{"id":"F2006B09646","name":"AD/F100/44 - No. 1 Pitot Tube AC Sensing Circuit","slug":"ad-f100-44-no-1-pitot-tube-ac-sensing-circuit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54466,"registerId":"commonwealth-F2006B09646-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)\n\nFokker F100 (F28 Mk 100) Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/F100/44 No 1 Pitot Tube AC Sensing Ci","sectionType":"part","heading":"AD/F100/44 No 1 Pitot Tube AC Sensing Circuit 7/2001","content":"# AD/F100/44 No 1 Pitot Tube AC Sensing Circuit 7/2001\n\nApplicability: All Model F.28 Mk.0070 and Mk.0100 aeroplanes with either Fokker Service Bulletin (SB) F100-30-019 or SB F100-30-020 embodied.\n\nRequirement: 1. Perform an operational check of the No 1 Pitot Tube Heating System, to establish whether both tube and mast heaters are serviceable, in accordance with Part 1 of the Accomplishment Instructions of Fokker SB F100-30-25 Revision 1 dated 14 March 2001.\n\n    2. If, as a result of the Requirement 1 operation check, either heating element is found to be inoperative, replace the defective Pitot Tube with a serviceable unit of the same part number.\n\n    3. Modify the No 1 Pitot Tube Alternating Current Sensing Circuit in accordance with Part 2, 3, 4, 5 or 6, as applicable, of the Accomplishment Instructions of Fokker SB F100-30-25 Revision 1.\n\nNote: RLD AD 2001-041 (A) refers\n\nCompliance: 1. Within three calendar months after the effective date of this Directive and thereafter at intervals not to exceed 12 months until the Requirement 3 modification is incorporated.\n\n    2. Before further flight after the Requirement1 check has been completed.\n\n    3. Within three calendar years after the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 12 July 2001.\n\nBackground: The RLD has advised that recently an operator reported the loss of indicated airspeed (IAS) on the captain’s speed indicator during a flight in icing conditions.\n\nInspection revealed an inoperative No 1 pitot tube heater caused by a short circuit in the heater element. Further investigation revealed that a short circuit in the No 1 pitot tube heaters can stay undetected, due to the characteristics of the DC/AC inverter supplying the AC current to the heater. This condition, if not corrected, may lead to further occurrences of undetected short circuits in the pitot tube heaters, with consequent loss the captain’s air speed indication.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The Directive targets Model F.28 Mk.0070 and Mk.0100 aeroplanes with SB F100-30-019 or SB F100-30-020 embodied. It does not expand applicability beyond those aircraft or introduce new affected types; the measures align with the unsafe-condition report about No.1 pitot heater short-circuits."},"complexity_factors":["Applicability limited to aircraft with specific Service Bulletins embodied (requires operators to check maintenance status).","Three-step requirement: operational check, immediate replacement if faulty, and a later circuit modification.","Multiple compliance timeframes (within 3 months, before further flight if defect found, and modification within 3 years) creating stepped obligations.","Modification refers to multiple Parts (2–6) of the manufacturer’s SB, requiring technical judgment which variant applies.","Dependence on manufacturer's Accomplishment Instructions (SB F100-30-25 Rev 1) for technical execution.","Safety-critical avionics/heater interaction (AC/DC inverter characteristics) increases consequence of non-compliance and may constrain scheduling."],"plain_english_summary":"Mechanically, this Directive requires operators of certain Fokker F28/F100 aeroplanes to: check the No.1 pitot-tube heater operation, replace any defective pitot tube with the same part number, and modify the No.1 pitot AC sensing circuit per Fokker SB F100-30-25 Rev 1. It applies only to Model F.28 Mk.0070 and Mk.0100 aircraft that have SB F100-30-019 or SB F100-30-020 embodied. CASA says the measures address undetected heater short-circuits that can cause loss of the captain’s indicated airspeed."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific identified hazard (undetected pitot tube heater failure). The scope remains precisely focused on the unsafe condition described in the background — no scope creep evident."},"complexity_factors":["Single-issue directive with only 3 requirements","No defined terms section — uses standard aviation terminology (pitot tube, service bulletin)","Clear sequential structure (check → replace if needed → modify)","Simple compliance timeline (3 months, 12-month intervals, 3 years)","References only one external document (Fokker Service Bulletin F100-30-25)","No nested exceptions or conditional cross-references"],"plain_english_summary":"This CASA safety order targets Fokker F100s with specific service updates: operators must inspect the captain’s pitot tube heater annually (replace if faulty) and install a permanent wiring modification within three years. It affects airlines and maintenance crews because an undetected heater failure can allow pitot icing and loss of captain’s airspeed indications."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f100-44-no-1-pitot-tube-ac-sensing-circuit","history":"/api/acts/ad-f100-44-no-1-pitot-tube-ac-sensing-circuit/history","analysis":"/api/acts/ad-f100-44-no-1-pitot-tube-ac-sensing-circuit/analysis","conflicts":"/api/acts/ad-f100-44-no-1-pitot-tube-ac-sensing-circuit/conflicts","importantCases":"/api/acts/ad-f100-44-no-1-pitot-tube-ac-sensing-circuit/important-cases","documents":"/api/acts/ad-f100-44-no-1-pitot-tube-ac-sensing-circuit/documents"}}