{"id":"F2006B08420","name":"AD/CESSNA 550/15 Amdt 1 - Flap Drain Holes","slug":"ad-cessna-550-15-amdt-1-flap-drain-holes","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115890,"registerId":"commonwealth-F2006B08420-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 550/15 Amdt 1 - Flap Drain Holes","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 550 (Citation II) Series Aeroplanes\n\nAD/CESSNA 550/15\n\nAmdt 1\n\n  \nFlap Drain Holes 10/88\n\nApplicability: S550 and 552 S/N S550-0001 to S550-0153 and 552-0001 to 552-0017. Requirement: 1. Action in accordance with Cessna Service Letter SLA S550-57-01.\n\n2. Repairs, if necessary, in accordance with Cessna SB S550-57-5.\n\nNote: FAA AD 88-11-07 refers.\n\nCompliance: 1. Prior to further flight after 13 June 1988.\n\n2. Must be accomplished prior to further flight for aeroplanes identified as having no drain holes or obstructed drain holes in the flaps by Service Letter SLA\n\nS550-57-01.\n\nBackground: There has been an incident where the outboard flap shattered in flight. Investigation revealed that the flap had no drain/vent holes which led to pressurization at altitude. Subsequently, other flaps have been found without drain/vent holes. Amendment 1 states SB that provides repair instructions and spares stock affected.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 adds a specific Service Bulletin that provides repair instructions and identifies affected spares stock, in addition to the original Service Letter inspection requirement. The AD therefore not only mandates inspection (Service Letter SLA S550-57-01) but also mandates repairs and parts considerations according to Cessna SB S550-57-5 (Requirement: 1–2; Background)."},"complexity_factors":["Narrow applicability limited to specific serial numbers (Applicability) — reduces operational complexity but requires serial-number verification.","Mandatory actions are technical and delegated to external manufacturer documents (Cessna Service Letter SLA S550-57-01 and Service Bulletin S550-57-5) (Requirement: 1–2) — compliance depends on following those documents.","Immediate compliance timeline for safety-critical findings (repairs required prior to further flight) creates operational urgency and potential grounding (Compliance: 1–2).","Amendment references repair instructions and affected spares stock, introducing logistical complexity around parts availability and maintenance capacity (Background; Requirement: 2).","Cross-reference to an FAA AD creates an external alignment requirement but does not itself add procedural steps within this AD (Note)."],"plain_english_summary":"What this instrument does (mechanically):\n\n- It requires operators of specified Cessna 550 and 552 aeroplanes (serial numbers S550-0001 to S550-0153 and 552-0001 to 552-0017) to have the flap assemblies inspected and, where required, repaired so that drain/vent holes are present and unobstructed. The inspections and any repairs must follow Cessna's published instructions (Cessna Service Letter SLA S550-57-01 and Cessna Service Bulletin S550-57-5). (Applicability; Requirement: 1–2)\n\nWho is affected and who decides:\n\n- Affected parties are the registered owners/operators of the listed Cessna 550/552 serial-numbered aeroplanes (Applicability).\n- The Civil Aviation Safety Authority issues the directive and makes compliance mandatory under the cited AD; the mechanical steps to be taken are prescribed by Cessna's Service Letter and Service Bulletin (Requirement: 1–2).\n\nWhen it must be done:\n\n- The inspections required by the Service Letter had to be carried out prior to further flight after 13 June 1988 (Compliance: 1). If an aeroplane is found to have no drain holes or has obstructed drain holes, repairs in accordance with the Service Bulletin must be completed prior to further flight (Compliance: 2).\n\nWhy the directive was issued (official rationale and its immediate testable implications):\n\n- The background statement reports an in-flight failure where an outboard flap shattered; investigation showed the flap had no drain/vent holes and became pressurised at altitude. The directive’s stated purpose is to prevent recurrence by ensuring drain/vent holes exist and are clear (Background). This purpose implies the following mechanically testable trade-offs and implementation items:\n  - Who pays: Owners/operators bear the direct costs of inspection and any necessary repairs or parts replacement required by the Service Bulletin (Requirement: 1–2; Compliance: 1–2).\n  - Compliance burden and operational effect: The requirement has an immediate operational effect because aeroplanes with missing or blocked holes must be repaired before further flight, which can ground an aircraft until work is done (Compliance: 2).\n  - Implementation risk and discretion: The AD mandates following Cessna's Service Letter and Service Bulletin; the AD itself delegates the technical repair method to those documents, which concentrates technical discretion in the manufacturer’s instructions (Requirement: 1–2).\n  - Supply and maintenance effects: Amendment 1 notes that the Service Bulletin provides repair instructions and identifies affected spares stock, so availability of approved parts and the capacity of maintenance providers to carry out the SB work will affect how quickly operators can return aircraft to service (Background; Requirement: 2).\n  - Administrative scope and targeting: The AD applies only to aeroplanes listed by serial number, so the compliance burden falls on a defined, limited group rather than all Cessna 550/552 models (Applicability).\n\nConcrete behavioural change required:\n\n- Inspect flaps for drain/vent holes per the Service Letter (Requirement: 1; Compliance: 1).\n- If holes are missing or obstructed, perform repairs per the Service Bulletin before flying the aircraft again (Requirement: 2; Compliance: 2).\n\nOther references noted in the instrument:\n\n- The AD cross-references an FAA AD (FAA AD 88-11-07) and states that Amendment 1 supplies the Service Bulletin with repair instructions and identifies affected spares stock (Requirement: 1–2; Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive. The amendment adds repair instructions (via Service Bulletin S550-57-5) and clarifies spare parts availability, but does not expand the scope beyond the original safety issue of flap drain holes. The applicability (which aircraft are affected) remains identical to the original AD."},"complexity_factors":["Very short document — approximately 150 words total","Only 2 defined applicability ranges (serial number blocks)","Simple two-step requirement structure (inspect, then repair if needed)","Single cross-reference to FAA AD 88-11-07 (informational only)","No nested conditions or exceptions — straightforward 'if problem found, fix before flight' logic","No interpretation section with defined terms","Clear, specific compliance deadline"],"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:**\nOrders owners and operators of certain **Cessna 550 Citation II business jets** (specific serial numbers S550-0001 through S550-0153, and 552-0001 through 552-0017) to inspect and fix a dangerous design flaw in the wing flaps.\n\n**The problem:**\nSome of these aircraft were built without proper drain/vent holes in the flaps. At high altitude, pressure can build up inside the sealed flap structure, causing it to **shatter in mid-flight** — which has actually happened. The directive was issued after an aircraft suffered exactly this failure.\n\n**What must be done:**\n- **Inspect** the flaps following Cessna's Service Letter SLA S550-57-01 to check for missing or blocked drain holes\n- **Repair** any damaged flaps using Cessna Service Bulletin S550-57-5 if needed\n- **When:** Immediately — before the aircraft flies again if the problem is found, and for all affected aircraft by June 13, 1988\n\n**Who it affects:**\nOwners and operators of early-model Cessna Citation II jets with specific serial numbers — roughly the first 150 aircraft of this type.\n\n**Why it matters:**\nThis is a **flight-critical safety issue**. A shattered flap at altitude could cause loss of control or structural damage. The directive makes compliance mandatory, not optional."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-550-15-amdt-1-flap-drain-holes","history":"/api/acts/ad-cessna-550-15-amdt-1-flap-drain-holes/history","analysis":"/api/acts/ad-cessna-550-15-amdt-1-flap-drain-holes/analysis","conflicts":"/api/acts/ad-cessna-550-15-amdt-1-flap-drain-holes/conflicts","importantCases":"/api/acts/ad-cessna-550-15-amdt-1-flap-drain-holes/important-cases","documents":"/api/acts/ad-cessna-550-15-amdt-1-flap-drain-holes/documents"}}