AD 51-22-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-51 | Airworthiness Directives; Sikorsky Model S-51 Helicopters |
Unsafe Condition
Failures of Gear Shaft (Generator Drive-Tail Drive Transmission System) P/N S-10-35-1004 due to improper alignment of the taper pin hole relative to the splines and sharp radii at the intersection with the taper pin hole.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace all in-service gear shafts with jig-drilled shafts where the taper pin hole aligns squarely with the splines, and stone/polish to deburr and remove sharp radii at the intersection of the taper pin hole and splines.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
within the next 25 hours of operation, but not later than November 1, 1951
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Affected Aircraft
All Model S-51 Helicopters manufactured by Sikorsky Aircraft Corporation.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Gear Shaft Replacement
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_51-22-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-22-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model S-51 Helicopters Subject: Gear Shaft Replacement 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Date: Make: Sikorsky Aircraft Corporation Model: S-51 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 51-22-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-22-01 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model S-51 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-22-01 SIKORSKY: Applies to All Model S-51 Helicopters. Compliance required within the next 25 hours of operation, but not later than November 1, 1951. Due to the reported failures of Gear Shaft (Generator Drive-Tail Drive Transmission System) P/N S-10-35-1004, all shafts in service shall be replaced by shafts which have been jig drilled (i.e., the taper pin hole is located squarely with respect to the splines) and which have been stoned and polished to deburr and remove any sharp radii where the taper pin hole intersects the splines. (Sikorsky Service Information Circular No. 172, dated August 30, 1951, covers this same subject.) FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_51-22-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-22-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model S-51 Helicopters Subject: Gear Shaft Replacement 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: 51-22-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-22-01 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model S-51 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-22-01 SIKORSKY: Applies to All Model S-51 Helicopters. Compliance required within the next 25 hours of operation, but not later than November 1, 1951. Due to the reported failures of Gear Shaft (Generator Drive-Tail Drive Transmission System) P/N S-10-35-1004, all shafts in service shall be replaced by shafts which have been jig drilled (i.e., the taper pin hole is located squarely with respect to the splines) and which have been stoned and polished to deburr and remove any sharp radii where the taper pin hole intersects the splines. (Sikorsky Service Information Circular No. 172, dated August 30, 1951, covers this same subject.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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