AD 81-07-51 R1
final rule
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-76A | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters |
Unsafe Condition
Fracture of main rotor spindles, P/N 76102-08001-041 series, due to cracks or excessive diametrical clearance in spindle bearings, which could result in loss of main rotor control.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect main rotor spindles for cracks via fluorescent penetrant inspection and replace if cracks are found. Replace spindles exceeding 700 hours time in service. Inspect shear bearing inner/outer races for diametrical clearance exceeding 0.015 inches and replace spindles if necessary. Replace spindle/cuff assemblies with P/N 76102-08001-043 and specific preload bolts by December 15, 1981.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Prior to further flight, within the next 5 hours time in service after March 20, 1981, within the next 25 hours time in service after March 20, 1981, or before December 15, 1981, depending on specific requirements. Thereafter, at intervals not to exceed 350 hours time in service or upon removal/replacement of components.
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 Spindles
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_81-07-51_R.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 81-07-51 R1 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters Subject: Main Rotor Spindles Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 09/21/1981 Make: Sikorsky Aircraft Corporation Model: S-76A Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 81-07-51 R1 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-4211 AD NUMBER: 81-07-51 R1 SUBJECT HEADING: Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters ACTION: SUMMARY: DATES: Effective September 21, 1981. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 81-07-51 R1 SIKORSKY AIRCRAFT: Amendment 39-4130 as amended by Amendment 39-4211. Applies to S-76A series helicopters certificated in all categories. Compliance required as indicated. To prevent fracture of main rotor spindles, accomplish the following: 1. For main rotor spindles, P/N 76102-08001-041 series, with more than 200 hours time in service on March 20, 1981, compliance required prior to further flight, unless already accomplished within the last 100 hours time in service, and thereafter for all spindles upon removal and/or replacement of either the main rotor spindle, P/N 76102-08001-041 series, the spindle bearing inner race, P/Ns SB 5206-102/-103/-104, or the spindle bearing outer race, P/N SB 5206-202. Remove and fluorescent penetrant inspect main rotor spindles, P/N 76102-08001-041 series, for cracks in accordance with Sikrosky Alert Service Bulletin 76-65-13A, paragraph G(6), dated April 24, 1980, or later FAA approved revision. If a crack indication is found, replace the main rotor blade spindle with a new or serviceable main rotor blade spindle, prior to next flight, in accordance with Sikorsky S-76A Maintenance Manual, SA4047-76-2, Section 65-12-02. 2. Prior to further flight, remove from service all main rotor spindles, P/N 76102-08001-041 series, with 700 or more hours time in service, and replace with a serviceable spindle in accordance with the instructions contained in Chapter 65 of the Sikorsky S-76A Maintenance Manual, SA4047-76-2. 3. Thereafter, remove from service all spindles, P/N 76102-08001-041 series, upon accumulation of 700 hours time in service, and replace with a serviceable spindle in accordance with the instructions contained in Chapter 65 of the Sikorsky S-76A Maintenance Manual, SA4047-76-2. 4. For main rotor spindles, P/N 76102-08001-041 series, or spindle shear bearing inner races, P/N SB 5206-202, with more than 200 hours time in service on March 20, 1981, compliance required within the next 5 hours time in service after March 20, 1981, unless already accomplished, and thereafter for all spindles upon removal and/or replacement of either the main rotor spindle, P/N 76102-08001-041 series, the spindle bearing inner race, P/Ns SB 5206-102/-103/-104, or the spindle bearing outer race, P/N SB 5206-202. Inspect the shear bearing inner/outer races fob diametrical clearance, and replace the main rotor spindle if the diametrical clearance exceeds 0.015 inches, in accordance with Sikorsky Customer Service Bulletin No. 76-65-22B, paragraph G(2), dated May 1, 1981, or later FAA-approved revision. Spindles known to have operated with less than 10 hours time in service with diametrical clearances in excess of 0.015 inches may be returned to service. 5. For all main rotor spindles with more than 200 hours time in service on March 20, 1981, and on all other spindles before the accumulation of 225 hours time in service which do not have a record of Kahr bearings installed, compliance required within the next 25 hours time in service after March 20, 1981, unless already accomplished, and thereafter for all spindle/bearings at intervals not to exceed 350 hours time in service. Inspect for wear and vendor origin the main rotor spindle shear bearings outer race, P/N SB 5206-202, and inner race, P/Ns SB 5206-102/-103/-104, and replace, as necessary, in accordance with Sikorsky Customer Service Bulletin No. 76-65-22B, paragraphs G(4) and G(5), dated May 1, 1981, or later FAA-approved revision. 6. Aircraft may be ferried to a base for compliance with this AD in accordance with Section 21.197 of the Federal Aviation Regulations. 7. Upon request of the operator, an alternate means of compliance with the requirements of this AD may be approved by the Chief, Engineering and Manufacturing Branch, FAA, New England Region. 8. Report within 24 hours any discrepancies found and the spindle time in service to the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803. Reporting approved by the Office of Management and Budget under OMB No. 04-R0174. 9. Prior to December 15, 1981, remove from service all spindle/cuff assemblies, P/N 76102-08001-041, and replace with spindle/cuff assemblies, P/N 76102-08001-043, with spindle preload bolt P/N 76102-08051-103/-104 in accordance with Sikorsky Service Bulletin No. 76-65-24B, dated 8-17-81, or later FAA approved revision. Mandatory requirements for the inspection and replacement of the spindle/cuff assemblies and the shear bearings continue in effect for the P/N 76102-08001-043 assemblies and have been incorporated in Chapter 4 of the Sikorsky S-76A Maintenance Manual, SA 4047-76-2, Airworthiness Limitations Section. 10. Installation of P/N 76102-08001-043 spindle/cuff assemblies with the 76102-08051-103 or -104 spindle preload bolts terminates the requirements of AD 81-07-51. The manufacturer's specifications and procedures identified and described in this directive are incorporated 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. Amendment 39-4130 became effective June 11, 1981, as to all persons except those persons to whom it was made immediately effective by the telegram dated March 20, 1981. This amendment 39-4211 becomes effective September 21, 1981. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_81-07-51_R.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 81-07-51 R1 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters Subject: Main Rotor Spindles Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 09/21/1981 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: 81-07-51 R1 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-4211 AD NUMBER: 81-07-51 R1 SUBJECT HEADING: Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters ACTION: SUMMARY: DATES: Effective September 21, 1981. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 81-07-51 R1 SIKORSKY AIRCRAFT: Amendment 39-4130 as amended by Amendment 39-4211. Applies to S-76A series helicopters certificated in all categories. Compliance required as indicated. To prevent fracture of main rotor spindles, accomplish the following: 1. For main rotor spindles, P/N 76102-08001-041 series, with more than 200 hours time in service on March 20, 1981, compliance required prior to further flight, unless already accomplished within the last 100 hours time in service, and thereafter for all spindles upon removal and/or replacement of either the main rotor spindle, P/N 76102-08001-041 series, the spindle bearing inner race, P/Ns SB 5206-102/-103/-104, or the spindle bearing outer race, P/N SB 5206-202. Remove and fluorescent penetrant inspect main rotor spindles, P/N 76102-08001-041 series, for cracks in accordance with Sikrosky Alert Service Bulletin 76-65-13A, paragraph G(6), dated April 24, 1980, or later FAA approved revision. If a crack indication is found, replace the main rotor blade spindle with a new or serviceable main rotor blade spindle, prior to next flight, in accordance with Sikorsky S-76A Maintenance Manual, SA4047-76-2, Section 65-12-02. 2. Prior to further flight, remove from service all main rotor spindles, P/N 76102-08001-041 series, with 700 or more hours time in service, and replace with a serviceable spindle in accordance with the instructions contained in Chapter 65 of the Sikorsky S-76A Maintenance Manual, SA4047-76-2. 3. Thereafter, remove from service all spindles, P/N 76102-08001-041 series, upon accumulation of 700 hours time in service, and replace with a serviceable spindle in accordance with the instructions contained in Chapter 65 of the Sikorsky S-76A Maintenance Manual, SA4047-76-2. 4. For main rotor spindles, P/N 76102-08001-041 series, or spindle shear bearing inner races, P/N SB 5206-202, with more than 200 hours time in service on March 20, 1981, compliance required within the next 5 hours time in service after March 20, 1981, unless already accomplished, and thereafter for all spindles upon removal and/or replacement of either the main rotor spindle, P/N 76102-08001-041 series, the spindle bearing inner race, P/Ns SB 5206-102/-103/-104, or the spindle bearing outer race, P/N SB 5206-202. Inspect the shear bearing inner/outer races fob diametrical clearance, and replace the main rotor spindle if the diametrical clearance exceeds 0.015 inches, in accordance with Sikorsky Customer Service Bulletin No. 76-65-22B, paragraph G(2), dated May 1, 1981, or later FAA-approved revision. Spindles known to have operated with less than 10 hours time in service with diametrical clearances in excess of 0.015 inches may be returned to service. 5. For all main rotor spindles with more than 200 hours time in service on March 20, 1981, and on all other spindles before the accumulation of 225 hours time in service which do not have a record of Kahr bearings installed, compliance required within the next 25 hours time in service after March 20, 1981, unless already accomplished, and thereafter for all spindle/bearings at intervals not to exceed 350 hours time in service. Inspect for wear and vendor origin the main rotor spindle shear bearings outer race, P/N SB 5206-202, and inner race, P/Ns SB 5206-102/-103/-104, and replace, as necessary, in accordance with Sikorsky Customer Service Bulletin No. 76-65-22B, paragraphs G(4) and G(5), dated May 1, 1981, or later FAA-approved revision. 6. Aircraft may be ferried to a base for compliance with this AD in accordance with Section 21.197 of the Federal Aviation Regulations. 7. Upon request of the operator, an alternate means of compliance with the requirements of this AD may be approved by the Chief, Engineering and Manufacturing Branch, FAA, New England Region. 8. Report within 24 hours any discrepancies found and the spindle time in service to the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803. Reporting approved by the Office of Management and Budget under OMB No. 04-R0174. 9. Prior to December 15, 1981, remove from service all spindle/cuff assemblies, P/N 76102-08001-041, and replace with spindle/cuff assemblies, P/N 76102-08001-043, with spindle preload bolt P/N 76102-08051-103/-104 in accordance with Sikorsky Service Bulletin No. 76-65-24B, dated 8-17-81, or later FAA approved revision. Mandatory requirements for the inspection and replacement of the spindle/cuff assemblies and the shear bearings continue in effect for the P/N 76102-08001-043 assemblies and have been incorporated in Chapter 4 of the Sikorsky S-76A Maintenance Manual, SA 4047-76-2, Airworthiness Limitations Section. 10. Installation of P/N 76102-08001-043 spindle/cuff assemblies with the 76102-08051-103 or -104 spindle preload bolts terminates the requirements of AD 81-07-51. The manufacturer's specifications and procedures identified and described in this directive are incorporated 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. Amendment 39-4130 became effective June 11, 1981, as to all persons except those persons to whom it was made immediately effective by the telegram dated March 20, 1981. This amendment 39-4211 becomes effective September 21, 1981. FOOTER:
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Retrieved: Apr 8, 2026
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