Aircraft Systems Quiz: A320/A321 FMS Techniques

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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?

The FMGC computes GW and CG based on ZFW, ZFWCG, fuel quantities, and fuel flow. Signup and view all the answers

What specific conditions are necessary for the FAC to use aerodynamic data for GW computation?

The conditions required are low altitude (below 14,625 ft), low speed (below 250 kt), and stabilized flight parameters. Signup and view all the answers

What happens if there is an error in entering ZFW or ZFWCG on the INIT B page?

An error in entering ZFW or ZFWCG induces calculation errors that need to be highlighted. Signup and view all the answers

During which phase of flight does the FAC utilize the GW FM computed?

On the ground, the FAC uses the GW computed by the FM. Signup and view all the answers

What displays on the ECAM are influenced by the computed GW?

The computed GW is displayed on the ECAM. Signup and view all the answers

What are the two independent systems that compute the Gross Weight (GW) and Centre of Gravity (CG) in the A320/A321?

The Flight Management (FM) and Flight Control (FAC) systems. Signup and view all the answers

Why are the FM computed GW and CG values important for the A320/A321?

They are used for FM predictions, ECAM displays, MCDU inputs, and computation of characteristic speeds. Signup and view all the answers

What consequences can arise from a ZFW or ZFWCG entry error in the MCDU INIT B page?

It can induce calculation errors that are highlighted during the flight. Signup and view all the answers

How does the FAC utilize the GW and CG values differently from the FM?

The FAC uses these values primarily for the flight control laws. Signup and view all the answers

In what two displays is the FM computed Gross Weight (GW) shown?

The ECAM and the MCDU. Signup and view all the answers

What role do characteristic speeds (VLS, F, S, GD) play in flight management?

They are computed based on GW and CG and displayed on the Primary Flight Display (PFD). Signup and view all the answers

What is the significance of accurately entering ZFW and ZFWCG in the MCDU?

Accurate entries prevent calculation errors that can disrupt flight operations. Signup and view all the answers

What does ECAM stand for and how is it related to the GW in the A320/A321?

ECAM stands for Electronic Centralized Aircraft Monitoring, and it displays the Gross Weight (GW). Signup and view all the answers

What happens to fuel figures once the engines of the A320/A321 are started?

The fuel figures are updated, correcting any erroneous data. Signup and view all the answers

How does an erroneous Zero Fuel Weight (ZFW) entry on the MCDU INIT B page affect the flight management?

It results in erroneous Gross Weight (GW) and Center of Gravity (CG) calculations by the Flight Management System (FM). Signup and view all the answers

What condition must be met for the GW FAC to be computed from aerodynamic data?

The conditions include being at low altitude (below 14,625 ft), low speed (below 250 kt), and stabilized flight parameters. Signup and view all the answers

What triggers a 'CHECK GW' message on the MCDU during flight?

The message is triggered when the FM and FAC GW differ beyond a specified threshold. Signup and view all the answers

What happens when the computed GW FM and GW FAC differ from a given threshold?

A CHECK GW message appears on the MCDU scratchpad. Signup and view all the answers

What is indicated by the values on the ECAM if erroneous ZFW is entered?

The Gross Weight (GW) displayed on the ECAM will be incorrect. Signup and view all the answers

How is GW and CG affected by erroneous ZFW entered on the MCDU INIT B page?

It induces erroneous calculations for GW and CG, affecting FM predictions and displayed values. Signup and view all the answers

What is the effect on characteristic speeds at take-off if erroneous GW is used?

Characteristic speeds on the PFD at take-off will be erroneous. Signup and view all the answers

What error is caused if the computed VLS is above V2 after erroneous ZFW entry?

SRS mode guidance is affected. Signup and view all the answers

How does the Flight Augmentation Computer (FAC) update GW once airborne?

FAC GW, based on FM GW on the ground, updates slowly using Angle of Attack (AOA) information. Signup and view all the answers

Why is the FOB displayed on ECAM considered correct?

The FOB on ECAM is correct since it is derived from FQI data. Signup and view all the answers

When is the GW FAC computed based on GW FM updated during flight?

It is updated once airborne through a slow calculation using AOA information. Signup and view all the answers

What impact does an incorrect GW and CG have on performance during flight?

It can lead to erroneous FM predictions and can affect speed management during different flight phases. Signup and view all the answers

What is the consequence of erroneous GW and CG calculations on the PFD?

The characteristic speeds displayed on the PFD become erroneous. Signup and view all the answers

What is the purpose of the MCDU FUEL PRED page for pilots?

It provides pilots with predictions of fuel usage and weight calculations during flight. Signup and view all the answers

What specific threshold difference triggers the CHECK GW message?

The threshold difference is not specified, but it is a predetermined value related to GW calculations. Signup and view all the answers

What is the significance of the fuel figures being updated once the engines are started?

The fuel figures are critical for accurate flight management; once the engines are started, they reflect correct fuel amounts instead of erroneous values. Signup and view all the answers

What should crew members do when the 'CHECK GW' amber warning is displayed?

They should compare the Load and Trim Sheet figures with the FM computed Gross Weight (GW) and the fuel used to identify discrepancies. Signup and view all the answers

How can crewmembers avoid entry errors in ZFW?

ZFW entries should be cross-checked by both crewmembers to ensure accuracy. Signup and view all the answers

What should be suspected if FM and LTS GW figures are correct but the FAC computed GW appears inaccurate?

The AOA sensor problem should be suspected as the cause of the discrepancy. Signup and view all the answers

What does FOB on ECAM represent, and why is it important?

FOB on ECAM represents Fuel On Board, which is accurate because it's derived from FQI data. Signup and view all the answers

What steps should be taken if an obvious entry error is detected during the comparison of GW figures?

The FM GW should be updated on the MCDU FUEL PRED page to correct the error. Signup and view all the answers

What consequences may result from erroneous fuel information before engine start?

Erroneous fuel information can lead to incorrect FM GW, potentially compromising flight safety. Signup and view all the answers

What is the role of characteristic speeds in flight operations?

Characteristic speeds provide essential data for flight maneuvers, particularly when there are suspicions about LTS GW. Signup and view all the answers

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.