Educational familiarization only. This is original TechOpsBase learning content created from privately supplied legacy training and MSG-3 source material. It does not reproduce manufacturer pages, proprietary diagrams, task steps, numerical maintenance limits, dispatch criteria or controlled maintenance data. Current approved aircraft data, effectivity and operator procedures govern all aircraft work.
Resource profile
- Aircraft: Airbus A350 family
- ATA chapter: 42 — Integrated Modular Avionics
- Resource: A350 ATA 42 CRDC Architecture and Remote I/O
- Level: Intermediate-to-advanced
- Status: Draft pending technical review
Learning objectives
- Explain CRDC functions.
- Describe remote installation.
- Understand signal conversion.
- Explain user-specific redundancy.
- Diagnose local versus network faults.
1. Purpose and operational value
CRDCs extend the IMA architecture to remote equipment by collecting, converting and distributing non-AFDX signals.
2. Architecture and system flow
CRDCs are installed close to remote equipment to reduce wiring and convert analog, discrete, ARINC 429 and CAN data to/from AFDX.
They provide data concentration, gateway and limited combinatorial logic but do not host aircraft-system applications.
Most critical signals are processed through more than one CRDC, but the combination is user-specific and not a fixed backup pair.
3. Major components and functions
Analog/discrete interfaces
Acquire and command local physical signals. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes channel, wiring, sensor/actuator and conversion. Command, feedback and physical effect must agree before hardware is condemned.
ARINC 429/CAN interfaces
Gateway serial data to/from AFDX. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes bus activity, label/message and conversion path. Command, feedback and physical effect must agree before hardware is condemned.
AFDX end system
Connects CRDC to network A/B. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes port, link and virtual-link status. Command, feedback and physical effect must agree before hardware is condemned.
Boolean logic
Performs limited simple I/O logic. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes input state, configured logic and output. Command, feedback and physical effect must agree before hardware is condemned.
Local power/installation
Supports remote module operation. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes power source, connector, environment and zone condition. Command, feedback and physical effect must agree before hardware is condemned.
4. Normal operating sequence
1. Acquire
CRDC samples local signals.
2. Convert
Data is formatted for AFDX transmission.
3. Transport
Network carries data to CPIOM/direct AFDX users.
4. Output
Commands are converted back to local signal form.
5. Redundancy
User-specific alternate CRDC paths preserve critical functions.
5. Control, monitoring and protection
Loss of one CRDC can affect a mixed collection of systems because user allocation is not by ATA chapter alone.
Some less-critical signals may have no redundant CRDC path.
6. Failure modes and maintenance reasoning
- One channel lost: Local wiring/interface channel.
- All signals through one CRDC lost: Power/module/AFDX interface.
- One direction affected: Input or output conversion path.
- Only one user affected: User-specific channel/virtual link/external equipment.
- Multiple systems affected: Common CRDC or local power/network.
7. Interfaces with other aircraft systems
- AFDX switches.
- CPIOM hosted applications.
- Remote sensors/actuators.
- FWS/CMS.
- Electrical/common installation.
8. Practical maintenance scenarios
Unrelated remote signals disappear together
Map them to the same CRDC.
One critical signal remains after CRDC loss
Use the alternate user-specific CRDC path.
New CRDC does not restore one signal
Check local channel/wiring and configuration.
9. Technician takeaways
- CRDCs host no aircraft applications.
- There is no fixed CRDC backup pair.
- Signal grouping identifies common hardware.
- Inspect remote-zone power and connectors.
Maintenance boundary
This resource explains architecture, operation, indications and system-level troubleshooting. It intentionally excludes removal/installation instructions, wiring-pin checks, maintenance limits, software part numbers, servicing quantities, inspection intervals and release-to-service criteria.
Review prompts
- What is the required system function?
- Which component commands, processes or physically performs it?
- Which power, fluid, pneumatic or data path is required?
- What command proves the function was requested?
- What feedback or physical effect proves correct operation?
- Which adjacent ATA system can create the same symptom?
- What evidence should be preserved before reset, draining, servicing or software action?
- What hygiene, electrical, pressure, network or safety boundary applies?
