What Is ARINC 600 and
Why It Matters for Avionics

The Standard That Keeps Aircraft Electronics Connected

Walk down the avionics bay of any Boeing 737, Airbus A320, or military transport aircraft, and you'll see rows of identical black boxes — each one slid into a metal tray, locked in place, and connected through a massive rectangular connector at the back. That connector is built to ARINC 600, and it is the most widely deployed avionics interconnection standard in commercial aviation.

ARINC (Aeronautical Radio, Incorporated) 600 defines the mechanical, electrical, and environmental requirements for Air Transport Avionics Equipment Interfaces. In plain terms: it standardizes how a Line Replaceable Unit (LRU) physically mates with the aircraft wiring — making it possible for airlines to swap a flight management computer from one vendor with a radio altimeter from another, and have both plug into the same tray in the same rack.

ARINC 600 Architecture: Rack, Tray, and Connector

The ARINC 600 system is a rack-and-panel architecture with three components:

1. The Tray (Mounting Base): Bolted to the aircraft structure. Contains the fixed half of the connector (receptacle), guide pins for alignment, and hold-down hooks to secure the LRU.
2. The LRU (Line Replaceable Unit): The avionics box itself — flight computer, transponder, satcom radio, or display processor. Slides into the tray on rails and blind-mates with the connector.
3. The ARINC 600 Connector: A rectangular, multi-insert connector mounted at the rear of the tray. The LRU's mating connector plugs in during insertion — no manual cable connection required.

This design means a technician can replace a failed LRU on the tarmac in under 5 minutes: release the hold-down hooks, slide the old box out, slide the new box in, lock. The connector blind-mates automatically — no tools, no torque wrenches, no pin alignment guesswork.

ARINC 600 Connector Sizes and Inserts

ARINC 600 connectors are designated by size (1, 2, or 3) and insert configuration (number and type of contact cavities). The size refers to the connector shell width:

Insert Arrangement Designators

Each insert station can hold different contact configurations designated by a numeric code:

• Insert 0: Blank (no contacts) — used as a filler
• Insert 60: 60× signal contacts (#22D)
• Insert 120: 120× signal contacts
• Insert 300: 300× signal contacts (Size 3 only)
• Insert 600: 600× signal contacts — maximum density (Size 3 only)
• Power inserts: Mixed power + signal, designated separately (e.g., 2× #8 power + 40× #22D signal)
• Coax/Twinax inserts: High-speed data, ARINC 429 bus, fiber optic termini

Keying: Preventing Wrong-Box Insertion

ARINC 600 uses mechanical keying pins in the connector to ensure that only the correct LRU type can be inserted into a given tray position. Keying is configured by installing keying pins in specific positions on the connector face — like a physical password. The aircraft wiring manual specifies which keying positions are populated for each LRU slot.

Common keying pin positions are designated by letters (A through Z, excluding I, O, and Q) and arranged in a matrix across the connector. This prevents dangerous mismatches — a flight management computer cannot be accidentally installed into a radio transponder slot, even if both use Size 2 trays.

ARINC 600 vs ARINC 404: What's the Difference?

Engineers sometimes confuse ARINC 600 with its predecessor, ARINC 404. The key differences:

Why ARINC 600 Still Matters in 2026

Despite being a 50-year-old standard, ARINC 600 continues to evolve. Modern insert configurations now support fiber optic termini for high-bandwidth avionics data buses, high-speed differential pairs for Ethernet-based aircraft networks (ARINC 664/AFDX), and composite-shell variants for weight reduction on next-generation platforms like the Boeing 777X and Airbus A350.

The standard's longevity is its strength: airlines operating mixed fleets of A320ceo, A320neo, 737 NG, and 737 MAX aircraft can stock a single set of ARINC 600 LRUs that fit across generations. That interchangeability saves millions in inventory costs and simplifies MRO logistics.