AD 47-21-09
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sierra Hotel Aero, Inc. | Navion (Army L-17A) | Airworthiness Directives; Navion All Serials Up to and Including Number NAV-4-947 |
Unsafe Condition
Malfunctioning of the hydraulic system resulting in failure of components including actuating cylinders.
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Required Actions
Rework the hydraulic power system to install manually controlled relief valve North American P/N 145-58027 and replace existing placard with 'Hyd. Power On'; install swivel head type nose gear actuating cylinder North American P/N 145-58014; visually inspect all flap and landing gear actuating cylinders for cracks or damage and replace damaged cylinders.
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Compliance Time
prior to September 1, 1947
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Affected Aircraft
Navion All Serials Up to and Including Number NAV-4-947
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Federal Register Abstract
Hydraulic System Modifications
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_47-21-09.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-21-09 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Navion All Serials Up to and Including Number NAV-4-947 Subject: Hydraulic System Modifications Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Sierra Hotel Aero, Inc. Model: Navion (Army L-17A) Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 47-21-09 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-21-09 SUBJECT HEADING: Airworthiness Directives; Navion All Serials Up to and Including Number NAV-4-947 ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-21-09 NAVION: (Was Mandatory Note 8 of AD-782-3.) Applies to All Serials Up to and Including Number NAV-4-947. Compliance required prior to September 1, 1947. Due to malfunctioning of the hydraulic system which has resulted in the failure of components of that system, including actuating cylinders, the following modifications must be accomplished: (a) If an engine-driven hydraulic pump is installed in the airplane, rework the hydraulic power system to install the manually controlled relief valve, North American P/N 145- 58027, and replace the existing placard "Hyd. System Pull Off" with new placard "Hyd. Power On". (North American Field Service Bulletin No. 26 covers this same subject.) (b) Install the swivel head type nose gear actuating cylinder, North American P/N 145-58014. (North American Field Service Bulletin No. 19 covers this same subject.) (c) Visually inspect all flap and landing gear actuating cylinders for evidence of cracks or other damage. Any cylinders found to be damaged should be replaced. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_47-21-09.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-21-09 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Navion All Serials Up to and Including Number NAV-4-947 Subject: Hydraulic System Modifications Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Sierra Hotel Aero, Inc. Model: Navion (Army L-17A) Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 47-21-09 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-21-09 SUBJECT HEADING: Airworthiness Directives; Navion All Serials Up to and Including Number NAV-4-947 ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-21-09 NAVION: (Was Mandatory Note 8 of AD-782-3.) Applies to All Serials Up to and Including Number NAV-4-947. Compliance required prior to September 1, 1947. Due to malfunctioning of the hydraulic system which has resulted in the failure of components of that system, including actuating cylinders, the following modifications must be accomplished: (a) If an engine-driven hydraulic pump is installed in the airplane, rework the hydraulic power system to install the manually controlled relief valve, North American P/N 145- 58027, and replace the existing placard "Hyd. System Pull Off" with new placard "Hyd. Power On". (North American Field Service Bulletin No. 26 covers this same subject.) (b) Install the swivel head type nose gear actuating cylinder, North American P/N 145-58014. (North American Field Service Bulletin No. 19 covers this same subject.) (c) Visually inspect all flap and landing gear actuating cylinders for evidence of cracks or other damage. Any cylinders found to be damaged should be replaced. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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Related Airworthiness Directives
2008-05-14 Recurring
final ruleAirworthiness Directives; 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 Airplanes
Unsafe Condition: Leaking or improperly operating fuel selector valves may disrupt fuel flow to the engine, leading to engine power loss.
68-20-06
final ruleAirworthiness Directives; Navion Models Navion through Navion H Airplanes
Unsafe Condition: Failure of the Rudder Horn, P/N 145-24401, due to horizontal cracks or corrosion in the edge, which may appear as delaminations or swelling under the paint.
62-03-03
final ruleAirworthiness Directives; Navion Models Navion, Navion A, Navion B, Navion D, Navion E, Navion F, and Navion G Aircraft
Unsafe Condition: The landing gear selector valve end fitting P/N 145-58145-3 (heat treated and non-heat treated) has a service history of failure during attempts to extend the gear.
47-31-03
final ruleAirworthiness Directives; Navion Serial Numbers NAV-4-2 Through NAV-4-1010 Which Incorporate Koehler Model 2250 Fuel Strainers
Unsafe Condition: Loss of fuel pressure due to air leakage into the fuel system through the CCA-1550-1/8 drain cock on the Koehler Model 2250 fuel strainer.
