AD 56-17-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Hartzell Propeller, Inc. | HC-12X20-1 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-2 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-3 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-4 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-5 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-6 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-7 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-8 | HARTZELL Model HC-12X20 Reversing Propellers |
| engine | Hartzell Propeller, Inc. | HC-12X20-9 | HARTZELL Model HC-12X20 Reversing Propellers |
Unsafe Condition
Failure of the valve tube A-57 due to vibration and weakening effect of the valve porthole, which could allow the propeller to go into reverse under certain conditions, forcing the airplane to land.
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Required Actions
Disassemble the valve assembly and inspect the A-57 valve tube around the valve port with a magnifying glass or magnetic inspection equipment. If no cracks are found, round the sharp edges at the sides of the porthole using a fine round file.
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Compliance Time
as soon as possible but not later than next 25 hours of operation and each 100 hours flight time thereafter
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Affected Aircraft
Hartzell Propeller, Inc. Model HC-12X20 Reversing Propellers installed on Downer (Republic) RC-3 Aircraft with B-55 Valve Assembly
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Federal Register Abstract
Valve Tube
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_56-17-03.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 56-17-03 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: HARTZELL Model HC-12X20 Reversing Propellers Subject: Valve Tube Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Hartzell Propeller, Inc. Model: HC-12X20-1 | HC-12X20-2 | HC-12X20-3 | HC-12X20-4 | HC-12X20-5 | HC-12X20-6 | HC-12X20-7 | HC-12X20-...Show more Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 56-17-03 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 56-17-03 SUBJECT HEADING: HARTZELL Model HC-12X20 Reversing Propellers ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 56-17-03 HARTZELL: Applies to All Model HC-12X20 Reversing Propellers Installed on Downer (Republic) RC-3 Aircraft Having B-55 Valve Assembly. Compliance required as soon as possible but not later than next 25 hours of operation and each 100 hours flight time thereafter. There have been two reported instances of broken valve tube A-57. These failures were due to vibration of the valve assembly and the weakening effect of the valve porthole. Failure of this part will allow the propeller to go into reverse under certain conditions, forcing the airplane to land. In view of the possible serious consequences resulting from inadvertent reversal of the propeller, disassemble the valve and inspect the A-57 valve tube around the valve port with a magnifying glass or with magnetic inspection equipment. If no cracks are found, the sharp edges at the sides of the porthole should be rounded slightly, using a fine round file. This inspection is not required for valve assembly B-299. (Hartzell Service Bulletin No. 38 dated June 16, 1956, covers the same subject.) FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_56-17-03.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 56-17-03 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: HARTZELL Model HC-12X20 Reversing Propellers Subject: Valve Tube Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Hartzell Propeller, Inc. Model: HC-12X20-1 | HC-12X20-2 | HC-12X20-3 | HC-12X20-4 | HC-12X20-5 | HC-12X20-6 | HC-12X20-7 | HC-12X20-...Show more Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 56-17-03 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 56-17-03 SUBJECT HEADING: HARTZELL Model HC-12X20 Reversing Propellers ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 56-17-03 HARTZELL: Applies to All Model HC-12X20 Reversing Propellers Installed on Downer (Republic) RC-3 Aircraft Having B-55 Valve Assembly. Compliance required as soon as possible but not later than next 25 hours of operation and each 100 hours flight time thereafter. There have been two reported instances of broken valve tube A-57. These failures were due to vibration of the valve assembly and the weakening effect of the valve porthole. Failure of this part will allow the propeller to go into reverse under certain conditions, forcing the airplane to land. In view of the possible serious consequences resulting from inadvertent reversal of the propeller, disassemble the valve and inspect the A-57 valve tube around the valve port with a magnifying glass or with magnetic inspection equipment. If no cracks are found, the sharp edges at the sides of the porthole should be rounded slightly, using a fine round file. This inspection is not required for valve assembly B-299. (Hartzell Service Bulletin No. 38 dated June 16, 1956, covers the same subject.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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