AD 51-29-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Scotts-Bell 47 Inc | 47B | Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47B3 | Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D | Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D1 | Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters |
Unsafe Condition
Tail rotor gearbox shaft (P/N 47-645-028-1 or 47-645-051-1) may develop cracks or elongation in the attachment bolt hole after accumulating 900 hours of operation, leading to tail rotor failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace the tail rotor gearbox shaft when it has accumulated 900 hours of operation. For shafts already over 900 hours, replace by February 1, 1952. Until then, inspect the attachment bolt hole after every 25 hours of operation for cracks or elongation over 0.010 inch and replace the shaft if found.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Replace by February 1, 1952 for shafts over 900 hours. Inspections required after every 25 hours of operation until replacement.
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Affected Aircraft
Bell Model 47B, 47B3, 47D, 47D1 helicopters
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Tail Rotor Gearbox Shaft
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_51-29-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-29-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters Subject: Tail Rotor Gearbox Shaft Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Scotts-Bell 47 Inc Model: 47B | 47B3 | 47D | 47D1 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 51-29-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-29-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-29-01 BELL: Applies to All Models 47B, 47B3, 47D, 47D1 Helicopters. Compliance required as indicated. 1. Replace the tail rotor gearbox shaft, P/N 47-645-028-1 or 47-645-051-1, when it has accumulated 900 hours of operation. 2. Any shaft having already accumulated 900 hours of operation must be replaced by February 1, 1952. In the interim, conduct the following inspection after every 25 hours of operation: Remove tail rotor and inspect attachment bolt hole for cracks. Replace the shaft if a crack is found, or the hole is elongated over 0.010 inch. (Bell Service Bulletin No. 83 covers this same subject.) FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_51-29-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 51-29-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters Subject: Tail Rotor Gearbox Shaft Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Scotts-Bell 47 Inc Model: 47B | 47B3 | 47D | 47D1 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: 51-29-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 51-29-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 47B, 47B3, 47D, 47D1 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 51-29-01 BELL: Applies to All Models 47B, 47B3, 47D, 47D1 Helicopters. Compliance required as indicated. 1. Replace the tail rotor gearbox shaft, P/N 47-645-028-1 or 47-645-051-1, when it has accumulated 900 hours of operation. 2. Any shaft having already accumulated 900 hours of operation must be replaced by February 1, 1952. In the interim, conduct the following inspection after every 25 hours of operation: Remove tail rotor and inspect attachment bolt hole for cracks. Replace the shaft if a crack is found, or the hole is elongated over 0.010 inch. (Bell Service Bulletin No. 83 covers this same subject.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.
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