# AD 79-20-05: Main Rotor Hub Assembly - Type: Airworthiness directive - Status: Historical - Products: Bell Helicopter Textron 204B, 205A-1 and 212 - Effective: January 18, 1980 - Superseded by: [AD 2012-17-08](https://openairdocs.org/ad/2012-17-08) - Product type: Aircraft, Rotorcraft - Amendment: 39-3662 - Registered aircraft: 125 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E43D83352479C75D86256E0D004DF72C.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/79-20-05 ## The airworthiness directive 79-20-05 BELL: Amendment 39-3572 as amended by Amendment 39-3626 is further amended by Amendment 39-3662. Applies to Models 204B, 205A-1, and 212 helicopters, certificated in all categories equipped with main rotor hub assembly, P/N 204-012-101 and yoke assembly, P/N 204-011-102 (Airworthiness Docket No. 79-ASW-25). For main rotor yokes having 500 hours or more total time in service on the effective date of this AD, compliance required prior to December 1, 1979, unless already accomplished, and thereafter at intervals not to exceed 2400 hours from the last inspection. For main rotor yokes having less than 500 hours' total time in service on the effective date of this AD, compliance required prior to attaining 1000 hours' total time in service and thereafter at intervals not to exceed 2400 hours' from the last inspection. To detect and preclude corrosion and possible cracks in the main rotor yoke, accomplish the following: (a) Remove the yoke assembly from the mainrotor hub assembly. (b) Conduct the following inspections: (1) Inspect yoke for corrosion pits, scratches, and damage in the pillow block bushing hole, in each spindle radius, and yoke web section by using a five power or higher magnifying glass. (2) Inspect the yoke for cracks using a magnetic particle inspection method. Note: Special attention should be directed to the center section web, spindles, radius, and pillow block bushing holes. (c) Remove corrosion pits, repair, refinish, and seal the yoke as prescribed by Model 212 Component Repair and Overhaul, Revision 4, Chapter 65 or Revision 12, Model 204B Maintenance and Overhaul Manual, or Revision 1, Model 205A-1 Component Repair and Overhaul Manual. (d) Replace yokes having a crack or that exceed repair limits specified in the appropriate model maintenance or repair and overhaul manual with a serviceable yoke before further flight. The serviceable yoke must have been refinished and sealed as prescribed byModel 212 Component Repair and Overhaul, Revision 4, Chapter 65, or Revision 12, Model 204B Maintenance and Overhaul Manual, or Revision 1, Model 205A-1 Component Repair and Overhaul Manual. (e) Equivalent means of compliance with this AD may be approved by the Chief, Engineering and Manufacturing Branch, FAA, Southwest Region. (f) The helicopter may be flown in accordance with FAR 21.197 to a base where inspections and repairs can be performed. (g) Upon request of the operator, an FAA maintenance inspector subject to prior approval of the Chief, Engineering and Manufacturing Branch, FAA Southwest Region, may adjust the repetitive inspection intervals specified in this AD if the request contains data justifying the increase. Amendment 39-3572 became effective October 31, 1979. Amendment 39-3626 became effective December 1, 1979. This Amendment 39-3662 becomes effective January 18, 1980. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS H1SW](https://openairdocs.org/tcds/H1SW): Bell Textron Inc.; names 2 of 5 models: 204B, 205A-1 - [TCDS H4SW](https://openairdocs.org/tcds/H4SW): Bell Textron Inc.; names 1 of 4 models: 212 ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 125 (125 by airframe model, 0 by engine model) - Makers: Bell 117, Bell Helicopter Textron 6, Bell/Southwest Florida Aviatio 2 Models with the most aircraft: - [Bell 205A-1](https://openairdocs.org/model/bell-205a-1): 56 aircraft (airframe model) - [Bell 212](https://openairdocs.org/model/bell-212): 54 aircraft (airframe model) - [Bell 204-B](https://openairdocs.org/model/bell-204-b): 7 aircraft (airframe model) - [Bell Helicopter Textron 212](https://openairdocs.org/model/bell-helicopter-textron-212): 5 aircraft (airframe model) - [Bell/Southwest Florida Aviatio 205 A1](https://openairdocs.org/model/bell-southwest-florida-aviatio-205-a1): 2 aircraft (airframe model) - [Bell Helicopter Textron 205A-1](https://openairdocs.org/model/bell-helicopter-textron-205a-1): 1 aircraft (airframe model) All 6 models: https://openairdocs.org/ad/79-20-05/models.md Every aircraft: https://openairdocs.org/ad/79-20-05/aircraft.md ## Related documents - [AD 2012-17-08](https://openairdocs.org/ad/2012-17-08): Main Rotor Head ยท Bell Helicopter Textron 204B, 205A, 205A-1 and 2 more. Effective Feb 27, 2013. Supersedes this AD Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.