{"id":"F2006B06192","name":"AD/PHS/15 Amdt 5 - Servo Ballscrew Internal Spline Wear","slug":"ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47057,"registerId":"commonwealth-F2006B06192-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PHS/15 Amdt 5 - Servo Ballscrew Internal Spline Wear","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nPropellers \\- Variable Pitch \\- Hamilton Standard\n\nAD/PHS/15\n\nAmdt 5\n\n  \nServo Ballscrew Internal Spline Wear 2/96\n\nApplicability: All 14RF-9, \\-19, \\-21, \\-23, 247F-1, 14SF-5, \\-7, \\-11, \\-15, \\-17, \\-19, \\-23, 14SFL11 and\n\n6/5500/F propellers installed on but not limited to Embraer EMB-120, EMB-120RT, SAAB-SCANIA SF340B, Aerospatiale ATR42-100, -300, -320, ATR72, -210, De\n\nHavilland DHC-8-100 series, \\-300, Construcciones Aeronauticas SA (CASA) CN- 235, CN-235-100, Canadair CL215T, CL415 and British Aerospace ATP aircraft.\n\nRequirement: Action in accordance with paragraphs (a) to (d) and (g) of FAA AD 95-22-12 Amdt 39-9420.\n\nNote 1: FAA AD 95-22-12 amdt 39-9420 supersedes FAA AD 94-22-12 Amdt\n\n39-9062, FAA AD 93-16-02 amdt 39-8659 and FAA AD 92-08-03 amdt 39-8214.\n\nNote 2: Brazilian Telegraphic AD No T903-03 R1 and BLA AD 94-156 (AB) refer to Amdt 4 of this Directive.\n\nCompliance: As specified in the Requirement Document with a revised effective date of 5 February 1996.\n\nBackground: The manufacturer has received reports that excessive wear has been observed in the servo ballscrew splines of the propeller control unit (PCU). This wear, if not corrected, could affect the aircraft airworthiness.\n\nAmendment 1 was raised after receipt of advice that a Dash 8 lost control of a propeller after landing. During the subsequent investigation extreme wear was discovered on the internal splines of the PCU. These splines had previously been inspected some 750 hours prior to the incident.\n\nAmendment 2 clarified the inspection requirements for PCU's that had operated more than 1800 hours time in service.\n\nAmendment 3 mandated inspection of the same type design propellers and reduced the reinspection interval to 500 hours time in service.\n\nAmendment 4 extended the reinspection period from 500 to 1500 hours time in service for those PCU's which have the ballscrew quill damper installed.\n\nAmendment 5 is being raised to increase the repetitive PCU servo ballscrew internal spline (BIS) teeth inspection interval from 1500 to 2500 hours TIS for propellers that have a ballscrew quill damper installed, to mandate installation of the secondary drive quill (SDQ) by 30 June 1998 and to introduce an initial and repetitive torque check inspection of the primary ballscrew quill once a secondary drive quill has been installed.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"The directive has evolved significantly from its original purpose. Initially focused on detecting spline wear through inspections (Amendment 1 following the Dash 8 incident), it has expanded to mandate physical hardware modifications (secondary drive quill installation) and additional inspection types (torque checks). The inspection intervals have been relaxed from 500 hours (Amendment 3) to 2,500 hours (Amendment 5) as confidence in the mitigation measures grew, but the compliance burden shifted toward mandatory equipment installation rather than purely monitoring wear."},"complexity_factors":["Multiple amendment history (5 versions) creating layered requirements that must be read together","Extensive cross-referencing to FAA AD 95-22-12 (US regulations) rather than setting out full requirements in the Australian text","Technical aviation terminology requiring specialist knowledge (servo ballscrew, quill damper, secondary drive quill, PCU)","Conditional compliance paths based on specific hardware configurations (with/without ballscrew quill damper, with/without secondary drive quill)","Mixed applicability covering 12+ propeller models across 8+ aircraft types with 'but not limited to' language creating potential uncertainty","Time-based compliance with multiple deadlines (repetitive intervals, specific calendar date of 30 June 1998)"],"plain_english_summary":"This CASA Airworthiness Directive requires inspections and hardware changes to Hamilton Standard variable‑pitch propellers after excessive wear was found in servo ballscrew splines that can cause loss of propeller control. It affects operators of regional types (Embraer EMB‑120, Saab 340, ATR 42/72, Dash 8, etc.).\n\nAmendment 5 extends inspection intervals for propellers with a ballscrew quill damper, mandates installation of a secondary drive quill by 30 June 1998, and adds torque checks on the primary quill once the backup is fitted."},"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"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"This amendment adjusts the enforcement and technical scope: it lengthens the repetitive inspection interval from 1500 to 2500 hours for propellers with a ballscrew quill damper, while simultaneously expanding mandatory obligations by requiring installation of a secondary drive quill by 30 June 1998 and adding an initial and repetitive torque check of the primary ballscrew quill after that retrofit. Operators therefore face both relaxed reinspection timing for a subset and new retrofit-plus-inspection duties."},"complexity_factors":["Cross-references FAA AD 95-22-12 (paragraphs (a)–(d) and (g)) rather than reproducing full procedures, requiring operators to consult an external document.","Technical specificity: distinguishes components (servo ballscrew, internal spline, ballscrew quill damper, secondary drive quill, primary ballscrew quill) and prescribes inspections and torque checks for them.","Differing compliance intervals based on equipment fitment (1500 → 2500 hours TIS for propellers with quill damper), creating branching compliance rules.","Mandated retrofit deadline (installation of secondary drive quill by 30 June 1998) imposes time-bound mandatory modifications on operators.","Amendment history and multiple superseded ADs increase traceability burden for maintenance records and regulatory interpretation.","Wide applicability across many propeller models and aircraft types increases operational reach and coordination needs for fleets.","Compliance measured in hours time-in-service (TIS), requiring accurate tracking of component hours and scheduled maintenance planning."],"plain_english_summary":"**What this does:** This airworthiness directive updates maintenance requirements for certain Hamilton Standard variable-pitch propellers by changing inspection timing, requiring a hardware retrofit and adding a new torque check. It applies to the listed propeller models installed on the named aircraft types.  \n\n**Why it matters:** Operators must follow the revised inspection interval, fit a secondary drive quill by 30 June 1998, and perform a primary ballscrew quill torque check after retrofit to address reported internal spline wear."}},"importantCases":[],"_links":{"self":"/api/acts/ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear","history":"/api/acts/ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear/history","analysis":"/api/acts/ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear/analysis","conflicts":"/api/acts/ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear/conflicts","importantCases":"/api/acts/ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear/important-cases","documents":"/api/acts/ad-phs-15-amdt-5-servo-ballscrew-internal-spline-wear/documents"}}