{"id":"F2008L02879","name":"AD/NAV/4 - Fuel System Selector Valves","slug":"ad-nav-4-fuel-system-selector-valves","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74763,"registerId":"commonwealth-F2008L02879-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Navion Series Aeroplanes","sectionType":"division","heading":"Navion Series Aeroplanes","content":"### Navion Series Aeroplanes\n\n| AD/NAV/4 | Fuel System Selector Valves | 9/2008 |\n| -------- | --------------------------- | ------ |\n\n| Applicability: | Sierra Hotel Aero, Inc. Models Navion (L-17A), Navion A (L-17B), (L-17C), Navion B, Navion D, Navion E, Navion F, Navion G, and Navion H aeroplanes. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement: | 1. Do a one-time inspection of the entire fuel system in accordance with Sierra Hotel Aero, Inc. Navion Service Bulletin (SB) No. 106A, dated 1 May 2007; or American Navion Society, Ltd. Field SB No. 1001, dated 30 April 2007.2. Unless within the last 5 years the fuel selector valve has been replaced with one of the valves specified in Requirement 3 of this AD. Do inspection and functional tests of the fuel selector valves.If using Sierra Hotel Aero, Inc. service information, an allowance may be made for a 1 inch of mercury reduction from the 24 inches of mercury standard for every 1000 feet of altitude over sea level testing conditions in accordance with Sierra Hotel Aero, Inc. Navion SB No. 106A, or American Navion Society, Ltd. Field SB No. 1001.3. If there are any defects discovered during any of the inspections or tests detailed in Requirement 1 or 2 of this AD, perform any corrective actions required including replacing the fuel selector valve with one of the Part Numbers (P/N) listed below.For replacement with Navion P/Ns 147-30013-201, 147-30013-202, or147-30013-203 fuel selector valves use the following service information:Sierra Hotel Aero, Inc. Navion Service Bulletin No. 106A, dated1 May 2007.Sierra Hotel Aero, Inc. Navion Service Bulletin No. 101A, dated23 August 2005.Navion Aircraft Corporation Navion Service letter # 87, dated20 February 1965.Where replacement with Navion P/Ns 145-48000-ANSI, 145-48000-ANS2,145-48000-ANS3, or Osborne Tank Co. P/N 4090 fuel selector valves is used, the valve installation will require exclusion application to CASA detailing aCAR 35 proposed installation procedure before approval for fitment can be granted. |\n| | Terminating ActionIf within the last 5 years or at any time after the effective date of this AD the fuel selector valve has been replaced with any of the valves specified in Requirement 3 of this AD the repetitive inspections and functional tests of the fuel selector valve detailed in Requirement 2 of this AD may be terminated.Note: FAA AD 2008-05-14 Amdt 39-15408 dated 28 February 2008 refers. |\n| Compliance: | For Requirement 1:Within the next 100 hours time-in-service (TIS) after the effective date of this AD or within the next 12 months after the effective date of this AD, whichever occurs first.For Requirement 2:Initially within the next 100 hours time-in-service (TIS) after the effective date of this AD or within the next 12 months after the effective date of this AD, whichever occurs first. Repetitively thereafter at intervals not to exceed 12 months until the replacement as detailed in Requirement 3 of this AD is accomplished.For Requirement 3:Before further flight. |\n| | This Airworthiness Directive becomes effective on 28 August 2008. |\n| Background: | The FAA has received reports from aeroplane accidents associated with leaking or improperly operating fuel system selector valves. The issuing of this AD is to detect and correct fuel system leaks or improperly operating fuel selector valves, which could result in the disruption of fuel flow to the engine. This failure could lead to engine power loss. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n16 July 2008","sortOrder":0},{"sectionNumber":"AD/NAV/4","sectionType":"part","heading":"AD/NAV/4","content":"## AD/NAV/4","sortOrder":1},{"sectionNumber":"Fuel System Selector Valves","sectionType":"part","heading":"Fuel System Selector Valves","content":"## Fuel System Selector Valves","sortOrder":2},{"sectionNumber":"9/2008","sectionType":"part","heading":"9/2008","content":"## 9/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"The directive remains focused on detecting and correcting leaking or malfunctioning fuel selector valves in the listed Navion aircraft (Background; Applicability). It does not broaden the set of affected aircraft but prescribes specific inspection frequencies, acceptable replacement part numbers, and an approval path for certain valves—i.e. it changes compliance mechanics (tests, replacement and administrative approvals) rather than the underlying scope of affected aeroplanes."},"complexity_factors":["Applicability covers multiple Navion variants, increasing affected-operator diversity (Applicability).","Multiple external service documents referenced (Sierra Hotel Aero SB No.106A, American Navion Society Field SB No.1001, others) creating coordination and interpretation burden (Requirement 1, Requirement 3).","Two-tier inspection regime: one-time full-system inspection plus initial and then annual functional tests until replacement—ongoing compliance tracking required (Requirement 1, Requirement 2; Compliance).","Termination condition depends on replacement with specified P/Ns within the last 5 years, adding record-keeping and retrospective proof obligations (Terminating Action).","Replacement parts list includes different P/Ns with distinct approval paths; some replacements require an exclusion application to CASA and CAR 35 procedure before fitment, adding administrative steps and potential delays (Requirement 3).","Immediate corrective-action requirement (‘before further flight’) for discovered defects imposes operational interruption and potential cost (Requirement 3; Compliance).","Altitude-based allowance for pressure-test readings (1 inHg per 1000 ft) adds technical adjustment to testing protocol (Requirement 2).","Cross-reference to FAA AD introduces inter-jurisdictional compliance considerations for operators using FAA material (Note).","Fixed short compliance windows (next 100 hours TIS or 12 months) increase near-term workload for operators (Compliance)."],"plain_english_summary":"Requires a one-time inspection of the entire fuel system and annual functional tests of the fuel selector valves on specified Navion models; defective valves must be corrected and replaced with listed part numbers or otherwise approved components. Owners/operators pay for inspections, testing and any replacements; CASA must approve some valve installations. The measure is intended to detect and fix leaking or improperly operating selector valves that can disrupt fuel flow and cause engine power loss."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains focused scope on fuel system safety for Navion aircraft. The original intent was to address fuel selector valve failures reported by the FAA, and the directive remains tightly constrained to that specific safety issue without expanding into unrelated aircraft systems."},"complexity_factors":["Multiple alternative compliance paths (Sierra Hotel Aero SB vs American Navion Society Field SB)","Nested conditional logic: Requirement 2 applies 'unless' valve replaced within last 5 years; Requirement 3 triggered 'if' defects found; Terminating action applies 'if' valve replaced","Specific part number references (8 different P/Ns across two manufacturers) with different installation requirements","Cross-reference to FAA AD 2008-05-14 and multiple service bulletins/letters","Altitude-adjusted testing standard (1 inch mercury reduction per 1000 feet) requiring calculation","Dual compliance timeframes (100 hours TIS OR 12 months, whichever first) for Requirements 1 and 2","CAR 35 procedural requirement for certain valve replacements (exclusion application to CASA)"],"plain_english_summary":"CASA requires owners/operators of Sierra Hotel Aero Navion aircraft (L‑17 variants and models B–H) to inspect the fuel system and fuel selector valves, replace faulty valves with approved parts, and continue annual functional tests until an approved replacement is fitted. The AD addresses leaking or malfunctioning selector valves that can cause fuel starvation and engine failure; initial inspection is due within 100 flight hours or 12 months and defects must be fixed before the next flight."},"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-nav-4-fuel-system-selector-valves","history":"/api/acts/ad-nav-4-fuel-system-selector-valves/history","analysis":"/api/acts/ad-nav-4-fuel-system-selector-valves/analysis","conflicts":"/api/acts/ad-nav-4-fuel-system-selector-valves/conflicts","importantCases":"/api/acts/ad-nav-4-fuel-system-selector-valves/important-cases","documents":"/api/acts/ad-nav-4-fuel-system-selector-valves/documents"}}