39155690 Airbus Fuel Accuracy.pdf

Operational Liaison Meeting FBW aircraft

Fuel accuracy

Content Introduction What systems to determine Fuel quantity in the aircraft? Fuel Quantity Indicator (FQI) System Manual Magnetic Indicators (MMI)

Why Fuel quantity discrepancies: On ground? In flight?

Conclusion

Fuel accuracy

2

FQI System description The FQI system is a computerized system that measure: the total fuel mass the total fuel volume fuel quantity in each tank

Fuel Volume and mass are determined using Fuel probes (capacitance is proportional to fuel level) densitometers

Fuel accuracy

3

FQI System description Example of Probes location in an A320 aircraft

Fuel accuracy

4

FQI System description Fuel Quantities are displayed on the ECAM A320

Fuel accuracy

A330

5

FQI System description Fuel Quantities are displayed on the ECAM A320 FQI is inaccurate

Fuel accuracy

6

Manual magnetic Indicators MMIs are installed in each wing tanks. Each tank’s fuel quantity on ground can be determined: reading the MMI dipstick number reading the aircraft attitude (grid square letter and number) using the MMI table

1

A320 MMI Fuel accuracy

Wing Tanks MMI Table (Liters) 7

Content Introduction What systems to determine Fuel quantity in the aircraft? Fuel Quantity Indicator (FQI) System Manual Magnetic Indicators (MMI)

Why Fuel quantity discrepancies: On ground? In flight?

Conclusion

Fuel accuracy

8

Why Fuel Quantity discrepancies on ground? At the end of refueling, discrepancies reported between: uplifted quantity measured by the bowsers uplifted quantity measured using FQI

Those discrepancies may be due to: Bowser quantity and density error APU fuel used FQI accuracy

Fuel accuracy

9

Why Fuel Quantity discrepancies on ground? Bowser quantity and density tolerances: Volume tolerance: generally less than 0.5% of fuel uplifted Density tolerance (both temperature accuracy and density reading error): 0.25% of fuel uplifted Total bowser tolerance: 0.75% of fuel uplifted

APU fuel used: To be taken into account when comparing FOB pre-refuel and FOB post-refuel depends on external condition and generator load APU fuel consumption: between 100 and 150Kg/h

Fuel accuracy

10

Why Fuel Quantity discrepancies on ground? The FQI is a gauging system. Bias and tolerances can affect FQI system accuracy: tank manufacturing tolerances FQI computer inaccuracies tolerances in density determination water that causes FQI over-reads wing deflection

Fuel accuracy

11

FQI accuracy on ground Single Aisle Aircraft FOB 0 to 0.5% Max FOB 0.5%Max FOB to Max FOB

OVERREAD 0 1% FOB

UNDERREAD - (0.5% Max FOB +0.5% FOB)

Long Range Aircraft: FOB Below 2% Max FOB 2% Max FOB to Max FOB

Fuel accuracy

OVERREAD Decrease linearly to 0 +(0.5% Max FOB +0.5% FOB)

UNDERREAD Decrease linearly to -1% Max FOB - (0.5% Max FOB +0.5% FOB)

12

FQI accuracy on ground Single Aisle Aircraft FOB 0 to 0.5% Max FOB 0.5%Max FOB to Max FOB

OVERREAD 0 1% FOB

UNDERREAD - (0.5% Max FOB +0.5% FOB)

Long Range Aircraft: FOB Below 2% Max FOB 2% Max FOB to Max FOB

OVERREAD Decrease linearly to 0 +(0.5% Max FOB +0.5% FOB)

UNDERREAD Decrease linearly to -1% Max FOB - (0.5% Max FOB +0.5% FOB)

FAR/JAR 25.1337: Each fuel quantity indicator shall be calibrated to read “zero” during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply Fuel accuracy

13

Why Fuel Quantity discrepancies on ground? Single Aisle FQI Accuracy (GROUND) MAX FOB= 19T 0.25

0.2

0.15

FQI TOLERANCE Tonnes

0.1

0.05

0

-0.05

-0.1

-0.15

-0.2

-0.25 0

2

4

6

8

10

12

14

16

18

Actual FOB Tonnes

Fuel accuracy

14

20

Why Fuel Quantity discrepancies on ground? LONG RANGE FQI ACCURACY (GROUND) MAX FOB=113T 1.5

FQI TOLERANCE Tonnes

1

0.5

0

-0.5

-1

-1.5 0

20

40

60

80

100

Actual FOB Tonnes

Fuel accuracy

15

120

Why Fuel Quantity discrepancies on ground?

Max discrepancy = Max [Fuel load(per bowser)- Fuel added on ECAM (FQI end-FQI start)]= [±Bowser dev ± FQI dev(end) ± FQI dev(start) +APU fuel (refuel)]

Fuel accuracy

16

Why Fuel Quantity discrepancies on ground? EXEMPLE: (A320-200) ACTUAL FOB before refueling: 3T ACTUAL FOB after refueling: 18T Max TOTAL Bowser inaccuracy : APU Fuel used for 30minutes Max FQI deviation* TOTAL:

115kg 50kg 220kg ______ 385kg

The FQI deviation is only significant when FQI Over/ Under-readings before and after refueling are very different Fuel accuracy

17

Why Fuel Quantity discrepancies on ground? Single Aisle FQI Accuracy (GROUND) MAX FOB= 19T 0.25

0.2

0.15

MAX FQI deviation during refueling

FQI TOLERANCE Tonnes

0.1

0.05

0

-0.05

-0.1

-0.15

-0.2

-0.25 0

2

4

6

8

10

12

14

16

18

Actual FOB Tonnes

Fuel accuracy

18

20

Why Fuel Quantity discrepancies on ground? LONG RANGE FQI ACCURACY (GROUND) MAX FOB=113T 1.5

FQI TOLERANCE Tonnes

1

0.5

0

-0.5

-1

-1.5 0

20

40

60

80

100

Actual FOB Tonnes

Fuel accuracy

19

120

Why Fuel Quantity discrepancies on ground? What about MMI use? MMI accuracy: +/-5% FOB

Fuel accuracy

20

Why Fuel Quantity discrepancies on ground? Single Aisle FQI Accuracy (GROUND) MAX FOB= 19T 1.5

FQI/MMI TOLERANCE Tonnes

1

0.5

FQI

0

MMI

-0.5

-1

-1.5 0

2

4

6

8

10

12

14

16

18

20

Actual FOB Tonnes

Fuel accuracy

21

Why Fuel Quantity discrepancies on ground? LONG RANGE FQI ACCURACY (FLIGHT) MAX FOB=113T 8

6

FQI/MMI TOLERANCE Tonnes

4

2

FQI

0 0

20

40

60

80

100

120

-2

-4

-6

-8 Actual FOB Tonnes

Fuel accuracy

22

MMI

Why Fuel Quantity discrepancies on ground? What about MMI use? MMI accuracy: +/-5% FOB

Do not use MMI to check FQI system Only use MMI when FQI is inoperative

Fuel accuracy

23

Content Introduction What systems to determine Fuel quantity in the aircraft? Fuel Quantity Indicator (FQI) System Manual Magnetic Indicators (MMI) Why Fuel quantity discrepancies: On ground? In flight?

Conclusion

Fuel accuracy

24

Why Fuel Quantity discrepancies in flight?

Fuel accuracy

25

Why Fuel Quantity discrepancies in flight?

Fuel accuracy

26

Why Fuel Quantity discrepancies in flight? When performing this check, discrepancies come from: BLOCK FUEL accuracy FU accuracy FOB accuracy

Fuel accuracy

27

FU accuracy FU is the integration of the Fuel Flow over time The accuracy of the Fuel Flow meter depends on: Fuel flow rate Temperature conditions

But, keep in mind that the FU indication does not take into account APU fuel consumption Fuel accuracy

28

FU accuracy

FU accuracy: Estimated to be better than +/-1.5% For normal Cruise conditions ~+/-1%

Fuel accuracy

29

FU accuracy on long Range Aircraft Maximum F.USED Deviation 0.7 0.6 0.5

Deviatio n tonnes

0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 0

10

20

30

40

50

60

70

80

90

100 110

FOB tonnes F.USED 31 tonnes Fuel accuracy

F.USED 67 tonnes

F.USED 103 tonnes 30

FQI accuracy in flight Single Aisle Aircraft FOB 0 to 0.5% Max FOB 0.5%Max FOB to Max FOB

OVERREAD 0 1% FOB

UNDERREAD - (1% Max FOB +0.5% FOB)

Long Range Aircraft: FOB Below 2% Max FOB

OVERREAD Decrease linearly to 0

2% Max FOB to Max FOB

+(0.3% Max FOB +0.95%FOB)

Fuel accuracy

UNDERREAD Decrease linearly to –0.64% Max FOB - (0.3% Max FOB +0.95% FOB)

31

Why Fuel Quantity discrepancies in flight? Single Aisle FQI Accuracy (Flight) MAX FOB= 19T 0.3

0.2

FQI TOLERANCE Tonnes

0.1

0

-0.1

-0.2

-0.3

-0.4 0

2

4

6

8

10

12

14

16

18

Actual FOB Tonnes

Fuel accuracy

32

20

Why Fuel Quantity discrepancies in flight? LONG RANGE FQI ACCURACY (FLIGHT) MAX FOB=113T

2

1.5

FQI TOLERANCE Tonnes

1

0.5

0 0

20

40

60

80

100

120

-0.5

-1

-1.5

-2 Actual FOB Tonnes

Fuel accuracy

33

Why Fuel Quantity discrepancies in flight? The maximum theoretical Combined FOB and FU deviation in indication is possible when: At departure the FQI system has the maximum deviation (positive or negative) At time X, the FQI system has the maximum deviation, but with the opposite sign to the FQI at departure, and the F. USED deviation moves in the same sense

Fuel accuracy

34

Why Fuel Quantity discrepancies in flight? EXEMPLES: A340 aircraft which takes off with 113 Tons on board. Fuel check with 10 Tons on board: MAX Theoretical Combined FOB and FU deviation:

2.554 Tons A340 aircraft which takes off with 41 Tons on board. Fuel check with 10 Tons on board: MAX Theoretical Combined FOB and FU deviation:

1.749 Tons Comparing FOB departure-FOB+FU is a good practice ! Fuel accuracy

35

Conclusion Your FQI system has a good accuracy On ground, only use MMI when FQI is inoperative In flight, continue to perform the FOB check, being confident on the Fuel Quantity Indications displayed on ECAM

Fuel accuracy

36