ISO 493:1975

Overview

ISO 493:1975 is an international standard that specifies the overall dimensions for single-hole mounting lever-operated manual switches used in aircraft. These switches fall under Class 1 and Class 2 categories and must comply with the performance requirements outlined in ISO 1466. The standard ensures uniformity in the physical dimensions and mounting methods, facilitating compatibility and interchangeability in aircraft control panels. It provides detailed dimensional requirements and mounting hole specifications essential for designers, manufacturers, and maintenance personnel in the aerospace industry.

Key Topics

• Scope: Defines dimensional specifications for single-hole mounting lever-operated switches with characteristics per ISO 1466.
• Dimensional Requirements: Specifies maximum sizes for switches based on pole count:
  • Single-pole: Max 16.8 mm length
  • Double-pole: Max 22.6 mm length
  • Three-pole: Max 35.1 mm length
  • Four-pole: Max 46.0 mm length
• Mounting Interface:
  • Switches feature a 12 mm diameter male thread at the center of the front face for fixing to the panel.
  • Mounting holes in panels are defined, with a keyway washer and a 3 mm diameter hole to prevent rotation.
• Lever Length: Acceptable lever length is 17.5 ± 0.8 mm, although this may vary slightly.
• Compatibility: The dimensions accommodate either terminal screws or integrated terminal connections on the face opposite the mounting bush.
• Standardization Process: Developed by ISO Technical Committee ISO/TC 20, involving multiple member countries, ensuring widespread acceptance and harmonization.

Applications

ISO 493:1975 is crucial in the aerospace sector, where consistent component dimensions directly impact safety, maintenance, and operational reliability. Applications include:

• Aircraft Cockpit Controls: Ensures manual switches fit standardized panel cutouts and mounting holes for lever-operated controls.
• Component Manufacturing: Helps manufacturers produce switches that meet international size and mounting criteria, simplifying procurement and inventory.
• Maintenance and Repair: Facilitates easy replacement of switches without custom modification due to standardized dimensions.
• Avionics Systems: Supports uniform integration of manual control switches within avionics panels and instrumentation.

Related Standards

• ISO 1466: Specifies the performance requirements for lever-operated manual switches in aircraft, forming the basis for the characteristics referenced by ISO 493.
• ISO/TC 20 Standards: Other aircraft and space vehicle-related standards developed by ISO Technical Committee 20, ensuring coordinated standardization efforts.
• Electrical Switch Standards: Complementary standards that define electrical characteristics and safety criteria for switches used in aerospace applications.

Keywords: ISO 493, aircraft switch dimensions, lever-operated manual switches, single-hole mounting, aerospace standards, ISO 1466, aircraft controls, panel mounting, switch size specifications, aviation maintenance.