Fuel - Leak Detection Warning Shown

TASK 28-11-00-810-805-A
Fuel - Leak Detection Warning Shown

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

1. Possible Causes

a difference between the results of the total fuel used calculations (FOB at first engine start minus actual FOB) and the sum of the engine fuel flow meters

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 28-11-00-810-806-A	Fuel - A Leak is Shown by Discrepancies in the Fuel On Board (FOB) and Fuel Used (FU) Calculations During Flight
AMM 31-60-00-860-001	EIS Start Procedure

3. Fault Confirmation
Subtask 28-11-00-710-054-A ** ON A/C NOT FOR ALL

A. Introduction

Read all of this introduction before you start the troubleshooting work steps in Para. 3.B.

At the first engine start, the FQIC monitors and records the total quantity of Fuel On Board (FOB) at that time.

During flight, or until the second engine shutdown, the FWC monitors the signals that follow:

FOB at first engine start (from the FQIC)
actual (current) FOB (from the FQIC)
engine 1 fuel used (from the fuel flow transmitter on ENG 1)
engine 2 fuel used (from the fuel flow transmitter on ENG 2)
fuel leak threshold (from FQIC).

At the FWC, the actual FOB, the engine 1 fuel used, and the engine 2 fuel used are added together.

The result of the addition is subtracted from the FOB at the first engine start.

If there is a difference between these two values that is more than the threshold value (and the aircraft is in flight phase 6) the FWC gives an indication of a possible fuel leak.
This is a single chime warning with the ECAM alert:
FUEL - F.USED/FOB DISAGREE.

The FQIC calculates the threshold value and sends the result to the FWC.
The threshold value is calculated from the FOB at the first engine start, and the FOB during the current flight leg. The APU fuel used between the first engine start and take off is part of the threshold value. This is because the fuel flow to the APU is not monitored. No tolerance is made if the APU is operated after that time.

NOTE: The fuel leak detection warning is only given in flight phase 6 (cruise).

The threshold values are given in the two tables that follow:

Table 1 gives the threshold values with no FQIS fuel-probe failures
Table 2 gives the threshold values with in-tank FQIS failures or one tank contents degraded.

Table 1 - Threshold Values (Normal, With No In-Tank Failures)

NOTE: All the values given are in Tonnes

NOTE: You can calculate the intermediate values (because the table scales are linear).

---------- ----------------------------------------------------------------

! FOB ! ! Current Fuel On Board (FOB !

! At First! !-----------------------------------------------------------------!

! Engine ! ! 21 ! 19 ! 18 ! 16 ! 14 ! 12.5! 10 ! 8 ! 6 ! 4 ! 2 !

! Start ! -----------------------------------------------------------------

!---------! -----------------------------------------------------------------

! 24.3 ! ! 0.66! 0.69! 0.70! 0.73! 0.76! 0.78! 0.82! 0.85! 0.88! 0.91! 0.94!

! 21.0 ! ! ! 0.60! 0.62! 0.65! 0.68! 0.70! 0.74! 0.77! 0.80! 0.83! 0.86!

! 19.0 ! ! ! ! 0.57! 0.60! 0.63! 0.65! 0.69! 0.72! 0.75! 0.78! 0.81!

! 18.0 ! ! ! ! ! 0.57! 0.60! 0.63! 0.66! 0.69! 0.72! 0.75! 0.78!

! 16.0 ! ! ! ! ! ! 0.55! 0.58! 0.61! 0.64! 0.67! 0.70! 0.73!

! 14.0 ! ! ! ! ! ! ! 0.53! 0.56! 0.59! 0.62! 0.65! 0.68!

! 12.5 ! ! ! ! ! ! ! ! 0.53! 0.56! 0.59! 0.62! 0.65!

! 10.0 ! ! ! ! ! ! ! ! ! 0.49! 0.52! 0.55! 0.58!

! 8.0 ! ! ! ! ! ! ! ! ! ! 0.47! 0.50! 0.53!

! 6.0 ! ! ! ! ! ! ! ! ! ! ! 0.45! 0.48!

! 4.0 ! ! ! ! ! ! ! ! ! ! ! ! 0.43!

--------- !-----------------------------------------------------------------!

! Threshold Value !

-----------------------------------------------------------------

Table 2 - Threshold Values (Normal, With In-Tank Failures 0r One Tank Degraded)

NOTE: All the values given are in Tonnes

NOTE: You can calculate the intermediate values (because the table scales are linear).

---------- ----------------------------------------------------------------

! FOB ! ! Current Fuel On Board (FOB) !

! At First! !-----------------------------------------------------------------!

! Engine ! ! 21 ! 19 ! 18 ! 16 ! 14 ! 12.5! 10 ! 8 ! 6 ! 4 ! 2 !

! Start ! -----------------------------------------------------------------

---------! -----------------------------------------------------------------

! 24.3 ! ! 1.33! 1.36! 1.37! 1.40! 1.43! 1.46! 1.49! 1.52! 1.55! 1.58! 1.61!

! 21.0 ! ! ! 1.28! 1.29! 1.32! 1.35! 1.37! 1.41! 1.44! 1.47! 1.50! 1.53!

! 19.0 ! ! ! ! 1.24! 1.27! 1.30! 1.32! 1.36! 1.39! 1.42! 1.45! 1.48!

! 18.0 ! ! ! ! ! 1.25! 1.28! 1.30! 1.34! 1.37! 1.40! 1.43! 1.46!

! 16.0 ! ! ! ! ! ! 1.23! 1.25! 1.29! 1.32! 1.35! 1.38! 1.41!

! 14.0 ! ! ! ! ! ! ! 1.20! 1.24! 1.27! 1.30! 1.33! 1.36!

! 12.5 ! ! ! ! ! ! ! ! 1.20! 1.23! 1.26! 1.29! 1.32!

! 10.0 ! ! ! ! ! ! ! ! ! 1.17! 1.20! 1.23! 1.26!

! 8.0 ! ! ! ! ! ! ! ! ! ! 1.15! 1.18! 1.21!

! 6.0 ! ! ! ! ! ! ! ! ! ! ! 1.13! 1.16!

! 4.0 ! ! ! ! ! ! ! ! ! ! ! ! 1.11!

--------- !-----------------------------------------------------------------!

! Threshold Value !

-----------------------------------------------------------------

The fuel leak detection function and warning will only operate, if the standards of equipment installed on the aircraft are as (or later than) those that follow:

FWC standard H2F2(Mod 33374)
DMC standard V50 EIS1(Mod 31056) OR DMC standard S3-1 EIS2 (Mod 30368)
SDAC standard H2D2(Mod 30365)
FQIC standard -13-10 (Mod 33877)
SDAC pin programming for fuel leak detection function (Mod 32650).

There is no built-in BITE or continuous monitoring of the fuel leak detection system additional to that in the sub-systems of the FQIC (or the FWC).

Subtask 28-11-00-710-055-A ** ON A/C NOT FOR ALL

B. Test

NOTE: An ECAM warning ESLD/01.28.740 has been shown that identifies a difference between the results of the total fuel used calculations (FOB at first engine start minus actual FOB) and the sum of the engine fuel flow meters.

(1) Read the TFU (Ref. TFU 28.42.00.043).
(2) Do the procedure that follows to see if a fuel leak has occurred.
(a) Set the Electronic Centralized Aircraft Monitoring (ECAM) system to on AMM 31-60-00-860-001.
(b) On the ECAM control panel:
1 Push (in) the FUEL P/BSW to get the FUEL page.
2 Make sure that the FUEL page shows on the ECAM lower Display Unit (DU).
(c) Examine the FUEL page and make a record of the fuel values that follow:
1 FOB.
2 Engine 1 fuel used (last leg).
3 Engine 2 fuel used (last leg).
(d) Examine the aircraft technical log.
1 Make a record of the running hours for the APU since the last take off. If applicable, include in-flight (last leg) and on the ground running time since the aircraft landed.

NOTE: The maximum fuel burn rate for the APU is 155 kg/hour.

2 If the APU was operated, make a record of the total APU fuel used after the last take off.
(3) Do the applicable calculations that follow to see if a fuel leak has occurred:
(a) Delta 1 = (FOB at 1st ENG start - current FOB) - (F.USED 1 + 2).

Where:

Delta 1 = A theorectical value (of fuel lost) that does not allow for the fuel used by the APU after the last take off.

FOB at 1st ENG start = Is self explanatory

Current FOB = Is self explanatory (use the current value of the FOB from the upper ECAM DU).

F.USED 1 + 2 = Is self explanatory (use the current value(s) of the F.USED from the upper ECAM DU).
1 If, since the last take off, the APU has:

been operated, do step (b)
not been operated, do step (4).

(b) Delta (Final) = Delta 1 - APU Fuel Used

Where:

Delta (Final) = A theorectical value that must be less than a threshold value given in Para. 3.A. - Introduction.

Delta 1 = The value calculated in step (3)(a).

APU Fuel Used = The value calculated in step 2.(d)2_.
(4) Get the related threshold value (FOB at first engine start and the current FOB) from the applicable Table 1 or 2 in Para. 3.A. - Introduction.
(5) Compare the result of your calculation(s) with the theorectical value from the applicable table.
(a) If the result is:

less than the threshold value, record the event in the aircraft technical log. No troubleshooting work steps are necessary, because the warning is spurious
more than the threshold value, do Para. 4.A.

4. Fault Isolation
Subtask 28-11-00-810-054-A ** ON A/C NOT FOR ALL

A. Procedure
(1) Do the TSM procedure for fuel leaks (Ref. TSM TASK 28-11-00-810-806).

NOTE: The referenced TSM Task is for fuel leaks on aircraft with or without the fuel leak detection system.

[Rev.8 from Aug 2018] 2026.04.04 04:28:25 UTC