Sim is reading CJ4 incorrect Fuel System Code

[BossRhombus85]

WT Response with details:

Sim is reading CJ4 incorrect Fuel System Code

Hi all, Upon additional investigation, the CJ4 does have the fuel_type parameter in the [FUEL_SYSTEM] section, but there was some unclarity in the SDK docs and it should be in the [FUEL] section, unless you’re using fuel system versions 6 or 7, then it goes in the [FUEL_SYSTEM] section. So right now, the sim itself is treating the fuel as Avgas density, not just the aircraft app and career load systems. To address this directly, this is definitely a miss on our end at WT, although the CJ4 is …

ISSUE DESCRIPTION

Description of the issue:

Honestly, can someone please answer me how this happens? How a “flight simulator” gets a basic, critical, and SIMPLE detail about an airplane wrong? We’re not talking about “it doesn’t turn as well as it should” or “the avionics aren’t accurately modeled.”

We’re literally talking about the amount of FUEL YOU CAN LOAD ON THE PLANE.

Fuel capacity, 5828 lbs. Citation CJ4 Gen3
Fuel capacity, 5828 lbs. Cessna CitationJet/M2 - Wikipedia

Except, in Microsoft Flight “Simulator,” it’s a mere 5219 lbs.

The other weights are probably wrong, but I’m done being an Alpha Tester.

If applicable, which aircraft is experiencing this issue:
Cessna Citation CJ4

[PC Only] Did you remove all your community mods/add-ons? If yes, are you still experiencing the issue?
N/A

FREQUENCY OF ISSUE

How often does this occur for you (Example: Just once, every time on sim load, intermittently)?
All the time

REPRODUCTION STEPS

Just look at the plane.

Please list clear steps you took in order to help our test team reproduce the same issue:

1. Look at the plane.

YOUR SETTINGS

If the issue still occurs with no mods and add-ons, please continue to report your issue. If not, please move this post to the User Support Hub.
N/A

What peripherals are you using, if relevant:
Maybe it’s my joystick, right?

[PC Only] Are you using Developer Mode or have you made any changes to it?
No

[PC, MSFS 2020 Only] Are you using DX11 or DX12?
N/A

[PC Only] What GPU (Graphics Card) do you use?
Does an AMD card give more fuel than an Nvidia card?

[PC Only] What other relevant PC specs can you share?

MEDIA

Please add a screenshot or video of the issue occurring.

[END OF FIRST USER REPORT]

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For anyone who wants to contribute on this issue, Click on the button below to use this template:

Do you have the same issue if you follow the OP’s steps to reproduce it?
•

Provide extra information to complete the original description of the issue:
•

If relevant, provide additional screenshots/video:
•

[Maki152]

-Disregard-

[Bishop398]

@BossRhombus85

Honestly, can someone please answer me how this happens? How a “flight simulator” gets a basic, critical, and SIMPLE detail about an airplane wrong? We’re not talking about “it doesn’t turn as well as it should” or “the avionics aren’t accurately modeled.”

We’re literally talking about the amount of FUEL YOU CAN LOAD ON THE PLANE.

The CJ4 has had the correct fuel load specifications since early 2021, and this continues into MSFS 2024. The flight_model.cfg defines each wing tank with 434.920013 gallons of fuel, for a total of 869.840026 gallons. It also defines the fuel_type as 2, which in the sim is Jet-A. At a Jet-A fuel density of 6.7lbs/gal, that is 5828lbs of total fuel.

Unfortunately, the EFB fuel screen appears to be always using the Avgas density of 6lbs/gal no matter the aircraft, which is causing the discrepancy. However, you should be able to fully load the aircraft with fuel regardless of this display issue.

[CasualClick]

Title edited to reflect actual defect.

[DementedCorn327]

Do you have the same issue if you follow the OP’s steps to reproduce it?
• yes

Provide extra information to complete the original description of the issue:
• using same example as OP and calculation explained by @Bishop398, CJ4 Jet-A full tanks represent a weight of 5828lbs

If relevant, provide additional screenshots/video:
•
Incorrect value is calculated on the Fuel and payload screen:

Incorrect value is calculated on the EFB Mass and balance screen:

Correct value is calculated on the EFB Payload & Fuel screen:

Loaded fuel weight is incorrect:

[WonkySteam89064]

I fly the career mode. And when it tells me it needs 450 kg for a mission, I fly with twice as much. Thus the mission was completed
Of course the EFB calculation is wrong.

[Bishop398]

Hi all,

Upon additional investigation, the CJ4 does have the fuel_type parameter in the [FUEL_SYSTEM] section, but there was some unclarity in the SDK docs and it should be in the [FUEL] section, unless you’re using fuel system versions 6 or 7, then it goes in the [FUEL_SYSTEM] section. So right now, the sim itself is treating the fuel as Avgas density, not just the aircraft app and career load systems.

@BossRhombus85

How a “flight simulator” gets a basic, critical, and SIMPLE detail about an airplane wrong?

To address this directly, this is definitely a miss on our end at WT, although the CJ4 is not particularly sensitive at all to loadout, not in climb rate, ceiling, nor fuel consumption. IRL the plane is usually just loaded up with a bunch of fuel (usually at or near full), as the fuel economy difference between full and empty is very minimal, and the plane’s mission profile is such that you don’t really see them extending towards ranges where an exact fuel amount would be important. Flights in the 800-1400NM range are the most common.

This is the first report we’ve had of this issue across all areas we get reports (including our own Discord, which has a disproportionately high number of CJ4 flyers), so it appears other folks were not adversely affected enough either to notice; nonetheless we do have it logged now and we will address it in a future sim update!

@CasualClick Please update the title to reflect this new information, thanks!

[DementedCorn327]

Could others aircraft WT is in charge of be affected by the same issue ?