Questions and Answers
What are the main applications of the GW and CG values computed by the FAC?
The GW and CG values computed by the FAC are used for flight control laws and the computation of characteristic speeds for display on the PFD.
What information does the flight crew input on the INIT B page, and how does it affect computation?
The flight crew inputs the ZFW and ZFWCG on the INIT B page, which are used by the FMGC to compute the current GW and CG.
How does the FAC compute its own GW and CG during flight?
The FAC computes its own GW and CG from aerodynamic data during flight under specific conditions.
What role does the FMGC play in the computation of GW and CG?
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What specific conditions are necessary for the FAC to use aerodynamic data for GW computation?
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What happens if there is an error in entering ZFW or ZFWCG on the INIT B page?
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During which phase of flight does the FAC utilize the GW FM computed?
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What displays on the ECAM are influenced by the computed GW?
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What are the two independent systems that compute the Gross Weight (GW) and Centre of Gravity (CG) in the A320/A321?
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Why are the FM computed GW and CG values important for the A320/A321?
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What consequences can arise from a ZFW or ZFWCG entry error in the MCDU INIT B page?
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How does the FAC utilize the GW and CG values differently from the FM?
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In what two displays is the FM computed Gross Weight (GW) shown?
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What role do characteristic speeds (VLS, F, S, GD) play in flight management?
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What is the significance of accurately entering ZFW and ZFWCG in the MCDU?
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What does ECAM stand for and how is it related to the GW in the A320/A321?
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What happens to fuel figures once the engines of the A320/A321 are started?
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How does an erroneous Zero Fuel Weight (ZFW) entry on the MCDU INIT B page affect the flight management?
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What condition must be met for the GW FAC to be computed from aerodynamic data?
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What triggers a 'CHECK GW' message on the MCDU during flight?
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What happens when the computed GW FM and GW FAC differ from a given threshold?
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What is indicated by the values on the ECAM if erroneous ZFW is entered?
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How is GW and CG affected by erroneous ZFW entered on the MCDU INIT B page?
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What is the effect on characteristic speeds at take-off if erroneous GW is used?
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What error is caused if the computed VLS is above V2 after erroneous ZFW entry?
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How does the Flight Augmentation Computer (FAC) update GW once airborne?
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Why is the FOB displayed on ECAM considered correct?
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When is the GW FAC computed based on GW FM updated during flight?
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What impact does an incorrect GW and CG have on performance during flight?
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What is the consequence of erroneous GW and CG calculations on the PFD?
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What is the purpose of the MCDU FUEL PRED page for pilots?
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What specific threshold difference triggers the CHECK GW message?
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What is the significance of the fuel figures being updated once the engines are started?
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What should crew members do when the 'CHECK GW' amber warning is displayed?
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How can crewmembers avoid entry errors in ZFW?
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What should be suspected if FM and LTS GW figures are correct but the FAC computed GW appears inaccurate?
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What does FOB on ECAM represent, and why is it important?
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What steps should be taken if an obvious entry error is detected during the comparison of GW figures?
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What consequences may result from erroneous fuel information before engine start?
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What is the role of characteristic speeds in flight operations?
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Study Notes
General Overview
- Aircraft Gross Weight (GW) and Centre of Gravity (CG) are computed independently by Flight Management (FM) and Flight Augmentation Computer (FAC).
- FM-calculated GW and CG are used for:
- Flight Management predictions and speeds.
- Electronic Centralized Aircraft Monitoring (ECAM) display for GW.
- Multi-Function Control Display Unit (MCDU) for both GW and CG.
- Characteristic speed computations for display on Primary Flight Display (PFD).
- FAC-calculated GW and CG are used for:
- Flight control laws.
ZFW and ZFWCG Entry Errors
- Erroneous Zero Fuel Weight (ZFW) or Zero Fuel Weight Center of Gravity (ZFWCG) entered on MCDU INIT B page leads to calculation errors.
- Miscalculations affect:
- FM predictions and speeds.
- MCDU Fuel Prediction page and ECAM displays.
- Characteristic speeds on PFD, particularly impacting Speed Reference System (SRS) mode guidance.
GW and CG Computation Process
- Flight crew inputs ZFW and ZFWCG on INIT B page.
- FMGC computes GW and CG based on:
- Entered ZFW and ZFWCG.
- Fuel quantities from Fuel Quantity Indicator (FQI).
- Fuel Flow data from Full Authority Digital Engine Control (FADEC).
- FAC computes its own GW and CG using aerodynamic data, allowing for minor adjustments in flight control laws.
Specific Conditions and Notifications
- On the ground, the FAC uses FM-calculated GW.
- In-flight conditions where low altitude (below 14,625 ft) and low speed (below 250 knots) stabilize allow the FAC to update GW and CG from aerodynamic data.
- A "CHECK GW" message displays on MCDU if there's a significant difference between FM and FAC-calculated GW.
Impact of Erroneous Entries
- Incorrect ZFW entry results in:
- Erroneous FM calculated GW, which also affects CG.
- Incorrect values for FM predictions, MCDU displays, and take-off characteristic speeds.
- Once engines start, fuel figures are updated, correcting FM values, although ECAM displays correct Fuel On Board (FOB) data from FQI.
Operational Recommendations
- ZFW entries should be cross-checked by both crew members to avoid errors.
- If a "CHECK GW" warning appears:
- Compare Load and Trim Sheet (LTS) data with FM GW and fuel used.
- Update MCDU FUEL PRED page if an obvious entry error is detected.
- Assess the integrity of FAC computed GW if FM and LTS match.
- Extract characteristic speeds from Quick Reference Handbook (QRH) if LTS GW is in question.
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Description
Test your knowledge on flight management systems and entry errors for the A320/A321 aircraft in this quiz. Learn about the intricacies of aircraft gross weight and center of gravity management through various criteria and techniques. Perfect for flight crew and aircraft systems enthusiasts.