AD 56-21-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Scotts-Bell 47 Inc | 47G | Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-2 | Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47H-1 | Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters |
Unsafe Condition
Malfunctioning of the hydraulic boost cylinder in service has necessitated the replacement of the hydraulic boost power cylinder barrels and clamps in the fore and aft and lateral cyclic boost power cylinder units.
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Required Actions
Replace hydraulic boost power cylinder barrels and clamps with P/N 1097 and 1029 as per Bell's Mandatory Service Bulletin No. 114. Establish a service life limit of 100 hours for unmodified cylinders.
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Compliance Time
by the time 100 hours service is obtained, except barrels that have already accumulated 100 hours prior to the date of this directive may be used until 125 hours are obtained or until December 1, 1956, whichever occurs first
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Affected Aircraft
Bell Model 47G, 47G2, and 47H1 Helicopters except noted below and spare hydraulic boost power cylinders P/N 1090, 1190, and 1270 cylinders up to serial 733. Specific serial ranges: Model 47G (1530, 1687 and up); Model 47G2 (1494, 1505, 1506, 1508, 1617 and up); Model 47H1 (1534 and up).
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Federal Register Abstract
Hydraulic Boost Cylinders
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_56-21-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 56-21-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters Subject: Hydraulic Boost Cylinders Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Scotts-Bell 47 Inc Model: 47G | 47G-2 | 47H-1 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 56-21-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 56-21-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 56-21-01 BELL: Applies to All Models 47G, 47G2, and 47H1 Helicopters Except As Noted Below and All Spare Hydraulic Boost Power Cylinders Part Numbers 1090, 1190 and All 1270 Cylinders Prior to and Including Serial Number 733. Model 47G, Serial Numbers 1530 and 1687 and Up; Model 47G2, Serial Numbers 1494, 1505, 1506, 1508, 1617 and Up; and Model 47H1, Serial Numbers 1534 and Up Will be Modified Prior to Delivery. Compliance required as indicated. Malfunctioning of the hydraulic boost cylinder in service has necessitated the replacement of the hydraulic boost power cylinder barrels and clamps in the fore and aft and lateral cyclic boost power cylinder units and the establishment of a service life of 100 hours on the cylinders which have not been modified. These hydraulic boost cylinder barrels must be replaced by the time 100 hours service is obtained, except barrels that have already accumulated 100 hours service prior to the date of this directive may be used until 125 hours are obtained or until December 1, 1956, whichever occurs first. (Detail procedures for installation of cylinder barrel P/N 1097 and clamps P/N 1029 are contained in Bell's Mandatory Service Bulletin No. 114 dated August 27, 1956.) FOOTER:
Document Text
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AD Final Rules - DRS_56-21-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 56-21-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters Subject: Hydraulic Boost Cylinders Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Scotts-Bell 47 Inc Model: 47G | 47G-2 | 47H-1 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: 56-21-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 56-21-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 56-21-01 BELL: Applies to All Models 47G, 47G2, and 47H1 Helicopters Except As Noted Below and All Spare Hydraulic Boost Power Cylinders Part Numbers 1090, 1190 and All 1270 Cylinders Prior to and Including Serial Number 733. Model 47G, Serial Numbers 1530 and 1687 and Up; Model 47G2, Serial Numbers 1494, 1505, 1506, 1508, 1617 and Up; and Model 47H1, Serial Numbers 1534 and Up Will be Modified Prior to Delivery. Compliance required as indicated. Malfunctioning of the hydraulic boost cylinder in service has necessitated the replacement of the hydraulic boost power cylinder barrels and clamps in the fore and aft and lateral cyclic boost power cylinder units and the establishment of a service life of 100 hours on the cylinders which have not been modified. These hydraulic boost cylinder barrels must be replaced by the time 100 hours service is obtained, except barrels that have already accumulated 100 hours service prior to the date of this directive may be used until 125 hours are obtained or until December 1, 1956, whichever occurs first. (Detail procedures for installation of cylinder barrel P/N 1097 and clamps P/N 1029 are contained in Bell's Mandatory Service Bulletin No. 114 dated August 27, 1956.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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