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Design Guidelines for Aerospace Gear Systems
AGMA 911-B21
AGMA 911-B21

SCOPE

This information sheet covers current gear design practices as they are applied to air vehicles and spacecraft. The material included goes beyond the design of gear meshes per se, and presents, for the consideration of the designer, the broad spectrum of factors which combine to produce a working gear system, whether it be a transmission, gearbox, or special purpose mechanism. Although a variety of gear types, such as wormgears, face gears and various proprietary tooth forms are used in aerospace applications, this document covers only conventional spur, helical, and bevel gears.

FOREWORD

AGMA 911-A94 supersedes AGMA Standard 411.02, Design Procedure for Aircraft Engine and Power Take-Off Spur and Helical Gears. Its purpose is to provide guidance to the practicing aerospace gear engineer in the design, manufacture, inspection, and assembly of aerospace gearing. In addition, it addresses the lubrication, environmental, and application conditions which impact the gearbox as a working system of components.

Material in the Information Sheet is supplemental to current AGMA Standards but does not constitute a Standard itself. By definition, Standards reflect established industry practice. In contrast, some of the practices discussed here have not seen enough usage to be considered standard, but they do provide insight to design techniques used in state-of-the-art aerospace equipment. It is expected that the user of this Information Sheet will have some general experience in gear and machine design, and some knowledge of current shop and inspection practices.

AGMA 911-B21 replaces AGMA 911-A94. This revision reorganized and updated the previous sections to current practices. The scope was expanded to include gear systems not just gearing. The title of the document was changed from Design Guidelines for Aerospace Gearing to Design Guidelines for Aerospace Gear Systems. Annexes C and D were added to cover alternative tooth geometry and asymmetric teeth. Annex E was added to give examples of rotorcraft regulations.

The first draft of AGMA 911-B21 was made in January 2013. It was approved by the technical committee in September 2020. It was approved by the Technical Division Executive Committee (TDEC) in May 2021.

ABSTRACT

This information sheet covers current gearbox design practices as they are applied to air vehicles and spacecraft. The material included goes beyond the design of gear meshes and presents the broad spectrum of factors which combine to produce a working gear system, whether it be a power gearbox or special purpose mechanism. Although a variety of gear types, such as wormgears, face gears and various proprietary tooth forms are used in aerospace applications, this document covers only spur, helical, and bevel gears. 

NORMATIVE REFERENCES

The following documents contain provisions which, through reference in this text, constitute provisions of this information sheet. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this information sheet are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below.

  • AGMA 901, A Rational Procedure for the Preliminary Design of Minimum-Volume Gears 
  • AGMA 904, Metric Usage 
  • AGMA 908, Geometry Factors for Determining the Pitting Resistance and Bending Strength of Spur, Helical and Herringbone Gear Teeth 
  • AGMA 923, Metallurgical Specifications for Steel Gearing 
  • AGMA 925, Effect of Lubrication on Gear Surface Distress 
  • AGMA 937-A12, Aerospace Bevel Gears 
  • AGMA 938, Shot Peening of Gears 
  • ANSI/AGMA 1010, Appearance of Gear Teeth – Terminology of Wear and Failure 
  • ANSI/AGMA 1012, Gear Nomenclature, Definition of Terms with Symbols 
  • ANSI/AGMA 2101-D04, Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth 
  • ANSI/AGMA 2003, Rating the Pitting Resistance and Bending Strength of Generated Straight Bevel, Zerol, Bevel, and Spiral Bevel Gear Teeth 
  • ANSI/AGMA 2004, Gear Materials and Heat Treatment Manual and Processing Manual 
  • ANSI/AGMA 2015-2, Gear Tooth Flank Tolerance Classification System – Definitions and Allowable Values of Double Flank Radial Composite Deviations
  • ANSI/AGMA ISO 1328-1, Cylindrical Gears – ISO System of Flank Tolerance Classification – Part 1: Definitions and Allowable Values of Deviations Relevant to Flanks of Gear Teeth 
  • ANSI/AGMA ISO 14104, Gears – Surface Temper Etch Inspection After Grinding, Chemical Method 
  • ANSI B92.1, Involute Splines and Inspection 
  • ANSI B92.2M, Metric Module Involute Splines and Inspection 
  • ISO 4156-1:2005, Straight cylindrical involute splines – Metric module, side fit – Part 1: Generalities 
  • ISO 4156-2:2005, Straight cylindrical involute splines – Metric module, side fit – Part 2: Dimensions 
  • ISO 4156-3:2005, Straight cylindrical involute splines – Metric module, side fit – Part 3: Inspection 
  • DOD-PRF-85734, Lubricating Oil, Helicopter Transmission System, Synthetic Base 
  • MIL-HDBK-310, Global Climatic Data for Developing Military Products 
  • MIL-PRF-23699, Lubricating Oil, Aircraft Turbine Engine, Synthetic Base, NATO Code Number O156 
  • MIL-PRF-7808, Lubricating Oil, Aircraft Turbine Engine, Synthetic Base 
  • MIL-STD-461, Electromagnetic Interference Characteristics Requirements for Equipment 
  • MIL-STD-462, Measurement of Electromagnetic Interference Characteristics 
  • MIL-STD-810, Environmental Test Methods and Engineering Guidelines 
  • NASA Technical Memorandum 82473, Terrestrial Environment (Climatic) Criteria Guidelines for Use in Aerospace Vehicle Development 
  • NASA-STD-6012, Corrosion Protection for Space Flight Hardware 
  • NASA-STD-8729.1, NASA Reliability and Maintainability (R&M) Standard for Spaceflight and Support Systems

Pages: 140

ISBN: 978-1-64353-094-9

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