{"id":"F2006B08339","name":"AD/CESSNA 400/53 - Auto Pilot System - Disabling - Modification","slug":"ad-cessna-400-53-auto-pilot-system-disabling-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115746,"registerId":"commonwealth-F2006B08339-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 400/53 - Auto Pilot System - Disabling - Modification","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)  \nCessna 400 Series Aeroplanes\n\nAD/CESSNA 400/53 Auto Pilot System \\- Disabling \\- Modification 6/78\n\nApplicability: Models 402B S/Nos. 402B1001 thru 402B1331 and 402B1333 thru 402B1338; 404 S/Nos. 404-0001 thru 404-0218 and 404-0220 thru 404-0222; 414 and 414A S/Nos. 414-0801 thru 414-0965, 414A0001 thru 414A0032, 414A0034 thru 414A0038 and\n\n414A0040 thru 414A0047; 421C S/Nos. 421C0001 thru 421C0479 and 421C0481\n\nthru 421C0488; incorporating ARC model 400B auto pilot installations.\n\nRequirement: 1. On aircraft not modified in accordance with Cessna SL No. AV78-6 dated 31 March 1978 or later revision, disable the model 400B auto pilot by pulling and banding AUTO PILOT COMPUTER (COMP) and ACTUATOR (ACT) circuit breakers.\n\n    2. Install a placard in plain view of the pilot indicating “AUTO PILOT INOPERATIVE”.\n\n    3. Upon accomplishment of the electrical auto pilot actuator modification set out in Cessna SL No. AV78-6, the auto pilot may be returned to service and the “AUTO PILOT INOPERATIVE” placard removed.\n\nCompliance: Paras. 1 and 2 \\- Before further flight.\n\nPara. 3 \\- Before further flight using autopilot.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific autopilot defect in specific aircraft models. It has not expanded beyond its original purpose of addressing the ARC 400B autopilot safety issue."},"complexity_factors":["Very short document (approximately 200 words)","Only 3 operative paragraphs with clear sequential requirements","Limited cross-referencing (only references to Cessna Service Letter AV78-6)","Specific but straightforward applicability section listing serial number ranges","No nested exceptions or conditional logic beyond the basic 'if modified do X, if not modified do Y' structure","No defined terms section — uses standard aviation terminology"],"plain_english_summary":"This AD requires owners/operators of certain Cessna 400-series twins (402B, 404, 414/414A, 421C) equipped with the ARC 400B autopilot to immediately disable that autopilot unless already modified per Cessna Service Letter AV78‑6. A warning placard must be fitted until the approved modification is completed.\n\nCompliance is mandatory before further flight — an urgent safety action because the unmodified autopilot presents a serious flight-safety defect."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies only to the listed models/serial ranges with ARC model 400B installations and exempts aircraft already modified per Cessna SL No. AV78‑6. It implements a temporary disable/placard requirement until the referenced modification is completed, without expanding applicability beyond those listed."},"complexity_factors":["Multiple specific model and serial‑number ranges must be checked to determine applicability (administrative burden).","Requirement depends on an external document (Cessna SL No. AV78‑6) for the corrective modification (cross‑reference needed).","Immediate compliance timing: actions must be done before further flight, creating operational scheduling pressure.","Physical tasks: pulling/banding circuit breakers and installing a cockpit placard require hands‑on maintenance/inspection.","Conditional restoration: autopilot may be restored only upon completion of the specified modification, creating staged compliance."],"plain_english_summary":"This airworthiness directive requires owners/operators of specified Cessna 400‑series aeroplanes with ARC model 400B autopilot installations to disable the autopilot by pulling and banding the AUTO PILOT COMPUTER (COMP) and ACTUATOR (ACT) circuit breakers and to install a pilot‑visible placard reading “AUTO PILOT INOPERATIVE” unless the aircraft has already been modified per Cessna Service Letter AV78‑6. The autopilot can be returned to service and the placard removed only after that specified modification is completed. Operators must complete the disablement and placarding before further flight (or before further flight using the autopilot)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-400-53-auto-pilot-system-disabling-modification","history":"/api/acts/ad-cessna-400-53-auto-pilot-system-disabling-modification/history","analysis":"/api/acts/ad-cessna-400-53-auto-pilot-system-disabling-modification/analysis","conflicts":"/api/acts/ad-cessna-400-53-auto-pilot-system-disabling-modification/conflicts","importantCases":"/api/acts/ad-cessna-400-53-auto-pilot-system-disabling-modification/important-cases","documents":"/api/acts/ad-cessna-400-53-auto-pilot-system-disabling-modification/documents"}}