Date: 201906
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Fuel Quantity-Pressure Indication
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Maintenance
When detected: Pre-flight
Contributing factors: Aircraft; Manuals; Procedure
Primary problem: Procedure

Narrative: I would like to take this time to address an issue with the procedures used in deferring inoperative fuel tank indications on the A320 family of aircraft. This issue affects XXX and XXY fleets. This misapplication of this MEL (Minimum Equipment List) has had a negative impact on our operations by causing numerous delays and cancellations. I would also like to thank everyone in advance for any help to resolve this issue. I will try to be as concise as possible in this correspondence; as this is a complex issue involving the MEL; fueling manual; [Maintenance Control] and Flight Dispatch. I will be using Aircraft X; since it is the most recent example and typical of the problems that we encounter. Aircraft X arrived at ZZZ on flight XYZA. The right wing tank fuel quantity was deferred as per MEL 28-XXX. This deferral was applied to this aircraft on [date] in ZZZ1. This is the second time that the right fuel quantity indication was deferred on this aircraft in the last 30 days. The reason for the deferral was a flight crew report of the right main tank quantity indicating XX. The fault was recorded on CFDS (Centralized Fault Display System) as probes 34QT2 and 30QT2 as inoperative. On the A320 series aircraft; the fuel quantity is displayed in the cockpit on a CRT (Cathode Ray Tube) screen. The wing has a separate fuel quantity indicator. A failure due to probe faults affects cockpit and wing indications simultaneously. Obviously if the fault occurs in flight there is no way of knowing that the wing gauge is also inoperative. This is an important point; since it will have an impact on how Flight Dispatch applies the MEL and can utilize the aircraft. When we (Maintenance) is required to comply with MEL 28-XXX; we are directed to fuel the aircraft as per the [company] fueling manual. When fueling as per the [company] fueling manual; we must fuel the airplane in accordance with section titled 'Refueling with Inoperative Fueling Quantity Indicators'. This section has three methods that can be used. Method 1; method 2 and method 3. Method 1 can only be used with an operative flight deck display and inoperative wing display. Since the cockpit display was deferred as inoperative; we cannot use method 1. That leaves us with methods 2 or method 3. Either method requires us to use the MLI (Magnetic Level Sticks) to verify the final fuel quantity. Most XXX and some XXY A320 series aircraft are only equipped with three (3) MLI indicators on the wing tanks. Aircraft X is one of those aircraft. One aircraft with three MLI indicators; the wing tank fuel can only be verified up to 1800 gallons or 12000 lbs. NOTE - a full wing tank has a capacity of 13500 lbs. This limitation is clearly spelled out in the fueling manual. With this in mind; the total fuel on board that can be verified by MLI is only 24;000 lbs. This is because: 1) Wing tank fuel quantity must remain even. 2) Center tank and ACT (Additional Center Tank) tank fuel cannot be added until the wing tanks are full. (13;500 lbs.). The trap here is that Dispatch and routing are not aware of this limitation because MEL 28-XXX does not give this restriction unless MEL 28-YYY (re-fuel panel indicator inop) is also issued. The problem now is that the MEL 28-XXX; as written; has created a situation where Maintenance cannot fuel the wing tanks to full due to MLI not being capable of reading a full wing tank; and Flight Dispatch is not aware of this restriction due to MEL 28-YYY not issued to the aircraft. I look forward to your feedback in solving this problem.

Callback: Maintenance Technician explained that The Minimum Equipment List (MEL) currently does not have sufficient instructions to enable maintenance to determine definitively whether the wing panel gauges are providing correct fuel quantity. If the main tanks are fueled to any amount greater than 12;000 lbs the exact amount cannot be verified. This is because the manual stick method of verifying fuel quantity is limited to 12;000 lbs max. Therefore unless the fuel is pumped out of the main tanks to a level below 12;000 lbs and verified by the stick you must flight plan the flight based on a maximum fuel load of 24;000 lbs. This of course assumes that you have verified that both left and right main tanks have at least 12;000 lbs each for a total of 24;000 lbs. The maximum of 24;000 lbs is due to the fact the Center Tank and Additional Center Tank (ACT) cannot be fueled unless the main tanks are filled to 13;500 lbs each. Therefore the Maintenance technician is recommending that the A320 MEL be revised to include guidance for Maintenance; Flight Planning and Dispatch in this regard.



Synopsis: A320 Maintenance Technician encounters Fuel Tank Minimum Equipment List (MEL) issue.