{"id":"F2006B10082","name":"AD/G159/39 - Flight Manual - Change to Metric Units","slug":"ad-g159-39-flight-manual-change-to-metric-units","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55542,"registerId":"commonwealth-F2006B10082-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/G159/39 - Flight Manual - Change to Metric Units","content":"COMMONWEALTH OF AUSTRALIA CIVIL AVIATION ORDERS CIVIL AVIATION SAFETY AUTHORITY PART 105 SCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nGULFSTREAM (GRUMMAN) G.159 SERIES AEROPLANES\n\nAD/G159/39 Flight Manual \\- Change to Metric Units 9/81\n\nApplicability: All Grumman G159 Series Aeroplanes.\n\nRequirement: The D.o.T. approved flight manual shall be amended to specify quantities in the following units;\n\n    (a) weight in kilograms,\n\n    (b) distances in metres,\n\n    (c) centre of gravity limits and moment arms in millimetres,\n\n    (d) fuel and oil quantities in litres, and\n\n    (e) pressures in kilopascals.\n\nWhere the installed aircraft instrumentation is calibrated in units other than the above the flight manual shall specify both systems of units.\n\nCompliance: By 1 January 1984.\n\nBackground: It is required that all Australian aircraft be provided with airworthiness limitations and operational data in the declared metric units.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The Background states a general requirement that all Australian aircraft be provided with airworthiness and operational data in declared metric units. This particular directive applies that requirement specifically to 'All Grumman G159 Series Aeroplanes' (Background; Applicability). Thus the instrument implements the broader metrication objective as a targeted requirement for the G.159 series rather than re‑stating a universal instrument‑level rule."},"complexity_factors":["Narrow applicability (only Grumman G.159 series) reduces scope for interpretation (Applicability).","A short, explicit list of required units (weights, distances, CG, fuel/oil, pressures) simplifies compliance (Requirement a–e).","Clear rule for dual‑unit presentation when instruments use other units reduces ambiguity (Requirement).","A fixed compliance deadline creates a binary timing obligation but no phased implementation or conditional exceptions (Compliance).","Administrative steps (amend D.o.T.‑approved flight manual) require operational action but little technical discretion, lowering legal complexity (Requirement)."],"plain_english_summary":"This AD requires D.o.T.‑approved flight manuals for all Grumman G.159 aeroplanes to be revised to show specified metric units (kg, metres, mm, litres, kPa), with both systems shown where instruments use other units. Operators must complete amendments by 1 January 1984 and bear the administrative cost. The rule standardizes operational data in metric units to reduce unit‑mismatch risk."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, technical directive with a single, specific purpose: metric conversion of flight manual data for one aircraft type. It has not expanded beyond its original intent."},"complexity_factors":["Very short document (approximately 150 words)","Only 5 specific unit conversion requirements listed in plain bullet points","Single simple exception clause (dual units where instrumentation differs)","No defined terms section","No cross-references to other legislation or technical standards","Clear, unambiguous compliance date","Straightforward applicability statement (all aircraft of one specific model series)"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety instruction) issued by Australia's aviation safety regulator for a specific type of aircraft: the **Grumman G.159 series** (also known as Gulfstream G.159).\n\n**What it does:**\nIt requires owners and operators of these aircraft to update their flight manuals to use **metric units** instead of imperial units for key measurements.\n\n**Specific changes required:**\n- **Weight** must be shown in **kilograms** (not pounds)\n- **Distances** must be shown in **metres** (not feet)\n- **Centre of gravity limits and moment arms** must be shown in **millimetres** (not inches)\n- **Fuel and oil quantities** must be shown in **litres** (not gallons)\n- **Pressures** must be shown in **kilopascals** (not psi or other units)\n\n**Important exception:** If the aircraft's actual instruments (gauges, dials) still show imperial units, the flight manual must display **both** systems side-by-side.\n\n**Who it affects:**\nAnyone who owns or operates a Grumman G.159 aircraft in Australia.\n\n**Why it matters:**\nAustralia was transitioning to the metric system, and this directive ensures pilots and ground crew work with consistent, standardised measurements to prevent dangerous confusion—such as miscalculating fuel loads or weight limits that could affect flight safety.\n\n**Deadline:**\nAll changes had to be completed by **1 January 1984**."}},"importantCases":[],"_links":{"self":"/api/acts/ad-g159-39-flight-manual-change-to-metric-units","history":"/api/acts/ad-g159-39-flight-manual-change-to-metric-units/history","analysis":"/api/acts/ad-g159-39-flight-manual-change-to-metric-units/analysis","conflicts":"/api/acts/ad-g159-39-flight-manual-change-to-metric-units/conflicts","importantCases":"/api/acts/ad-g159-39-flight-manual-change-to-metric-units/important-cases","documents":"/api/acts/ad-g159-39-flight-manual-change-to-metric-units/documents"}}