{"id":"F2006B11451","name":"AD/TPE 331/52 - PT2 Sensor Icing","slug":"ad-tpe-331-52-pt2-sensor-icing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57399,"registerId":"commonwealth-F2006B11451-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TPE 331/52 - PT2 Sensor Icing","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)  \nAlliedSignal (Garrett/AiResearch) Turbine Engines \\- TPE 331 Series\n\nAD/TPE 331/52 PT2 Sensor Icing 11/97\n\nApplicability: TPE331-3, \\-5, \\-6, \\-10, \\-11, \\-12 series engines not incorporating a Pt2 sensor modified in accordance with AlliedSignal Service Bulletins (SB) TPE331-73-0235 or TPE331- 73-0236 as applicable by engine model.\n\nRequirement: 1. All applicable aircraft:\n\nTo prevent the loss of control of engine power when operating in icing conditions, modify the Pt2 sensor in accordance with the requirements of AlliedSignal SB TPE331-73-0235 or TPE331-73-0236 as applicable by engine model number.\n\n2. Aircraft equipped with engine inlet ice protection:\n\nTo address the possible loss of control of engine power when operating in icing conditions; pending the issue of an amendment to the Approved Flight Manual, a copy of this directive shall be placed in the Approved Flight Manual as the first page of the emergency or abnormal procedures section to reflect:\n\n“NON RESPONSIVE POWER LEVER:\n\nIf a lack of response to power lever is observed, turn on the ignition and anti-ice for both engines. After the condition has cleared and normal operations are observed, which occurs in approximately three minutes, anti-ice and ignition can be turned off.”\n\nNote 1: Compliance with the requirements of SB TPE331-73-0235 or TPE331-73- 0236 constitutes a terminating action for the requirements of this directive.\n\nNote 2: FAA Airworthiness Directive 97-15-10 refers.\n\nCompliance: 1. As detailed in the requirement documents.\n\n2. Within 30 days from the effective date of this directive.\n\nThis airworthiness directive becomes effective on 9 October 1997.\n\nBackground: This directive has been issued to address reports of ice blockage of the Pt2 probe.\n\nIcing of the Pt2 probe can result in erroneous signals to the fuel control unit causing little or no response to power lever movement. This directive requires the modification of the Pt2 sensor to provide Pt2 sensing in the event of the probe icing and to increase anti-ice flow to the Pt2 sensor to optimise the de-icing time.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This airworthiness directive maintains its original narrow scope — addressing a specific icing hazard in a specific engine series. The dual requirement (hardware modification plus interim flight manual amendment for ice-protected aircraft) represents standard aviation safety practice for urgent hazards, not scope creep."},"complexity_factors":["Single, specific technical requirement with clear applicability criteria","Only 2 defined compliance paths (modification vs. interim flight manual procedure)","Minimal cross-referencing (only to specific manufacturer service bulletins and one FAA directive)","Straightforward conditional logic: applies to specific engine models unless already modified per listed SBs","No nested exceptions or complex definitional sections","Short document (approximately 250 words) with clear structure"],"plain_english_summary":"This safety order requires owners/operators of certain AlliedSignal TPE331 small-turbine engines to install an improved Pt2 sensor and increase anti-ice airflow to prevent sensor icing that can render the throttle unresponsive. It applies to TPE331-3, -5, -6, -10, -11, and -12 series engines not already upgraded per the manufacturer’s service bulletins.\n\nThe rule also mandates adding an emergency procedure for affected aircraft with ice protection systems. The modification is terminating action."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive implements a focused safety measure for specific TPE331 models not already modified per the named service bulletins. It retains that narrow scope and adds a short-term AFM procedural insertion pending formal amendment. No broader classes of engines or additional operational regimes are introduced beyond what the directive explicitly prescribes (see Applicability; Requirement 1; Requirement 2; Note 1)."},"complexity_factors":["Technical specificity: applies only to listed TPE331 engine models and to Pt2 sensor modification per AlliedSignal SB TPE331-73-0235 or -73-0236 (Requirement 1; Note 1).","Dual obligations: a physical modification requirement plus a temporary operational/procedural change in the Approved Flight Manual (Requirement 1 & Requirement 2).","Clear compliance timing: AFM insertion required within 30 days from effective date (Compliance 2).","Terminating action clearly defined: compliance with the named SBs ends the directive’s continuing obligations (Note 1).","Dependence on external documents: the directive mandates work per manufacturer service bulletins and references an FAA AD (Note 2).","Safety-critical nature: action responds to reports of Pt2 probe icing that can cause loss of engine power control (Background).","Limited administrative discretion: mandated actions and timelines leave little room for alternative compliance (Requirement; Compliance).","Operational coordination burden: requires maintenance capability, parts/technical support and AFM amendment processes (implicit from Requirement and Requirement 2).","Enforceability and legal effect: effective date and compliance provisions create a binding regulatory duty on operators (Compliance)."],"plain_english_summary":"This airworthiness directive requires operators of specified AlliedSignal TPE331 engine models (unless already modified) to modify the Pt2 sensor to prevent engine power loss from icing. For aircraft with inlet ice protection, the directive must be copied into the Approved Flight Manual’s emergency/abnormal procedures until the AFM is amended. Operators pay for and arrange the modifications and AFM update; the directive names specific service bulletins as the required work and sets the timelines and a terminating action."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tpe-331-52-pt2-sensor-icing","history":"/api/acts/ad-tpe-331-52-pt2-sensor-icing/history","analysis":"/api/acts/ad-tpe-331-52-pt2-sensor-icing/analysis","conflicts":"/api/acts/ad-tpe-331-52-pt2-sensor-icing/conflicts","importantCases":"/api/acts/ad-tpe-331-52-pt2-sensor-icing/important-cases","documents":"/api/acts/ad-tpe-331-52-pt2-sensor-icing/documents"}}