{"id":"F2006B02992","name":"AD/B737/91 - Main Deck Cargo Door Hinge, Shim and Fairing","slug":"ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42351,"registerId":"commonwealth-F2006B02992-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/91 - Main Deck Cargo Door Hinge, Shim and Fairing","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBoeing 737 Series Aeroplanes\n\nAD/B737/91 Main Deck Cargo Door Hinge, Shim and Fairing 8/95\n\nApplicability: B737-300 Series with main deck cargo door installed in accordance with Supplemental Type Certificate (STC) SA2969SO and listed in Pemco Aeroplex Inc. Service Bulletin 737-52-0012, Revision 2.\n\nRequirement: Replace the forward and aft hinge shims and the lower hinge fairings of the main deck cargo door, with new hinge shims and fairings in accordance with Pemco Aeroplex Inc. Service Bulletin 737-52-0012, Revision 2.\n\nNote: FAA AD 94-12-12 refers.\n\nCompliance: Before 12000 landings from the date of installation of the STC SA2969S0 modification or before 15 December 1995 whichever occurs later.\n\nBackground: Modification is required to prevent loss of structural integrity of the main deck cargo door hinge, possible loss of the cargo door and subsequent rapid decompression.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive limits its scope to B737-300 series aeroplanes that have the specific STC SA2969S0 installed and listed in Pemco Aeroplex Inc. Service Bulletin 737-52-0012 Revision 2, and requires a particular parts replacement per that service bulletin. The stated purpose (preventing hinge failure and possible cargo door loss and decompression) aligns with the mechanical change mandated. There is no indication in the text that the scope was broadened or narrowed beyond that stated applicability and requirement (see \"Applicability\", \"Requirement\", \"Background\")."},"complexity_factors":["Narrow applicability to B737-300 aircraft with STC SA2969S0 installed and listed in a specific Pemco service bulletin (see \"Applicability\")","Technical prescription requiring replacement of particular parts in accordance with a specific manufacturer's service bulletin (see \"Requirement\")","Compliance condition tying the action to an installation-dependent landing-count threshold and a calendar date (creates record-keeping and scheduling complexity) (see \"Compliance\")","Need to coordinate parts supply and maintenance resources consistent with the Pemco specification (supply-chain and service-provider matching) (see \"Requirement\")","Reference to an external FAA AD (cross-jurisdictional regulatory alignment) (see \"Note\")"],"plain_english_summary":"What this instrument does, simply:\n\n- It requires certain Boeing 737-300 airplanes to have specific parts of the main deck cargo door replaced. The parts are the forward and aft hinge shims and the lower hinge fairings. (See \"Requirement\".)\n- The rule only applies to B737-300 aeroplanes that have had a particular Supplemental Type Certificate (STC SA2969S0) modification installed and are listed in Pemco Aeroplex Inc. Service Bulletin 737-52-0012, Revision 2. (See \"Applicability\".)\n- Operators must carry out the replacement in accordance with Pemco Aeroplex Inc. Service Bulletin 737-52-0012, Revision 2. (See \"Requirement\".)\n- The work must be completed before the aeroplane has accumulated 12,000 landings since the STC was installed or before 15 December 1995, whichever is later. (See \"Compliance\".)\n\nWhy the rule exists (the official claim):\n\n- The stated purpose is to prevent loss of structural integrity of the main deck cargo door hinge, which the directive says could lead to loss of the cargo door and rapid decompression. The instrument cites that safety-related background as the reason for the modification. (See \"Background\".)\n\nHow it operates, who pays, and who decides:\n\n- The Civil Aviation Safety Authority (CASA) issues the directive under the airworthiness directives schedule (Part 39). The directive obliges operators of affected aircraft to do the replacement work. (See header and \"Applicability\"/\"Requirement\".)\n- The direct monetary burden falls on operators of the affected B737-300 aircraft: they must obtain the replacement shims and fairings and arrange and pay for the maintenance actions required by the service bulletin. (See \"Requirement\" and \"Applicability\".)\n- The directive channels the technical specification for the replacement to Pemco Aeroplex Inc.'s Service Bulletin Revision 2. That means parts and procedures must conform to Pemco's specification. (See \"Requirement\".)\n- The directive cross-references an FAA airworthiness directive (FAA AD 94-12-12) (See \"Note\").\n\nPractical trade-offs, compliance and implementation notes:\n\n- Timing and operational disruption: the compliance condition is tied to a landing-count threshold and a calendar deadline, so operators must know the installation date of the STC and track landings to determine the compliance window. That creates scheduling and record-keeping obligations and may force out-of-service maintenance at a time chosen to meet the directive. (See \"Compliance\" and \"Applicability\".)\n- Supply and service concentration: because the replacement must be done in accordance with Pemco's service bulletin, demand is directed to suppliers and maintenance providers capable of meeting that specification. That concentrates demand on those who can supply parts and procedures conforming to the Pemco bulletin. (See \"Requirement\".)\n- Safety benefit vs implementation cost: the directive asserts a safety risk (possible loss of cargo door and rapid decompression) if the modification is not made. Operators must weigh the direct cost of parts and maintenance and operational downtime against the safety risk the directive identifies. (See \"Background\" and \"Requirement\".)\n- Implementation risk for operators: failure to comply by the specified landing count or date would leave the aircraft outside the mandated mitigation; compliance requires accurate records of STC installation dates and landing counts. (See \"Compliance\" and \"Applicability\".)\n\nConcentrated benefits and potential for substitution:\n\n- The requirement to follow Pemco's service bulletin means suppliers or overhaul providers that can supply parts and carry out the work per that bulletin receive the business. Other suppliers could compete only if they can meet the same technical standard or be accepted under the bulletin. (See \"Requirement\".)\n\nSummary in one sentence:\n\n- CASA requires replacement of specified hinge shims and lower hinge fairings on certain B737-300s modified by STC SA2969S0, to be performed per Pemco Service Bulletin 737-52-0012 Revision 2 before 12,000 post-STC landings or 15 December 1995, in order to address a stated risk of hinge failure and potential rapid decompression. (See \"Applicability\", \"Requirement\", \"Compliance\", \"Background\".)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific aircraft modification. It has not expanded beyond its original purpose of mandating a particular hardware replacement."},"complexity_factors":["Single, specific technical requirement with clear reference to external service bulletin","Only one applicability criterion (specific STC and aircraft series)","Simple binary compliance deadline (whichever occurs later of two dates)","No defined terms section, no cross-references to other legislation beyond noting related FAA directive","Total length: approximately 150 words"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific **Boeing 737-300 aircraft** that have been modified to include a main deck cargo door.\n\n**What it requires:**\n- Aircraft owners/operators must **replace certain hinge shims and fairings** (metal spacers and protective covers) on the main deck cargo door.\n- The work must follow specific instructions in a **Pemco Aeroplex service bulletin** (a technical repair guide).\n\n**Why it matters:**\n- The original parts can fail, potentially causing the cargo door to separate from the aircraft in flight.\n- A door failure at altitude could cause **rapid decompression** — a dangerous loss of cabin pressure that endangers everyone on board.\n\n**Who must comply:**\n- Operators of affected Boeing 737-300s with this specific cargo door modification (STC SA2969SO).\n- The deadline is whichever comes **later**: either 12,000 landings after the cargo door was installed, or 15 December 1995.\n\n**Key point:** This is not optional. Airworthiness Directives are legally binding safety requirements. Non-compliance means the aircraft cannot fly legally in Australian airspace."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing","history":"/api/acts/ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing/history","analysis":"/api/acts/ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing/analysis","conflicts":"/api/acts/ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing/conflicts","importantCases":"/api/acts/ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing/important-cases","documents":"/api/acts/ad-b737-91-main-deck-cargo-door-hinge-shim-and-fairing/documents"}}