04/26/21
Message Overview:
Message Description:
The amber 'PIT' caution flag identifies that the IRS pitch attitude is inaccurate or the IRSs cannot cross compare to each other.
- Pitch attitude is derived from the IRS computer, the system requires alignment prior to aircraft movement, cycling the system and verifying a good alignment and comparing the pitch attitude may isolate to a IRS component.
- The IRS racks are leveled in production with shims, assure the racks are secured. For cross communication problems. Cross comparator problems could be associated with a bad IOC, IRS or data bus failure.
- MDC trouble shooting information may help isolate data validity, prior to component replacement and data bus ring-out.
Possible Causes:
- Input/Output Concentrator (IOC) (A4-IOC)
- Inertial Reference Unit 1 (IRS 1) (A233)
- Inertial Reference Unit 2 (IRS 2) (A232)
- Data Bus Failure
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| 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 |
| Operational Test of the Inertial Reference System (IRS) | AMM 34-45-00-710-801 |
| Removal of the Inertial Reference Unit (IRU) | AMM 34-45-01-000-801 |
| Installation of the Inertial Reference Unit (IRU) | AMM 34-45-01-400-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
Troubleshooting Recommendations:
- None