AD 52-21-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Scotts-Bell 47 Inc | 47 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47B | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47B3 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D1 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47E | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-2 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-2A | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-2A-1 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-3 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-3B | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-3B-1 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-3B-2 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-3B-2A | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-4 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-4A | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-5 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-5A | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47H-1 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47J | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47J-2 | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47J-2A | Airworthiness Directives; Bell Model 47 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47K | Airworthiness Directives; Bell Model 47 Helicopters |
Unsafe Condition
Engine mount shifting on the rubber Lord mounts due to insufficient torque offset between engine mount clamp and rubber Lord mounts.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install two 47-612-123-1 guards on engine mounts for 178 HP engines (Models 47B, 47B3, 47D) to achieve a 5/32 inch torque offset. For 200 HP engines (all Models 47), inspect or replace guards with new type if ears are less than 3/16 inch to ensure 7/32 inch ears and 1/4 inch torque offset.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
October 15, 1952
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Bell Model 47 Helicopters: Models 47, 47B, 47B3, 47D, 47D1, 47E, 47G, 47G-2, 47G-2A, 47G-2A-1, 47G-3, 47G-3B, 47G-3B-1, and others as noted.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Lord Mount Guards
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_52-21-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 52-21-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47 Helicopters Subject: Lord Mount Guards Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Scotts-Bell 47 Inc Model: 47 | 47B | 47B3 | 47D | 47D1 | 47E | 47G | 47G-2 | 47G-2A | 47G-2A-1 | 47G-3 | 47G-3B | 47G-3B-1 | 4...Show more 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: 52-21-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 52-21-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 52-21-01 BELL: Applies to Model 47 Helicopters as Noted Below. Compliance required by October 15, 1952. To prevent engine mount shifting on the rubber Lord mounts, the following applicable Lord mount guards must be installed: 1. 178 H. P. Engines - Models 47B, 47B3, and 47D Helicopters. If not already incorporated, install two 47-612-123-1 guards on engine mount. When properly installed, a 5/32 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount. 2. 200 H. P. Engines - All Model 47 Helicopters. Inspect the two 47-612-123-3 guards to be sure they have 7/32 inch ears. If no guards are installed or the ears are less than 3/16 inch they must be replaced with the new type guards. When properly installed, a 1/4 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount. (Bell Service Bulletin No. 79, Revision A, dated July 7, 1952, covers this same subject.) This supersedes AD 52-01-04. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_52-21-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 52-21-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47 Helicopters Subject: Lord Mount Guards Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Scotts-Bell 47 Inc Model: 47 | 47B | 47B3 | 47D | 47D1 | 47E | 47G | 47G-2 | 47G-2A | 47G-2A-1 | 47G-3 | 47G-3B | 47G-3B-1 | 4...Show more 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: 52-21-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 52-21-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 52-21-01 BELL: Applies to Model 47 Helicopters as Noted Below. Compliance required by October 15, 1952. To prevent engine mount shifting on the rubber Lord mounts, the following applicable Lord mount guards must be installed: 1. 178 H. P. Engines - Models 47B, 47B3, and 47D Helicopters. If not already incorporated, install two 47-612-123-1 guards on engine mount. When properly installed, a 5/32 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount. 2. 200 H. P. Engines - All Model 47 Helicopters. Inspect the two 47-612-123-3 guards to be sure they have 7/32 inch ears. If no guards are installed or the ears are less than 3/16 inch they must be replaced with the new type guards. When properly installed, a 1/4 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount. (Bell Service Bulletin No. 79, Revision A, dated July 7, 1952, covers this same subject.) This supersedes AD 52-01-04. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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