspection/replacement), compliance (timing), and background","Clear conditional logic: applies only if specific engine type present AND specific modification NOT incorporated","Simple cross-reference to external technical document (B-N Group Ltd Service Bulletin SB 95-Issue 5)","No nested exceptions or layered definitions","Straightforward compliance timeline with single terminating condition (installation of alternative hose on both engines)"],"plain_english_summary":"This AD revokes and replaces the earlier BN-2 directive, requiring owners/operators of Pilatus Britten‑Norman BN‑2 series aircraft fitted with Textron Lycoming IO‑540 engines (and without factory modification NB‑M‑1615) to carry out recurring visual inspections of engine air intake hoses and replace any defective hose. The hose failure can cause engine power loss; installing the alternative NB‑M‑1615 hose on both engines terminates the inspection requirement. Effective 16 May 2002."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment alters the original AD by adopting the manufacturer's revised service bulletin and explicitly recognising the alternative air intake hose modification (NB‑M‑1615) as a terminating action. That change narrows the on‑going scope for aircraft that incorporate the alternative hose on both engines (they are exempted), while preserving mandatory inspection/replacement for affected aircraft that do not have the modification. In other words, the amendment keeps the original safety objective (preventing engine power loss from hose failure) but adds a path (installing NB‑M‑1615) to remove the recurring inspection obligation and reflects updated technical instructions (SB 95 Issue 5)."},"complexity_factors":["Single, narrow applicability (BN‑2 with IO‑540 engines not incorporating NB‑M‑1615)","Three operational requirements (inspect, replace if defective, terminating action via modification)","Simple timing rules (initial within 5 hours, then every 60 hours; replace before further flight)","Delegation of technical steps to an external document (B‑N Group SB 95 Issue 5) rather than full procedures in the AD","Small number of cross‑references (modification NB‑M‑1615; CAA(UK) mandatory declaration of SB)","No layered exceptions or nested conditional logic beyond the terminating‑action exemption"],"plain_english_summary":"**What this instrument is and who it affects**\n\n- This is an Airworthiness Directive (AD) applying to Pilatus Britten‑Norman BN‑2 series aeroplanes that have Textron Lycoming IO‑540 engines and that have not already had modification NB‑M‑1615 fitted (the \"alternative air intake hose\").\n- An AD is a binding safety requirement issued by the regulator (here, the CASA delegate) that aircraft operators and owners must follow.\n\n**What the AD requires (mechanically)**\n\n- Inspect the engine air intake hose following the instructions in B‑N Group Ltd Service Bulletin (SB) No. SB 95 — Issue 5. (The SB contains the step‑by‑step inspection procedure.)\n- If the hose is found to be defective, replace it in accordance with SB 95 — Issue 5.\n- Timing rules: the initial inspection must be done within 5 hours time in service after 16 May 2002 (unless already done under an earlier version). After that, inspections must be repeated at intervals not exceeding 60 hours time in service. Any defective hose identified must be replaced before further flight.\n- Aircraft that have both engines fitted with the alternative air intake hose modification NB‑M‑1615 are exempt from these requirements (that modification is a \"terminating action\").\n\n**Why the rule exists (stated reason) and how that affects incentives**\n\n- The AD was issued because there were reported engine power‑loss events caused by failure of the air intake hose. The stated safety objective is to prevent further engine power loss by ensuring hoses are inspected and defective hoses replaced promptly (Requirement; Background).\n- The AD relies on a manufacturer service bulletin (SB 95 Issue 5) for the technical inspection and replacement procedures. The SB is also noted as having been declared mandatory by the UK CAA, so the AD delegates the detailed method to that external document.\n\n**Who pays and who decides**\n\n- Aircraft owners/operators pay the cost: technician labour for the inspections, parts and labour if hoses are replaced, and aircraft downtime while work is carried out. Maintenance organisations will carry out the work and are paid for that service.\n- The CASA delegate (under subregulation 39.1(1) of CAR 1998) issues the AD and sets the compliance schedule; the technical steps are prescribed by the manufacturer's service bulletin.\n\n**Practical trade‑offs, risks and implementation notes**\n\n- Compliance burden: periodic inspections every 60 hours add recurring maintenance time and scheduling. Replacement before further flight imposes immediate downtime where a defect is found.\n- Terminating action: operators can avoid the recurring inspection burden by incorporating modification NB‑M‑1615 on both engines; that creates a one‑off upgrade cost in exchange for exemption from the AD. That transfers ongoing costs (inspection) into an upfront capital/maintenance expense.\n- Supply / availability risk: the AD depends on the availability of replacement hoses and competent maintenance to perform the SB procedures. Delays sourcing parts or qualified labour could extend downtime.\n- Enforcement and clarity: the AD delegates detailed technical procedure to an external SB (SB 95 Issue 5). Operators must obtain and comply with that SB — the AD does not restate the detailed technical steps. Reliance on an external document creates an administrative step for operators to access and interpret the SB.\n- Concentrated benefits vs diffuse costs: the safety benefit primarily protects operators, passengers and the airframe/engine owners (concentrated beneficiaries), while costs (inspection and replacement) fall on the aircraft owners/operators (concentrated payers). The wider public benefit (reduced risk of engine failure) is more diffuse.\n- Supplier effects: maintenance providers and the manufacturer (who supplies the alternative hose and replacement parts) stand to gain business from inspections, replacements and modifications. That is a predictable market effect when compliance is mandatory.\n\n**Key document references in the AD**\n\n- Applicability clause: identifies affected aircraft (BN‑2 series with IO‑540 engines not incorporating NB‑M‑1615).\n- Requirement clauses: inspection and replacement steps (referencing B‑N Group Ltd SB 95 — Issue 5).\n- Compliance clauses: initial 5‑hour window and repeating 60‑hour interval; replacement before further flight.\n- Background: explains the safety events prompting the AD and notes that installing the alternative hose on both engines terminates the AD obligation.\n\nOverall, the AD imposes a focused, recurring inspection and replacement duty targeted at a specific component on a defined subset of BN‑2 aeroplanes, while offering an optional one‑off modification that eliminates the recurring requirement."},"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-bn-2-57-amdt-2-engine-air-intake-hose","history":"/api/acts/ad-bn-2-57-amdt-2-engine-air-intake-hose/history","analysis":"/api/acts/ad-bn-2-57-amdt-2-engine-air-intake-hose/analysis","conflicts":"/api/acts/ad-bn-2-57-amdt-2-engine-air-intake-hose/conflicts","importantCases":"/api/acts/ad-bn-2-57-amdt-2-engine-air-intake-hose/important-cases","documents":"/api/acts/ad-bn-2-57-amdt-2-engine-air-intake-hose/documents"}}