{"id":"F2006B10901","name":"AD/JETSTREAM/33 - Inhibition of TTL Test and Stall Protection Test Functions During Flight","slug":"ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56438,"registerId":"commonwealth-F2006B10901-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JETSTREAM/33 - Inhibition of TTL Test and Stall Protection Test Functions During Flight","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  British Aerospace BAe 3100 (Jetstream) Series Aeroplanes\n\n \n\n# AD/JETSTREAM/33 Inhibition of TTL Test and Stall Protection\n\nTest Functions During Flight\n\nApplicability: As listed in Requirement Document.\n\n \n\nRequirement: Action in accordance with British Aerospace SB 24-JM7657A. Compliance:  Prior to 31 August 1989.\n\n# 6/89\n\nBackground:  This AD is raised to ensure that inadvertent selection of the TTL or stall protection test switches during flight will not result in an unsafe condition.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD's scope aligns with its stated purpose: to prevent inadvertent in-flight selection of TTL and stall protection test functions on the listed BAe 3100 (Jetstream) series aeroplanes. The requirement is limited to the aircraft identified in the separate Requirement Document and is implemented by following the specified manufacturer service bulletin. There is no indication in the text that the scope was broadened or narrowed from its stated safety objective."},"complexity_factors":["Narrow technical scope limited to specific aircraft models (BAe 3100/Jetstream series) and specific switches (TTL and stall protection test switches). (Applicability: As listed in Requirement Document.)","Mandatory compliance tied to an external manufacturer document (British Aerospace SB 24-JM7657A), requiring operators to obtain and implement that SB. (Requirement: Action in accordance with British Aerospace SB 24-JM7657A.)","Fixed compliance deadline imposes scheduling constraints on operators and maintenance organisations. (Compliance: Prior to 31 August 1989.)","Applicability depends on a separate Requirement Document, so determining whether a particular airframe is covered requires consulting another source. (Applicability: As listed in Requirement Document.)","Implementation requires certified maintenance action (potential parts, labour and downtime), creating operational and cost considerations for owners/operators.","The AD does not state alternate means of compliance within the text, so any deviation would require regulatory engagement or approval."],"plain_english_summary":"What this instrument changes, mechanically:\n\n- Requires the actions set out in British Aerospace Service Bulletin 24-JM7657A to be carried out on the affected aeroplanes so that the TTL (test) and stall-protection test switches cannot be inadvertently selected during flight. (Requirement: Action in accordance with British Aerospace SB 24-JM7657A. Compliance: Prior to 31 August 1989.)\n\nWho is affected:\n\n- Owners and operators of the British Aerospace BAe 3100 (Jetstream) series aeroplanes listed in the separate Requirement Document. (Applicability: As listed in Requirement Document.)\n\nWho decides and who pays:\n\n- The Civil Aviation Safety Authority issued the airworthiness directive requiring compliance with the manufacturer's service bulletin. Operators (aircraft owners or their maintenance organisations) are responsible for carrying out the required work and paying for parts, labour and any associated downtime. (Requirement: Action in accordance with British Aerospace SB 24-JM7657A.)\n\nWhy it matters (stated purpose and practical effect):\n\n- The AD was issued to prevent an unsafe condition caused by inadvertent selection of TTL or stall-protection test switches during flight. The practical effect is to reduce the risk that in-flight selection of those test functions could affect aircraft behaviour. (Background: This AD is raised to ensure that inadvertent selection of the TTL or stall protection test switches during flight will not result in an unsafe condition.)\n\nCompliance mechanics, burdens and trade-offs:\n\n- Operators must follow the steps in the referenced service bulletin by the compliance date specified. That typically means arranging maintenance to modify switch circuitry, install inhibitors, change switch covers or update procedures as described in the SB. The immediate costs are parts, certificated maintenance labour and aircraft downtime. The benefit is reduced risk of an unsafe in-flight activation of test functions.\n\n- The AD ties the regulator's mandatory requirement to a manufacturer document (the SB). That reduces regulatory drafting detail but makes compliance dependent on the technical content of the external SB. Operators must obtain and implement that SB to meet the AD. (Requirement: Action in accordance with British Aerospace SB 24-JM7657A.)\n\n- Applicability is determined by a separate Requirement Document. Operators must check that document to confirm whether a specific airframe is covered. (Applicability: As listed in Requirement Document.)\n\nIncentives, discretion and implementation risks:\n\n- The direct incentive for operators is to eliminate a safety risk and remain airworthy; failure to comply would leave aircraft non-compliant with the AD. The AD prescribes following the manufacturer's SB rather than offering a detailed alternative method in the AD text itself, so any alternative means of compliance would require regulatory approval outside the AD text.\n\n- Implementation risks include scheduling and carrying out the work correctly (certified maintenance), obtaining parts or service instructions from the manufacturer, and ensuring the Requirement Document correctly identifies affected serial numbers or variants. The AD sets a firm compliance timeframe. (Compliance: Prior to 31 August 1989.)\n\nMarket and private-enterprise effects (practical observations):\n\n- The cost burden falls on the relatively small, identifiable group of affected aircraft owners/operators rather than being spread widely. The requirement is technical and specific to the listed aircraft; it does not, on its face, change market structure, competition or pricing beyond the maintenance costs and downtime faced by those operators.\n\n- There is no procedural change to operating rules other than the mandated physical or procedural modification; the AD does not itself create ongoing regulatory fees or obligations beyond compliance with the SB.\n\nSource pointers: the core obligations and timelines are given in the AD's Requirement and Compliance lines; applicability is defined by a separate Requirement Document; the Background line states the stated safety rationale. (Requirement: Action in accordance with British Aerospace SB 24-JM7657A. Compliance: Prior to 31 August 1989.) (Applicability: As listed in Requirement Document.) (Background: This AD is raised to ensure that inadvertent selection of the TTL or stall protection test switches during flight will not result in an unsafe condition.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive focused specifically on preventing inadvertent activation of test functions during flight. It has not expanded beyond its original narrow technical purpose."},"complexity_factors":["Extremely short document — only a few paragraphs","No defined terms section; all terminology is industry-standard aviation shorthand","Single, unambiguous requirement: comply with one referenced service bulletin","No conditional logic, exceptions, or nested provisions","Cross-reference is external (to manufacturer bulletin) rather than internal legislative cross-referencing","Clear applicability statement pointing to external document"],"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) for specific aircraft.\n\n**What it does:** It requires owners or operators of British Aerospace BAe 3100 (Jetstream) series aeroplanes to take specific action to prevent two particular test functions — the \"TTL Test\" and \"Stall Protection Test\" — from being accidentally activated during flight.\n\n**Why it matters:** If someone accidentally hits these test switches while the plane is flying, it could create a dangerous situation. The \"TTL\" likely refers to a thrust or trim-related system, while \"stall protection\" is a safety system that prevents the aircraft from stalling (losing lift). Running these tests mid-flight could confuse the flight controls or give false warnings, potentially putting the aircraft at risk.\n\n**Who must act:** Anyone operating the affected Jetstream aircraft models listed in the accompanying Requirement Document.\n\n**What they must do:** Follow the instructions in British Aerospace Service Bulletin SB 24-JM7657A — a technical document from the manufacturer detailing the fix. This had to be done before 31 August 1989 (so this is a historical directive, though it remains on the books for reference)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight","history":"/api/acts/ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight/history","analysis":"/api/acts/ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight/analysis","conflicts":"/api/acts/ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight/conflicts","importantCases":"/api/acts/ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight/important-cases","documents":"/api/acts/ad-jetstream-33-inhibition-of-ttl-test-and-stall-protection-test-functions-during-flight/documents"}}