Overview
ISO 5866:1983 specifies clearance and fixing dimensions and the designation rules for aircraft plug-in base change-over relays (Type II) with crimped connections. It defines the mechanical envelope, base and support hole layouts, terminal arrangements and connector details for 2 A (two-pole) and 3 A (two- and four-pole) plug-in relays intended for aircraft applications. Note: electrical characteristics and performance requirements are to be covered in separate, forthcoming International Standards.
Key topics and technical requirements
- Scope: Dimensions, fixing details and designation of Type II plug-in change-over relays with crimped connections for aircraft use.
- Relay configurations covered:
- 2 A two-pole change-over relays
- 3 A two-pole and 3 A four-pole change-over relays
- Mechanical variants: Relays with and without a mechanical protection device for connections - separate dimensional figures and tables are provided for each.
- Base and terminal arrangement:
- Two‑pole bases use 8 holes, four‑pole bases use 16 holes; minimum hole depth 5 mm for male contacts.
- Position and concentricity tolerances for base holes must be compatible with relay pin tolerances to ensure correct mounting.
- Contact dimensions: Male and female contact geometries and electrical contact zone dimensions are defined (figures provided in the standard).
- Connections for crimping: Rear part of crimp contacts accommodates wires with cross-sectional areas 0.22 mm² to 0.60 mm² (insulated wire sizes equivalent to AWG 20–24).
- Marking and designation: All connections must be marked on the relay base; at least one coil connection must be identified, polarity indicated with a “+” if needed; operating diagram and contact locations must be indelibly marked.
- Referenced tolerancing practice: Geometrical tolerancing and drawing conventions follow ISO 1101.
Practical applications and users
ISO 5866:1983 is primarily useful for:
- Aerospace component designers and mechanical engineers specifying relay envelopes and mounting interfaces in avionics and aircraft electrical systems.
- OEMs and relay manufacturers producing plug-in change-over relays compatible with established aircraft bases and supports.
- Avionics assemblers, maintenance organizations and procurement/specification teams ensuring mechanical interchangeability and correct connector interfaces.
- Test labs and quality teams verifying dimensional conformity and marking requirements during incoming inspection.
Practical benefits include improved interchangeability, reduced mechanical integration risk, and clearer procurement specifications for aircraft-grade relays.
Related standards
- ISO 1101 (geometrical tolerancing) - referenced for drawing tolerances.
- Future ISO standards (forthcoming) will specify electrical characteristics and performance requirements for these relay types.
Keywords: ISO 5866:1983, aircraft relays, plug-in base relays, change-over relays, crimped connections, relay dimensions, fixing dimensions, terminal arrangement, avionics.