AD 47-21-10
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sierra Hotel Aero, Inc. | Navion (Army L-17A) | Airworthiness Directives; Navion Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzell HC-12X20-1 Propellers. |
Unsafe Condition
The propeller control piston guide pins, Hartzell P/N A-11, may loosen and cause subsequent loss of engine oil.
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Required Actions
Install a 3/32-inch steel dowel through the guide pin to safety the propeller control piston guide pins.
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Compliance Time
not later than September 1, 1947
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Affected Aircraft
Sierra Hotel Aero, Inc. Navion (Army L-17A) serial numbers NAV-4-2 through HAV-4-1010 incorporating Hartzell HC-12X20-1 propellers.
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Federal Register Abstract
Propeller Guide Pin Dowel
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_47-21-10.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-21-10 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Navion Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzel...Show more Subject: Propeller Guide Pin Dowel 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Sierra Hotel Aero, Inc. Model: Navion (Army L-17A) Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 47-21-10 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-21-10 SUBJECT HEADING: Airworthiness Directives; Navion Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzell HC-12X20-1 Propellers. ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-21-10 NAVION: (Was Mandatory Note 9 of AD-782-3.) Applies to Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzell HC-12X20-1 Propellers. To be accomplished not later than September 1, 1947. The propeller control piston guide pins, Hartzell P/N A-11, require additional safetying in order to prevent loosening and subsequent loss of engine oil. This is accomplished by the installation of a 3/32-inch steel dowel through the guide pin. (NAA Field Service Bulletin No. 30 covers this rework.) FOOTER:
Document Text
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AD Final Rules - DRS_47-21-10.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-21-10 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Navion Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzel...Show more Subject: Propeller Guide Pin Dowel 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: 47-21-10 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-21-10 SUBJECT HEADING: Airworthiness Directives; Navion Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzell HC-12X20-1 Propellers. ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-21-10 NAVION: (Was Mandatory Note 9 of AD-782-3.) Applies to Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzell HC-12X20-1 Propellers. To be accomplished not later than September 1, 1947. The propeller control piston guide pins, Hartzell P/N A-11, require additional safetying in order to prevent loosening and subsequent loss of engine oil. This is accomplished by the installation of a 3/32-inch steel dowel through the guide pin. (NAA Field Service Bulletin No. 30 covers this rework.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.
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.
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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
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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.
