{"id":"F2006B08927","name":"AD/DH114/17 - Landing Gear Actuator Piston - Inspection and Replacement","slug":"ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52494,"registerId":"commonwealth-F2006B08927-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DH114/17 - Landing Gear Actuator Piston - Inspection and Replacement","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)  DH114 (Heron) Series Aeroplanes\n\n \n\nAD/DH114/17 Landing Gear Actuator Piston - Inspection NK\n\nand Replacement\n\n \n\nApplicability: All models fitted with Dunlop actuators P/N AC 11130 in which pistons P/N AHO 19742 are installed.\n\n \n\nRequirement: 1. Remove the piston from the jack and inspect the piston crown for signs of cracking.\n\n \n\n2. Remove from service Dunlop piston Part Number AHO 19742. Compliance: For Para. 1 - At intervals not exceeding 200 landings after 15 June 1966.\n\nFor Para. 2 - Whenever a cracked piston crown is detected or at intervals not exceeding 5000 landings whichever occurs first.\n\n \n\nNote: Incorporation of Heron Mod. No. 1161 cancels these requirements. DH114 (HERON).\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, targeted safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of ensuring landing gear piston integrity."},"complexity_factors":["Single, specific technical subject matter (one piston part on one aircraft type)","Only 2 substantive requirements with clear compliance intervals","Minimal defined terms (only standard aviation part numbers and references)","No cross-references to other legislation or complex conditional logic","Straightforward exception noted (Modification 1161 cancels requirements)","Document appears to be a historical directive from 1966 with simple periodic maintenance obligations"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **DH114 Heron aircraft**.\n\n**What it does:**\n- Requires owners/operators to inspect and replace specific landing gear parts that could fail catastrophically.\n\n**Who must comply:**\n- Anyone operating a DH114 Heron aeroplane fitted with **Dunlop actuators** (part number AC 11130) containing **pistons** (part number AHO 19742).\n\n**The requirements:**\n1. **Inspection:** Remove the piston from the landing gear jack and check the piston crown (the top surface) for cracks — must be done every **200 landings** after 15 June 1966.\n2. **Replacement:** Remove the specific piston from service entirely — either when a crack is found, or every **5,000 landings** (whichever comes first).\n\n**Why it matters:**\nCracked landing gear pistons can cause landing gear collapse — potentially destroying the aircraft and killing occupants. This directive prevents that by forcing proactive inspection and replacement.\n\n**How to cancel these requirements:**\nInstall **Heron Modification No. 1161** — a permanent design fix that makes these recurring inspections unnecessary."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The directive applies to a specific subset of Heron aircraft (those with Dunlop actuator P/N AC 11130 fitted with piston P/N AHO 19742) and mandates recurring inspections and removal-from-service rules (Applicability; Requirement; Compliance). The Note states that incorporation of Heron Mod. No. 1161 cancels the AD requirements; therefore the AD’s scope is explicitly conditional and can be narrowed (cancelled) for aircraft that incorporate that modification (Note)."},"complexity_factors":["Narrow applicability limited to DH114 (Heron) aeroplanes fitted with Dunlop actuator P/N AC 11130 and piston P/N AHO 19742 (Applicability).","Two distinct mandated actions: periodic removal/inspection (every 200 landings) and removal-from-service conditions (cracked crown or 5,000 landings) (Requirement; Compliance).","Conditional termination of requirements upon incorporation of Heron Mod. No. 1161 (Note) introduces an operational choice for operators.","Technical action requires physical removal from jack and visual inspection of piston crown (Requirement), implying varying labour/time costs depending on aircraft configuration and maintenance setup.","Historical date reference (inspections after 15 June 1966) — administrative detail but not technically complex (Compliance)."],"plain_english_summary":"Operators and maintainers of DH114 (Heron) aeroplanes with Dunlop actuators P/N AC 11130 (pistons P/N AHO 19742) must remove the actuator piston to visually inspect the piston crown every 200 landings and retire pistons if cracked or at 5,000 landings. Operators bear inspection, removal and replacement costs and scheduling burdens. Incorporating Heron Mod No. 1161 cancels these AD inspection/replacement requirements, creating an upfront-versus-recurring-costs choice."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement","history":"/api/acts/ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement/history","analysis":"/api/acts/ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement/analysis","conflicts":"/api/acts/ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement/conflicts","importantCases":"/api/acts/ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement/important-cases","documents":"/api/acts/ad-dh114-17-landing-gear-actuator-piston-inspection-and-replacement/documents"}}