{"id":"F2017L00536","name":"AD/PW100/4 Amdt 1 - Fuel Pump Input Drive Shaft","slug":"ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":96313,"registerId":"commonwealth-F2017L00536-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Pratt and Whitney Canada Turbine Engines","sectionType":"part","heading":"Pratt and Whitney Canada Turbine Engines - PW100 Series","content":"# Pratt and Whitney Canada Turbine Engines - PW100 Series\n\n| AD/PW100/4 Amdt 1 | Fuel Pump Input Drive Shaft | 10/2017 |\n| ----------------- | --------------------------- | ------- |\n\n| Applicability: | Pratt and Whitney Canada PW123, PW123AF, PW124B, PW125B, PW126 and PW126A engines as detailed in Pratt and Whitney Canada Service Bulletin No. 20946 as in force from time to time.                                                                                                                                                                                                                                                                                                                                                    |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with the Technical Requirements of Transport Canada Airworthiness Directive CF-91-02 as in force at the commencement of this AD.                                                                                                                                                                                                                                                                                                                                                                                  |\n| Compliance:    | Prior to 31 October 1991.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n|                | This AD commences on 26 May 2017.Note 1: Compliance with the original AD remains unchanged.Note 2: The words “as in force from time to time” require compliance with the most recent version of the referenced document.                                                                                                                                                                                                                                                                                                               |\n| Background:    | The engine manufacturer has determined that fuel pump input drive shaft torsional vibration can induce oscillations of the main fuel control governor, which may result in large torque fluctuations or torque drop during flight. This Directive requires the modification of the fuel pump to incorporate an input drive shaft with increased torsional stiffness.Amendment 1 to this directive is issued to add PW126A engines to the applicability. This engine model was inadvertently omitted from the original issue of the AD. |\n\n![](image.001.jpeg)\n\nPieter van Dijk  \nDelegate of the Civil Aviation Safety Authority\n\n12 May 2017","sortOrder":0},{"sectionNumber":"AD/PW100/4 Amdt 1","sectionType":"part","heading":"AD/PW100/4 Amdt 1","content":"## AD/PW100/4 Amdt 1","sortOrder":1},{"sectionNumber":"Fuel Pump Input Drive Shaft","sectionType":"part","heading":"Fuel Pump Input Drive Shaft","content":"## Fuel Pump Input Drive Shaft","sortOrder":2},{"sectionNumber":"10/2017","sectionType":"part","heading":"10/2017","content":"## 10/2017","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the applicability by adding the PW126A engine model that was omitted from the original AD (Background). The technical requirement—modify the fuel pump to an input drive shaft with increased torsional stiffness—remains as set by Transport Canada AD CF-91-02; operators must also follow the most recent Pratt & Whitney Canada Service Bulletin (Requirement; Note 2)."},"complexity_factors":["Cross-reference to an external Transport Canada Airworthiness Directive (CF-91-02) for the technical requirements, creating dependency on another regulator's instrument (Requirement).","Dynamic incorporation of manufacturer Service Bulletin No. 20946 “as in force from time to time”, which requires operators to follow the most recent version rather than a fixed text (Note 2).","Limited technical detail in this AD itself—technical steps are delegated to the referenced Transport Canada AD and Service Bulletin, increasing lookup and interpretation burden (Requirement; Applicability).","Narrow applicability to specific PW100-series engine models, requiring operators to check model fitment against Service Bulletin No. 20946 (Applicability).","Amendment 1 modifies scope by adding PW126A, so duty-holders must check both original and amended applicability (Background).","Potential chronological ambiguity: the AD ‘commences 26 May 2017’ while the Compliance line states ‘Prior to 31 October 1991’, which may cause confusion about required action timing and recordkeeping (Compliance).","Compliance cost and operational burden fall on aircraft operators and maintainers who must implement the pump modification; the AD does not quantify costs or provide alternatives (Requirement; Background)."],"plain_english_summary":"Requires modification of the fuel pump to incorporate an input drive shaft with increased torsional stiffness on specified Pratt & Whitney Canada PW100-series engines. The change addresses torsional vibration that can cause main fuel control governor oscillations and in‑flight torque fluctuations (Background).\n\nOperators of the listed engines must comply with Transport Canada Airworthiness Directive CF-91-02 and the latest Pratt & Whitney Canada Service Bulletin; the amendment adds PW126A to the affected models (Requirement; Note 2)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope. It is a technical correction adding the PW126A engine model to the applicability list, explicitly described as an inadvertent omission from the original directive. No expansion of regulatory purpose or new requirements introduced."},"complexity_factors":["Very short document (approximately 200 words of substantive content)","Only 6 specific engine models listed in applicability","Single technical requirement referencing an external Transport Canada directive","No defined terms section","No nested conditional logic or exceptions","Straightforward amendment adding one engine model to existing list","Clear compliance date with explicit note that original AD compliance unchanged"],"plain_english_summary":"This is an **airworthiness directive** (a mandatory safety order for aircraft) that requires owners and operators of specific Pratt & Whitney Canada aircraft engines to modify the fuel pump. \n\n**What it does:**\n- Requires installation of a stronger fuel pump input drive shaft on certain engine models\n- This prevents dangerous torque fluctuations during flight caused by vibration problems\n\n**Who it affects:**\n- Owners and operators of aircraft with PW123, PW123AF, PW124B, PW125B, PW126 and PW126A engines\n- Specifically, this amendment adds the PW126A model which was accidentally left out of the original directive\n\n**Why it matters:**\n- The original vibration problem could cause sudden torque drops during flight — a serious safety risk\n- The compliance deadline was 31 October 1991 (this 2017 amendment doesn't change that)\n- The amendment simply expands the list of affected engines to include one model that was mistakenly omitted"},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft","history":"/api/acts/ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft/history","analysis":"/api/acts/ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft/analysis","conflicts":"/api/acts/ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft/conflicts","importantCases":"/api/acts/ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft/important-cases","documents":"/api/acts/ad-pw100-4-amdt-1-fuel-pump-input-drive-shaft/documents"}}