How do I change an add-on aircraft's fuel capacity?

To change an add-on aircraft’s fuel capacity, edit the aircraft definition—not the pre-flight fuel slider. Back up the add-on, locate its fuel-tank configuration, change each tank’s capacity in the units expected by that simulator, then reload the aircraft and verify the total. Protected or plugin-driven add-ons may ignore or prevent the edit.

Fuel load and fuel capacity are different

Fuel capacity is the maximum each tank can hold; fuel load is the amount placed in it for a particular flight. Across Microsoft Flight Simulator 2020 and 2024, FSX, Prepar3D and X-Plane, the normal loading screen cannot increase the underlying capacity.

If the existing tanks are large enough and you only want a different departure quantity, change the operational fuel load through the simulator or aircraft loader instead. Edit the aircraft definition only to correct an inaccurate tank size, modify a development project or model an approved auxiliary-fuel installation.

Where is add-on aircraft fuel capacity stored?

The location depends on the simulator and on whether the aircraft uses a native or custom fuel system.

On console versions of Microsoft Flight Simulator, package files are not exposed for ordinary user editing. Capacity changes are therefore limited to options supplied by the aircraft itself.

How do I edit the fuel capacity safely?

1. Close the simulator and make a backup. Copy the complete aircraft folder or at least every configuration file you will touch. For FSX, our explanation of locating the aircraft folder and protecting aircraft.cfg covers the relevant folder structure.

2. Find the authoritative fuel definition. Search for existing tank names such as LeftMain, RightMain or Center1. Do not add a second fuel section if the aircraft already uses a modern fuel system or custom code elsewhere.

3. Identify the capacity and unusable-fuel fields. A legacy Microsoft-format tank line generally follows this schema:

   LeftMain = longitudinal, lateral, vertical, capacity, unusable

   The first three values place the tank relative to the aircraft reference point. The fourth is its capacity and the fifth represents unusable fuel. This is a field guide, not a paste-ready line; preserve the aircraft’s existing tank names, separators and coordinates.

4. Convert the published figure into the correct units. Legacy Microsoft tank capacities are normally expressed in US gallons, while specifications and loading screens may show litres, kilograms or pounds. For equal left and right tanks, divide the intended combined capacity between them rather than assigning the combined figure to both. If MSFS displays an unexpected figure, check the distinction between fuel mass, volume and the selected MSFS units.

5. Edit only the required values. Keep paired wing tanks equal unless the real aircraft is asymmetric. Do not alter tank coordinates merely to change capacity; those coordinates influence the fuel’s centre-of-gravity effect. In X-Plane, use Plane Maker rather than treating the .acf file as an ordinary text document.

6. Save, reload and test at several quantities. Restart or fully reload the aircraft, select 100% fuel and compare the displayed tank and total capacities with the intended figures. Then test partial fuel, selectors, pumps, transfer logic, gauges and engine feed. Our guide to checking usable capacity and fuel weight helps confirm that the resulting total is credible.

Keep a decimal point where the format expects one. In comma-delimited Microsoft configuration lines, replacing a decimal point with a regional decimal comma can shift every following field and stop the aircraft loading correctly.

Why does the edited fuel capacity reset or stay unchanged?

An unchanged or resetting value usually means the wrong file was edited, another system owns the fuel data, or an update restored the original package.

• Wrong aircraft variant: Several liveries or variants may point to one base aircraft. Edit the shared base configuration, not a texture-only folder.
• Custom EFB or loader: A tablet, gauge or plugin may write its own fuel limits after the aircraft loads. Use its supported loading system or locate the corresponding development setting if the add-on is editable.
• Modern fuel-system definition: Changing a legacy [fuel] entry has no effect when a newer tank-and-line system is authoritative.
• Protected package: Encrypted or signed commercial files cannot be modified reliably. Altering them may also break support, package validation or multiplayer integrity checks.
• Simulator still holding the old aircraft: Switching liveries is not always a full reload. Return to the main menu or restart the simulator before judging the change.
• Update overwrite: Add-on and simulator updates can replace edited files. Store the backup and a note of every changed value outside the live package.
• Gauge-specific limit: Native gauges usually scale with tank quantity, but custom gauges can have hard-coded capacities that require a separate change.

Can I add an auxiliary or ferry tank instead?

Adding a new tank is a larger aircraft-development task than increasing an existing tank’s capacity. The simulator needs the new tank’s volume, position, usable fuel, feed or transfer path, selector behaviour and gauge representation.

Choose a simple capacity edit when correcting the stated size of an existing tank. For a real auxiliary or ferry installation, define a separate tank through the simulator’s supported aircraft-development tools and reproduce its plumbing or transfer procedure. Merely enlarging the wing tanks produces the right total fuel but the wrong centre of gravity and operating logic.

Does changing capacity affect weight, CG and performance?

Changing maximum capacity usually affects performance only when the additional fuel is loaded. More fuel raises gross weight, changes take-off and climb performance, and shifts the centre of gravity according to the tank coordinates.

The edit does not automatically raise maximum take-off weight or add the structural weight and drag of a larger or external tank. Loading every enlarged tank to 100% can therefore put the aircraft beyond its certified limit even though the simulator accepts the quantity. Check loaded weight, CG and usable fuel before flying.