AD 71-21-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-61A | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61D | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61E | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61L | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61N | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61NM | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61R | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61V | Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters |
Unsafe Condition
Fracture of the servo valve input linkage causing a hardover in the auxiliary servo system.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install a secondary link in the servo valve input linkage within the next 50 hours' time in service following the effective date, in accordance with Sikorsky Service Bulletin No. 61B65-6A or approved equivalent. Also install secondary links on all spare units prior to their installation on the aircraft.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
within the next 50 hours' time in service after the effective date of this AD
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Model S-61A, S-61D, S-61E, S-61L, S-61N, S-61NM, S-61R, S-61V helicopters certified in all categories.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Link in Servo Valve Input Linkage
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_71-21-03.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 71-21-03 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters Subject: Link in Servo Valve Input Linkage Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 10/07/1971 Make: Sikorsky Aircraft Corporation Model: S-61A | S-61D | S-61E | S-61L | S-61N | S-61NM | S-61R | S-61V 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: 71-21-03 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-1303 AD NUMBER: 71-21-03 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters ACTION: SUMMARY: DATES: Effective October 7, 1971. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 71-21-03 SIKORSKY: Amdt. 39-1303. Applies to all S-61 Type Helicopters certified in all categories. Compliance required as indicated. To prevent a hardover in the auxiliary servo system, as the result of fracture of the servo valve input linkage, accomplish the following: a. Within the next 50 hours' time in service after the effective date of this AD, unless already accomplished, install a secondary link in the servo valve input linkage in accordance with Section 2, paragraphs A., B., C., and G., of Sikorsky Service Bulletin No. 61B65-6A, dated 1 July 1971, or later approved revisions or an equivalent installation, both approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. b. Install secondary links per paragraph (a) on all spare units, prior to installation on the aircraft. This amendment is effective October 7, 1971. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_71-21-03.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 71-21-03 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters Subject: Link in Servo Valve Input Linkage Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 10/07/1971 Make: Sikorsky Aircraft Corporation Model: S-61A | S-61D | S-61E | S-61L | S-61N | S-61NM | S-61R | S-61V 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: 71-21-03 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-1303 AD NUMBER: 71-21-03 SUBJECT HEADING: Airworthiness Directives; Sikorsky Model All S-61 Type Helicopters ACTION: SUMMARY: DATES: Effective October 7, 1971. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 71-21-03 SIKORSKY: Amdt. 39-1303. Applies to all S-61 Type Helicopters certified in all categories. Compliance required as indicated. To prevent a hardover in the auxiliary servo system, as the result of fracture of the servo valve input linkage, accomplish the following: a. Within the next 50 hours' time in service after the effective date of this AD, unless already accomplished, install a secondary link in the servo valve input linkage in accordance with Section 2, paragraphs A., B., C., and G., of Sikorsky Service Bulletin No. 61B65-6A, dated 1 July 1971, or later approved revisions or an equivalent installation, both approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. b. Install secondary links per paragraph (a) on all spare units, prior to installation on the aircraft. This amendment is effective October 7, 1971. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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