11/04/24
Message Overview:
Message Name:
NO L-IOC-8 BUS INPUT
Message Code:
B3-681665
Associated CAS:
| Reporting LRU: | Auto Throttle (AT) Computer |
| Effectivity: | Post SB350-22-002 Aircraft 20937 and Subs |
| System Description: | 22-30-00 - Auto Throttle System (ATS) |
| Schematic Diagram: | 22-30-00-801 - Auto Throttle System (ATS) 31-45-00-101 - Integrated-Avionics Processor System (IAPS) |
| Wiring Diagram: |
22-30-00-801 - Auto Throttle System (ATS) |
Message Description:
L-IOC-8 bus input fault Indicates an absent, failed, or unreasonable input on the indicated ARINC 429 input bus. The AT FAIL Advisory CAS is associated with this fault but may not post if the offside ADS is the current selected source.
Possible Causes:
- Auto Throttle (AT) Computer (A252)
- Integrated Avionics Processing System (IAPS) (A4)
- IAPS Input/Output Concentrator (IOC) card
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
NOTE: Review the Auto Throttle "AT Diagnostic Information", to find details about the MDC Data Reader Labels & bits.
NOTE: Bombardier recommends referencing the elements one (1) through eleven(11) of the "Wiring & Connections" Troubleshooting Tips document. The intent of the document is to ensure the Maintenance Technician has the information needed to perform a comprehensive check of an aircraft system wiring circuit, while also doing checks found in the From - To tables called out in the Troubleshooting Recommendations element.
| From | To | Expected Results | Results |
|---|---|---|---|
| XXXX-XX | XXXX-XX | Continuity |
Quick Links:
| Removal of the Auto Throttle Computer | AMM 22-30-01-000-801 |
| Installation of the Auto Throttle Computer | AMM 22-30-01-400-801 |
| Functional Test of the Auto Throttle Computer | AMM 22-30-01-720-801 |
| Removal of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) | AMM 31-45-01-000-801 |
| Installation of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) | AMM 31-45-01-400-801 |
| Operational Test of the Integrated-Avionics Processor System (IAPS) | AMM 31-45-00-710-801 |
| Removal of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-000-801 |
| Installation of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-400-801 |
| Operational Test of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-710-801 |
| Safety Precautions - Maintenance Practices - ALL | SPM 20-00-01-02-01 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02-01 |
Troubleshooting Recommendations:
- On the Cursor Control Panel press “A/ICE”, “ECS”, “FUEL” buttons simultaneously, access the MDC on MFD #2.
- Highlight “LRU INDEX/OPERATIONS” then press “ENTER” button.
- Highlight “AT COMPUTER” then press the “ENTER” button.
- Review label 352 looking for any interfacing system issues.
NOTE: Refer to the "AT Diagnostic Information" document available in the Troubleshooting Tips element. - If any issues are posted, resolve the issue prior to continuing this troubleshooting.
- Remove the Autothrottle (AT) computer and disconnect Integrated Avionics Processing System (IAPS) connector A4P1.
- Do a wiring check between the AT Computer (A252) and the IAPS (A4) as follows:
NOTE: Refer to the "Wiring & Connections" document found in the Troubleshooting Tips element of this page.
From To Result A252P1-50 A4P1-69 A252P1-51 A4P1-70 - If wiring defects are found, repair defective wiring as required and do close out.
- If no defects are found, continue with next step.
- Interchange the left Input/Output Concentrator (IOC) card in the IAPS with the right IOC card. Is the fault still present on the same side?
- If YES, return the IOC cards to their original position and continue with next step.
- If NO, replace defective IOC card.
- Replace the AT Computer (A252)
- Do close out.