01/22/25
Message Overview:
Message Name:
PACK DUCT AIR LEAK
Message Code:
B3-007406
| Reporting LRU: | Pack Air Duct |
| Associated CAS: | PACK LEAK (Warning) |
| System Description: | 21-51-00 - Filtering and Flow Control System 30-12-00 - Wing Anti-Ice System |
| Schematic Diagram: | SSM 36-21-00-101 - Bleed-Air Leak-Detection System |
| Wiring Diagram: | WM 36-21-11-1_001 - Sheet 1 - Pack Loop - ALL |
Message Description:
A hot air leak has been detected in the PACK DUCTING running from the Left Flow Control Valve to the Pack Inlet and the Precooler Crossover Valve. This message will post when one loop in a Dual Loop System detects an overheat for more than five minutes and the other loop does not.
Possible Causes:
- Pack Air Duct
- Pack Loop Sensor 1 Channel A (MT73)
- Pack Loop Sensor 1 Channel B (MT141)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None
Flight Operation Notifications Manual (FONM): None
NOTES:
Quick Links:
| Component Location | AMM 36-21-00-992-801 |
| Operational Test of the Bleed-Air Leak-Detection and Warning System | AMM 36-21-00-710-801 |
| Initiation Test of the Bleed-Air Leak-Detection Loops | AMM 36-21-00-740-801 |
| Resistance Check of the Bleed-Air Leak-Detection Loops | AMM 36-21-00-760-801 |
| Removal of the Pack-Inlet Leak-Detection Element | AMM 36-21-11-000-801 |
| Installation of the Pack-Inlet Leak-Detection Element | AMM 36-21-11-400-801 |
| Fenwal Safety Systems | CMM 26-14-47 |
| Safety Precautions - Maintenance Practices - ALL | SPM 20-00-01-02 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Interrogate the Leak Event Location on both IASC 1 and IASC 2 channel B with the Maintenance Diagnostic Computer to determine the exact location of the leak.
- Once the percentage value is obtained from the MDC, refer to mapping tool representing all potential bleed leak locations in term of percentage, for each metered bleed air hole and LRU connections point. This will help to quickly troubleshoot source of the leak.
PACK LEAK
- Once the leak event location is isolated ducting inspection is required. Repair leak as required.
NOTE: Before replacing a loop always look at the loop for routing, ensure loop is not too close to the plumbing or the bleed hole on a valve. - If no leaks are found then use a Tegam meter to check capacitance and inductance between the inner and outer conductor of the corresponding loop. Perform the impedance check per the Leak Detection How To.
- Replace affected loop as required.
- Do close out.