AD 51-23-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-51 | Airworthiness Directives; Sikorsky Model S-51 Helicopters |
Unsafe Condition
Main rotor link assemblies (P/N S510348) with identification stamp 'F' in critical areas or exceeding 960 flight hours may fail, leading to loss of rotor control.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect main rotor link assemblies (P/N S510348) for 'F' stamp location and flight time. Retire links with 'F' stamped on inner faces of ears or exceeding 960 flight hours. Polish noncritical 'F' stamps and return to service.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
prior to next flight
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
All Sikorsky Model S-51 Helicopters with main rotor link assemblies (P/N S510348) received from the manufacturer between June 1 and September 6, inclusive.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Rotor Link Assemblies
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_51-23-04.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-23-04 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model S-51 Helicopters Subject: Rotor Link Assemblies 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Date: Make: Sikorsky Aircraft Corporation Model: S-51 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 51-23-04 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-23-04 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model S-51 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-23-04 SIKORSKY: Applies to All Model S-51 Helicopters. Compliance required as indicated. 1. Compliance required prior to next flight. Inspect all main rotor link assemblies (P/N S510348) received from the manufacturer between June 1 and September 6, inclusive for location of the identification stamp "F". Links with the "F" metal-stamped in the critical area on the inner faces of the ears should be retired from service. Those with the "F" stamped on the outer faces or on noncritical areas of the inner faces of the ears should be polished locally with emery and crocus cloth to remove the "F" and the links may be returned to service. (See Figure 6.) AD 51-23-04 (Sikorsky Information Circular No. 175, dated September 7, 1951, covers this same subject.) 2. Main rotor link assemblies (P/N S510348) shall be retired from service when a total flight time of 960 hours on the links has been accumulated. (Sikorsky Information Circular No. 122, Revision B, dated September 10, 1951, covers this same subject.) FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_51-23-04.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-23-04 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model S-51 Helicopters Subject: Rotor Link Assemblies 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: 51-23-04 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-23-04 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model S-51 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-23-04 SIKORSKY: Applies to All Model S-51 Helicopters. Compliance required as indicated. 1. Compliance required prior to next flight. Inspect all main rotor link assemblies (P/N S510348) received from the manufacturer between June 1 and September 6, inclusive for location of the identification stamp "F". Links with the "F" metal-stamped in the critical area on the inner faces of the ears should be retired from service. Those with the "F" stamped on the outer faces or on noncritical areas of the inner faces of the ears should be polished locally with emery and crocus cloth to remove the "F" and the links may be returned to service. (See Figure 6.) AD 51-23-04 (Sikorsky Information Circular No. 175, dated September 7, 1951, covers this same subject.) 2. Main rotor link assemblies (P/N S510348) shall be retired from service when a total flight time of 960 hours on the links has been accumulated. (Sikorsky Information Circular No. 122, Revision B, dated September 10, 1951, covers this same subject.) 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
2023-11-07
final ruleAirworthiness Directives; Various Helicopters
Unsafe Condition: unsafe condition on these products.
67-29-06
final ruleAirworthiness Directives; Sikorsky Model S-51 Helicopters
Unsafe Condition: Failure of sleeve and tube assembly P/N S535180 could lead to loss of tail rotor power.
50-08-01
final ruleAirworthiness Directives; Sikorsky Model S-51 Helicopters
Unsafe Condition: Cracks in the upper longerons of the S-10-20-3003 tail cone mounting assembly adjacent to the generator support plate, clamps, and welds.
56-16-03
final ruleAirworthiness Directives; Sikorsky Models S-55 and S-51 Helicopters
Unsafe Condition: Fine cuts on the spar beneath the edges of the pockets of main rotor blades, resulting from repairs to blade pockets, which act as serious stress raisers and may reduce blade service life.