{"id":"F2006L04101","name":"AD/S-92/3 - Main Gearbox Upper Housing","slug":"ad-s-92-3-main-gearbox-upper-housing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":61032,"registerId":"commonwealth-F2006L04101-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Sikorsky S-92 Series Helicopters","sectionType":"division","heading":"Sikorsky S-92 Series Helicopters","content":"### Sikorsky S-92 Series Helicopters\n\n| AD/S-92/3 | Main Gearbox Upper Housing | 2/2007 TX |\n| --------- | -------------------------- | --------- |\n\n| Applicability: | Sikorsky Model S-92A helicopter, with main gearbox (MGB) upper main housing assembly (housing assembly), part number 92351-15110-042, installed.                                                                        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---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Replace each MGB housing with 2700 or more hours time-in-service (TIS) with an airworthy MGB housing with less than 2700 hours TIS.Revise the Airworthiness Limitations section of the maintenance manual by establishing a new retirement life for the MGB housing assembly of 2700 hours TIS.Note: FAA AD 2006-15-19 Amdt 39-14700 dated 26 July 2006 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                        |\n| Compliance:    | Before further flight.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n|                | This Airworthiness Directive becomes effective on 18 December 2006.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n| Background:    | This action requires, before further flight, replacing a certain MGB upper main housing assembly (housing assembly) that has 2700 or more hours time-in-service (TIS) with an airworthy part. This action also requires, before further flight, revising the Airworthiness Limitations section (ALS) of the maintenance manual by establishing a new retirement life for the MGB housing assembly of 2700 hours TIS. This amendment is prompted by testing of the MGB housing assembly that resulted in premature fatigue failure due to a manufacturing process creating an oxide skin defect in the housing. The actions specified in this AD are intended to prevent fatigue failure of the MGB housing, loss of MGB lube oil, loss of main and tail rotor drive, and subsequent loss of control of the helicopter. |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n13 December 2006","sortOrder":0},{"sectionNumber":"AD/S-92/3","sectionType":"part","heading":"AD/S-92/3","content":"## AD/S-92/3","sortOrder":1},{"sectionNumber":"Main Gearbox Upper Housing","sectionType":"part","heading":"Main Gearbox Upper Housing","content":"## Main Gearbox Upper Housing","sortOrder":2},{"sectionNumber":"2/2007 TX","sectionType":"part","heading":"2/2007 TX","content":"## 2/2007 TX","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive is a targeted corrective action addressing a specific manufacturing defect in a particular MGB housing part. It does not expand scope beyond that original safety purpose: it mandates replacement for housings at or above 2,700 hours and establishes a 2,700‑hour retirement life going forward. The instrument remains narrowly focused on preventing the cited fatigue failure and does not introduce additional regulatory areas, broad obligations, or new categories of affected equipment."},"complexity_factors":["Single, specific applicability: one helicopter model (Sikorsky S‑92A) with one specific part number (92351‑15110‑042).","Single numeric threshold: one hours‑in‑service limit (2,700 TIS) determining action and retirement life.","One mandatory action type: replacement of the part (no alternative inspections or options allowed).","Immediate compliance required ('before further flight'), creating straightforward but urgent implementation.","Short text with limited cross‑references (only a note referencing FAA AD 2006‑15‑19).","Administrative requirement to revise maintenance manual (Airworthiness Limitations section) but no layered exceptions or nested conditions."],"plain_english_summary":"**What this instrument does (mechanically)\n\n- Requires immediate removal from service of a specific main gearbox (MGB) upper housing assembly installed on Sikorsky S‑92A helicopters if that housing has accumulated 2,700 or more hours time‑in‑service (TIS). Those housings must be replaced with an \"airworthy\" (legally serviceable) housing that has less than 2,700 hours TIS. (Applicability & Requirement)\n- Requires the helicopter maintenance manual's Airworthiness Limitations section to be updated to set a retirement life of 2,700 hours TIS for that MGB upper housing assembly, so no such housing may be used beyond 2,700 hours. (Requirement)\n- Requires compliance before further flight (i.e. affected helicopters cannot fly until the housing is replaced and the manual revised). (Compliance)\n\nWho is affected\n\n- Operators and owners of Sikorsky Model S‑92A helicopters that have the specific MGB upper main housing assembly with part number 92351‑15110‑042 installed. (Applicability)\n- Maintenance organisations and engineers who perform maintenance, control component parts, or update the maintenance manuals for those helicopters.\n\nWhy it matters (stated reason and operational effect)\n\n- The directive was prompted by test evidence that the specified MGB housing can fail prematurely because of a manufacturing oxide‑skin defect that causes fatigue cracking. (Background)\n- The mechanical intent is to prevent fatigue failure of the housing, which could lead to loss of gearbox lubrication, loss of main and tail rotor drive, and consequent loss of helicopter control. (Background)\n\nOperational and economic mechanics (who pays, who decides, what changes)\n\n- Who pays: the operator/owner of the affected helicopter pays for sourcing and fitting the replacement MGB housing and for the downtime while the work is carried out. (Requirement; Compliance)\n- Who decides: the regulator (Civil Aviation Safety Authority via this directive) mandates the action; maintenance providers and the operator implement it and update the maintenance manual. The replacement part must be \"airworthy\" under the relevant airworthiness rules. (Applicability; Requirement)\n- What behavior changes: affected operators must (a) remove and replace any specified housing that is at or above 2,700 TIS before the aircraft flies again, and (b) retire all such housings at 2,700 TIS going forward. This shortens the permitted service life of that part and forces earlier replacement than some operators may have planned. (Requirement)\n\nImplementation trade‑offs, risks and likely secondary effects\n\n- Compliance cost and downtime: immediate grounding of helicopters with the affected housing at or over 2,700 TIS imposes direct costs (replacement parts, labour, lost flight time). (Compliance)\n- Spare‑parts availability and market effects: demand for housings with less than 2,700 hours will rise; that can increase procurement pressure and prices for operators needing replacements quickly. (Requirement)\n- No inspection alternative: the directive mandates replacement rather than permitting a repetitive inspection regime; that eliminates a lower‑cost compliance route and concentrates cost on replacement. (Requirement)\n- Safety benefit vs. economic cost: the action directly reduces the risk of the identified fatigue failure mode by removing suspect housings or retiring them earlier. The directive trades operator cost and operational disruption for reduced risk of catastrophic mechanical failure. (Background)\n- Administrative burden: maintenance manuals must be revised to record the new retirement life; maintenance organisations must track part hours to enforce retirement. (Requirement)\n\nSource attribution and cross‑reference\n\n- The directive references FAA AD 2006‑15‑19, indicating harmonisation with a foreign regulator's action on the same defect. (Requirement/Note)\n\nSummary statement\n\nThis airworthiness directive imposes an immediate, mandatory replacement and a new 2,700‑hour retirement life for a specifically‑identified MGB upper housing on Sikorsky S‑92A helicopters because of an identified manufacturing defect that can cause premature fatigue failure. The regulator requires replacement before further flight for housings at or above 2,700 hours, and a maintenance‑manual update to retire housings at 2,700 hours thereafter. The operator bears the direct costs and operational disruption; the directive eliminates inspection alternatives and increases demand for compliant spare housings."},"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 single aircraft component. The scope remains precisely limited to the identified safety risk without expansion into broader operational or maintenance requirements."},"complexity_factors":["Single, clearly defined applicability criterion (one helicopter model, one specific part number)","Two straightforward compliance requirements with no conditional branches or exceptions","Single, unambiguous compliance deadline ('before further flight')","No defined terms section or interpretive provisions","No cross-references to other legislation (only a non-binding note referencing the related FAA directive)","Short document length (approximately 250 words of substantive content)"],"plain_english_summary":"This AD requires owners/operators of Sikorsky S‑92A helicopters fitted with main gearbox upper housing P/N 92351‑15110‑042 to replace any housing with 2,700+ flight hours and to amend the maintenance manual to set a 2,700‑hour retirement life for that part. It responds to an oxide‑skin manufacturing defect that can cause housing cracking, loss of gearbox oil pressure and power, and potential loss of control. Aircraft cannot fly until both actions are done."}},"importantCases":[],"_links":{"self":"/api/acts/ad-s-92-3-main-gearbox-upper-housing","history":"/api/acts/ad-s-92-3-main-gearbox-upper-housing/history","analysis":"/api/acts/ad-s-92-3-main-gearbox-upper-housing/analysis","conflicts":"/api/acts/ad-s-92-3-main-gearbox-upper-housing/conflicts","importantCases":"/api/acts/ad-s-92-3-main-gearbox-upper-housing/important-cases","documents":"/api/acts/ad-s-92-3-main-gearbox-upper-housing/documents"}}