{"id":"F2008L02525","name":"AD/CESSNA 525/8 - Firewall Sealant","slug":"ad-cessna-525-8-firewall-sealant","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74498,"registerId":"commonwealth-F2008L02525-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Cessna 525 Series Aeroplanes","sectionType":"division","heading":"Cessna 525 Series Aeroplanes","content":"### Cessna 525 Series Aeroplanes\n\n| AD/CESSNA 525/8 | Firewall Sealant | 8/2008 |\n| --------------- | ---------------- | ------ |\n\n| Applicability: | Model 525 aircraft, serial numbers 525-0600 through 525-0662.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Inspect between the 6352225 aft firewall assembly and 6352226 seal assembly for missing firewall sealant, in accordance with Cessna Aircraft Company Citation Service Letter SL525-71-05 Revision 1, dated 6 February 2008, or later FAA approved revision.If firewall sealant is found to be missing between the aft firewall and seal assembly, before further flight, seal the gap between the aft firewall and seal assembly with U000117S firewall sealant in accordance with the Requirement document.Note: FAA AD 2008-12-01 Amdt 39-15544 refers. |\n| Compliance:    | Within 60 hours time in service or 60 days after 31 July 2008, whichever occurs first.                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n|                | This Airworthiness Directive becomes effective on 31 July 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| Background:    | The FAA received a report that firewall sealant may not have been applied between the aft firewall assembly and seal assembly during manufacture of certain Model 525 aircraft. Such a condition could result in failure of the fire extinguishing system to prevent the spread of fire through the firewall gap, and could lead to an uncontrolled fire.                                                                                                                                                                                                 |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n18 June 2008","sortOrder":0},{"sectionNumber":"AD/CESSNA 525/8","sectionType":"part","heading":"AD/CESSNA 525/8","content":"## AD/CESSNA 525/8","sortOrder":1},{"sectionNumber":"Firewall Sealant","sectionType":"part","heading":"Firewall Sealant","content":"## Firewall Sealant","sortOrder":2},{"sectionNumber":"8/2008","sectionType":"part","heading":"8/2008","content":"## 8/2008","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific manufacturing defect in a limited production run. The scope remains precisely focused on the original safety issue — missing firewall sealant in specific Cessna 525 aircraft — with no evidence of scope creep or expansion beyond this discrete technical problem."},"complexity_factors":["Single, specific mechanical issue (firewall sealant gap)","Clear applicability criteria (specific serial number range)","One primary action required (inspection) with one conditional follow-up (repair if needed)","Single compliance deadline with simple 'whichever occurs first' logic","References external technical document (Cessna Service Letter) but provides specific part numbers and sealant specification","No nested exceptions or complex conditional logic","Short length (under 300 words of substantive content)"],"plain_english_summary":"This CASA AD applies to Cessna 525 jets (SN 525-0600–525-0662) and requires inspection of the firewall area for missing sealant and mandatory repair following the Cessna service bulletin before the aircraft flies again.\n\nIt matters because the sealant prevents engine-compartment fires from breaching the firewall into the cabin or fuel systems; compliance is required within 60 flight hours or 60 days after 31 July 2008."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive remains tightly focused on a single manufacturing omission (missing firewall sealant between the aft firewall and seal assembly) for a limited set of serial-numbered aircraft. It does not broaden the obligations beyond inspection and sealing per the service letter; therefore it does not materially change or expand the original safety objective or scope."},"complexity_factors":["Short single-issue directive (one inspection requirement and one corrective action).","Small, specific applicability (only Model 525 serial numbers 525-0600 through 525-0662).","One external normative reference: Cessna Service Letter SL525-71-05 Rev 1 (or later FAA-approved revision).","One specified material for repair (U000117S firewall sealant).","Simple compliance window (60 hours time-in-service or 60 days after a fixed date).","Minimal cross-references (notes reference FAA AD 2008-12-01 but no layered conditional logic)."],"plain_english_summary":"**What this directive does**\n\n- Orders an inspection and, if necessary, a repair on certain Cessna Model 525 (Citation) aeroplanes.  Specifically it covers serial numbers 525-0600 through 525-0662.\n\n- Requires an inspection for missing firewall sealant in the gap between the aft firewall assembly (part 6352225) and the seal assembly (part 6352226), using the procedures in Cessna Service Letter SL525-71-05 Revision 1 (6 February 2008) or a later FAA-approved revision.\n\n- If sealant is missing, the gap must be sealed with U000117S firewall sealant before the aircraft is next flown.\n\n- Sets a compliance window: the inspection must be done within 60 hours time-in-service or within 60 days after 31 July 2008, whichever comes first. The directive became effective on 31 July 2008.\n\n**Who it affects**\n\n- Owners and operators of the specific Cessna 525 aircraft listed by serial number (525-0600 through 525-0662).\n- Maintenance providers who perform the inspection and sealing work, and any supply chains that provide the specified sealant.\n\n**Why it matters (mechanics and risks)**\n\n- The stated safety concern is that, during manufacture, firewall sealant may not have been applied in the gap between the aft firewall and seal assembly on some aircraft. A missing seal could allow fire and fire-suppressant gases to pass through the firewall gap and defeat the fire extinguishing system, increasing the risk of an uncontrolled fire.\n\n**Practical effects and who pays/decides**\n\n- Owners/operators bear the cost and responsibility for arranging and paying for the inspection and any sealing work. That may include labour, the specified sealant (U000117S) and potential aircraft downtime while work is done.\n\n- The regulator (the Civil Aviation Safety Authority delegate enforcing the directive, referencing FAA AD 2008-12-01) decides compliance standards by mandating the service letter procedures or any later FAA-approved revision.\n\n**Costs, incentives and trade-offs**\n\n- Direct costs are concentrated on operators of the listed serial-number aircraft. The work is a short inspection and, if needed, sealing; it can often be scheduled into existing maintenance to reduce additional downtime.\n\n- If an aircraft is found without sealant, it must be grounded until the sealing is completed (\"before further flight\"), creating short-term availability costs.\n\n- The directive prescribes a specific sealant (U000117S) and a particular service-letter procedure. That narrows technical discretion for maintenance providers but reduces uncertainty about acceptable repair methods; operators must source the approved sealant or an FAA-approved equivalent.\n\n- Implementation risk is moderate: the action is simple to perform but depends on correct inspection (identifying an absence of sealant) and correct application of the specified material per the service letter. Using a later FAA-approved revision is permitted, so there is a clear pathway for acceptable changes to the procedure.\n\n**Market and operational impacts**\n\n- The measure primarily affects a small, identifiable set of aircraft and their operators; it does not change market rules or ownership rights.\n\n- Maintenance providers that already service these aircraft can perform the work; the directive does not create material entry barriers for qualified maintenance businesses but does require compliance with the specified procedure and material.\n\n**Source claim and testing**\n\n- The directive claims a manufacturing omission (missing sealant) could reduce firewall effectiveness and allow fire spread. Mechanically, the AD addresses that specific manufacturing defect by inspecting and sealing the identified gap. The cost is a short inspection plus sealing where required; the benefit is restored firewall integrity as defined by the service procedures.\n\n\n"},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-525-8-firewall-sealant","history":"/api/acts/ad-cessna-525-8-firewall-sealant/history","analysis":"/api/acts/ad-cessna-525-8-firewall-sealant/analysis","conflicts":"/api/acts/ad-cessna-525-8-firewall-sealant/conflicts","importantCases":"/api/acts/ad-cessna-525-8-firewall-sealant/important-cases","documents":"/api/acts/ad-cessna-525-8-firewall-sealant/documents"}}