{"id":"F2006B02993","name":"AD/B737/92 - Thrust Reverser Fan Cowl Firewall","slug":"ad-b737-92-thrust-reverser-fan-cowl-firewall","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42352,"registerId":"commonwealth-F2006B02993-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/92 - Thrust Reverser Fan Cowl Firewall","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/B737/92 Thrust Reverser Fan Cowl Firewall 10/95\n\nApplicability: Boeing 737-300, \\-400, and \\-500 series aircraft with line numbers 2137 through 2271 inclusive.\n\nRequirement: 1. Inspect the inner wall of the thrust reverser fan duct cowl in accordance with Boeing Alert Service Bulletin 737-78A1056 to determine if the correct firewall insulation topcoat material is present and rectify as required.\n\nNote: FAA AD 95-09-01 also refers.\n\nCompliance: 1. Unless previously accomplished, at next “C” check but no later than 31 December 1996.\n\nBackground: Boeing has advised that a change to the fireproof insulation on the thrust reverser fan duct firewall to decrease aircraft weight has resulted in the firewall not meeting certification requirements.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a defined aircraft population. It has not expanded beyond its original purpose of ensuring firewall fireproofing compliance."},"complexity_factors":["Single, specific technical requirement with clear reference to external Boeing documentation","Narrow applicability limited to specific aircraft models and production line numbers","Simple compliance deadline structure (next C-check or fixed date)","No nested exceptions, conditional logic, or extensive defined terms","Background explanation provided in plain language","Total length is extremely short (under 200 words)"],"plain_english_summary":"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:**\nOrders airlines and aircraft operators to inspect and fix a fire safety problem on certain Boeing 737 planes. The issue involves the **thrust reverser fan cowl firewall** — a protective barrier near the engine that stops fire from spreading. Boeing had changed the fireproof insulation material to save weight, but this change meant the firewall no longer met safety certification standards.\n\n**Who it affects:**\n- **Boeing 737-300, -400, and -500 series aircraft** with specific production line numbers (2137 through 2271)\n- Airlines and operators flying these specific planes in Australia\n\n**What must be done:**\nOperators must inspect the inner wall of the engine cowl (the covering around the engine) to check if the correct fireproof insulation is installed. If the wrong material is found, it must be replaced or fixed according to Boeing's technical instructions (Alert Service Bulletin 737-78A1056).\n\n**When:**\nBy the next scheduled \"C\" check (a major maintenance inspection) or by 31 December 1996, whichever comes first — unless the fix was already done.\n\n**Why it matters:**\nFirewalls are critical safety barriers. If they fail during an engine fire, flames and toxic fumes could reach the passenger cabin or fuel tanks. This directive prevents that catastrophic failure mode by ensuring the proper fireproof material is in place."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies to a clearly defined set of aeroplanes and imposes a specific inspection and rectification obligation tied to a manufacturer service bulletin; it implements the stated corrective objective in the Background (to address a firewall insulation change that failed certification). The AD does not expand beyond that technical, aircraft‑specific remit, so there is no evidence in the source text of a change in scope from that stated intent."},"complexity_factors":["Narrow applicability limited to specific airframe line numbers (Applicability)","Technical compliance tied to a manufacturer service bulletin rather than detailed steps in the AD (Requirement 1)","Requirement to \"rectify as required\" leaves specific remedial actions to the service bulletin, creating operational dependence on that document (Requirement 1)","Fixed compliance deadline tied to maintenance scheduling (next \"C\" check but no later than 31 December 1996) introduces scheduling urgency (Compliance 1)","Cross-reference to an FAA AD adds a parallel regulatory reference but does not expand the AD’s procedural content (Note)"],"plain_english_summary":"This AD requires owners/operators of certain Boeing 737-300/-400/-500 aeroplanes (line numbers 2137–2271) to inspect the thrust‑reverser fan‑duct cowl inner wall for the correct fireproof insulation topcoat and carry out any corrective work per Boeing Alert Service Bulletin 737‑78A1056, scheduled at the next “C” check (or by 31 Dec 1996). It was issued after Boeing reported a weight‑saving insulation change that no longer met certification; costs and downtime are for the operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-92-thrust-reverser-fan-cowl-firewall","history":"/api/acts/ad-b737-92-thrust-reverser-fan-cowl-firewall/history","analysis":"/api/acts/ad-b737-92-thrust-reverser-fan-cowl-firewall/analysis","conflicts":"/api/acts/ad-b737-92-thrust-reverser-fan-cowl-firewall/conflicts","importantCases":"/api/acts/ad-b737-92-thrust-reverser-fan-cowl-firewall/important-cases","documents":"/api/acts/ad-b737-92-thrust-reverser-fan-cowl-firewall/documents"}}