{"id":"F2006B11114","name":"AD/LEARJET 35/35 - Mach Limit","slug":"ad-learjet-35-35-mach-limit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56778,"registerId":"commonwealth-F2006B11114-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET 35/35 - Mach Limit","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nGates Learjet 35 and 36 Series Aeroplanes\n\nAD/LEARJET 35/35 Mach Limit 2/97\n\nApplicability: All Model 35, 35A, 36 and 36A aeroplanes that have been modified in accordance with United States Federal Aviation Administration (FAA) Supplemental Type Certificate (STC) SA766NW.\n\nRequirement: To prevent deterioration of the aeroplanes lateral control characteristics, unless previously accomplished, perform either of the following options:\n\nOption 1 \\- Permanently reduce the aeroplanes maximum operating Mach limit (MMO) by accomplishing the following:\n\n    Remove the Mach Overspeed Warning Switch and reset it from Mach .83 to .80. Contact the manufacturer, Precision Sensor, PO Box 509, Milford CT 06460 USA (telephone +1 203 877 2795 or facsimile +1 203 877 8752) to have the switch recalibrated. Reidentify the recalibrated Mach Overspeed Warning Switch by ink stamping the words “Mach limit .80’ adjacent to the part number. Reinstall the recalibrated switch.\n\n    2. Remove the pilot’s and copilot’s airspeed indicators and have them modified by changing the “barber pole” from Mach number .83 to number .80. The airspeed indicators must be recalibrated by either the manufacture or a facility approved by CASA. Reidentify the modified airspeed indicators by ink stamping “Mach limit\n\n.80” adjacent to the part number. Reinstall the modified airspeed indicators.\n\nNote 1: A Flight Manual Supplement Particular Amendment reducing the Mach limit number from .83 to .80 is required if Option 1 is followed. This is available from CASA District Airworthiness Offices.\n\nOption 2 \\- Remove the modifications installed in accordance with FAA STC SA766NW and return the aeroplane to either the original type design configuration or to the Gates Learjet “Softflight” configuration.\n\nNote 2: FAA AD 85-16-04 Amdt 39-5110 and AD 96-19-13 Amdt 39-9759 refer.\n\nCompliance: Within 200 hours time in service after 30 January 1997 or prior to 31 July 1997, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 30 January 1997.\n\nBackground: The FAA has received reports of incidents of aileron buffet or buzz being experienced during high speed cruise. The actions specified by this Directive are intended to prevent aileron buffet or buzz conditions, which could result in deterioration of the aeroplanes lateral system characteristics to an unacceptable level.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific safety issue (aileron buffet) in a specific subset of aircraft (Learjet 35/36 series with STC SA766NW modification). The two compliance options both directly address the identified safety risk without expanding into unrelated operational areas."},"complexity_factors":["Single, clearly defined applicability (4 specific aircraft models with one specific modification)","Two mutually exclusive compliance options with detailed procedural steps","Specific technical requirements (Mach numbers, part numbers, manufacturer contact details)","Cross-reference to two related FAA Airworthiness Directives (Note 2)","Dual compliance deadline structure (hours-based OR calendar-based, whichever first)","Limited defined terms (only standard aviation abbreviations: MMO, STC, FAA, CASA)"],"plain_english_summary":"The Civil Aviation Safety Authority requires owners/operators of Learjet 35/36 aircraft modified under FAA STC SA766NW to fix a high‑speed aileron buffet/vibration hazard. Within 200 flight hours after 30 Jan 1997 or by 31 Jul 1997 they must either reduce operating speed from Mach 0.83 to 0.80 (recalibrate warnings/indicators and update the flight manual) or remove the modification and return to an approved configuration to restore safe controllability."},"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"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"This Directive changes the operating envelope for affected, modified aeroplanes by lowering the maximum operating Mach from 0.83 to 0.80 unless the STC modifications are removed. It therefore alters the post-modification certification outcome for aircraft modified under FAA STC SA766NW and imposes mandatory hardware, marking and flight manual changes or reversion to prior configurations."},"complexity_factors":["Technical avionics work: recalibration of Mach overspeed warning switch and modification/recalibration of pilot and copilot airspeed indicators (changing the barber pole)","Requirement to contact and use a specific manufacturer (Precision Sensor) or an approved facility for recalibration","Administrative update: Flight Manual Supplement/Particular Amendment required when option to reduce MMO is followed","Two compliance pathways (permanent MMO reduction or removal of FAA STC SA766NW modifications) introducing operational choice and potential downtime","Narrow applicability: only Model 35/35A/36/36A aeroplanes modified under FAA STC SA766NW are affected","Strict compliance deadline tied to flight hours (within 200 hours after 30 Jan 1997) or calendar date (by 31 July 1997)","Physical marking requirement (ink stamping ‘Mach limit .80’ adjacent to part numbers) adding maintenance steps","Cross-references to FAA ADs (85-16-04 and 96-19-13), indicating inter-jurisdictional conformity issues","Potential operational impact from reduced MMO on flight planning and performance"],"plain_english_summary":"This Airworthiness Directive applies to Gates Learjet 35/35A/36/36A aeroplanes modified under FAA STC SA766NW. It requires operators either to permanently reduce the maximum operating Mach from 0.83 to 0.80 (by recalibrating the Mach overspeed warning switch and changing the airspeed “barber pole”, plus a flight manual amendment) or to remove the STC modifications and revert to the original or “Softflight” configuration. The stated safety purpose is to prevent aileron buffet; aircraft owners/operators bear the modification or reversion costs and compliance burden."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-35-35-mach-limit","history":"/api/acts/ad-learjet-35-35-mach-limit/history","analysis":"/api/acts/ad-learjet-35-35-mach-limit/analysis","conflicts":"/api/acts/ad-learjet-35-35-mach-limit/conflicts","importantCases":"/api/acts/ad-learjet-35-35-mach-limit/important-cases","documents":"/api/acts/ad-learjet-35-35-mach-limit/documents"}}