{"id":"F2006B02146","name":"AD/AC/85 Amdt 1 - Flight in Icing Conditions","slug":"ad-ac-85-amdt-1-flight-in-icing-conditions","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41376,"registerId":"commonwealth-F2006B02146-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC/85 Amdt 1 - Flight in Icing Conditions","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)  \nTwin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes\n\nAD/AC/85\n\nAmdt 1\n\n  \nFlight in Icing Conditions 7/95\n\nApplicability: All 690, 690A, 690B, 690C, 690D, 695, 695A and 695B aircraft not incorporating an automatic engine ignition relight system per Gulfstream Aerospace Custom Kit 138 or 139.\n\nRequirement: 1. Inspect both engines and determine if both;\n\nthe part number of the engine ignition unit on each engine complies with AlliedSignal Service Bulletin TPE/TSE331-74-0003, and\n\nthe anti-ice shield assemblies are in accordance with AlliedSignal Service Bulletin TPE/TSE331-75-0004.\n\nEnter the part number of the ignition units and the anti-ice shield service bulletin status in the aircraft log book and in each engine log book.\n\n    2. Arrange for the Ignition Unit/Anti-ice Shield configuration to be made available in the cockpit for flight crew information.\n\nNote: This information is required by the crew for compliance with the Ignition Override Time Limits specified in the aircraft flight manual.\n\n    3. If, following inspection per Requirement 1 of this Directive, an aircraft is found to have either one or both engines not in compliance with AlliedSignal Service Bulletins TPE/TSE331-74-0003 and/or TPE/TSE331-75-0004, then an appropriate placard shall be securely affixed to the aircraft instrument panel in clear view of the pilot in command. (“DYMO” tape is not considered to be an appropriate placard for the purpose of this Directive)\n\nThe placard shall state in capital letters, white on a red background, a minimum of 3mm high:\n\n“THIS AIRCRAFT IS PROHIBITED FROM FLIGHT INTO ACTUAL OR FORECAST ICING CONDITIONS”.\n\nRemoval of the placard is only permitted if:-\n\n    (a) The aircraft is modified to incorporate the automatic engine ignition relight system per Gulfstream Aerospace Custom Kit 138 or 139, as applicable, or\n\n    (b) Both engines comply fully with Allied Signal Service Bulletins TPE/TSE331-74-0003 and TPE/TSE331-75-0004.\n\nNote: FAA Airworthiness Directive 87-24-07 R1 refers.\n\n    4. Revise applicable engine maintenance programs as necessary to ensure Requirements 1, 2 and 3 are carried out at each occasion either an engine or an ignition unit is replaced.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n    5. Unless Ignition Override Time Limits associated with ignition unit/anti-ice shield configurations are already incorporated in the Limitations Section of the Aircraft Flight Manual (AFM), incorporate the approved AFM amendment which reflects this information.\n\nThe applicable AFM amendment is to be provided by the Authority.\n\nCompliance: Within 25 hours’ time in service after 22 June 1995 or prior to flight into actual or forecast icing conditions, whichever occurs first.\n\nBackground: This Directive has been issued to mandate requirements necessary to reduce the possibility of an engine flameout which may result from operating certain aircraft in icing conditions.\n\nThis amendment re-formats the original requirement for inspection of the engines to determine engine ignition unit and anti-ice shield status and for installation of a placard on the instrument panel for aircraft not incorporating extended cycle ignition units and modified anti-ice shields on both engines. The amendment also introduces a flight manual amendment that specifies the ignition system duty cycles and a requirement to revise engine maintenance programs to ensure the requirements of this Directive are carried out at each engine or ignition unit replacement.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment does not materially expand the population of aircraft or the safety aim of the original Directive. It primarily re-formats the inspection requirement, prescribes the placard text and format, and introduces explicit requirements to incorporate Ignition Override Time Limits into the AFM and to revise maintenance programs so the checks occur when engines or ignition units are replaced. Those changes increase procedural specificity and ongoing administrative obligations but do not broaden the Directive's substantive scope beyond its original purpose of preventing engine flameouts in icing conditions."},"complexity_factors":["Applies to 8 specific aircraft model variants (690, 690A, 690B, 690C, 690D, 695, 695A, 695B)","Cross-references to 2 AlliedSignal Service Bulletins (TPE/TSE331-74-0003 and TPE/TSE331-75-0004)","Cross-reference to 2 Gulfstream Custom Kit numbers (138 and 139) as an alternative compliance path","Five discrete mandatory requirements (numbered 1–5) with administrative, operational and maintenance elements","Prescriptive placard format and exact wording requirement (colour, lettering size, capitalization)","Conditional logic: placard required only if one or both engines are non-compliant; placard removable only upon specified modifications or full compliance","Recurring compliance hook: maintenance program revisions must ensure checks at each engine or ignition unit replacement","Compliance deadline with a short operational window (25 hours time-in-service) creates scheduling complexity for operators"],"plain_english_summary":"**What this directive does (mechanically)\n\n- Applies to: Twin Commander series aeroplanes 690, 690A, 690B, 690C, 690D, 695, 695A and 695B that do NOT have the automatic engine ignition relight system installed by Gulfstream Aerospace Custom Kit 138 or 139.\n\n- Mandatory actions for operators/owners (Requirements 1–5):\n  - Inspect both engines and record whether each engine's ignition unit part number complies with AlliedSignal Service Bulletin TPE/TSE331-74-0003 and whether the anti-ice shield assemblies comply with AlliedSignal Service Bulletin TPE/TSE331-75-0004. Enter these details in the aircraft log book and in each engine log book. (Req. 1)\n  - Make the ignition unit/anti-ice shield configuration available in the cockpit so flight crew can see it. This is needed so crews can follow the Ignition Override Time Limits in the Aircraft Flight Manual (AFM). (Req. 2)\n  - If one or both engines are not compliant with the two AlliedSignal service bulletins, fix a permanent, visible placard on the instrument panel that reads in white capital letters on a red background (letters at least 3 mm high): “THIS AIRCRAFT IS PROHIBITED FROM FLIGHT INTO ACTUAL OR FORECAST ICING CONDITIONS”. (Handwritten or DYMO tape is not acceptable.) The placard can only be removed if the aircraft is modified with Gulfstream Kit 138 or 139 as applicable, or both engines are brought into full compliance with the two service bulletins. (Req. 3)\n  - Update engine maintenance programs so the checks and placarding steps are done whenever an engine or an ignition unit is replaced. (Req. 4)\n  - If the AFM does not already include Ignition Override Time Limits for the particular ignition unit/anti-ice shield combinations, incorporate the approved AFM amendment supplied by the Authority that sets out those limits. (Req. 5)\n\n- Compliance timeframe: Complete the inspection and related actions within 25 hours time-in-service after 22 June 1995, or before any flight into actual or forecast icing conditions, whichever comes first.\n\nWhy it matters (stated purpose and practical effect)\n\n- Stated purpose: To reduce the possibility of an engine flameout when operating these aircraft in icing conditions.\n- Practical effect: Aircraft that lack the specified ignition and anti-ice configuration are explicitly prevented (by placard) from flying into actual or forecast icing conditions until they are modified or verified compliant. That imposes an operational restriction on affected aircraft and requires owners/operators to either accept the restriction or invest to meet the required configuration.\n\nWho pays, who decides, and what behaviour changes\n\n- Who pays: the aircraft owner/operator bears the costs (inspection labour, record entries, possible parts and modification costs to meet the service bulletins or fit Gulfstream Kit 138/139, and associated downtime). (Reqs. 1, 3, 4)\n- Who decides: the Civil Aviation Safety Authority mandates the required actions and supplies the approved AFM amendment; the operator decides whether to modify the aircraft or operate under the placard limitation. (Req. 5)\n- Behaviour changes required: operators must inspect and document engine configurations; make cockpit information available; affix and retain a strict placard if engines are non‑compliant; update maintenance programs; incorporate AFM limits or use the AFM amendment provided.\n\nCosts, incentives, trade-offs and implementation points to consider\n\n- Direct costs: inspection and record-keeping are low-cost; costs rise if parts, shield modification, or Gulfstream kit installation are required. Downtime for paperwork and modifications may be material for operators with tight schedules.\n- Incentives: the ban on flight into icing creates a clear incentive to upgrade to the compliant ignition/anti-ice arrangement or to install Kit 138/139 to restore full operational capability.\n- Trade-offs: operators choose between (a) accepting an operational limitation that restricts flights in forecast or actual icing, or (b) paying for hardware/installation to remove the restriction. The AFM amendment formalises operational limits (Ignition Override Time Limits), shifting operational decision-making to crews within those technical limits.\n- Compliance burden: record updates in aircraft and engine log books, cockpit placarding, and maintenance program revisions are recurring administrative obligations, especially because Requirement 4 mandates the check whenever an engine or ignition unit is replaced.\n- Implementation risks: availability of approved parts/kits, correct identification of part numbers and shield condition (requires qualified maintenance personnel), and correct permanent placarding (format is prescriptive). Misidentification or improper placarding could lead to regulatory non‑compliance.\n- Distribution of effects: benefits (reduced flameout risk) are concentrated on aircraft occupants and third parties; costs are concentrated on the small set of operators flying the listed Twin Commander models without Kit 138/139.\n\nSource mechanics: the Directive cross-references AlliedSignal Service Bulletins TPE/TSE331-74-0003 and TPE/TSE331-75-0004, Gulfstream Custom Kits 138/139, and notes an FAA AD for related background. The Authority provides the approved AFM amendment. (See Requirements 1–5 and Background.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is an amendment (Amdt 1) to an existing directive, but it does not expand beyond the original safety purpose. The amendment reformats inspection requirements, adds flight manual amendment requirements, and introduces maintenance program updates—all directly related to the original goal of preventing engine flameout in icing conditions. The scope remains tightly focused on the specific aircraft models and the specific safety issue of engine ignition reliability in icing conditions."},"complexity_factors":["Multiple specific aircraft model numbers listed in applicability section","Cross-references to two AlliedSignal Service Bulletins and two Gulfstream Aerospace Custom Kits","Conditional logic: different requirements based on inspection findings (Requirement 3 branches based on compliance status)","Specific formatting requirements for the warning placard (colour, size, capital letters)","Reference to external FAA Airworthiness Directive 87-24-07 R1","Time-based compliance deadline with alternative trigger condition"],"plain_english_summary":"This is a safety rule (called an Airworthiness Directive) issued by Australia's Civil Aviation Safety Authority for specific Twin Commander aircraft models. It requires owners and operators to check whether their aircraft engines have proper ignition units and anti-ice shields installed. If the engines don't meet the safety standards, the aircraft must display a prominent red warning placard stating it cannot fly into icing conditions. The rule also requires updating maintenance records and flight manuals. The goal is to prevent engines from failing (flameout) when flying through ice-forming weather conditions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-85-amdt-1-flight-in-icing-conditions","history":"/api/acts/ad-ac-85-amdt-1-flight-in-icing-conditions/history","analysis":"/api/acts/ad-ac-85-amdt-1-flight-in-icing-conditions/analysis","conflicts":"/api/acts/ad-ac-85-amdt-1-flight-in-icing-conditions/conflicts","importantCases":"/api/acts/ad-ac-85-amdt-1-flight-in-icing-conditions/important-cases","documents":"/api/acts/ad-ac-85-amdt-1-flight-in-icing-conditions/documents"}}