{"id":"F2006B08354","name":"AD/CESSNA 400/70 - Elevator Horn Inboard Tip Rib - Modification","slug":"ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115761,"registerId":"commonwealth-F2006B08354-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 400/70 - Elevator Horn Inboard Tip Rib - 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)  Cessna 400 Series Aeroplanes\n\n \n\n# AD/CESSNA 400/70 Elevator Horn Inboard Tip Rib - Modification\n\nApplicability: All model 441 with S/Nos. 441-0001 to -0106 and 0109. Document:  Cessna Propjet SIL No. PJ79-32.\n\n# 4/80\n\nCompliance: Unless already accomplished, within 25 hours time in service after 28 February 1980.\n\n \n\nBackground: Sealing of the inboard tip rib of the elevator horn is required to preclude foreign material from entering or exiting the elevator tip rib.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive for a specific aircraft type. It has not expanded beyond its original purpose of mandating a single structural modification to prevent elevator contamination."},"complexity_factors":["Extremely short document (under 200 words)","Only 2 defined applicability criteria (model number and serial number range)","Single compliance requirement with clear deadline","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","No conditional logic, exceptions, or nested provisions","Straightforward technical reference to a single manufacturer document (Cessna SIL PJ79-32)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nRequires owners and operators of certain Cessna 400 series aircraft (specifically Model 441 Conquest II planes with serial numbers 441-0001 through 441-0106 and 441-0109) to modify the elevator horn's inboard tip rib by sealing it.\n\n**Why it matters:**\nWithout this seal, foreign material (dirt, debris, moisture) could get into or out of the elevator tip rib. This could potentially jam or damage the elevator — the control surface that makes the plane pitch up and down — creating a serious flight safety risk.\n\n**Who must comply:**\nAnyone operating these specific Cessna 441 aircraft. The work had to be completed within 25 flight hours after 28 February 1980 (unless already done).\n\n**What owners had to do:**\nFollow the instructions in Cessna's Service Information Letter PJ79-32 to seal the rib and prevent contamination."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied text prescribes a specific modification for a defined set of serial-numbered aircraft and sets a single compliance deadline. There is no indication in the text that the scope has been expanded or narrowed from an earlier intention; the directive is limited to the listed models/serial numbers and the sealing action described (Applicability; Compliance; Background; Document)."},"complexity_factors":["Narrow, specific applicability (exact serial numbers listed)","Single, clearly described required action (sealing of the inboard tip rib of the elevator horn)","Short, explicit compliance window (25 hours time in service after a specific date)","Technical method delegated to an external manufacturer document (Cessna Propjet SIL PJ79-32)","No stated exemptions, alternative compliance methods, or procedural complexity within the text supplied"],"plain_english_summary":"What this directive requires (mechanical change)\n\n- The directive requires sealing the inboard tip rib of the elevator horn on certain Cessna 441 aeroplanes. The technical method for doing this is given by the referenced Cessna Propjet Service Information Letter (SIL No. PJ79-32). (Document; Applicability)\n- The requirement applies to all model 441 aircraft with serial numbers 441-0001 through 441-0106 and 441-0109. (Applicability)\n- The work had to be completed within 25 hours time in service after 28 February 1980, unless it had already been done. (Compliance)\n\nWhy the change is required (stated purpose)\n\n- The stated reason in the directive is to prevent foreign material from entering or exiting the elevator tip rib. (Background)\n\nWho it affects and who decides\n\n- The directive affects owners and operators of the listed Cessna 441 serial numbers because they are the persons responsible for ensuring the aircraft complies with airworthiness directives. (Applicability; Compliance)\n- The directive points to Cessna Propjet SIL No. PJ79-32 as the document that contains the technical instructions for the modification; that document is the source of the procedure to be followed. (Document)\n\nWho pays, compliance burden and timing\n\n- The directive text does not state who bears the cost of parts or labour. The AD imposes an obligation to have the modification accomplished within the stated time window; therefore the practical cost and scheduling burden will fall on whoever operates or owns the affected aircraft and arranges for the work. (Compliance; Applicability)\n- The time-in-service limit (25 hours after 28 February 1980) creates a short compliance window relative to normal flight hours, so operators would need to schedule the work promptly or during the next maintenance opportunity. (Compliance)\n\nDiscretion, enforcement and implementation risk\n\n- The directive sets a mandatory action and a deadline; it does not include stated exemptions, alternative methods of compliance, or discretion for delay in the text supplied. (Compliance)\n- The directive references a manufacturer service instruction for the method; following that document will be necessary to meet the AD’s technical requirement. The AD does not itself set out the step-by-step procedure. (Document)\n- The AD does not state enforcement mechanisms, penalties, or post-work inspection/recording requirements in the supplied text; those matters may be governed by broader regulatory practice but are not described here. (Compliance)\n\nEffects on businesses and operational choices (mechanisms, not value judgments)\n\n- Maintenance providers or the aircraft owners/operators will perform or contract the sealing work. The directive creates a straightforward demand for that specific modification for a small, identifiable set of airframes. (Applicability; Document)\n- Because the applicability is limited to specific serial numbers, the cost and workload are concentrated on a narrow group of operators rather than being broadly distributed across the fleet. (Applicability)\n\nTrade-offs and practical considerations (drawn from the text)\n\n- The directive’s stated safety aim is to prevent ingress or egress of foreign material at the elevator tip rib. Achieving that requires taking aircraft out of normal use for the work (or scheduling the work during existing maintenance). The AD does not quantify costs, downtime, or alternatives. (Background; Compliance; Document)\n\nSource citations: Applicability; Compliance; Background; Document (Cessna Propjet SIL No. PJ79-32)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification","history":"/api/acts/ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification/history","analysis":"/api/acts/ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification/analysis","conflicts":"/api/acts/ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification/conflicts","importantCases":"/api/acts/ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification/important-cases","documents":"/api/acts/ad-cessna-400-70-elevator-horn-inboard-tip-rib-modification/documents"}}