AD 52-28-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Scotts-Bell 47 Inc | 47B | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47B3 | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47D1 | Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters |
Unsafe Condition
Tail rotor pinion shaft, P/N 30-613-361, may have damage or cracks originating from the keyway or fillet area, leading to failure.
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Required Actions
Magnetically inspect the tail rotor pinion shaft for damage or cracks. Replace immediately if worn, damaged, cracked, or fails inspection. If acceptable, rework recesses at each side of bearing boss with a 1/8-inch grinding wheel to create 0.030 to 0.040 inch radius at recess bottoms, ensuring reworked diameters do not drop below 0.763 inch and 0.604 inch respectively, and recess widths do not exceed 0.140 inch.
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Compliance Time
as soon as possible, but not later than January 10, 1953
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Affected Aircraft
Bell Model 47B, 47B3, 47D and 47D1 Helicopters (Prior to Serial Number 477)
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Federal Register Abstract
Tail Rotor Pinion Shaft
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_52-28-04.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 52-28-04 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters Subject: Tail Rotor Pinion 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Make: Scotts-Bell 47 Inc Model: 47B | 47B3 | 47D | 47D1 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 52-28-04 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 52-28-04 SUBJECT HEADING: Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 52-28-04 BELL: Applies to Models 47B, 47B3, 47D and 47D1 Helicopters (Prior to Serial Number 477). Compliance required as soon as possible, but not later than January 10, 1953. Magnetically inspect tail rotor pinion shaft, P/N 30-613-361, for damage and for cracks originating the keyway or fillet area. Replace shaft immediately if worn, damaged, cracked or if it does not pass the magnetic inspection satisfactorily. If the shaft passes the above inspections satisfactorily, or if a new shaft is being installed, accomplish the following prior to assembly: Place shaft in a lathe which is equipped with a grinding attachment. Use a 1/8-inch grinding wheel to increase the width of the recess at each side of bearing boss and grind a 0.030 to 0.040 inch radius at bottom of recesses. Reworked diameters of the shaft at the recesses at each side of the bearing boss are acceptable down to 0.763 inch and 0.604 inch respectively. These minimums must not be exceeded. Width of recesses are not to exceed 0.140 inch. There must not be any signs of the old radii or scratches. (Bell Mandatory Service Bulletin No. 84, Revision B, dated April 29, 1953, covers the same subject.) FOOTER:
Document Text
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AD Final Rules - DRS_52-28-04.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 52-28-04 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters Subject: Tail Rotor Pinion 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: 52-28-04 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 52-28-04 SUBJECT HEADING: Airworthiness Directives; Bell Model 47B, 47B3, 47D and 47D1 Helicopters ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 52-28-04 BELL: Applies to Models 47B, 47B3, 47D and 47D1 Helicopters (Prior to Serial Number 477). Compliance required as soon as possible, but not later than January 10, 1953. Magnetically inspect tail rotor pinion shaft, P/N 30-613-361, for damage and for cracks originating the keyway or fillet area. Replace shaft immediately if worn, damaged, cracked or if it does not pass the magnetic inspection satisfactorily. If the shaft passes the above inspections satisfactorily, or if a new shaft is being installed, accomplish the following prior to assembly: Place shaft in a lathe which is equipped with a grinding attachment. Use a 1/8-inch grinding wheel to increase the width of the recess at each side of bearing boss and grind a 0.030 to 0.040 inch radius at bottom of recesses. Reworked diameters of the shaft at the recesses at each side of the bearing boss are acceptable down to 0.763 inch and 0.604 inch respectively. These minimums must not be exceeded. Width of recesses are not to exceed 0.140 inch. There must not be any signs of the old radii or scratches. (Bell Mandatory Service Bulletin No. 84, Revision B, dated April 29, 1953, covers the same subject.) FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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