AD 75-07-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Bell Helicopter Textron, Inc. | 212 | Airworthiness Directives; Bell Model 212 Helicopters |
Unsafe Condition
Improperly manufactured nuts (P/N 212-040-631-1) with specific serial numbers (A20-00427, A20-00469, A20-00472, A20-00475, A20-00476, A20-00477, A20-00478) on the main drive shaft assembly may fail, leading to high frequency vibration and potential loss of main drive shaft function.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect the exposed nut for serial numbers listed in the AD; remove and replace any nuts with the specified serial numbers using an acceptable nut per maintenance manual instructions. Notify Bell Helicopter Company or FAA if non-compliant nuts are found.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next 25 hours' time in service after the effective date of this AD, or before next flight if an unusual high frequency vibration is detected.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Bell Helicopter Textron, Inc. Model 212 helicopters, serial numbers 30501 through 30658 and 30671.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
High Frequency Vibration
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_75-07-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 75-07-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 212 Helicopters Subject: High Frequency Vibration Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 04/21/1975 Make: Bell Helicopter Textron, Inc. Model: 212 Product Type: Aircraft Product Subtype: Rotorcraft Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 75-07-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-2131 AD NUMBER: 75-07-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 212 Helicopters ACTION: SUMMARY: DATES: Effective April 21, 1975. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 75-07-01 BELL: Amendment 39-2131. Applies to Bell Model 212 helicopters, S/N 30501 through S/N 30658 and 30671, certificated in all categories. Compliance required as indicated, unless already accomplished. Within the next 25 hours' time in service after the effective date of this AD, or before next flight if an unusual high frequency vibration is detected. a. Gain access to and remove the main drive shaft assembly in accordance with Section 65-30-01 of the Model 212 helicopter maintenance manual. b. Inspect the exposed nut, P/N 212-040-631-1, for serial number. Nuts with the following serial numbers are improperly manufactured and must be removed from service: A20-00427, A20-00469, A20-00472, A20-00475, A20-00476, A20-00477, A20-00478 Nuts which have no serial number and nuts with serial numbers other than those listed are acceptable. c. Reinstall the drive shaft with an acceptable nut in accordance with instructions in Section 65-30-01 of the Model 212 maintenance manual. Notify Bell Helicopter Company or the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, if nuts identified in paragraph b. are found following inspection. (Reporting approved by the Office of Management and Budget under OMB No. 04- R0174). d. Bell Service Bulletin No. 212-75-1 dated February 19, 1975, pertains to this inspection and replacement procedure. e. Equivalent methods of compliance with this airworthiness directive must be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, 4400 Blue Mound Road, Fort Worth, Texas 76101. This amendment becomes effective April 21, 1975. FOOTER:
Document Text
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AD Final Rules - DRS_75-07-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 75-07-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; Bell Model 212 Helicopters Subject: High Frequency Vibration Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 04/21/1975 Make: Bell Helicopter Textron, Inc. Model: 212 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: 75-07-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-2131 AD NUMBER: 75-07-01 SUBJECT HEADING: Airworthiness Directives; Bell Model 212 Helicopters ACTION: SUMMARY: DATES: Effective April 21, 1975. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 75-07-01 BELL: Amendment 39-2131. Applies to Bell Model 212 helicopters, S/N 30501 through S/N 30658 and 30671, certificated in all categories. Compliance required as indicated, unless already accomplished. Within the next 25 hours' time in service after the effective date of this AD, or before next flight if an unusual high frequency vibration is detected. a. Gain access to and remove the main drive shaft assembly in accordance with Section 65-30-01 of the Model 212 helicopter maintenance manual. b. Inspect the exposed nut, P/N 212-040-631-1, for serial number. Nuts with the following serial numbers are improperly manufactured and must be removed from service: A20-00427, A20-00469, A20-00472, A20-00475, A20-00476, A20-00477, A20-00478 Nuts which have no serial number and nuts with serial numbers other than those listed are acceptable. c. Reinstall the drive shaft with an acceptable nut in accordance with instructions in Section 65-30-01 of the Model 212 maintenance manual. Notify Bell Helicopter Company or the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, if nuts identified in paragraph b. are found following inspection. (Reporting approved by the Office of Management and Budget under OMB No. 04- R0174). d. Bell Service Bulletin No. 212-75-1 dated February 19, 1975, pertains to this inspection and replacement procedure. e. Equivalent methods of compliance with this airworthiness directive must be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, 4400 Blue Mound Road, Fort Worth, Texas 76101. This amendment becomes effective April 21, 1975. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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