WING TO CTR LEAK
(Caution)

Fuel quantity in the center tank has increased by 600 pounds or more, after an engine or APU is selected ON and the aircraft is not in a refueling mode.

• Engine Feed Tubing Leak
• Wing Fuel Transfer Tubing Leak
• Center Tank Fuel Compensator/Probe
• Fuel Probe Excitation "TED" Connectors
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW700-28-0496 - Fuel Quantity Indication Fluctuation

Forum Articles/Infoservice/Newsletter: None

Notice To Operators (NTO): None

Flight Operation Notifications Manual (FONM): None

NOTES: 

• WING TO CTR LEAK (Caution) cannot be identified through BIT functions or an operational test. A wing to center leak is caused by a leak in the engine feed tubing, or the wing fuel transfer tubing, that passes through the center tank. You must operate the fuel feed system (pressurize the engine feed tubing) to find leaks in the engine feed tubing. Operate the fuel transfer system (pressurize the wing fuel transfer tubing) to find leaks in the wing fuel transfer tubing.
• At the time the CAS message is/was posted, if the Fuel qty in the center tank fluctuated drastically, if the indication is intermittent or if fuel qty in the center tank increased without seeing a decrease in the left or right wing tanks fuel qty, it may be a good clue that this is an indication issue rather than an actual leak. A CTR FUEL XFER FAIL CAS message could be posted as well at the same time since the center transfer pump pressure switches do not detect actual fuel pressure.
• As viewed in CAIMS, the Probe Status "GOOD PROBE" indicates the probe is communicating with FMQGC and the probe is reporting a capacitance within a nominal range (between full dry and full wet). The OMS may report the Probe Status as "GOOD PROBE", yet a dry capacitance check per the AMM may find a probe out of AMM limits. The only way to verify if a probe is reporting accurately is to do the Dry Capacitance check IAW AMM task 28−41−00−760−801 Capacitance Test of the Fuel Quantity Probes.
  

1. At the time the CAS message is/was posted, if the Fuel qty in the center tank fluctuated drastically, if the indication is/was intermittent or if fuel qty in the center tank increased without seeing a decrease in the left or right wing tanks fuel qty, it may be a good clue that this is an indication issue rather than an actual leak. The CTR FUEL XFER FAIL CAS message could be displayed as well at the same time, if the center transfer pump pressure switches do not detect actual fuel pressure.

   1. If you suspect that the WING TO CTR LEAK CAS message was displayed as a result of an indication issue, go to step 8.
   2. If you suspect that the WING TO CTR LEAK CAS message was displayed as a result of a real fuel leak into the center tank, continue with next step.

2. Operate fuel feed system.
3. Examine for a leak in the left and right engine feed tubing. You may refer to AMM task 28-21-00-210-801 - Visual Check of the Shroud Drains.

   1. If a leak is identified, repair/rectify as required and do close out.
   2. If no leak is found, continue with next step.

4. Operate the fuel transfer system.
5. Examine for a leak in the left to right and right to left fuel transfer tubing.

   1. If a leak is identified, repair/rectify as required and do close out.
   2. If there is no leak, continue with next step.

6. Access the center transfer check valves and inspect for any FOD or damage that would prevent the check valve from closing.

   1. If a leak is found, repair/rectify as required and do close out.
   2. If no leak is found, continue with next step.

7. Inspect the center tank structural items for any apparent leaks and repair/rectify as required.
8. Perform a dry capacitance check of the center fuel tank probes using CAIMS (AMM 28-41-00-760-801) and record values on the following data entry form.

   1. If one or more fuel probe does not pass the test, continue with next step.
   2. If the test results are satisfactory, go to step 10.

9. Inspect the affected probe(s) for water contamination, installation, wiring installation and corrosion. Clean the probe(s) if required.

   1. If no obvious defects can be found or fault persists after cleaning the probe(s), replace defective probe(s).
   2. If the probe(s) condition and installation is satisfactory, continue with next step.

10. Inspect all the fuel probe excitation wiring. Pay close attention to the "coax" (TED) connectors along the circuit. Have someone monitor the capacitance values while the excitation wiring is being "shaken" or "wiggled" along the circuit to detect any sudden fluctuation.

    1. If no defects were noted, continue with next step.
    2. If a connection is found to cause intermittent fluctuations, repair/replace connector or wiring as required.

11. Use the aircraft Wiring Manual (28-41-04) to perform resistance checks, continuity checks and CAIMS to perform capacitance checks. Record and report findings to the Bombardier Customer Response Center if needed.

    1. If defects with wiring or fuel probes are identified, repair/rectify as required and do close out.
    2. If NO defects are identified, continue with next step.

12. Check wiring from FMQGC to DAU 1 and DAU 2.
    

    From	To	Expected Results	Results
    A47EP1-A1	A17CP1-A9	Continuity
    A47EP1-A2	A17CP1-A10	Continuity
    A47EP1-C1	A17CP1-K1	Continuity
    A47EP1-C2	A17CP1-K2	Continuity
    A47EP1-E1	A18CP1-A9	Continuity
    A47EP1-E2	A18CP1-A10	Continuity
    A47EP1-G1	A18CP1-K1	Continuity
    A47EP1-G2	A18CP1-K2	Continuity

    1. If wiring defects are found, repair defective wiring as required and do close out.
    2. If NO defects are found, contact the Customer Response Center (CRC) for further troubleshooting.

13. Do the close out.