{"id":"F2006B07265","name":"AD/TAY/4 - Fuel Flow Regulator Life Limit","slug":"ad-tay-4-fuel-flow-regulator-life-limit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49181,"registerId":"commonwealth-F2006B07265-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TAY/4 - Fuel Flow Regulator Life Limit","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nRolls Royce Turbine Engines \\- Tay Series\n\nAD/TAY/4 Fuel Flow Regulator Life Limit 7/99\n\nApplicability: Rolls Royce Tay fuel flow regulators listed by serial number in RR Service Bulletin TAY-73-1459.\n\nRequirement: Remove from service applicable fuel flow regulators for rework as in Rolls Royce Service Bulletin TAY-73-1459.\n\nNote: UK CAA AD 002-01-99 also refers.\n\nCompliance: At a period not exceed 6500 hours time in service since new or last overhaul.\n\nThis Airworthiness Directive becomes effective on 15 July 1999.\n\nBackground: Rolls Royce has advised a number of fuel flow regulators in a foreign operator’s fleet have been exposed to contaminated fuel. FFR drive gear failures have been attributed to using contaminated fuel. Limiting the time in service will prevent FFR failure due to excessive gear wear.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive implements a time‑in‑service removal and rework requirement (6,500 hours) for specific Rolls-Royce Tay fuel flow regulators to address drive gear wear attributed to contaminated fuel, matching the stated purpose in the Background. It does not broaden or narrow that stated safety objective beyond prescribing the removal interval and referring to the service bulletin for rework (Background; Requirement; Compliance)."},"complexity_factors":["Narrow technical scope limited to specific Rolls-Royce Tay fuel flow regulator serial numbers (Applicability)","Single, fixed compliance interval (6,500 hours) that requires operators to track time-in-service (Compliance)","External cross-reference to Rolls-Royce Service Bulletin TAY-73-1459 for the required rework method (Requirement)","Dependence on maintenance capacity and parts availability for rework (Requirement)","Low regulatory discretion: prescriptive action (remove and rework) rather than principles-based obligations (Requirement)"],"plain_english_summary":"The directive mandates removal and rework, per Rolls‑Royce Service Bulletin TAY‑73‑1459, of specified Rolls‑Royce Tay fuel‑flow regulators listed by serial number, at intervals not exceeding 6,500 hours TIS. It aims to prevent FFR drive‑gear failures linked to contaminated fuel.\n\nAffected parties are aircraft operators and maintenance organizations; operators must track hours, schedule removals, and pay for downtime and rework, while maintenance providers perform the prescribed service."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific mechanical failure mode. It has not expanded beyond its original purpose of preventing fuel flow regulator failures due to contaminated fuel exposure."},"complexity_factors":["Very short document (under 200 words)","Only one substantive requirement with a single numerical threshold (6500 hours)","No defined terms section — relies on external Rolls Royce Service Bulletin for part identification","Single cross-reference to UK aviation authority directive (informational only)","No conditional logic, exceptions, or nested provisions","Clear, unambiguous compliance deadline"],"plain_english_summary":"This is a **safety order for aircraft engines**. It requires airlines and aircraft operators to remove specific Rolls Royce Tay engine fuel flow regulators from service after they've been used for no more than 6,500 hours.\n\n**What it does:**\n- Sets a **maximum lifespan** (called a \"life limit\") for certain fuel flow regulators — parts that control how much fuel flows to the engine\n- Requires these parts to be taken out of aircraft and **reworked** (repaired/overhauled) once they hit 6,500 hours of use\n- Applies only to specific serial numbers listed in a Rolls Royce technical bulletin\n\n**Who it affects:**\n- Airlines and operators using Rolls Royce Tay engines (typically on aircraft like the Fokker 70 and some Gulfstream business jets)\n- Maintenance crews responsible for tracking component hours and scheduling replacements\n\n**Why it matters:**\nRolls Royce discovered that contaminated fuel was causing **gear failures** in these regulators overseas. Rather than wait for failures to happen, CASA is mandating preventive maintenance — removing parts before they can fail in flight. This prevents potential engine problems, fuel leaks, or in-flight shutdowns.\n\n**Key detail:** The 6,500-hour clock starts from when the part is new or last overhauled."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tay-4-fuel-flow-regulator-life-limit","history":"/api/acts/ad-tay-4-fuel-flow-regulator-life-limit/history","analysis":"/api/acts/ad-tay-4-fuel-flow-regulator-life-limit/analysis","conflicts":"/api/acts/ad-tay-4-fuel-flow-regulator-life-limit/conflicts","importantCases":"/api/acts/ad-tay-4-fuel-flow-regulator-life-limit/important-cases","documents":"/api/acts/ad-tay-4-fuel-flow-regulator-life-limit/documents"}}