AD 81-21-04

final rule

Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters

AD Number
81-21-04
Status
final_rule
Effective Date
Product Category
aircraft
Docket
Unknown
FR Citation
This information is not available.
Technical illustration of a helicopter rotor hub assembly
Problem area Rotor system

Applicability

TypeManufacturerModelDetails
aircraft Sikorsky Aircraft Corporation S-76A Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters

Unsafe Condition

Fatigue failures of the main rotor scissors assembly due to the use of P/Ns 76104-08020-044, -045, -046, and 76070-10005-042 main rotor rotating scissors assemblies.

AI-generated summary from the source AD text. Verify against the official source before acting.

Required Actions

Replace specified main rotor rotating scissors assemblies with serviceable parts before accumulating 500 hours time in service or within 25 hours after AD effective date, whichever is later. Conduct inspections within 50 hours after AD effective date (if not done in last 50 hours) and every 100 hours thereafter for hub/scissors bearings play/wear and scissors center pivot bolt fretting/scoring/corrosion pits per specified manuals.

AI-generated summary from the source AD text. Verify against the official source before acting.

Compliance Time

before further flight

AI-generated summary from the source AD text. Verify against the official source before acting.

Affected Aircraft

Sikorsky Aircraft Corporation Model S-76A series helicopters certificated in all categories.

AI-generated summary from the source AD text. Verify against the official source before acting.

Federal Register Abstract

Main Rotor Scissors Assembly

Applicability Source Text

Show captured applicability text from the source AD
AD Final Rules - DRS_81-21-04.html
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AD Number:
81-21-04
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters
Subject:
Main Rotor Scissors Assembly
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
10/08/1981
Make:
Sikorsky Aircraft Corporation
Model:
S-76A
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Superseded AD: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Superseded By: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: 81-21-04
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:   39-4228

AD NUMBER:   81-21-04

SUBJECT HEADING:   Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters

ACTION:  

SUMMARY:  

DATES:   Effective October 8, 1981.

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:  
81-21-04 SIKORSKY AIRCRAFT: Amendment 39-4228. Applies to S-76A series helicopters certificated in all categories.

To prevent fatigue failures of the main rotor scissors assembly:

1. Replace P/Ns 76104-08020-044, -045, and -046, and P/N 76070-10005-042 main rotor rotating scissors assemblies with a serviceable part prior to the accumulation of 500 hours time in service or within 25 hours time in service after the effective date of this AD, whichever occurs later.

2. Within the next 50 hours time in service after the effective date of this AD, unless already accomplished within the last 50 hours time in service, and thereafter at intervals not to exceed 100 hours from the last inspection, conduct inspections of the hub/scissors bearings for play and wear and the scissors center pivot bolt for fretting, scoring, and corrosion pits in accordance with Temporary Revision No. 5-24, dated September 8, 1981, or an FAA approved equivalent, Items 42A (Inspection Check 65-14-00, Page 207, dated February 16, 1980, including Temporary Revision No. 65-15, dated September 8, 1981, or an FAA approved equivalent) and 42B of the Sikorsky S-76A Maintenance Manual, 5A 4047-76-2.

NOTE: "FAA approved" means approved by the Chief, Engineering and Manufacturing Branch, New England Region.

The manufacturer's specifications and procedures identified and described herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Sikorsky Aircraft, Division of United Technologies Corporation, Stratford, Connecticut 06602. These documents may also be examined at FAA, New England Region, 12 New England Executive Park, Burlington, Massachusetts, and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C.

This amendment becomes effective October 8, 1981.

FOOTER:

Document Text

Show stored source text (verify against official source)
AD Final Rules - DRS_81-21-04.html
Copy URL
Print/Save as PDF
Document Versions
 Feedback
Details
AD Number:
81-21-04
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters
Subject:
Main Rotor Scissors Assembly
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
10/08/1981
Make:
Sikorsky Aircraft Corporation
Model:
S-76A
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: 81-21-04
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:   39-4228

AD NUMBER:   81-21-04

SUBJECT HEADING:   Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters

ACTION:  

SUMMARY:  

DATES:   Effective October 8, 1981.

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:  
81-21-04 SIKORSKY AIRCRAFT: Amendment 39-4228. Applies to S-76A series helicopters certificated in all categories.

To prevent fatigue failures of the main rotor scissors assembly:

1. Replace P/Ns 76104-08020-044, -045, and -046, and P/N 76070-10005-042 main rotor rotating scissors assemblies with a serviceable part prior to the accumulation of 500 hours time in service or within 25 hours time in service after the effective date of this AD, whichever occurs later.

2. Within the next 50 hours time in service after the effective date of this AD, unless already accomplished within the last 50 hours time in service, and thereafter at intervals not to exceed 100 hours from the last inspection, conduct inspections of the hub/scissors bearings for play and wear and the scissors center pivot bolt for fretting, scoring, and corrosion pits in accordance with Temporary Revision No. 5-24, dated September 8, 1981, or an FAA approved equivalent, Items 42A (Inspection Check 65-14-00, Page 207, dated February 16, 1980, including Temporary Revision No. 65-15, dated September 8, 1981, or an FAA approved equivalent) and 42B of the Sikorsky S-76A Maintenance Manual, 5A 4047-76-2.

NOTE: "FAA approved" means approved by the Chief, Engineering and Manufacturing Branch, New England Region.

The manufacturer's specifications and procedures identified and described herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Sikorsky Aircraft, Division of United Technologies Corporation, Stratford, Connecticut 06602. These documents may also be examined at FAA, New England Region, 12 New England Executive Park, Burlington, Massachusetts, and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C.

This amendment becomes effective October 8, 1981.

FOOTER:

Source: Official FAA Source ↗

Retrieved: Apr 8, 2026

Rights: U.S. Government Public Domain

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