39155690 Airbus Fuel Accuracy.pdf

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Fuel accuracy

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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?

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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

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FQI System description

Example of Probes

location in an

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FQI System description

Fuel Quantities are displayed on the ECAM

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FQI System description

Fuel Quantities are displayed on the ECAM

A320

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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

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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

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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

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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

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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

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FQI accuracy on ground

Single Aisle Aircraft

Long Range Aircraft:

FOB OVERREAD UNDERREAD

0 to 0.5% Max FOB 0

0.5%Max FOB to Max FOB 1% FOB

- (0.5% Max FOB +0.5% FOB)

Below 2% Max FOB Decrease linearly to 0 Decrease linearly to -1% Max FOB 2% Max FOB to Max FOB +(0.5% Max FOB +0.5% FOB) - (0.5% Max FOB +0.5% FOB)

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FQI accuracy on ground

Single Aisle Aircraft

Long Range Aircraft:

0 to 0.5% Max FOB 0

- (0.5% Max FOB +0.5% FOB)

Below 2% Max FOB Decrease linearly to 0 Decrease linearly to -1% Max FOB 2% Max FOB to Max FOB +(0.5% Max FOB +0.5% FOB) - (0.5% Max FOB +0.5% FOB)

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Why Fuel Quantity discrepancies on ground?

Single Aisle FQI Accuracy (GROUND) MAX FOB= 19T

-0.25 -0.2 -0.15 -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 20 FQ I T O LE R A N C E T onne s

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Why Fuel Quantity discrepancies on ground?

LONG RANGE FQI ACCURACY (GROUND) MAX FOB=113T

-1 -0.5 0 0.5 1 1.5 FQ I T O L ER A N C E T o n n e s

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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)]

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Why Fuel Quantity discrepancies on ground?

EXEMPLE: (A320-200)

ACTUAL FOB before refueling: 3T ACTUAL FOB after refueling: 18T

Max TOTAL Bowser inaccuracy : 115kg

APU Fuel used for 30minutes 50kg

Max FQI deviation* 220kg

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TOTAL: 385kg

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Why Fuel Quantity discrepancies on ground?

-0.25 -0.2 -0.15 -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 20 FQ I T O LE R A N C E T onne s

MAX FQI

deviation

during

refueling

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Why Fuel Quantity discrepancies on ground?

LONG RANGE FQI ACCURACY (GROUND) MAX FOB=113T

-1 -0.5 0 0.5 1 1.5 FQ I T O L ER A N C E T o n n e s

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Why Fuel Quantity discrepancies on ground?

What about MMI use?

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Why Fuel Quantity discrepancies on ground?

-1 -0.5 0 0.5 1 1.5 FQ I/M M I T O L E R A N C E T o n ne s FQI MMI

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Why Fuel Quantity discrepancies on ground?

LONG RANGE FQI ACCURACY (FLIGHT) MAX FOB=113T

-8 -6 -4 -2 0 2 4 6 8 0 20 40 60 80 100 120

Actual FOB Tonnes

FQ I/M M I T O L ER A N C E T o n n e s FQI MMI

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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

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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?

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Why Fuel Quantity discrepancies in flight?

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Why Fuel Quantity discrepancies in flight?

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Why Fuel Quantity discrepancies in flight?

When performing this check, discrepancies come from:

BLOCK FUEL accuracy FU accuracy

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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

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FU accuracy

FU accuracy:

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

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FU accuracy on long Range Aircraft

Maximum F.USED Deviation

-0.7 -0.6 -0.5 -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 Dev ia ti o n t o n n es

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FQI accuracy in flight

Single Aisle Aircraft

Long Range Aircraft:

0 to 0.5% Max FOB 0

- (1% Max FOB +0.5% FOB)

Below 2% Max FOB Decrease linearly to 0 Decrease linearly to –0.64% Max FOB

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Why Fuel Quantity discrepancies in flight?

Single Aisle FQI Accuracy (Flight) MAX FOB= 19T

-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0 2 4 6 8 10 12 14 16 18 20

Actual FOB Tonnes

FQ I TO LE R A N C E Tonne s

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Why Fuel Quantity discrepancies in flight?

LONG RANGE FQI ACCURACY (FLIGHT) MAX FOB=113T

-1 -0.5 0 0.5 1 1.5 2 0 20 40 60 80 100 120 FQ I T O L ER A N C E T o n n e s

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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

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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: