Overview
ISO 3456:1975 specifies performance requirements for aircraft lever-operated manual switches (Class 3). It covers single- and triple-hole mounting forms for use on nominal 28 V d.c. and 115/200 V, 400 Hz a.c. systems. Class 3 switches are fully environmentally sealed and designed for higher altitude and temperature operation than Class 2 switches; they do not include the positive-action features of Class 1/2 switches (see ISO 1466).
Key topics and technical requirements
- Environmental and operating limits
- Usable to altitudes up to 20 000 m.
- Operating temperature range: -40 °C to +70 °C; storage up to -65 °C to +85 °C.
- Fully sealed construction; must meet the referenced ISO environmental test series (ISO 2650 et al.).
- Electrical ratings
- Intended for 28 V d.c. and 115/200 V, 400 Hz a.c. aircraft power systems; usable down to 4 V.
- Rated currents (nominal): DC resistive 15 A, DC inductive (40 mH) 10 A, DC tungsten lamp 4 A; AC resistive 11 A, AC inductive 7 A (pf 0.7), AC tungsten 2 A.
- Mechanical design and mounting
- Single- or three-hole mounting to ISO 3282 dimensions; mounting via threaded ring or M4 fasteners.
- Lever motion in a plane perpendicular to the panel; two- or three-position types, single or multipole.
- Lever operating force between 2.7 N and 45 N; angular movement and minimum pre-switch travel follow ISO 3282 or specific customer specifications.
- Lever must resist a 90 N force without damage; mounting ring torque and terminal strength test requirements are specified.
- Durability, safety and testing
- Mechanical endurance: switches must be capable of at least 20 000 operations under nominal voltage/current; type tests include up to 40 000 cycles and environmental stress sequences.
- Electrical tests include dielectric (1 500 V), insulation resistance (≥100 MΩ at 500 V), drop-in voltage, contact resistance and heating limits.
- Accessibility and terminal design requirements for aircraft wiring and servicing.
Applications and users
- Used by aircraft designers, avionics engineers, and component manufacturers specifying aircraft lever-operated manual switches for cockpits, panels and systems where environmental sealing, high-altitude and temperature capability are required.
- Relevant to procurement teams, maintenance organizations, certification authorities and test labs preparing type-approval, qualification testing or supplier specifications.
Related standards
- ISO 1466 (lever switches Class 1 & 2), ISO 3282 (switch dimensions and mounting), ISO 1540 (aircraft electrical network characteristics), ISO 2650–2658 (environmental tests), ISO 2668/2669 (vibration/acceleration).
Keywords: ISO 3456:1975, aircraft lever-operated manual switches, Class 3, performance requirements, 28 V d.c., 115/200 V 400 Hz a.c., environmental sealing, altitude, endurance testing.