{"id":"F2006B09709","name":"AD/F27/142 Amdt 1 - Main Landing Gear Actuating Ram","slug":"ad-f27-142-amdt-1-main-landing-gear-actuating-ram","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115879,"registerId":"commonwealth-F2006B09709-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F27/142 Amdt 1 - Main Landing Gear Actuating Ram","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)  \nFokker F27 Series Aeroplanes\n\nAD/F27/142\n\nAmdt 1\n\n  \nMain Landing Gear Actuating Ram 5/98\n\nApplicability: All Fokker F27 Mk 100 through Mk 700 series aircraft fitted with Dunlop main landing gear actuating ram, P/N AC67132, AC67134, AC67848 or AC67850.\n\nRequirement: Modify the main landing gear actuating ram in accordance with Dunlop Equipment Division SB 32-1142 dated October 22, 1996, or Dunlop Aviation Australia (DAA) Service Bulletin 36-24 dated May 21, 1984.\n\nNote: RLD AD BLA nr 1996-142(A) dated November 29, 1996, and Fokker SB F27/32-168 dated October 23, 1996, refers.\n\nCompliance: Unless previously accomplished, at next repair or overhaul or within the next 4000 hours time in service or 24 calendar months, whichever occurs first.\n\nThis amendment becomes effective on 23 April 1998.\n\nBackground: Several operators have reported broken main landing gear lockstruts. Investigation by Fokker has confirmed failure of the lockstrut was due to loss of damping within the main landing gear actuating ram. To dampen the gear movement during extension the actuating ram is equipped with a damping chamber filled with silicon oil which is forced through a restrictor during ram extension. If a bobbin “O” ring seal fails then the silicon oil can leak past the seal and this may not be noticed during routine maintenance. Silicon oil loss usually leads to a gradual loss in damping which can be detected by an increase in landing gear extension speed or shaking of the aircraft at gear extension.\n\nDunlop Australia in 1984 developed a modification that also addresses the problem, however it changes the actuator ram seal configuration preventing fitment of the DED modification. This amendment reflects the suitability of the Dunlop Australia modification.\n\nThe original issue of this airworthiness directive became effective on 27 March 1997.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is an amendment (Amdt 1) to an existing Airworthiness Directive. The amendment specifically expands compliance options by recognising the 1984 Dunlop Aviation Australia modification as an acceptable alternative to the 1996 Dunlop Equipment Division modification. This does not represent scope creep beyond the original safety purpose (preventing landing gear lockstrut failure); rather, it provides regulatory flexibility by acknowledging an existing industry solution that achieves the same safety outcome through different technical means."},"complexity_factors":["Single discrete technical requirement with two alternative compliance paths (1996 Dunlop SB or 1984 DAA SB)","Precise applicability criteria limited to specific aircraft series and four part numbers","Standard aviation compliance formula ('whichever occurs first' time/calendar/hours threshold)","Minimal cross-referencing (only background references to related bulletins)","No nested exceptions or conditional logic — straightforward mandate with clear alternatives","Technical terminology requires aviation engineering knowledge but is standard for the domain"],"plain_english_summary":"This mandatory Airworthiness Directive requires owners/operators of certain Fokker F27 Mk100–700 aircraft fitted with specified Dunlop landing-gear actuating rams to modify the ram’s damping/seal arrangement. Silent O‑ring leaks can drain silicon oil, causing dangerously rapid gear extension and lockstrut failures that risk gear collapse.\n\nCompliance must follow Dunlop service instructions (1996 or 1984 approved modifications) by the next repair/overhaul or within 4,000 flight hours or 24 months, whichever comes first."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The amendment recognises an alternative approved modification (Dunlop Aviation Australia SB 36-24) in addition to the Dunlop Equipment Division SB, and notes that the DAA modification alters seal configuration and prevents fitment of the DED modification. Applicability to aircraft and the compliance timetable remain specified, but acceptable compliance methods and compatibility rules have been altered."},"complexity_factors":["Specific applicability limited to Fokker F27 Mk100–Mk700 with listed Dunlop part numbers (P/N AC67132, AC67134, AC67848, AC67850).","Multiple acceptable compliance methods (DED SB 32-1142 or DAA SB 36-24) requiring technicians to select compatible modification.","Compliance timing options tied to maintenance events or fixed service hours/calendar time (next repair/overhaul or 4000 hours or 24 months).","Compatibility constraint: DAA modification changes seal configuration and prevents fitment of the DED modification, creating a maintenance-choice trade-off.","Cross-references to earlier ADs and Fokker service bulletin for technical background and history of the issue.","Technical root cause (damping-chamber oil leak past bobbin O‑ring) requires inspection and modification rather than simple replacement, implicating maintenance procedures and diagnostic detection."],"plain_english_summary":"Requires modification of the main landing gear actuating ram on Fokker F27 Mk100–Mk700 aeroplanes fitted with specified Dunlop part numbers, using Dunlop Equipment Division SB 32-1142 (22 Oct 1996) or Dunlop Aviation Australia Service Bulletin 36-24 (21 May 1984). It addresses loss of damping caused by silicon-oil leakage past an O‑ring, which can speed gear extension and risk broken lockstruts.\n\nAircraft operators must arrange the modification at the next repair/overhaul or within 4000 flight hours or 24 months, whichever is earlier; operators bear the compliance cost."},"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-f27-142-amdt-1-main-landing-gear-actuating-ram","history":"/api/acts/ad-f27-142-amdt-1-main-landing-gear-actuating-ram/history","analysis":"/api/acts/ad-f27-142-amdt-1-main-landing-gear-actuating-ram/analysis","conflicts":"/api/acts/ad-f27-142-amdt-1-main-landing-gear-actuating-ram/conflicts","importantCases":"/api/acts/ad-f27-142-amdt-1-main-landing-gear-actuating-ram/important-cases","documents":"/api/acts/ad-f27-142-amdt-1-main-landing-gear-actuating-ram/documents"}}