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(WARNING)
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WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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04/07/21

Message Overview:

Message Name:

L PYLON DUCT AIR LEAK

Message Code:

B3-007118

Associated CAS:

L PYLON BLEED LEAK
(Warning)

Reporting LRU: L PYLON AIR LEAK
System Description: 30-11-00
36-20-00
Schematic Diagram: 36-21-00
Wiring Diagram: 36-21-11
36-21-13

Message Description:

An hot air leak has been detected in the LEFT PYLON DUCTING running from the left engine FIREWALL to the Left Bleed Valve (intermediate pressure ducting) or to the Left High Pressure Valve (high pressure ducting).

350_l-pylon-loop

Possible Causes:

  • L Pylon Duct
  • L Pylon Loop 1A (MT63)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Bleed Loop Routing and Visual Aid Guide

Troubleshooting Guide for Bleed Loops

Fault Confirmation Procedure:

  1. Message# = 1
  2. {Term Definitions}

    1. IAS1A-28 XX 351 01 EXCT XXXX-XXXX XXXX-XXXX XXXX-TXXX 351B: 12; LEFT PYLON LEAK DETECTED

Quick Links:

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
Bleed-Air Leak-Detection System - Component Location AMM 36-21-00-992-801
Removal of the Left Pylon-Loop Element AMM 36-21-05-000-801
Installation of the Left Pylon-Loop Element AMM 36-21-05-400-801
Removal of the Left Pylon Anti-Ice Leak-Detection Element AMM 36-21-05-000-802
Installation of the Left Pylon Anti-Ice Leak-Detection Element AMM 36-21-05-400-802
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:

  1. Go into the system diagnostics to the IASC #1 channel B (L Pylon Loop). The IASC LRU test page will provide pages to perform a leak detection system test and check past event locations.

    1. Locate the short circuit or leak using the Leak Event location function.
    2. Check for short circuit at the corresponding connector.
    3. Check the loop routing for a fouling condition on a hot surface (loop touching duct).
      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. Review AMM 36-21-00-992-801 for component location. See individual loops for specific routing information.
    4. 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.
    5. If L Pylon Bleed loop is shorted replace loop.

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