AD 55-16-01
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
Failure of the tail rotor hubs P/N 47-641-025-1 and 47-641-057-1 due to imperfections such as corrosion, tool marks, scratches, and pitting in the fillet area causing stress concentrations and hub spindle failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect the inboard fillet area on both spindles of the hub using a 10-power magnifying glass for accurate radius and smooth machine finish free of corrosion, pitting, and copper plating. Replace hubs not meeting requirements.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
prior to next flight
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
All Model 47 Helicopters with 47-641-025-1 or 47-641-057-1 Tail Rotor Hubs and all spares.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Tail Rotor Hub Fillet
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_55-16-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 55-16-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47 Helicopters Subject: Tail Rotor Hub Fillet 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: 55-16-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 55-16-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 55-16-01 BELL: Applies to All Model 47 Helicopters With 47-641-025-1 or 47-641-057- 1 Tail Rotor Hubs, and All Spares. Compliance required prior to next flight. Recent serious accidents have been caused by failure of the tail rotor hubs P/N 47-641- 025-1 and 47-641-057-1. Imperfections such as corrosion, tool marks, scratches, and pitting in the fillet set up stress concentrations which cause failure of the hub spindle. Consequently, immediate and complete inspection of the fillet area of the tail rotor hub must be accomplished as follows: 1. Inspect the inboard fillet area on both spindles of the hub for accuracy of the radius using a 10-power magnifying glass. Fillets must have a true continuous radius all around the spindles and also must have a smooth machine finish free of corrosion and pitting. When inspected under a magnifying glass, tool marks appear greatly exaggerated, and by a smooth machine finish is meant having extremely fine, uniform, closely-spaced and uninterrupted tool marks. No copper plating is allowed in the fillet. 2. Hubs not meeting these requirements must be replaced. (Bell Service Bulletin No. 96, Revision B dated July 15, 1955, covers this subject.) (This covers the same inspection as the CAA telegram of July 13, 1955.) FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_55-16-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 55-16-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47 Helicopters Subject: Tail Rotor Hub Fillet 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: 55-16-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 55-16-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 55-16-01 BELL: Applies to All Model 47 Helicopters With 47-641-025-1 or 47-641-057- 1 Tail Rotor Hubs, and All Spares. Compliance required prior to next flight. Recent serious accidents have been caused by failure of the tail rotor hubs P/N 47-641- 025-1 and 47-641-057-1. Imperfections such as corrosion, tool marks, scratches, and pitting in the fillet set up stress concentrations which cause failure of the hub spindle. Consequently, immediate and complete inspection of the fillet area of the tail rotor hub must be accomplished as follows: 1. Inspect the inboard fillet area on both spindles of the hub for accuracy of the radius using a 10-power magnifying glass. Fillets must have a true continuous radius all around the spindles and also must have a smooth machine finish free of corrosion and pitting. When inspected under a magnifying glass, tool marks appear greatly exaggerated, and by a smooth machine finish is meant having extremely fine, uniform, closely-spaced and uninterrupted tool marks. No copper plating is allowed in the fillet. 2. Hubs not meeting these requirements must be replaced. (Bell Service Bulletin No. 96, Revision B dated July 15, 1955, covers this subject.) (This covers the same inspection as the CAA telegram of July 13, 1955.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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