A320 FCB7 - FQI Accuracy
 

Dear all,
I'm going through this Flight Crew Bulletin concerning fuel quantity accuracy on the A320.
Most of the operators have a policy to perform a dipstick check in case of a significant discrepancy (normally above 3%) between aircraft indicated fuel QTY and bowser figures. This on the basis that, a major discrepancy would be either due to a bowser error, or due to an aircraft system failure leading to a wrong fuel quantity indication.
The above mentioned FCB states that a dipstick check is less accurate than the aircraft FQI system, therefore it has to be done only in case of dispatch with FQI system inoperative.
To my understanding, as the A320 FQI system performs continuosly several self tests, a technical problem leading to fuel quantity indication issues would generate an ECAM alert. On this basis, in case of a significant discrepancy between aircraft indication and bowser figures, in the absence of any ECAM failure message, the discrepancy has to be related to the bowser and no maintenance action and/or dipstick checks are required.
Is this interpretation correct?

The FQI on the airbus is one of the most sophisticated fuel indication systems that I have ever seen and had most of us on the maintenance course ( back in 1988 ) quite surprised at the number of sensors that can be inoperative and it still have a reasonable level of accuracy.

Errors are most likely to come from the fuel truck and are likely to be exaggerated by changes in the SG of the fuel, other factors that might cause errors are if the aircraft was refueled with the IRS system off line as this has an input into the FQI system.

We have seen, a 500kg error, with no failure message.