AD 47-50-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-51 | Airworthiness Directives; Sikorsky Model S-51 Helicopters |
Unsafe Condition
Failure of vertical hinge pins and bearings due to wear or damage could result in loss of main rotor control.
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Required Actions
Disassemble and inspect vertical hinge pins and bearings at each 200-hour inspection period. Replace Torrington No. 4479 bearings at each inspection. Inspect Smith 14TR-X1 bearings and replace only if wear or damage is found. Owners may rework to use Smith bearings instead of Torrington.
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Compliance Time
at each 200-hour inspection period
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Affected Aircraft
Sikorsky Model S-51 Helicopters using Torrington No. 4479 or Smith 14TR-X1 bearings at vertical hinge pins.
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Federal Register Abstract
Vertical Hinge Pins
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_47-50-08.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-50-08 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model S-51 Helicopters Subject: Vertical Hinge Pins Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Sikorsky Aircraft Corporation Model: S-51 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 47-50-08 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-50-08 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model S-51 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-50-08 SIKORSKY: Applies to Model S-51 Helicopters. Compliance required at each 200-hour inspection period. Disassembly and inspection of the vertical hinge pins and bearings is a mandatory procedure and should be accomplished at each 200-hour inspection period. The helicopters which utilize Torrington No. 4479 bearings at the vertical hinge pins are subject to replacement of these bearings at each 200-hour inspection period. The procedure followed is explained on page 4 of Sikorsky Service Bulletin No. 7 dated August 4, 1947. Helicopters which utilize Smith 14TR-X1 bearings at the vertical hinge pins are subject to inspection at each 200-hour interval and replacement of the bearings is not required unless the installation shows sign of serious wear or damage. Helicopters which utilize Torrington No. 4479 bearings at the vertical hinge pins can be reworked to incorporate Smith 14TR-X1 bearings at the vertical hinge pins if desired by the owner. (The procedure to follow for this exchange of bearings is as explained on page 2 of Sikorsky Service Bulletin No. 7 dated August 4, 1947.) FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_47-50-08.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-50-08 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model S-51 Helicopters Subject: Vertical Hinge Pins Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Sikorsky Aircraft Corporation Model: S-51 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 47-50-08 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-50-08 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model S-51 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-50-08 SIKORSKY: Applies to Model S-51 Helicopters. Compliance required at each 200-hour inspection period. Disassembly and inspection of the vertical hinge pins and bearings is a mandatory procedure and should be accomplished at each 200-hour inspection period. The helicopters which utilize Torrington No. 4479 bearings at the vertical hinge pins are subject to replacement of these bearings at each 200-hour inspection period. The procedure followed is explained on page 4 of Sikorsky Service Bulletin No. 7 dated August 4, 1947. Helicopters which utilize Smith 14TR-X1 bearings at the vertical hinge pins are subject to inspection at each 200-hour interval and replacement of the bearings is not required unless the installation shows sign of serious wear or damage. Helicopters which utilize Torrington No. 4479 bearings at the vertical hinge pins can be reworked to incorporate Smith 14TR-X1 bearings at the vertical hinge pins if desired by the owner. (The procedure to follow for this exchange of bearings is as explained on page 2 of Sikorsky Service Bulletin No. 7 dated August 4, 1947.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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