{"id":"F2006B09505","name":"AD/EMB-120/17 Amdt 1 - Landing Gear - Door Blockage","slug":"ad-emb-120-17-amdt-1-landing-gear-door-blockage","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54058,"registerId":"commonwealth-F2006B09505-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/EMB-120/17 Amdt 1 - Landing Gear - Door Blockage","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/EMB-120/17 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)\n\nEmbraer EMB-120 (Brasilia) Series Aeroplanes\n\nAD/EMB-120/17\n\nAmdt 1\n\n  \nLanding Gear \\- Door Blockage 9/2002\n\nApplicability: Embraer EMB 120 (Brasilia) aircraft serial numbers 120003,120004, and 120006 through 120331 inclusive.\n\nRequirement: 1. Check for the correct installation of check valve P/N CKRC1875005A in landing gear wheel well door closure line as per Embraer Service Bulletin (SB) 120-32- 0077 Revision 3.\n\n    2. If the check valve is fitted correctly no further action is required.\n\n    3. If the check valve is not fitted, or fitted incorrectly, carry out correct installation as per Embraer Service Bulletin (SB) 120-32-0077 Revision 3.\n\nNote 1: Brazilian AD 97-05-03R3 refers.\n\nNote 2: Aircraft flight manual amendments detailed in AD 97-05-03 are required by CAR 55.\n\nCompliance: Unless previously accomplished; within the next 100 flight hours after the effective date of this Directive.\n\nThis amendment becomes effective on 5 September 2002.\n\nBackground: The original issue of this Directive was in response to investigation into aircraft incidents has shown that it is possible to lock up the landing gear doors when performing the emergency landing gear extension procedures in the event of the loss of the green hydraulic system. With the landing gear doors locked, the landing gear cannot be extended even by free fall. Installation of the check valve eliminates the possibility of the doors locking up in this situation.\n\nEmbraer EMB-120 (Brasilia) Series Aeroplanes\n\nAD/EMB 120/17 Amdt 1 (continued)\n\nAmendment 1 was issued to address the possibility of incorrect installation or the non- installation of the check valve as required by the original version of this\n\nDirective. Revision 3 of Brazilian AD 97-05-03 was issued to address these problems.\n\nThe original issue of this Airworthiness Directive became effective on 14 August 1997.\n\n![Signature of Eugene Paul Holzapfel, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 26 July 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 14 August 2002.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope — ensuring the check valve is correctly installed to prevent landing gear door jamming. It does not expand beyond the original safety purpose; it merely tightens compliance by addressing cases where the original directive was not properly implemented."},"complexity_factors":["Short, single-purpose directive with only 3 numbered requirements","Only one defined technical reference (Embraer Service Bulletin 120-32-0077 Rev 3)","Simple conditional logic (if fitted correctly → stop; if not → install)","Limited applicability (specific aircraft serial number range)","Single compliance timeframe (100 flight hours)","No nested exceptions or cross-references to other legislation beyond one Brazilian AD reference and CAR 55 note"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of specified Embraer EMB-120 (S/N 120003, 120004, 120006–120331) to inspect for and, if missing or incorrectly fitted, install check valve CKRC1875005A in the landing-gear system per Embraer SB 120-32-0077 Rev 3.  \n\nThe valve prevents landing-gear doors jamming closed during emergency extension; without it, the gear may not deploy (including by gravity), creating a serious forced-landing hazard. Compliance is required within 100 flight hours."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment expanded the original AD’s practical scope from merely requiring installation to explicitly requiring verification that the check valve is present and correctly installed, and mandating corrective installation where it was missing or fitted incorrectly. It therefore increases the compliance and quality-control obligation on operators and maintenance providers, by adding an inspection/verification step and tying the action to a specific service bulletin revision (SB 120-32-0077 Rev 3). The AD also reiterates AFM amendment obligations (Note 2), preserving prior ancillary requirements."},"complexity_factors":["Short directive: single-page style AD with three numbered requirements","Limited applicability: specific serial-number range (120003, 120004, 120006–120331)","Few cross-references: references Embraer SB 120-32-0077 Revision 3, Brazilian AD 97-05-03R3, and CAR 55 / subregulation 39.1(1)","Single compliance condition/timeframe: within 100 flight hours","One specific part number mandated (P/N CKRC1875005A)","Amendment adds verification step (check of correct installation) but does not introduce multiple nested exceptions"],"plain_english_summary":"**What this instrument does (mechanically)\n\n- This is an Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA) that requires operators of certain Embraer EMB-120 (Brasilia) aeroplanes to inspect and, if needed, install a specific check valve (part number CKRC1875005A) in the landing-gear wheel-well door closure hydraulic line. (See Requirement paragraphs 1–3.)\n\n- The check is to be carried out in accordance with Embraer Service Bulletin (SB) 120-32-0077 Revision 3. If the check valve is already fitted and correctly installed, no further action is required. If it is missing or incorrectly fitted, the operator must carry out the correct installation per the service bulletin. (Requirement 1–3.)\n\n- The work must be done within 100 flight hours after the directive’s effective date unless it was already done earlier. (Compliance.)\n\n- The AD applies only to the subset of EMB-120 aircraft listed by serial number: 120003, 120004, and 120006 through 120331 inclusive. (Applicability.)\n\nWhy CASA requires it (stated rationale and the mechanism addressed)\n\n- The background states that investigations showed that, during emergency landing-gear extension after a loss of the green hydraulic system, landing-gear doors could become locked. If the doors lock, the gear cannot extend even by gravity (free fall). Installing the check valve prevents the doors from locking in that failure mode. (Background.)\n\n- The amendment (Amdt 1) specifically addresses cases where the check valve was never fitted or was fitted incorrectly under the original AD; Revision 3 of the Brazilian AD and the referenced Embraer service bulletin are intended to correct those issues. (Amendment note and Requirement.)\n\nWho is affected and who decides\n\n- Who decides: CASA, via its delegate, issued this AD and specified the required action and compliance timeframe. (Header and signature.)\n\n- Who pays / who acts: the aircraft operator or owner is responsible for arranging the inspection and any corrective work and paying the costs of parts, labour, and downtime. The AD mandates the inspection/installation be performed to the Embraer service bulletin standard. (Requirement and Compliance.)\n\nConcrete compliance and ancillary obligations\n\n- The AD requires following Embraer SB 120-32-0077 Rev 3 for both the inspection and any installation work. That service bulletin will set out detailed steps, torque, sealing, testing, and paperwork. (Requirement 1 and 3.)\n\n- Note 2 cross-references earlier AD requirements for amendments to the Aircraft Flight Manual (AFM) which remain required under regulation CAR 55; those AFM changes (if not yet done) are a separate regulatory obligation. (Note 2.)\n\nCosts, incentives, and trade-offs (practical assessment)\n\n- Direct costs: time for a maintenance inspection and, if necessary, cost of the check valve part and installation labour. The magnitude of cost depends on local labour rates and whether the aircraft is at a line station or maintenance base.\n\n- Operational costs: aircraft downtime while the inspection/installation is done (within 100 flight hours), and any rebooking or scheduling impacts for operators.\n\n- Incentives: operators have a clear, time-limited incentive to inspect and fix affected aircraft to restore full emergency landing-gear capability and satisfy the AD; if already correctly fitted, they avoid further cost. The AD also reduces the incentive to ignore the installation because regulatory compliance by the stated deadline is mandatory.\n\n- Implementation risk and compliance burden: the AD ties compliance to a specific service bulletin revision. That creates a reliance on OEM instructions; if the SB is complex or requires specialist tooling/personnel, smaller operators may need to contract maintenance support. The amendment exists because some installations under the original AD were absent or incorrect, which indicates a non-trivial compliance and quality-control risk in the field. (Amendment note.)\n\n- Substitution and scope effects: the AD prescribes a particular part number and installation procedure; an operator cannot substitute an alternative solution without further approval. This centralises the corrective method around Embraer’s SB and the specified part number. (Requirement citing P/N and SB.)\n\nRegulatory connections and enforcement risk\n\n- The AD is issued under subregulation 39.1(1) of CAR 1998; non-compliance with an AD can expose operators to regulatory enforcement action under the Civil Aviation Regulations. The AD itself does not set penalties in the text, but it creates a legally binding maintenance requirement.\n\nBottom-line plain statement\n\n- If you operate one of the listed EMB-120 serial-numbered aircraft, you must inspect for the presence and correct installation of check valve CKRC1875005A in the landing-gear door closure line within 100 flight hours, and install it correctly per Embraer SB 120-32-0077 Rev 3 if it is missing or fitted incorrectly. The purpose stated by the AD is to prevent landing-gear door lock-up during emergency gear extension following loss of the green hydraulic system. (Applicability, Requirement, Compliance, Background.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-emb-120-17-amdt-1-landing-gear-door-blockage","history":"/api/acts/ad-emb-120-17-amdt-1-landing-gear-door-blockage/history","analysis":"/api/acts/ad-emb-120-17-amdt-1-landing-gear-door-blockage/analysis","conflicts":"/api/acts/ad-emb-120-17-amdt-1-landing-gear-door-blockage/conflicts","importantCases":"/api/acts/ad-emb-120-17-amdt-1-landing-gear-door-blockage/important-cases","documents":"/api/acts/ad-emb-120-17-amdt-1-landing-gear-door-blockage/documents"}}