{"id":"F2005L01349","name":"AD/B737/238 Amdt 1 - Digital Transient Suppression Units","slug":"ad-b737-238-amdt-1-digital-transient-suppression-units","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":35135,"registerId":"commonwealth-F2005L01349-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/238 Amdt 1 | Digital Transient Suppression Units | 7/2005 |\n| ------------------ | ----------------------------------- | ------ |\n\n| Applicability: | Model 737-300, -400 and -500 series aeroplanes, modified in accordance with United States Federal Aviation Administration (FAA) Supplemental Type Certificate (STC) ST00127BO.                                                                                                                                                                                                                         |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | 1. If not previously accomplished in accordance with the original issue of this Directive, modify the safe side harness connectors at the fuel tank penetrations and the digital transient suppression devices, in accordance with the Accomplishment Instructions of Goodrich Fuel & Utility Systems Service Bulletin 737-300766-28-2, Revision 2, dated 28 July 2004.                                |\n|                | 2. Safe side harness, part number 50367-01XX may not be installed on any aeroplane as a replacement spare or part of a new installation, unless that safe side harness has been modified in accordance with SB 737-300766-28-2, Revision 2.                                                                                                                                                            |\n|                | Note: FAA AD 2005-05-17 Amdt 39-14006 correction refers.                                                                                                                                                                                                                                                                                                                                               |\n| Compliance:    | For Requirement 1 - Within 12 months after the effective date of this Directive.                                                                                                                                                                                                                                                                                                                       |\n|                | For Requirement 2 - As of the effective date of this Amendment.                                                                                                                                                                                                                                                                                                                                        |\n|                | This Amendment becomes effective on 7 July 2005.                                                                                                                                                                                                                                                                                                                                                       |\n| Background:    | The FAA has received a report of the results of fuel system reviews conducted by the STC holder which identified deficiencies in the system. These deficiencies could allow unsafe levels of current or energy to enter the fuel tank, due to electrical short faults or threat conditions associated with the safe side harness assembly, which could result in a fire or explosion of the fuel tank. |\n|                | The original issue of this Directive required installation of bonding straps to the safe side harnesses of the digital transient suppression device of the fuel quantity indicating system to correct the identified deficiencies.                                                                                                                                                                     |\n\n|     | This Amendment continues the requirements of the original issue and introduces a restriction on new or replacement installations of safe side harnesses unless they have been modified. |\n| --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|     | The original issue of this Directive became effective on12 May 2005.                                                                                                                    |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n19 May 2005","sortOrder":0},{"sectionNumber":"AD/B737/238 Amdt 1","sectionType":"part","heading":"AD/B737/238 Amdt 1","content":"## AD/B737/238 Amdt 1","sortOrder":1},{"sectionNumber":"Digital Transient Suppression Units","sectionType":"part","heading":"Digital Transient Suppression Units","content":"## Digital Transient Suppression Units","sortOrder":2},{"sectionNumber":"7/2005","sectionType":"part","heading":"7/2005","content":"## 7/2005","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The Amendment keeps the original corrective work (installation of bonding straps/modification) and extends scope by adding a prophylactic prohibition: it bars installation of safe-side harness part number 50367-01XX as a replacement or new-install part unless that harness has been modified per the Goodrich Service Bulletin (Requirement 2). That change moves the instrument beyond a one-off retrofit requirement into an ongoing installation control affecting spare-part supply and future maintenance practice (Requirement 2; Background)."},"complexity_factors":["Narrow applicability limited to 3 Boeing 737 sub-series modified under one specific FAA STC (ST00127BO)","Two substantive requirements (modify existing items; ban installation of unmodified spare part) with a single compliance deadline for Requirement 1","One external normative technical document referenced: Goodrich Service Bulletin 737-300766-28-2 Revision 2 (dated 28 July 2004)","Cross-reference to FAA AD 2005-05-17 noted (administrative/correction reference)","Short text with few defined terms and little conditional or nested exception logic","Single part number specifically prohibited unless modified (50367-01XX)"],"plain_english_summary":"Banshee Directive requires operators of Boeing 737-300/-400/-500 aircraft modified under STC ST00127BO to, within 12 months, modify safe‑side fuel‑tank harness connectors and digital transient suppression devices per Goodrich SB 737‑300766‑28‑2 Rev 2. It also bars installing harness P/N 50367‑01XX as a spare or in new installs unless already modified.\n\nThis targets aircraft owners/operators (who pay and schedule work) to eliminate pathways for hazardous electrical energy into fuel tanks, reducing fire/explosion risk; CASA enforces compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment stays tightly within the original scope of the directive. The original AD addressed electrical safety deficiencies in digital transient suppression units on modified 737 aircraft. Amendment 1 simply adds a restriction on future installation of unmodified spare parts — a logical extension of the same safety purpose rather than an expansion into new regulatory territory. The scope remains limited to the same aircraft models, same STC modification, and same fuel system components."},"complexity_factors":["Single, specific technical subject matter (fuel system electrical safety)","Only 2 substantive requirements with clear compliance deadlines","Narrow applicability limited to specific aircraft models with specific prior modification (STC ST00127BO)","Heavy reliance on external technical document (Goodrich Service Bulletin 737-300766-28-2 Rev 2) for actual implementation details — the AD itself does not contain the technical specifications","One cross-reference to related FAA AD (2005-05-17)","Minimal defined terms (only standard aviation acronyms like STC, FAA)","Clear conditional logic ('if not previously accomplished') but no nested exceptions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's aviation regulator (CASA) requiring specific repairs or modifications to aircraft.\n\n**What it does:**\nOrders owners and operators of certain Boeing 737 aircraft (models 300, 400, and 500 series) to fix a dangerous electrical fault in the fuel system. The fault involves \"digital transient suppression units\" — safety devices meant to prevent electrical spikes — and their \"safe side harness\" wiring connectors at fuel tank entry points.\n\n**The safety problem:**\nThe original equipment could allow unsafe electrical current or energy to leak into the fuel tank during short circuits or other electrical faults. This creates a risk of **fire or explosion**.\n\n**What must be done:**\n- **Existing aircraft:** Within 12 months, modify the wiring connectors and suppression devices following specific instructions in a Goodrich service bulletin (Revision 2, dated 28 July 2004).\n- **New or replacement parts:** Immediately from 7 July 2005, a specific part number (50367-01XX) cannot be installed as new or replacement equipment unless it has already been modified per that same service bulletin.\n\n**Who it affects:**\nOperators of Boeing 737-300, -400, and -500 series aircraft that were modified under a specific US FAA certification (Supplemental Type Certificate ST00127BO). This is a relatively narrow subset of the 737 fleet.\n\n**Why it matters:**\nThis is an urgent safety fix to prevent fuel tank explosions. The amendment tightens the original 2005 directive by adding a ban on installing unmodified spare parts, closing a loophole that could have allowed the unsafe condition to persist through maintenance activities."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-238-amdt-1-digital-transient-suppression-units","history":"/api/acts/ad-b737-238-amdt-1-digital-transient-suppression-units/history","analysis":"/api/acts/ad-b737-238-amdt-1-digital-transient-suppression-units/analysis","conflicts":"/api/acts/ad-b737-238-amdt-1-digital-transient-suppression-units/conflicts","importantCases":"/api/acts/ad-b737-238-amdt-1-digital-transient-suppression-units/important-cases","documents":"/api/acts/ad-b737-238-amdt-1-digital-transient-suppression-units/documents"}}