{"id":"F2006B11141","name":"AD/LEARJET/24 - Automatic Flight Controls Systems - Inspection and Modification","slug":"ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56825,"registerId":"commonwealth-F2006B11141-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET/24 - Automatic Flight Controls Systems - Inspection and Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Gates Learjet 24 & 25 Series Aeroplanes\n\n \n\n# AD/LEARJET/24  Automatic Flight Controls Systems - Inspection and Modification\n\nApplicability: All models 24 with S/Nos. 24-218 and subsequent;\n\n \n\nAll models 25 with S/Nos. 25-003 to 25-061; 25-067 to 25-201, 25-204 and subsequent;\n\n \n\nAll Models 28 with S/Nos. 28-001 and subsequent; All Models 29 with S/Nos. 29-001 and subsequent.\n\n# 8/80\n\nRequirement: Conduct the following inspections to assure capability of manually overriding the Automatic Flight Control Systems:\n\n \n\n1. Energize the aircraft electrical system by applying 28 VDC electrical power.\n\n\n \n\n2.        Roll Axis On aircraft equipped with FC-110 autopilot, remove the electrical power from the FC-110 Autopilot Computer. Open the computer and identify the Roll Calibration Board. On the Roll Calibration Board, temporarily install, in parallel with R18 (82 ohm) resistor, a 39 ohm, one watt resistor. Restore the electrical power and engage the Autopilot with the control wheel centered and veify that the roll slip clutch breakaway occurs by rotating the control wheel briskly (45 degrees per second) in both directions. If slippage is not verified, remove the capstan and adjust to proper torque per the appropriate Gates Learjet Service Manual. Return Autopilot Computer to original configuration and accomplish a functional check of the autopilot.\n\n \n\n3.        Yaw Axis Effective on all Models; Check and adjust the yaw capstan slip clutch torque (primary and secondary where applicable) in accordance with the appropriate Gates Learjet Service Manual.\n\n \n\n4.        Pitch Axis\n\n \n\n(a) Effective on Models 24D, 24D-A, 24E, 24F, 24F-A, 25B, 25C, 25D, 25F, 28 or 29 aircraft and aircraft incorporating Gates Learjet Kits AAK71-12 or AMK80-3 (torquers):\n\n \n\nWith the Autopilot disengaged, turn on both stall warning switches and move the control wheel forward and aft at a rapid rate (one second - stop to stop). Note the drag associated with control movement. Turn off the stall warning switches and repeat the rapid fore and aft movement. Note the decrease in drag, which is an indication that the electric disconnect clutch functions properly by disconnecting the drag of the pitch servo (torquer) from the control system.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n(b) Effective on Models 23, 24, 24B, 24B-A, 24C, 25 and 25A aircraft except aircraft incorporating Gates Learjet Kits AAK71-12 or AMK80-3:\n\n \n\nCheck and adjust the pitch capstan slip clutch for proper torque in accordance with the appropriate Gates Learjet Service Manual. 5. Submit a major defect report (MDR) to the local Airworthiness office if any out of tolerance of roll, yaw or pitch axis capstan slip torque is evident.\n\n \n\n6.        To assure proper operation of the Stall Warning Accelerometer Unit, perform an inspection of the Stall Warning Accelerometer in accordance with appropriate Gates Learjet Service Bulletin SB 23, 24, 25-301, SB 28, 29-27-3.\n\n \n\n7.        Submit a major defect report (MDR) to the local Airworthiness office if any discrepancy is discovered during the paragraph 6 inspection.\n\n \n\nCompliance: Within 50 hours time in service after 25 August 1980.\n\n \n\nBackground:  In conjunction with the Gates Learjet Corporation, the Federal Aviation Administration is currently in the process of a review of the adequancy of the certification basis of Lear aircraft, including the adequacy of the certification rules applicable to these type aircraft. While this review is still in its initial stages, preliminary information developed as a result of joint FAA and Gates Learjet Corporation flight evaluations has evidenced characteristics of these aircraft at the limits of their operating envelope which in combination with presently approved operating procedures could adversely affect safety of flight. In light of the foregoing, immediate adoption and effectiveness of this AD is necessary to assure safe operation of the affected aircraft.\n\n \n\nThis AD has been formulated from the FAA produced directive.\n\n \n\nThe flight manual amendments specified in the FAA Directive have been actioned separately.\n\n \n\nFAA have requested details of any discrepancies found during the inspections hence the request for MDRs to be submitted. The MDRs will be collated by this Department and forwarded to the FAA.\n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":7,"scope_assessment":{"changed":false,"description":"The AD adopts the FAA‑produced directive (Background) and applies to the specified Learjet models and serial ranges listed in the Applicability. The text shows no indication that this instrument expands or narrows scope relative to the FAA directive; it reproduces the FAA requirements (Requirement ¶1–¶7) and adds local MDR routing to the Airworthiness office (Requirement ¶5, ¶7)."},"complexity_factors":["Technical procedures require opening and modifying the FC‑110 autopilot computer and temporarily installing a resistor (Requirement ¶2), which demands avionics skill and risk controls.","Multiple distinct mechanical adjustments across three axes (roll, yaw, pitch) with different methods depending on model and kit configuration (Requirement ¶2–¶4).","References to and reliance on Gates Learjet Service Manuals and Service Bulletins for procedural detail and torque specifications (Requirement ¶2, ¶3, ¶4, ¶6).","Mandatory submission of Major Defect Reports (MDRs) to the local Airworthiness office when out‑of‑tolerance or discrepancies are found (Requirement ¶5, ¶7), creating administrative and surveillance burden for operators.","Short compliance window (within 50 hours time in service after 25 August 1980) increases scheduling pressure and potential operational disruption (Compliance).","Applicability is limited by specific model and serial number ranges, requiring operator-level fleet identification effort (Applicability).","Background linkage to FAA directive and ongoing certification review implies coordination with foreign authority and potential follow‑up actions (Background)."],"plain_english_summary":"Requires inspections and adjustments to automatic flight‑control components on specified Gates Learjet 24, 25, 28 and 29 serial numbers so pilots can manually override the autopilot. Tasks include opening the FC‑110 autopilot computer to fit a temporary resistor for a roll‑slip test, checking and adjusting roll, yaw and pitch capstan slip clutches, and inspecting the stall‑warning accelerometer.\n\nApplies to operators of the affected aircraft; compliance is required within 50 flight hours and any discrepancies must be reported to the local Airworthiness office."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original scope as a targeted safety inspection and modification order for specific Learjet aircraft automatic flight control systems. The directive does not appear to have expanded beyond its initial purpose of ensuring manual override capability following joint FAA-Gates Learjet flight evaluations."},"complexity_factors":["Multiple aircraft model variants with different serial number applicability requiring careful cross-referencing","Different technical procedures for different aircraft sub-models (e.g., Models 24D, 24E, 24F vs 23, 24, 24B, 24C)","Conditional logic based on whether specific modification kits (AAK71-12 or AMK80-3) are installed","Technical aviation terminology requiring specialized knowledge (capstan slip clutch, torquers, accelerometer units, MDRs)","Specific electrical and mechanical testing procedures with precise parameters (28 VDC, 39 ohm resistor, 45 degrees per second rotation rate)","Cross-reference to external documents (Gates Learjet Service Manuals and Service Bulletins SB 23, 24, 25-301, SB 28, 29-27-3) for complete compliance","Dual reporting requirements to both Australian and US aviation authorities"],"plain_english_summary":"This mandatory CASA Airworthiness Directive requires owners/operators of specified Gates Learjet 24/25/28/29 series to have their Automatic Flight Control Systems inspected and adjusted within 50 flight hours after 25 August 1980. Maintenance checks ensure roll, pitch and yaw controls (including slip clutches and stall warning units) allow prompt pilot manual override; defects must be reported to CASA (and forwarded to the FAA). This fixes a safety risk where autopilot could impede recovery in critical flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification","history":"/api/acts/ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification/history","analysis":"/api/acts/ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification/analysis","conflicts":"/api/acts/ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification/important-cases","documents":"/api/acts/ad-learjet-24-automatic-flight-controls-systems-inspection-and-modification/documents"}}