What are A320 ZFW and ZFWCG, and how are they used?

On the Airbus A320, ZFW is the loaded aircraft’s mass excluding usable fuel, while ZFWCG is its centre of gravity at that mass, expressed as %MAC. In our Aviation & Real-World Flying coverage, the simulator procedure is to obtain both from the completed payload load and enter or confirm them on MCDU INIT B.

What do ZFW and ZFWCG mean on an Airbus A320?

ZFW describes how heavy the aircraft is without usable fuel; ZFWCG describes where that same load balances. The two figures must therefore come from the same completed passenger, baggage and cargo load.

The basic calculation is ZFW = dry operating weight + payload. Dry operating weight normally includes the aircraft, crew, catering, operating equipment, fluids and unusable fuel. Simpler simulators may start with an empty-weight figure instead, so check whether crew and cabin equipment are already included before adding them again.

ZFWCG means zero fuel weight centre of gravity. It is expressed as a percentage of mean aerodynamic chord: a larger %MAC places the centre of gravity farther aft along the reference chord. It is not a percentage of fuselage length, a fuel percentage or a mass.

Moving passengers or cargo between loading stations changes ZFWCG without changing total ZFW. That physical distribution matters because weight and centre of gravity alter acceleration, rotation and pitch response in a properly modelled simulator.

Why can ZFW exceed a limit when take-off weight does not?

Maximum zero fuel weight (MZFW) is a structural limit separate from maximum take-off weight. Its value depends on the A320 variant and certification represented by the add-on, so use that aircraft’s loading page or documentation rather than a generic number.

If ZFW exceeds MZFW, remove payload; reducing fuel cannot fix it. Conversely, a legal ZFW can produce an excessive ramp or take-off weight after fuel is loaded. If ZFW is acceptable but ZFWCG lies outside the permitted envelope, redistribute passengers or cargo rather than entering a more convenient CG.

Where do you find the correct ZFW and ZFWCG?

Use the figures calculated for the payload physically loaded into that specific simulated aircraft.

• Integrated EFB or load manager: Prefer this when it controls the add-on’s passenger and cargo stations. Finish loading, allow it to synchronise, then read the resulting ZFW and ZFWCG.
• Completed load sheet: Use its figures only when the A320 variant, engine option, cabin configuration and payload distribution match the simulator load.
• Simulator weight-and-balance screen: Use a CG figure only if it explicitly identifies zero-fuel CG. A single CG shown after fuel is loaded may instead be gross-weight or take-off CG.

Changing fuel alone must not change ZFW or ZFWCG because usable fuel is excluded from both. If the displayed CG moves when fuel is added, the screen is probably reporting the aircraft’s total CG rather than ZFWCG.

How do you enter ZFW/ZFWCG in an A320 simulator?

Load and verify the aircraft before transferring the matching ZFW/ZFWCG pair to INIT B or the add-on’s equivalent fuel-prediction page.

1. Select the exact configuration: Confirm the A320 variant, engine option and cabin layout. Do not reuse figures from an A319, A321 or differently configured A320.
2. Load the payload once: Set passengers, baggage and cargo through the system that writes to the aircraft’s payload stations. Avoid loading through both the simulator and an add-on manager, which can duplicate the payload.
3. Record and check the results: Confirm ZFW is below MZFW and that the zero-fuel and take-off loading points remain inside their permitted envelopes.
4. Open INIT B: Locate the ZFW/ZFWCG field on the MCDU. Our guide to the A320 cockpit controls and MCDU layout helps identify the unit if it is unfamiliar. Complete this page before engine start where practical because some implementations restrict or replace it after the pre-flight phase.
5. Enter the paired values: Follow the units and order displayed by the aircraft. If a load manager reports an illustrative ZFW of 61.2 tonnes and ZFWCG of 27.4% MAC, the common entry is 61.2/27.4. Here, 27.4 means 27.4% MAC, not 0.274; the example is not a recommended load.
6. Enter block fuel separately: Never add block fuel to ZFW. Ramp weight should broadly equal ZFW plus fuel on board, while take-off weight will be lower after taxi burn.
7. Finish performance setup: Calculate take-off speeds, flap setting and stabiliser trim for the verified load. If payload changes afterwards, update ZFW/ZFWCG and repeat the performance calculation.

Some A320 add-ons transfer these values from the EFB automatically. Check the transferred pair against the final load sheet rather than accepting it blindly; a later payload change makes the stored values stale.

Why does the MCDU reject or disagree with ZFW/ZFWCG?

Rejected or implausible entries usually come from formatting, units or a mismatch between planned data and the aircraft actually loaded.

• FORMAT ERROR: Check the decimal format, slash and value order expected by that MCDU. A field labelled ZFW/ZFWCG normally expects mass first and CG second.
• ENTRY OUT OF RANGE: Confirm whether mass is displayed in tonnes, kilograms or pounds, and enter CG as %MAC. A loading index from a load sheet is not ZFWCG unless the loading tool converts it.
• Gross weight is implausibly high: Ramp or gross weight may have been entered as ZFW, causing the FMGS to add fuel a second time.
• EFB and MCDU disagree: Resynchronise the physical payload and then refresh or re-enter the MCDU data. Typing a different number into the MCDU does not necessarily move passengers or cargo in the flight model.
• Planned and simulated loads differ: Match the simulator payload to the plan rather than forcing planned figures into an aircraft with a different actual weight or CG.

Is ZFWCG the A320 take-off trim setting?

No. ZFWCG helps the simulated FMGS determine the loading condition, but take-off CG also includes the effect of usable fuel and its distribution. Use the take-off CG and stabiliser setting produced by the aircraft’s load sheet or supported performance tool; do not copy ZFWCG directly into the trim field.

The actual payload stations determine the modelled balance and handling. The MCDU entry alone may not move that physical CG. An excessively forward load or incorrect nose-up trim can make rotation difficult, while an aft load reduces longitudinal stability.

Do ZFW and ZFWCG change as fuel burns?

ZFW and ZFWCG normally remain constant during flight because fuel burn changes gross weight and gross CG, not the zero-fuel values. They change only if payload or operating contents change.

Predicted landing weight is approximately ZFW + predicted landing fuel. Burning fuel can bring landing weight below its limit, but it cannot correct an excessive ZFW. Our explanation of how fuel changes gross weight and aircraft balance covers the distinction in more detail.